JP7268488B2 - vehicle steering system - Google Patents

Description

The present invention relates to a vehicle steering system.

As a vehicle steering device, a steering reaction force generating device (FFA: Force Feedback Actuator, steering mechanism) for steering by a driver and a tire steering device (RWA: Road Wheel Actuator, steering mechanism) for steering the vehicle. There is a steer-by-wire (STB: Steer By Wire) type vehicle steering system in which the and are mechanically separated from each other. In such a SBW vehicle steering system, the steering mechanism and the steering mechanism are electrically connected via a control unit, and control between the steering mechanism and the steering mechanism is performed by an electric signal. be.

In the SBW type vehicle steering system, the steering mechanism and the steering mechanism are mechanically separated as described above. It is necessary to determine the steering angle corresponding to the steering angle (hereinafter also referred to as "maximum steering angle"). For example, in Patent Document 1 below, in an SBW vehicle steering system, when a predetermined steering angle is reached, a steering reaction force equivalent to the steering torque is applied to lock the steering wheel. Are listed.

JP 2010-280312 A

Although the above prior art discloses that the target steering angle is corrected according to the vehicle speed, the steering angle at which the steering wheel is locked is constant. Therefore, depending on the conditions, it is conceivable that the steering angle in the locked state and the maximum turning angle do not match.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and provides a steering system for a vehicle that can limit the operation of the steering wheel in accordance with the maximum mechanical steering angle that is determined structurally. The purpose is to

In order to achieve the above object, a vehicle steering system according to one aspect of the present invention includes a reaction force device that applies a steering reaction force to a steering wheel, and a drive device that steers tires according to the steering of the steering wheel. , a control unit that controls the reaction force device and the drive device, the control unit including a target steering torque generation unit that generates a target steering torque that is a target value of the steering torque; a steering angle of the steering wheel; Then, based on the end steering angle corresponding to the maximum steering angle, the absolute value of the steering angle of the steering wheel becomes zero in a region where the steering angle is less than the end steering angle, and the absolute value of the steering angle becomes equal to or greater than the end steering angle. and an end target steering torque generating section that generates a first torque signal that increases from zero at a predetermined rate of change in the region, wherein the target steering torque generating section generates a predetermined torque signal corresponding to at least the vehicle speed and the steering angle of the vehicle. A second torque signal is generated based on the basic map, and the first torque signal is added to the second torque signal to generate the target steering torque.

According to the above configuration, in a region in which the absolute value of the steering angle corresponding to the maximum steering angle is equal to or greater than the end steering angle, the reaction force that the driver receives from the steering wheel increases, and the driver's manipulation of the steering wheel is restricted. . As a result, it is possible to limit the operation of the steering wheel according to the maximum steering angle.

As a preferred aspect of the vehicle steering system, the second torque signal increases along a curve in which the rate of change gradually decreases at least as the absolute value of the steering angle increases, and the absolute value of the steering angle A rate of change of the first torque signal in a region equal to or larger than the end steering angle is preferably larger than a maximum rate of change of the second torque signal.

As a preferred aspect of the vehicle steering system, the end target steering torque generation unit may set the first torque signal as Tref_e, the steering angle as θh, the end steering angle as θh_e, and the absolute value of the steering angle as the end steering torque. It is preferable to generate the first torque signal by using the following equation (1), where Ke is a coefficient that determines the slope of the first torque signal in the region above the corner.

Tref_e=Ke×max(0, (|θh|−θh_e))×sign(θh)
... (1)

As a preferred aspect of the vehicle steering system, the control unit includes an end steering angle setting unit that sets the end steering angle according to at least the vehicle speed, and a target steering angle of the tire based on the end steering angle. It is preferable to include a steering ratio gain calculation unit that calculates a steering ratio gain to be multiplied by the steering angle when generating the steering ratio gain.

According to the above configuration, by changing the end steering angle corresponding to the maximum turning angle according to the vehicle speed, it is possible to limit the operation of the steering wheel by the steering angle according to the vehicle speed.

As a desirable aspect of the vehicle steering system, the steering ratio gain calculation unit may be configured to set the steering ratio gain to G, the steering angle to θh, the end steering angle to θh_e, the maximum steering angle to θt_max, and the steering ratio gain to θt_max. Assuming that the reference value of the steering ratio gain is Kt, the steering ratio gain may be generated using the following equation (2).

G=(θt_max/Kt)/θh_e (2)

As a preferred aspect of the vehicle steering system, the end steering angle setting unit may set a region where the vehicle speed is equal to or higher than a first vehicle speed as a first region, and a speed equal to or higher than a third vehicle speed which is lower than the first vehicle speed. Further, when a region below the first vehicle speed is defined as a second region, and a region where the vehicle speed is 0 or more and less than the third vehicle speed is defined as a third region, the end steering angle in the third region is: It is preferable to set the value smaller than the end steering angle in the first region.

As a result, sudden changes in the steering angle of the tires due to changes in vehicle speed can be suppressed, and a stable steering feel can be obtained.

As a preferred aspect of the vehicle steering system, the end steering angle setting unit sets the end steering angle in the first region to a constant value, and sets the end steering angle in the third region to the end steering angle in the first region. The end steering angle in the second region is set to a constant value different from , and the end steering angle in the second region gradually decreases within the range from the end steering angle in the first region to the end steering angle in the third region. It is preferable to set

As a result, the steering ratio gain can be changed in conjunction with the end steering angle corresponding to the vehicle speed, which contributes to the improvement of running stability.

As a preferred aspect of the vehicle steering system, the end steering angle setting unit may include an end steering angle map in which a basic end steering angle corresponding to the vehicle speed of the vehicle is set, and based on the steering angle and the basic end steering angle. and an end steering angle calculator for calculating the end steering angle.

As a result, it is possible to reduce the sense of incompatibility given to the driver's steering feeling due to changes in vehicle speed and steering angle.

As a preferred aspect of the vehicle steering system, the end steering angle calculator outputs the basic end steering angle when the absolute value of the steering angle is less than a predetermined first threshold value, and calculates the absolute value of the steering angle. It is preferable to output the previous value of the end steering angle when the value is equal to or greater than the first threshold.

Accordingly, when the absolute value of the steering angle is equal to or greater than the first threshold, the change in the end steering angle is restricted. As a result, it is possible to suppress the change in the steering angle of the tires due to the change in vehicle speed in the large steering angle region where the rate of change is relatively large, and it is possible to reduce the sense of incompatibility given to the driver's steering feeling.

As a preferred aspect of the vehicle steering system, the end steering angle calculator outputs the basic end steering angle when the absolute value of the steering angle is less than the basic end steering angle, and calculates the absolute value of the steering angle. If the value is greater than or equal to the basic end steering angle and the absolute value of the steering angle is less than the previous value of the end steering angle, the absolute value of the steering angle is output, and the absolute value of the steering angle is It is preferable to output the previous value of the end steering angle when the value is equal to or greater than the basic end steering angle and the absolute value of the steering angle is equal to or greater than the previous value of the end steering angle.

As a result, when the absolute value of the steering angle is in a region equal to or larger than the basic end steering angle, the change in the end steering angle is restricted. As a result, it is possible to suppress the change in the end steering angle due to the change in vehicle speed, and to reduce the sense of incompatibility given to the driver's steering feeling.

As a preferred aspect of the vehicle steering system, the end steering angle setting section further includes a change amount limiting section that limits the amount of change in the end steering angle, and the end steering angle calculation section calculates the absolute value of the steering angle. is less than a predetermined first threshold value, the basic end steering angle is output; when the absolute value of the steering angle is equal to or greater than the first threshold value, the last value of the end steering angle is output; The change amount limiter outputs the end steering angle when an absolute value of a difference value between the end steering angle and a previous value of the end steering angle is less than a predetermined second threshold value, and outputs the end steering angle and When the absolute value of the difference value from the previous value of the end steering angle is equal to or greater than the second threshold, and the value obtained by subtracting the previous value of the end steering angle from the end steering angle is equal to or greater than the second threshold. and adding the second threshold value to the previous value of the end steering angle and outputting the result, wherein the absolute value of the difference between the end steering angle and the previous value of the end steering angle is equal to or greater than the second threshold value, and Preferably, when a value obtained by subtracting the previous value of the end steering angle from the end steering angle is less than the second threshold, the second threshold is subtracted from the previous value of the end steering angle and output.

Accordingly, when the absolute value of the steering angle is equal to or greater than the first threshold, the change in the end steering angle is restricted. As a result, it is possible to suppress the change in the steering angle of the tires due to the change in vehicle speed in the large steering angle region where the rate of change is relatively large, and it is possible to reduce the sense of incompatibility given to the driver's steering feeling. Further, when the amount of change in the end steering angle is equal to or greater than the second threshold value, the value obtained by adding or subtracting a predetermined value to or from the last value of the end steering angle is taken as the end steering angle. As a result, the amount of change over time in the steering ratio gain is limited. Therefore, it is possible to suppress a sudden change in the behavior of the vehicle that accompanies a sudden change in the turning angle, and reduce the sense of incompatibility given to the driver's steering feeling.

As a preferred aspect of the vehicle steering system, the end steering angle setting section further includes a change amount limiting section that limits the amount of change in the end steering angle, and the end steering angle calculation section calculates the absolute value of the steering angle. is less than the basic end steering angle, the absolute value of the steering angle is equal to or greater than the basic end steering angle, and the absolute value of the steering angle is the end steering angle the absolute value of the steering angle is equal to or greater than the basic end steering angle, and the absolute value of the steering angle is equal to or greater than the previous value of the end steering angle If the absolute value of the difference between the end steering angle and the previous value of the end steering angle is equal to or greater than the predetermined second threshold value, the change amount limiting unit outputs the previous value of the end steering angle. is less than the end steering angle, the absolute value of the difference between the end steering angle and the previous value of the end steering angle is equal to or greater than the second threshold, and When the value obtained by subtracting the previous value of the end steering angle is equal to or greater than the second threshold value, the second threshold value is added to the previous value of the end steering angle and output. When the absolute value of the difference value from the previous value is equal to or greater than the second threshold, and the value obtained by subtracting the previous value of the end steering angle from the end steering angle is less than the second threshold, the end steering Preferably, the second threshold value is subtracted from the previous value of the angle and output.

As a result, when the absolute value of the steering angle is in a region equal to or larger than the basic end steering angle, the change in the end steering angle is restricted. As a result, it is possible to suppress the change in the end steering angle due to the change in vehicle speed, and to reduce the sense of incompatibility given to the driver's steering feeling. If the amount of change in the end steering angle is greater than or equal to the second threshold, the value obtained by adding or subtracting the second threshold to or from the last value of the end steering angle is taken as the end steering angle. As a result, the amount of change over time in the steering ratio gain is limited. Therefore, it is possible to suppress a sudden change in the behavior of the vehicle that accompanies a sudden change in the turning angle, and reduce the sense of incompatibility given to the driver's steering feeling.

According to the present invention, it is possible to provide a vehicle steering system capable of restricting the operation of the steering wheel in accordance with the maximum mechanical steering angle determined structurally.

FIG. 1 is a diagram showing the overall configuration of a steer-by-wire type vehicle steering system according to a first embodiment. FIG. 2 is a schematic diagram showing the hardware configuration of a control unit that controls the SBW system. 3 is a diagram illustrating an example of an internal block configuration of a control unit according to the first embodiment; FIG. FIG. 4 is a block diagram showing a configuration example of the target steering torque generator. FIG. 5 is a diagram showing an example of characteristics of a basic map held by the basic map unit. FIG. 6 is a diagram showing a characteristic example of a damper gain map held by a damper gain map section. FIG. 7 is a diagram showing an example of characteristics of the hysteresis corrector. FIG. 8 is a block diagram showing a configuration example of a twist angle control section. FIG. 9 is a block diagram showing a configuration example of a target steering angle generation section. FIG. 10 is a block diagram showing a configuration example of a turning angle control section. FIG. 11 is a flowchart illustrating an operation example of the first embodiment; 12 is a block diagram showing a configuration example of a steering end control unit according to the first embodiment; FIG. 13 is a diagram showing an example of a torque signal Tref_e output from the end target steering torque generator according to the first embodiment; FIG. FIG. 14 is a diagram showing an example of the target steering torque Tref output from the target steering torque generator in the first embodiment. 15 is a diagram illustrating an example of an internal block configuration of a control unit according to the second embodiment; FIG. FIG. 16 is a block diagram showing one configuration example of a steering end control unit according to the second embodiment. FIG. 17 is a diagram showing an example of an end steering angle map according to the second embodiment. FIG. 18 is a diagram showing an example of the torque signal Tref_e output from the end target steering torque generator according to the second embodiment. FIG. 19 is a diagram showing an example of the target steering torque Tref output from the target steering torque generator in the second embodiment. 20 is a diagram showing an example of the steering ratio gain output from the steering ratio gain calculator in the example shown in FIG. 17. FIG. FIG. 21 is a block diagram showing one configuration example of a steering end control unit according to the third embodiment. FIG. 22 is a flow chart showing a first example of processing by an end steering angle calculator according to the third embodiment. FIG. 23 is a flow chart showing a second example of processing by the end steering angle calculator according to the third embodiment. FIG. 24 is a block diagram showing one configuration example of a steering end control unit according to the fourth embodiment. FIG. 25 is a flow chart showing a first example of processing by an end steering angle calculator and a variation limiter according to the fourth embodiment. FIG. 26 is a flow chart showing a second example of the processing of the end steering angle calculator and the variation limiter according to the fourth embodiment.

EMBODIMENT OF THE INVENTION Hereinafter, it demonstrates in detail, referring drawings for the form (henceforth embodiment) for implementing invention. In addition, the present invention is not limited by the following embodiments. In addition, components in the following embodiments include those that can be easily assumed by those skilled in the art, those that are substantially the same, and those that fall within a so-called equivalent range. Furthermore, the constituent elements disclosed in the following embodiments can be combined as appropriate.

(Embodiment 1)
FIG. 1 is a diagram showing the overall configuration of a steer-by-wire type vehicle steering system according to a first embodiment. The steer-by-wire (SBW) type vehicle steering system (hereinafter also referred to as "SBW system") shown in FIG. It is a system that transmits to the rudder mechanism. As shown in FIG. 1, the SBW system includes a reaction device 60 and a drive device 70, and a control unit (ECU) 50 controls both devices.

The reaction force device 60 includes a torque sensor 10 for detecting a steering torque Ts of the steering wheel 1, a steering angle sensor 14 for detecting a steering angle θh, a speed reduction mechanism 3, an angle sensor 74, a reaction force motor 61, and the like. Each of these components is provided on the column shaft 2 of the handle 1 .

The reaction force device 60 detects the steering angle θh with the steering angle sensor 14, and at the same time, transmits the motion state of the vehicle transmitted from the steered wheels 8L, 8R to the driver as reaction torque. The reaction torque is generated by the reaction force motor 61 . A torque sensor 10 detects a steering torque Ts. Also, the angle sensor 74 detects the motor angle θm of the reaction force motor 61 .

The driving device 70 includes a driving motor 71, a gear 72, an angle sensor 73, and the like. The driving force generated by the drive motor 71 is connected to the steering wheels 8L, 8R via the gear 72, the pinion rack mechanism 5, the tie rods 6a, 6b, and further via the hub units 7a, 7b.

The driving device 70 drives a driving motor 71 in accordance with the steering of the steering wheel 1 by the driver, applies the driving force to the pinion rack mechanism 5 via the gear 72, and passes through the tie rods 6a and 6b to drive the driving motor 71. The direction wheels 8L and 8R are steered. An angle sensor 73 is arranged near the pinion rack mechanism 5 to detect the turning angle θt of the steered wheels 8L, 8R. In order to cooperatively control the reaction force device 60 and the drive device 70, the ECU 50 controls the vehicle speed Vs and the like from the vehicle speed sensor 12 in addition to information such as the steering angle θh and the turning angle θt output from both devices. A voltage control command value Vref1 for driving and controlling the reaction force motor 61 and a voltage control command value Vref2 for driving and controlling the drive motor 71 are generated.

A control unit (ECU) 50 is supplied with electric power from a battery 13 and receives an ignition key signal via an ignition key 11 . The control unit 50 calculates a current command value based on the steering torque Ts detected by the torque sensor 10 and the vehicle speed Vs detected by the vehicle speed sensor 12, and supplies the current command value to the reaction force motor 61 and the drive motor 71. control the current.

The control unit 50 is connected to an in-vehicle network such as a CAN (Controller Area Network) 40 that exchanges various types of vehicle information. Also, the control unit 30 can be connected to a non-CAN 41 for transmitting/receiving communications other than the CAN 40, analog/digital signals, radio waves, and the like.

The control unit 50 is mainly composed of a CPU (including MCU, MPU, etc.). FIG. 2 is a schematic diagram showing the hardware configuration of a control unit that controls the SBW system.

A control computer 1100 constituting the control unit 50 includes a CPU (Central Processing Unit) 1001, a ROM (Read Only Memory) 1002, a RAM (Random Access Memory) 1003, an EEPROM (Electrically Erasable Programmable ROM) 1004, an interface (I/F ) 1005, an A/D (Analog/Digital) converter 1006, a PWM (Pulse Width Modulation) controller 1007, etc., which are connected to a bus.

The CPU 1001 is a processing device that executes a computer program for controlling the SBW system (hereinafter referred to as a control program) to control the SBW system.

ROM 1002 stores a control program for controlling the SBW system. Also, the RAM 1003 is used as a work memory for operating the control program. The EEPROM 1004 stores control data and the like input/output by the control program. The control data is used in the control computer program developed in the RAM 1003 after the control unit 30 is powered on, and overwritten in the EEPROM 1004 at a predetermined timing.

A ROM 1002, a RAM 1003, an EEPROM 1004, and the like are storage devices that store information, and are storage devices (primary storage devices) that the CPU 1001 can directly access.

The A/D converter 1006 receives signals such as the steering torque Ts and the steering angle θh and converts them into digital signals.

Interface 1005 is connected to CAN 40 . The interface 1005 is for receiving a vehicle speed V signal (vehicle speed pulse) from the vehicle speed sensor 12 .

The PWM controller 1007 outputs a PWM control signal for each UVW phase based on current command values for the reaction force motor 61 and the driving motor 71 .

A configuration of Embodiment 1 in which the present disclosure is applied to such an SBW system will be described.

3 is a diagram illustrating an example of an internal block configuration of a control unit according to the first embodiment; FIG. In the present embodiment, control of the torsion angle Δθ (hereinafter referred to as “torsion angle control”) and control of the turning angle θt (hereinafter referred to as “turning angle control”) are performed, and the reaction force device is controlled by the torsion angle control, and the driving device is controlled by steering angle control. Note that the driving device may be controlled by other control methods.

The control unit 50 includes a target steering torque generation section 200, a torsion angle control section 300, a conversion section 500, a steering end control section 900, a target turning angle generation section 910, and a turning angle control section 920 as internal block configurations. ing.

The target steering torque generation unit 200 generates a target steering torque Tref, which is a target value of the steering torque when performing assist control on the steering system of the vehicle in the present disclosure. Conversion unit 500 converts target steering torque Tref into target twist angle Δθref. The torsion angle control unit 300 generates a motor current command value Imc, which is a control target value for the current supplied to the reaction force motor 61 .

Here, first, the target steering torque generator 200 will be described with reference to FIG.

FIG. 4 is a block diagram showing a configuration example of the target steering torque generator. As shown in FIG. 4, the target steering torque generation unit 200 includes a basic map unit 210, a multiplication unit 211, a differentiation unit 220, a damper gain map unit 230, a hysteresis correction unit 240, a SAT information correction unit 250, a multiplication unit 260, and Adders 261 , 262 and 263 are provided. FIG. 5 is a diagram showing an example of characteristics of a basic map held by the basic map unit. FIG. 6 is a diagram showing a characteristic example of a damper gain map held by a damper gain map section.

The steering angle θh and the vehicle speed Vs are input to the basic map portion 210 . Basic map unit 210 uses the basic map shown in FIG. 5 to output torque signal Tref_a0 having vehicle speed Vs as a parameter. That is, basic map unit 210 outputs torque signal Tref_a0 corresponding to vehicle speed Vs.

As shown in FIG. 5, the torque signal Tref_a0 has a characteristic of increasing along a curve in which the rate of change gradually decreases as the magnitude (absolute value) |θh| of the steering angle θh increases. Moreover, the torque signal Tref_a0 has a characteristic that it increases as the vehicle speed Vs increases. In FIG. 5, the map is formed according to the magnitude |θh| of the steering angle θh, but the map may be formed according to the positive or negative steering angle θh. In this case, the value of the torque signal Tref_a0 can take positive and negative values, and the sign calculation described later is unnecessary. In the following description, a mode of outputting the torque signal Tref_a0, which is a positive value corresponding to the magnitude |θh| of the steering angle θh shown in FIG. 5, will be described.

A sign extractor 213 extracts the sign of the steering angle θh. Specifically, for example, the value of the steering angle θh is divided by the absolute value of the steering angle θh. Accordingly, the sign extractor 213 outputs "1" when the sign of the steering angle θh is "+" and outputs "-1" when the sign of the steering angle θh is "-".

The steering angle θh is input to the differentiating section 220 . A differentiating section 220 differentiates the steering angle θh to calculate a steering angular velocity ωh, which is angular velocity information. The differentiation section 220 outputs the calculated steering angular velocity ωh to the multiplication section 260 .

The vehicle speed Vs is input to the damper gain map section 230 . The damper gain map section 230 outputs a damper gain _DG according to the vehicle speed Vs using the vehicle speed sensitive damper gain map shown in FIG.

As shown in FIG. 6, the damper gain _DG has the characteristic of gradually increasing as the vehicle speed Vs increases. The damper gain _DG may be varied according to the steering angle θh.

Multiplying section 260 multiplies steering angular velocity ωh output from differentiating section 220 by damper gain _DG output from damper gain map section 230, and outputs the result to adding section 262 as torque signal Tref_b.

The hysteresis correction unit 240 calculates a torque signal Tref_c using the following equations (1) and (2) based on the steering angle θh and the steering state signal STs. Although the description of the steering state signal STs is omitted here, it is a state signal indicating the result of determining whether the steering direction is right-turning or left-turning based on the sign of the motor angular velocity ωm. In the following equations (1) and (2), x is the steering angle θh, y _R =Tref_c and y _L =Tref_c are the torque signal (fourth torque signal) Tref_c. Also, the coefficient a is a value greater than 1, and the coefficient c is a value greater than 0. The coefficient Ahys indicates the output width of the hysteresis characteristic, and the coefficient c indicates the roundness of the hysteresis characteristic.

y _R =Ahys{1−a ^−c(xb) } (1)

y _L =-Ahys {1- ^ac(x-b') } (2)

During right-turn steering, the torque signal (fourth torque signal) Tref_c(y _R ) is calculated using the above equation (1). During left-turn steering, the torque signal (fourth torque signal) Tref_c(y _L ) is calculated using the above equation (2). When switching from right-turn steering to left-turn steering, or when switching from left-turn steering to right-turn steering, the final coordinates (x ₁ , y ₁ ) of the previous values of the steering angle θh and the torque signal Tref_c are , the coefficient b or b' shown in the following equation (3) or (4) is substituted into the above equations (1) and (2) after steering switching. As a result, continuity before and after steering switching is maintained.

b=x ₁ +(1/c) log _a {1−(y ₁ /Ahys)} (3)

b′=x ₁ −(1/c) log _a {1−(y ₁ /Ahys)} (4)

The above formulas (3) and (4) can be derived by substituting x ₁ for x and y ₁ for y _R and y _L in the above formulas (1) and (2). .

For example, when Napier's number e is used as the coefficient a, the above equations (1), (2), (3), and (4) are respectively the following equations (5), (6), and (7 ) and (8).

y _R =Ahys[1-exp{-c(xb)}] (5)

y _L =-Ahys[{1-exp{c(xb')}] (6)

b=x ₁ +(1/c) log _e {1−(y ₁ /Ahys)} (7)

b′=x ₁ −(1/c)log _e {1−(y ₁ /Ahys)} (8)

FIG. 7 is a diagram showing an example of characteristics of the hysteresis corrector. In the example shown in FIG. 7, in the above equations (7) and (8), Ahys = 1 [Nm], c = 0.3, start from 0 [deg], +50 [deg], -50 FIG. 10 shows a characteristic example of a hysteresis-corrected torque signal Tref_c when steering is performed by [deg]. As shown in FIG. 7, the torque signal Tref_c output from the hysteresis correction unit 240 has hysteresis characteristics such as the origin of 0→L1 (thin line)→L2 (dashed line)→L3 (thick line).

Ahys, which is a coefficient representing the output width of the hysteresis characteristic, and c, which is a coefficient representing roundness, may be variable according to one or both of the vehicle speed Vs and the steering angle θh.

Further, the steering angular velocity ωh is obtained by a differential operation with respect to the steering angle θh, but is moderately subjected to low-pass filter (LPF) processing in order to reduce the influence of high-frequency noise. Alternatively, the differential operation and LPF processing may be performed using a high-pass filter (HPF) and gain. Furthermore, instead of the steering angle θh, the steering angular velocity ωh may be calculated by performing differentiation and LPF processing on the steering wheel angle θ1 detected by the upper angle sensor or the column angle θ2 detected by the lower angle sensor. . The motor angular velocity ωm may be used as the angular velocity information instead of the steering angular velocity ωh, in which case the differentiating section 220 becomes unnecessary.

The multiplication unit 211 multiplies the torque signal Tref_a0 output from the basic map unit 210 by “1” or “−1” output from the sign extraction unit 213, and outputs the result to the addition unit 261 as a torque signal Tref_a. .

The torque signal Tref_a in this embodiment corresponds to the "second torque signal" of the present disclosure.

The torque signals Tref_a, Tref_b, and Tref_c obtained as described above, and a torque signal Tref_e output from a steering end control unit 900, which will be described later, are added by addition units 261, 262, and 263 to obtain a target steering torque Tref. output.

In the torsion angle control, control is performed such that the torsion angle Δθ follows the target torsion angle Δθref calculated through the target steering torque generation section 200 and conversion section 500 using the steering angle θh and the like. The motor angle θm of the reaction force motor 61 is detected by the angle sensor 74 , and the motor angular velocity ωm is calculated by differentiating the motor angle θm by the angular velocity calculator 951 . Further, the current control unit 130 controls the reaction force motor 61 based on the motor current command value Imc output from the torsion angle control unit 300 and the current value Imr of the reaction force motor 61 detected by the motor current detector 140 . to control the current.

The torsion angle control section 300 will be described below with reference to FIG.

FIG. 8 is a block diagram showing a configuration example of a twist angle control section. Torsion angle control section 300 calculates motor current command value Imc based on target torsion angle Δθref, torsion angle Δθ, and motor angular velocity ωm. The torsion angle control unit 300 includes a torsion angle feedback (FB) compensation unit 310, a torsion angular velocity calculation unit 320, a speed control unit 330, a stabilization compensation unit 340, an output limiter 350, a subtraction unit 361 and an addition unit 362. .

The target twist angle Δθref output from the conversion unit 500 is added to the subtraction unit 361 . The twist angle Δθ is subtracted and input to the subtractor 361 and also input to the torsional angular velocity calculator 320 . The motor angular velocity ωm is input to stabilization compensator 340 .

The torsion angle FB compensator 310 multiplies the deviation Δθ0 between the target torsion angle Δθref and the torsion angle Δθ calculated by the subtraction unit 361 by a compensation value CFB (transfer function) so that the torsion angle Δθ follows the target torsion angle Δθref. A target torsional angular velocity ωref is output. The compensation value CFB may be a simple gain Kpp or a generally used compensation value such as a PI control compensation value.

The target torsional angular velocity ωref is input to velocity control section 330 . The torsion angle FB compensating section 310 and the speed control section 330 allow the torsion angle Δθ to follow the target torsion angle Δθref, thereby realizing a desired steering torque.

The torsion angular velocity calculation unit 320 performs differential operation processing on the torsion angle Δθ to calculate a torsion angular velocity ωt. The torsional angular velocity ωt is output to velocity control section 330 . The torsional angular velocity calculator 320 may perform pseudo-differentiation using the HPF and the gain as the differential calculation. Further, the torsion angular velocity calculator 320 may calculate the torsion angular velocity ωt using another means or other than the torsion angle Δθ, and output it to the velocity controller 330 .

Speed control unit 330 calculates a motor current command value Imca1 such that torsional angular velocity ωt follows target torsional angular velocity ωref by IP control (proportional leading PI control).

The subtractor 333 calculates the difference (ωref-ωt) between the target twist angular velocity ωref and the twist angular velocity ωt. The integrator 331 integrates the difference (ωref−ωt) between the target torsional angular velocity ωref and the torsional angular velocity ωt, and adds the integration result to the subtractor 334 .

The torsional angular velocity ωt is also output to the proportional section 332 . The proportional section 332 performs proportional processing with the gain Kvp on the torsional angular velocity ωt, and subtracts and inputs the proportional processing result to the subtraction section 334 . The subtraction result of the subtraction unit 334 is output as the motor current command value Imca1. Note that the speed control unit 330 performs PI control, P (proportional) control, PID (proportional-integral-derivative) control, PI-D control (differential-preceding PID control), model matching control, and model reference control, instead of IP control. The motor current command value Imca1 may be calculated by a commonly used control method such as control.

Stabilization compensator 340 has compensation value Cs (transfer function), and calculates motor current command value Imca2 from motor angular velocity ωm. If the gains of the torsion angle FB compensator 310 and the speed controller 330 are increased in order to improve the followability and disturbance characteristics, a controllable high-frequency oscillation phenomenon occurs. As a countermeasure, a transfer function (Cs) necessary for stabilizing the motor angular velocity ωm is set in the stabilization compensator 340 . This makes it possible to stabilize the entire EPS control system.

Addition unit 362 adds motor current command value Imca1 from speed control unit 330 and motor current command value Imca2 from stabilization compensation unit 340, and outputs the result as motor current command value Imcb.

The output limiter 350 is preset with an upper limit value and a lower limit value for the motor current command value Imcb. Output limiter 350 limits the upper and lower limits of motor current command value Imcb and outputs motor current command value Imc.

Note that the configuration of the torsion angle control unit 300 in the present embodiment is an example, and a configuration different from the configuration shown in FIG. 8 may be used. For example, the torsion angle control section 300 may be configured without the stabilization compensation section 340 .

In the steering angle control, a target steering angle θtref is generated by a target steering angle generator 910 based on a steering angle θh and a steering ratio gain G output from a steering end controller 900, which will be described later. The target turning angle θtref is input to the turning angle control section 920 together with the turning angle θt. is calculated. Then, based on the motor current command value Imct and the current value Imd of the drive motor 71 detected by the motor current detector 940, the current control unit 930 controls the drive motor 71 with the same configuration and operation as the current control unit 130. 71 is driven to perform current control.

The target steering angle generator 910 will be described below with reference to FIG.

FIG. 9 is a block diagram showing a configuration example of a target steering angle generation section. The target steering angle generator 910 includes a limiter 931 , a rate limiter 932 and a corrector 933 .

A limiting unit 931 outputs a steering angle θh1 obtained by limiting the upper and lower limits of the steering angle θh. Similar to the output limiter 350 in the torsion angle controller 300 shown in FIG. 8, the upper limit and lower limit of the steering angle θh are preset and limited.

A rate limiter 932 limits the amount of change in the steering angle θh1 by setting a limit value to avoid a sudden change in the steering angle, and outputs a steering angle θh2. For example, if the amount of change is the difference from the steering angle θh1 one sample before, and the absolute value of the amount of change is greater than a predetermined value (limit value), the steering angle The steering angle .theta.h2 is output by adding or subtracting .theta.h1. If the steering angle .theta.h2 is equal to or less than the limit value, the steering angle .theta.h1 is directly output as the steering angle .theta.h2. Instead of setting a limit value for the absolute value of the amount of change, an upper limit value and a lower limit value may be set for the amount of change to limit the amount of change. You may make it restrict|limit with respect to a rate.

A correction unit 933 corrects the steering angle θh2 and outputs a target steering angle θtref. In this embodiment, the steering angle θh2 is multiplied by a later-described coefficient Kt and a steering ratio gain G output from the steering end control section 900 to obtain the target steering angle θtref.

The steering angle control section 920 will be described below with reference to FIG.

FIG. 10 is a block diagram showing a configuration example of a turning angle control section. The steering angle control unit 920 calculates a motor current command value Imct based on the target steering angle θtref and the steering angle θt of the steered wheels 8L, 8R. The turning angle control section 920 includes a turning angle feedback (FB) compensating section 921 , a turning angular velocity calculating section 922 , a speed controlling section 923 , an output limiting section 926 and a subtracting section 927 .

The target steering angle θtref output from the target steering angle generation section 910 is added to and input to the subtraction section 927 . The steering angle θt is input to the subtractor 927 and input to the steering angular velocity calculator 922 .

A turning angle FB compensation unit 921 multiplies a deviation Δθt0 between the target turning angular velocity ωtref calculated by the subtracting unit 927 and the turning angle θt by a compensation value CFB (transfer function) to obtain the target turning angle θtref. A target steering angular velocity ωtref that the steering angle θt follows is output. The compensation value CFB may be a simple gain Kpp or a generally used compensation value such as a PI control compensation value.

The target steering angular velocity ωtref is input to the speed control section 923 . The steering angle FB compensator 921 and the speed controller 923 allow the steering angle θt to follow the target steering angle θtref, thereby realizing a desired torque.

The steering angular velocity calculation unit 922 performs differential operation processing on the steering angle θt to calculate a steering angular velocity ωtt. The steering angular velocity ωtt is output to the speed control section 923 . The speed control unit 923 may perform pseudo-differentiation using the HPF and the gain as the differential calculation. Further, the speed control section 923 may calculate the turning angular velocity ωtt using another means or other than the turning angle θt, and output it to the speed control section 923 .

The speed control unit 923 calculates a motor current command value Imcta such that the steering angular velocity ωtt follows the target steering angular velocity ωtref by IP control (proportional leading PI control). Note that the speed control unit 923 performs PI control, P (proportional) control, PID (proportional-integral-derivative) control, PI-D control (differential-preceding PID control), model matching control, and model reference control, instead of IP control. The motor current command value Imcta may be calculated by a commonly used control method such as control.

A subtraction unit 928 calculates the difference (ωtref−ωtt) between the target steering angular velocity ωtref and the steering angular velocity ωtt. The integrating section 924 integrates the difference (ωtref−ωtt) between the target turning angular velocity ωtref and the turning angular velocity ωtt, and adds the integration result to the subtracting section 929 .

The steering angular velocity ωtt is also output to the proportional section 925 . The proportional section 925 performs proportional processing on the turning angular velocity ωtt, and outputs the result of the proportional processing to the output limiting section 926 as the motor current command value Imcta.

The output limiter 926 is preset with an upper limit value and a lower limit value for the motor current command value Imcta. Output limiter 926 limits the upper and lower limits of motor current command value Imcta and outputs motor current command value Imct.

Note that the configuration of the turning angle control section 920 in the present embodiment is an example, and a configuration different from the configuration shown in FIG. 10 may be used.

In such a configuration, an operation example of the first embodiment will be described with reference to the flowchart of FIG. FIG. 11 is a flowchart illustrating an operation example of the first embodiment;

When the operation starts, the angle sensor 73 detects the steering angle θt, the angle sensor 74 detects the motor angle θm (step S110), the steering angle θt is sent to the steering angle control unit 920, and the motor angle θm is the angular velocity. They are input to the calculation unit 951 respectively.

The angular velocity calculator 951 differentiates the motor angle θm to calculate the motor angular velocity ωm, and outputs it to the twist angle controller 300 (step S120).

After that, the target steering torque generation unit 200 generates a target steering torque Tref (step S130), and the conversion unit 500 converts the target steering torque Tref generated by the target steering torque generation unit 200 into a target twist angle Δθref ( Step S140), the torsion angle control unit 300 calculates a motor current command value Imc based on the target torsion angle Δθref, the torsion angle Δθ, and the motor angular velocity ωm (step S150). Current control unit 130 then performs current control based on motor current command value Imc output from torsion angle control unit 300, and motor 20 is driven (step S160).

On the other hand, in steering angle control, the target steering angle generator 910 inputs the steering angle θh, and the steering angle θh is input to the limiter 931 . The limiting unit 931 limits the upper and lower limits of the steering angle θh with preset upper and lower limits (step S170), and outputs the steering angle θh1 to the rate limiting unit 932 . The rate limiter 932 limits the amount of change in the steering angle θh1 with a preset limit value (step S180), and outputs it to the correction unit 933 as the steering angle θh2. The correction unit 933 corrects the steering angle θh2 to obtain the target turning angle θtref (step S190), and outputs the target turning angle θtref to the turning angle control unit 920 .

The turning angle control unit 920, which receives the turning angle θt and the target turning angle θtref, calculates the deviation Δθt0 by subtracting the turning angle θt from the target turning angle θtref in the subtraction unit 927 (step S200). ). The deviation Δθt0 is input to the turning angle FB compensator 921, and the turning angle FB compensator 921 compensates for the deviation Δθt0 by multiplying the deviation Δθt0 by a compensation value (step S210), and converts the target turning angular velocity ωtref into the speed. Output to the control unit 923 . The steering angular velocity calculator 922 inputs the steering angle θt, calculates the steering angular velocity ωtt by differential calculation with respect to the steering angle θt (step S 220 ), and outputs it to the speed controller 923 . Speed control unit 923 calculates motor current command value Imcta by IP control in the same manner as speed control unit 330 (step S 230 ), and outputs it to output limiting unit 926 . The output limiter 926 limits the upper and lower limits of the motor current command value Imcta by preset upper and lower limits (step S240), and outputs the motor current command value Imct (step S250).

The motor current command value Imct is input to the current control unit 930 , and the current control unit 930 controls the drive motor 71 based on the motor current command value Imct and the current value Imd of the drive motor 71 detected by the motor current detector 940 . 71 is driven to perform current control (step S260).

Note that the order of data input and calculation in FIG. 11 can be changed as appropriate. In addition, follow-up control in steering angle control section 920 may be performed with a generally used control structure. The turning angle control unit 920 is used in a vehicle device if it has a control configuration in which the actual angle (here, the turning angle θt) follows the target angle (here, the target turning angle θtref). The control configuration is not limited, and for example, a control configuration used in industrial positioning devices, industrial robots, etc. may be applied.

Further, in this embodiment, as shown in FIG. 1, one ECU 50 controls the reaction device 60 and the drive device 70. You may set each. In this case, the ECUs transmit and receive data through communication.

12 is a block diagram showing a configuration example of a steering end control unit according to the first embodiment; FIG. As shown in FIG. 12 , the steering end control section 900 includes an end target steering torque generation section 901 and a steering ratio gain calculation section 905 .

The steering angle θh and the end steering angle θh_e are input to the steering end control unit 900 according to the first embodiment. In this embodiment, the steering angle corresponding to the maximum steering angle θt_max is set as the end steering angle θh_e. Here, the maximum steering angle θt_max is a value slightly smaller than the maximum steering angle of the mechanical tire angle that is determined structurally in the steering mechanism including the driving device 70, or a value that takes control errors into consideration. indicates The end steering angle θh_e may be stored, for example, in the EEPROM 1004 or the like of the control computer 1100 constituting the control unit 50, or may be held by the steering end control section 900. FIG.

Based on the steering angle θh and the end steering angle θh_e, the end target steering torque generation unit 901 generates and outputs a torque signal Tref_e for limiting the operation of the steering wheel 1 by the driver.

The torque signal Tref_e in this embodiment corresponds to the "first torque signal" of the present disclosure.

A turning ratio gain calculation unit 905 calculates and outputs a turning ratio gain G to be applied to the above-described target turning angle generation unit 910 based on the end steering angle θh_e.

A specific operation of the steering end control section 900 according to the first embodiment will be described with reference to FIGS. 12 to 14. FIG. 13 is a diagram showing an example of a torque signal Tref_e output from the end target steering torque generator according to the first embodiment; FIG. FIG. 14 is a diagram showing an example of the target steering torque Tref output from the target steering torque generator in the first embodiment. In FIG. 13, the horizontal axis indicates the absolute value |θh| of the steering angle θh, and the vertical axis indicates the absolute value |Tref_e| of the torque signal Tref_e. In FIG. 14, the horizontal axis indicates the absolute value |θh| of the steering angle θh, and the vertical axis indicates the absolute value |Tref| of the target steering torque Tref.

As shown in FIG. 13, the torque signal Tref_e (first torque signal) has a characteristic of increasing from zero at a predetermined rate of change in a region where the absolute value |θh| of the steering angle θh is equal to or greater than the end steering angle θh_e. are doing. Further, the rate of change of the torque signal Tref_e (first torque signal) in the region where the absolute value |θh| big.

In this embodiment, the end target steering torque generator 901 calculates the torque signal Tref_e using the following equation (9).

Tref_e=Ke×max(0, (|θh|−θh_e))×sign(θh)
... (9)

In the equation (9), the coefficient Ke is a coefficient value that determines the slope of the torque signal Tref_e in the region (see FIG. 13) where the absolute value |θh| of the steering angle θh is equal to or greater than the end steering angle θh_e. As shown in FIG. 13, the absolute value |Tref_e| of the torque signal Tref_e is 0 in a region where the absolute value |θh| of the steering angle θh is less than the end steering angle θh_e. Further, as shown in FIG. 13, in a region where the absolute value |θh| of the steering angle θh is equal to or greater than the end steering angle θh_e, the absolute value |Tref_e| As the value of the coefficient Ke increases, the torque signal Tref_e sharply rises in a region where the absolute value |θh| of the steering angle θh is greater than or equal to the end steering angle θh_e.

The target steering torque generation unit 200 adds the torque signal Tref_b, the torque signal Tref_c, and the torque signal Tref_e to the torque signal Tref_a (second torque signal) to generate the target steering torque Tref (Fig. 4). As a result, as shown in FIG. 14, it is possible to generate the target steering torque Tref that sharply rises in a region where the absolute value |θh| of the steering angle θh is greater than or equal to the end steering angle θh_e. The vehicle steering system (SBW system) according to the present embodiment applies this target steering torque Tref to control the reaction force motor 61 so that the absolute value |θh| of the steering angle θh becomes the end steering angle θh_e In the region above, the reaction force that the driver receives from the steering wheel 1 increases, and the operation of the steering wheel 1 by the driver is restricted.

Further, in the present embodiment, the steering ratio gain calculation section 905 calculates the steering ratio gain G using the following equation (10).

G=(θt_max/Kt)/θh_e (10)

In the above equation (10), the coefficient Kt is a reference value of the steering ratio gain G (tire angle/steering angle basic conversion gain, hereinafter simply referred to as "basic conversion gain"). The basic conversion gain Kt represents the basic ratio of the amount of change in the steering angle θt of the tire to the steering angle θh, which is the amount of operation of the steering wheel. For example, when the steering angle is 360 [deg] and the tire turning angle θt is 30 [deg], Kt=30/360=1/12. That is, for example, when the vehicle speed Vs of the vehicle is 30 [km/h] or more and the steering ratio gain G is constant at 1, the amount of change in the steering angle θt with respect to the operation amount of the steering angle θh is the basic conversion gain Varies with Kt. Further, for example, when the steering ratio gain G>1 in a region where the vehicle speed Vs of the vehicle is less than 30 [km/h], the amount of change in the steering angle θt with respect to the operation amount of the steering angle θh is greater than the basic conversion gain Kt. will also change at a high rate.

As described above, the vehicle steering system (SBW system) according to the first embodiment includes the target steering torque generator 200 that generates the target steering torque Tref, which is the target value of the torque, the steering angle θh of the steering wheel 1, and , based on the end steering angle θh_e corresponding to the maximum turning angle θt_max, the absolute value |θh| of the steering angle θh becomes zero in a region where the absolute value |θh| and an end target steering torque generator 901 that generates a torque signal Tref_e (first torque signal) that linearly increases from zero with a predetermined inclination in a region equal to or larger than the angle θh_e. Target steering torque generator 200 generates torque signal Tref_e for torque signal Tref_a (second torque signal) that increases along a curve whose rate of change gradually decreases as at least the absolute value |θh| of steering angle θh increases. (first torque signal) is added to generate the target steering torque Tref.

As a result, in a region where the absolute value |θh| of the steering angle θh is equal to or greater than the end steering angle θh_e, the reaction force that the driver receives from the steering wheel 1 increases, and the driver's operation of the steering wheel 1 is restricted.

Thus, according to the present embodiment, it is possible to limit the operation of the steering wheel 1 according to the maximum turning angle θt_max.

(Embodiment 2)
15 is a diagram illustrating an example of an internal block configuration of a control unit according to the second embodiment; FIG. FIG. 16 is a block diagram showing one configuration example of a steering end control unit according to the second embodiment. In addition, the same code|symbol is attached|subjected to the same structure part as the structure demonstrated in Embodiment 1 mentioned above, and the overlapping description is abbreviate|omitted.

As shown in FIG. 15, in addition to the steering angle θh, the vehicle speed Vs is input to the steering end control unit 900a according to the second embodiment. Further, as shown in FIG. 16, the steering end control section 900a includes an end steering angle setting section 904 in addition to the configuration of the first embodiment.

The end steering angle setting section 904 has an end steering angle map 906 . In the end steering angle map 906, an end steering angle θh_e corresponding to the vehicle speed Vs is set. The end steering angle map 906 may be stored in, for example, the EEPROM 1004 of the control computer 1100 constituting the control unit 50, or may be held by the steering end control section 900a.

The vehicle speed Vs of the vehicle is input to the end steering angle setting section 904 of the steering end control section 900a according to the second embodiment. An end steering angle setting unit 904 outputs an end steering angle θh_e corresponding to the vehicle speed Vs based on an end steering angle map 906 . An example in which the basic conversion gain Kt is set such that θt_max/Kt is 360 [deg] will be described below.

FIG. 17 is a diagram showing an example of an end steering angle map according to the second embodiment. In FIG. 17, the horizontal axis indicates the vehicle speed Vs, and the vertical axis indicates the end steering angle θh_e. FIG. 18 is a diagram showing an example of the torque signal Tref_e output from the end target steering torque generator according to the second embodiment. FIG. 19 is a diagram showing an example of the target steering torque Tref output from the target steering torque generator in the second embodiment. In FIG. 18, the horizontal axis indicates the absolute value |θh| of the steering angle θh, and the vertical axis indicates the absolute value |Tref_e| of the torque signal Tref_e. In FIG. 19, the horizontal axis indicates the absolute value |θh| of the steering angle θh, and the vertical axis indicates the absolute value |Tref| of the target steering torque Tref.

In the example shown in FIG. 17, the region where the magnitude of the vehicle speed Vs is equal to or greater than the first vehicle speed V1 is defined as the first region, and the end steering angle θh_e in this first region is a constant value of 360 [deg]. A second region is defined as a region in which the vehicle speed Vs is equal to or higher than a third vehicle speed V3, which is smaller than the first vehicle speed V1, and less than the first vehicle speed V1. ] and less than 360 [deg], and as the vehicle speed Vs decreases, the end steering angle θh_e gradually decreases within the range from 360 [deg] to 180 [deg]. there is A region where the magnitude of the vehicle speed Vs is 0 [km/h] or more and less than the third vehicle speed V3 is defined as a third region, and the end steering angle θh_e in this third region is set to a constant value of 180 [deg]. there is

In the example shown in FIG. 17, the end steering angle θh_e is 240 [deg] at a second vehicle speed V2, which is higher than the third vehicle speed V3 and lower than the first vehicle speed V1.

In the example shown in FIG. 17, the third vehicle speed V3 may be 10 [km/h], the second vehicle speed V2 may be 20 [km/h], and the first vehicle speed V1 may be 30 [km/h].

A specific operation of the steering end control section 900a according to the second embodiment will be described with reference to FIGS. 16 to 20. FIG. 20 is a diagram showing an example of the steering ratio gain output from the steering ratio gain calculator in the example shown in FIG. 17. FIG. In FIG. 20, the horizontal axis indicates the vehicle speed Vs, and the vertical axis indicates the steering ratio gain G. In FIG.

In this embodiment, the specific operations of the end target steering torque generator 901 and the steering ratio gain calculator 905 are the same as in the first embodiment. The difference is that the value is changed according to the vehicle speed Vs. Further, by setting the change curve of the end steering angle θh_e to the mode shown in FIG. 17, the steering ratio gain G in the first region becomes a constant value of "1.0" as shown in FIG. The steering ratio gain G in the area becomes a constant value of "2.0", and the steering ratio gain G in the second area becomes "2.0" as the magnitude of the vehicle speed Vs increases from the third vehicle speed V3. to "1.0". The examples shown in FIGS. 17 to 20 are only examples, and specific numerical values of the third vehicle speed V3, the second vehicle speed V2, and the first vehicle speed V1, specific numerical values of the end steering angle θh_e, and the steering ratio gain A specific numerical value of G is not limited to this.

As described above, in the high speed region where the magnitude of the vehicle speed Vs is equal to or higher than the first vehicle speed V1, that is, in the first region, the steering ratio gain G is set to " 1.0” can be a constant value. As a result, the behavior of the vehicle in the high speed range can be stabilized.

In addition, in the low speed region where the magnitude of the vehicle speed Vs is 0 or more and less than the third vehicle speed V3, that is, in the third region, the steering ratio gain G can be a constant value of "2.0". As a result, the behavior of the vehicle in the low speed range can be stabilized, and the vehicle can stably travel on crossroads, cranks, and the like.

In the middle speed range where the magnitude of the vehicle speed Vs is equal to or higher than the third vehicle speed V3 and less than the first vehicle speed V1, i.e., in the second region, as the magnitude of the vehicle speed Vs decreases, the end steering angle θh_e increases to 360 degrees. ] to 180 [deg], as the magnitude of the vehicle speed Vs increases from the third vehicle speed V3, the steering ratio gain G increases from "2.0" It can be gradually decreased within the range up to "1.0". As a result, it is possible to suppress sudden changes in the steering angle of the tires that accompany changes in the vehicle speed Vs, and to obtain a stable steering feel.

As described above, in the present embodiment, the end steering angle setting unit 904 that sets the end steering angle θh_e according to at least the vehicle speed Vs of the vehicle, and the end steering angle setting unit 904 that generates the target tire steering angle based on the end steering angle θh_e. and a steering ratio gain calculation unit 905 for calculating a steering ratio gain G to be multiplied by the steering angle θh.

Specifically, the end steering angle setting unit 904 sets a region where the vehicle speed Vs is a first vehicle speed V1 or higher as a first region, a third vehicle speed V3 or higher where the vehicle speed Vs is lower than the first vehicle speed V1, and a third vehicle speed V3 or higher. When the region where the vehicle speed Vs is less than one vehicle speed V1 is defined as the second region, and the region where the vehicle speed Vs is 0 or more and less than the third vehicle speed V3 is defined as the third region, the end steering angle θh_e in the third region is defined as the first region. is set to a value smaller than the end steering angle θh_e at . Furthermore, the end steering angle θh_e in the first region is set to a constant value (eg, 360 [deg]), and the end steering angle in the third region is set to a constant value (eg, 360 degrees) different from the end steering angle θh_e in the first region 180 [deg]), and the end steering angle θh_e in the second region is changed from the end steering angle θh_e in the first region (eg, 360 [deg]) to the end steering angle θh_e in the third region (eg, 180 [deg]). ) is set so that the value becomes gradually smaller within the range up to

As a result, the turning ratio gain G can be changed in conjunction with the end steering angle θh_e corresponding to the vehicle speed Vs.

Specifically, in a high-speed region where the magnitude of the vehicle speed Vs is equal to or higher than the first vehicle speed V1, that is, in the first region, the steering ratio gain G is set to " 1.0” can be a constant value.

In addition, in the low speed region where the magnitude of the vehicle speed Vs is 0 or more and less than the third vehicle speed V3, that is, in the third region, the steering ratio gain G can be a constant value of "2.0".

In the middle speed range where the magnitude of the vehicle speed Vs is equal to or higher than the third vehicle speed V3 and less than the first vehicle speed V1, i.e., in the second region, as the magnitude of the vehicle speed Vs decreases, the end steering angle θh_e increases to 360 degrees. ] to 180 [deg], as the magnitude of the vehicle speed Vs increases from the third vehicle speed V3, the steering ratio gain G increases from "2.0" It can be gradually decreased within the range up to "1.0".

As described above, according to the present embodiment, by changing the end steering angle θh_e corresponding to the maximum steering angle θt_max according to the vehicle speed Vs, the operation of the steering wheel 1 is limited to the steering angle according to the vehicle speed Vs. , and the steering ratio gain G can be changed in conjunction with the end steering angle θh_e corresponding to the vehicle speed Vs, thereby contributing to improvement in running stability.

(Embodiment 3)
FIG. 21 is a block diagram showing one configuration example of a steering end control unit according to the third embodiment. In addition, the same code|symbol is attached|subjected to the same structure part as the structure demonstrated by Embodiment 1, 2 mentioned above, and the overlapping description is abbreviate|omitted.

The configuration of the steering end control section 900b according to the third embodiment differs from that of the second embodiment in that the end steering angle setting section 904a includes an end steering angle calculation section 907. FIG. The end steering angle map 906a is substantially similar to the end steering angle map 906 of the second embodiment. In the end steering angle map 906a, a basic end steering angle θh_e0 corresponding to the vehicle speed Vs is set. The end steering angle map 906a may be stored, for example, in the EEPROM 1004 of the control computer 1100 constituting the control unit 50, or may be held by the steering end control section 900b.

End steering angle calculator 907 calculates end steering angle θh_e based on steering angle θh and basic end steering angle θh_e0 and outputs the result to end target steering torque generator 901 and steering ratio gain calculator 905 .

The processing of the end steering angle calculator 907 will be described below. FIG. 22 is a flow chart showing a first example of processing by an end steering angle calculator according to the third embodiment. In the first example of the processing of the end steering angle calculator 907 according to the third embodiment, θh_e′ indicates the previous value of the end steering angle θh_e output from the end steering angle calculator 907 .

When the steering angle θh and the basic end steering angle θh_e0 are input (step S101), the end steering angle calculator 907 determines whether or not the previous value θh_e′ of the end steering angle θh_e is held (step S102). . Note that the previous value θh_e′ of the end steering angle θh_e may be held by the end steering angle calculator 907, or may be held in the RAM 1003 or EEPROM 1004 of the control computer 1100 constituting the control unit 50, for example. Alternatively, the data may be read out in step S102.

If the previous value θh_e′ of the end steering angle θh_e is not held (step S102; No), the end steering angle calculator 907 outputs the basic end steering angle θh_e0 as the end steering angle θh_e (step S103), The steering angle θh_e is stored as the previous value θh_e′ of the end steering angle θh_e (step S104). Thereafter, the process returns to step S101, and the same process is repeated.

If the previous value θh_e′ of the end steering angle θh_e is held (step S102; Yes), the end steering angle calculator 907 determines that the absolute value |θh| |<θhth1) is determined (step S105). Here, the first threshold value θhth1 used for determination in step S105 can be set to 180 [deg], for example. Note that the first threshold value θhth1 used for determination in step S105 is an example, and is not limited to this.

If the absolute value |θh| of the steering angle θh is less than the first threshold value θhth1 (|θh|<θhth1) (step S105; Yes), the end steering angle calculator 907 converts the basic end steering angle θh_e0 to the end steering angle θh_e (step S103), and the end steering angle θh_e is stored as the previous value θh_e′ of the end steering angle θh_e (step S104). Thereafter, the process returns to step S101, and the same process is repeated.

If the absolute value |θh| of the steering angle θh is greater than or equal to the first threshold value θhth1 (|θh|≧θhth1) (step S105; No), the end steering angle calculator 907 calculates the previous value θh_e′ of the end steering angle θh_e. The end steering angle θh_e is output (step S106), and the end steering angle θh_e is stored as the previous value θh_e′ of the end steering angle θh_e (step S104). Thereafter, the process returns to step S101, and the same process is repeated.

According to the processing of the first example of the processing of the end steering angle calculator 907 according to the third embodiment described above, when the absolute value |θh| In some cases, the change in end steering angle θh_e is limited. As a result, it is possible to suppress the change in the steering angle of the tires due to the change in vehicle speed in the large steering angle region where the rate of change is relatively large, and it is possible to reduce the sense of incompatibility given to the driver's steering feeling.

FIG. 23 is a flow chart showing a second example of processing by the end steering angle calculator according to the third embodiment. Also in the second example of the processing of the end steering angle calculation unit 907 according to the third embodiment, θh_e′ is calculated by the end steering angle calculation unit The previous value of the end steering angle θh_e output from 907 is shown.

In the second example of the processing of the end steering angle calculation section 907 according to Embodiment 3 shown in FIG. It is the same as the processing from step S101 to step S104 of the example.

If the previous value θh_e′ of the end steering angle θh_e is held (step S202; Yes), the end steering angle calculator 907 determines that the absolute value |θh| <θh_e0) is determined (step S205).

If the absolute value |θh| of the steering angle θh is less than the basic end steering angle θh_e0 (|θh|<θh_e0) (step S205; Yes), the end steering angle calculator 907 calculates the basic end steering angle θh_e0 as the end steering angle. θh_e is output (step S203), and the end steering angle θh_e is stored as the previous value θh_e′ of the end steering angle θh_e (step S204). Thereafter, the process returns to step S201, and the same process is repeated.

If the absolute value |θh| is less than the previous value θh_e' of the end steering angle θh_e (|θh|<θh_e') (step S206).

If the absolute value |θh| of the steering angle θh is less than the previous value θh_e′ of the end steering angle θh_e (|θh|<θh_e′) (step S206; Yes), the end steering angle calculator 907 calculates the steering angle θh. The absolute value |θh| is output as the end steering angle θh_e (step S207), and the end steering angle θh_e is stored as the previous value θh_e' of the end steering angle θh_e (step S204). Thereafter, the process returns to step S201, and the same process is repeated.

If the absolute value |θh| of the steering angle θh is greater than or equal to the previous value θh_e′ of the end steering angle θh_e (|θh|≧θh_e′) (step S206; No), the end steering angle calculator 907 calculates the end steering angle θh_e is output as the end steering angle .theta.h_e (step S208), and the end steering angle .theta.h_e is stored as the previous value .theta.h_e' of the end steering angle .theta.h_e (step S204). Thereafter, the process returns to step S201, and the same process is repeated.

In the second embodiment described above, for example, when the end steering angle map as shown in FIG. When the vehicle speed Vs is reduced from 30 [km/h] to 10 [km/h] while steering, the steering wheel 1 is pushed back until the steering angle θh reaches 180 [deg], and the steering feeling of the driver becomes uncomfortable. may give. According to the processing of the second example of the processing of the end steering angle calculation unit 907 according to the third embodiment described above, when the absolute value |θh| A change in the steering angle θh_e is restricted. As a result, it is possible to suppress the change in the end steering angle that accompanies the change in the vehicle speed Vs, and to reduce the sense of incompatibility given to the driver's steering feeling.

As described above, the vehicle steering system (SBW system) according to the third embodiment includes the end steering angle map 906 in which the basic end steering angle θh_e0 corresponding to the vehicle speed Vs is set, the steering angle θh and the basic end and an end steering angle calculator 907 that calculates an end steering angle θh_e based on the steering angle θh_e0.

As a result, it is possible to reduce the sense of incompatibility given to the driver's steering feeling due to fluctuations in the vehicle speed Vs and the steering angle θh.

(Embodiment 4)
FIG. 24 is a block diagram showing one configuration example of a steering end control unit according to the fourth embodiment. The same reference numerals are assigned to the same components as those described in the first to third embodiments, and overlapping descriptions will be omitted.

The configuration of the steering end control section 900c according to the fourth embodiment differs from that of the third embodiment in that the end steering angle setting section 904b includes a change amount limiting section 908. FIG.

The end steering angle map 906a is substantially similar to the end steering angle map 906 of the second embodiment. In the end steering angle map 906a, a basic end steering angle θh_e0 corresponding to the vehicle speed Vs is set. The end steering angle map 906a may be stored, for example, in the EEPROM 1004 of the control computer 1100 constituting the control unit 50, or may be held by the steering end control section 900b.

The end steering angle calculator 907a is substantially the same as the end steering angle calculator 907 of the third embodiment. The end steering angle calculator 907a calculates an end steering angle θh_e1 based on the steering angle θh and the basic end steering angle θh_e0, and outputs the calculated end steering angle θh_e1 to the variation limiter 908.

Change amount limiting section 908 limits the amount of change in end steering angle θh_e 1 and outputs end steering angle θh_e to end target steering torque generation section 901 and steering ratio gain calculation section 905 .

The processing of the end steering angle calculator 907a and the variation limiter 908 will be described below. FIG. 25 is a flow chart showing a first example of processing by an end steering angle calculator and a variation limiter according to the fourth embodiment. In the first example of the processing of the end steering angle calculator 907a according to the fourth embodiment, θh_e1' indicates the previous value of the end steering angle θh_e1 output from the end steering angle calculator 907a. θh_e′ indicates the previous value of the end steering angle θh_e output from the change amount limiting section 908 .

When the steering angle θh and the basic end steering angle θh_e0 are input (step S301), the end steering angle calculator 907a determines whether or not the previous value θh_e1′ of the end steering angle θh_e1 is held (step S302). . The previous value θh_e1′ of the end steering angle θh_e1 may be held by the end steering angle calculation section 907a. Alternatively, the data may be read out in step S302.

If the previous value θh_e1′ of the end steering angle θh_e1 is not held (step S302; No), the end steering angle calculator 907a outputs the basic end steering angle θh_e0 as the end steering angle θh_e1 (step S304), The steering angle θh_e1 is stored as the previous value θh_e1′ of the end steering angle θh_e1 (step S305).

If the previous value θh_e1′ of the end steering angle θh_e1 is held (step S302; Yes), the end steering angle calculator 907a determines that the absolute value |θh| |<θhth1) is determined (step S303). Here, the first threshold value θhth1 used for determination in step S303 can be set to 180 [deg], for example. Note that the first threshold value θhth1 used for determination in step S303 is an example, and is not limited to this.

If the absolute value |θh| of the steering angle θh is less than the first threshold value θhth1 (|θh|<θhth1) (step S303; Yes), the end steering angle calculator 907a converts the basic end steering angle θh_e0 to the end steering angle θh_e1. (step S304), and the end steering angle θh_e1 is stored as the previous value θh_e1′ of the end steering angle θh_e1 (step S305).

When the absolute value |θh| of the steering angle θh is greater than or equal to the first threshold value θhth1 (|θh|≧θhth1) (step S303; No), the end steering angle calculation unit 907a calculates the previous value θh_e1′ of the end steering angle θh_e1. The end steering angle θh_e1 is output (step S306), and the end steering angle θh_e1 is stored as the previous value θh_e1′ of the end steering angle θh_e1 (step S305).

When the end steering angle θh_e1 is inputted to the change amount limiting section 908, the change amount limiting section 908 sets the absolute value of the difference between the inputted end steering angle θh_e1 and the previous value θh_e′ of the end steering angle θh_e to a predetermined value. It is determined whether or not it is less than the second threshold value θhth2 (|θh_e1−θh_e′|<θhth2) (step S307). Here, the second threshold value θhth2 used for determination in step S307 can be set to a value corresponding to 10 [deg/s], for example. Note that the second threshold θhth2 used for determination in step S307 is an example, and is not limited to this.

If the absolute value of the difference between the end steering angle θh_e1 and the previous value θh_e′ of the end steering angle θh_e is less than the second threshold value θhth2 (|θh_e1−θh_e′|<θhth2) (step S308; Yes), the amount of change is limited. The unit 908 outputs the basic end steering angle θh_e1 as the end steering angle θh_e (step S308), and stores the end steering angle θh_e as the previous value θh_e' of the end steering angle θh_e (step S309). Thereafter, the process returns to step S301, and the same process is repeated.

If the absolute value of the difference between the end steering angle θh_e1 and the previous value θh_e′ of the end steering angle θh_e is greater than or equal to the second threshold value θhth2 (|θh_e1−θh_e′|≧θhth2) (step S307; No), then, The change amount limiting unit 908 determines whether or not the value obtained by subtracting the previous value θh_e′ of the end steering angle θh_e from the end steering angle θh_e1 is equal to or greater than the second threshold value θhth2 (θh_e1−θh_e′≧θhth2) (step S310). ).

The absolute value of the difference between the end steering angle θh_e1 and the previous value θh_e′ of the end steering angle θh_e is greater than or equal to the second threshold θhth2 (|θh_e1−θh_e′|≧θhth2) (step S307; No), and the end steering If the value obtained by subtracting the previous value θh_e′ of the end steering angle θh_e from the angle θh_e1 is greater than or equal to the second threshold value θhth2 (θh_e1−θh_e′≧θhth2) (step S310; Yes), the change amount limiter 908 reduces the end steering angle The second threshold value θhth2 is added to the previous value θh_e′ of θh_e and output as the end steering angle θh_e (step S311), and the end steering angle θh_e is stored as the previous value θh_e′ of the end steering angle θh_e (step S309). Thereafter, the process returns to step S301, and the same process is repeated.

The absolute value of the difference between the end steering angle θh_e1 and the previous value θh_e′ of the end steering angle θh_e is greater than or equal to the second threshold θhth2 (|θh_e1−θh_e′|≧θhth2) (step S307; No), and the end steering If the value obtained by subtracting the previous value θh_e′ of the end steering angle θh_e from the angle θh_e1 is less than the second threshold value θhth2 (θh_e1−θh_e′<θhth2) (step S310; No), that is, θh_e1−θh_e′≦(−θhth2 ) is satisfied, the change amount limiting unit 908 subtracts the second threshold value θhth2 from the previous value θh_e′ of the end steering angle θh_e and outputs it as the end steering angle θh_e (step S312). The previous value θh_e' of the angle θh_e is stored (step S309). Thereafter, the process returns to step S301, and the same process is repeated.

According to the processing of the first example of the processing of the end steering angle calculation section according to the fourth embodiment described above, the absolute value |θh| , the change in the end steering angle θh_e1 is limited. As a result, it is possible to suppress the change in the steering angle of the tires due to the change in vehicle speed in the large steering angle region where the rate of change is relatively large, and it is possible to reduce the sense of incompatibility given to the driver's steering feeling.

If the amount of change in the end steering angle θh_e1 is greater than or equal to a predetermined value, the end steering angle θh_e is obtained by adding or subtracting a predetermined value from the previous value θh_e′ of the end steering angle θh_e. As a result, the amount of change over time of the steering ratio gain G is limited. Therefore, it is possible to suppress a sudden change in the behavior of the vehicle that accompanies a sudden change in the turning angle, and reduce the sense of incompatibility given to the driver's steering feeling.

FIG. 26 is a flow chart showing a second example of the processing of the end steering angle calculator and the variation limiter according to the fourth embodiment.

When the steering angle θh and the basic end steering angle θh_e0 are input (step S401), the end steering angle calculator 907a determines whether or not the previous value θh_e1′ of the end steering angle θh_e1 is held (step S402). .

If the previous value θh_e1′ of the end steering angle θh_e1 is held (step S402; Yes), the end steering angle calculator 907a determines that the absolute value |θh| <θh_e0) is determined (step S403).

If the absolute value |θh| of the steering angle θh is less than the basic end steering angle θh_e0 (|θh|<θh_e0) (step S403; Yes), the end steering angle calculator 907a converts the basic end steering angle θh_e0 to the end steering angle. θh_e1 is output (step S404), and the end steering angle θh_e1 is stored as the previous value θh_e1′ of the end steering angle θh_e1 (step S405).

If the absolute value |θh| of the steering angle θh is greater than or equal to the basic end steering angle θh_e0 (|θh|≧θh_e0) (step S403; No), the end steering angle calculator 907a calculates the absolute value |θh| is less than the previous value θh_e' of the end steering angle θh_e (|θh|<θh_e') (step S406).

If the absolute value |θh| of the steering angle θh is less than the previous value θh_e′ of the end steering angle θh_e (|θh|<θh_e′) (step S406; Yes), the end steering angle calculator 907a calculates the steering angle θh. The absolute value |θh| is output as the end steering angle θh_e1 (step S404), and the end steering angle θh_e1 is stored as the previous value θh_e1′ of the end steering angle θh_e1 (step S405).

When the absolute value |θh| of the steering angle θh is greater than or equal to the previous value θh_e′ of the end steering angle θh_e (|θh|≧θh_e′) (step S406; No), the end steering angle calculator 907a calculates the end steering angle θh_e1 is output as the end steering angle θh_e1 (step S408), and the end steering angle θh_e1 is stored as the previous value θh_e1′ of the end steering angle θh_e1 (step S405).

In the second example of the processing of the end steering angle calculator 907a and the change amount limiter 908 according to the fourth embodiment shown in FIG. The processing from step S307 to step S312 of the first example of the processing of the unit 907a and the change amount limiting unit 908 is the same.

According to the processing of the second example of the processing of the end steering angle calculation unit 907a and the change amount limiting unit 908 according to the fourth embodiment described above, the absolute value |θh| In some cases, the change in end steering angle θh_e1 is limited. As a result, it is possible to suppress the change in the end steering angle that accompanies the change in the vehicle speed Vs, and to reduce the sense of incompatibility given to the driver's steering feeling.

If the amount of change in the end steering angle θh_e1 is greater than or equal to a predetermined value, the end steering angle θh_e is obtained by adding or subtracting a predetermined value from the previous value θh_e′ of the end steering angle θh_e. As a result, the amount of change over time of the steering ratio gain G is limited. Therefore, it is possible to suppress a sudden change in the behavior of the vehicle that accompanies a sudden change in the turning angle, and reduce the sense of incompatibility given to the driver's steering feeling.

As described above, the vehicle steering system (SBW system) according to the fourth embodiment includes the end steering angle map 906 in which the basic end steering angle θh_e0 corresponding to the vehicle speed Vs is set, the steering angle θh and the basic end An end steering angle calculator 907a calculates an end steering angle θh_e1 based on the steering angle θh_e0, and an end target steering torque generator 901 and a steering ratio gain calculator 905 limit the end steering angle θh_e1 to calculate the end steering angle θh_e. and a change amount limiting unit 908 that outputs to .

As a result, it is possible to reduce the sense of incompatibility given to the driver's steering feeling due to fluctuations in the vehicle speed Vs and the steering angle θh.

In addition, it is possible to suppress a sudden change in the behavior of the vehicle that accompanies a sudden change in the turning angle, and to reduce the sense of incompatibility given to the driver's steering feeling.

In the fourth embodiment described above, an example in which the amount of change in the end steering angle θh_e1 is limited has been described. may be limited.

Also, the diagrams used above are conceptual diagrams for qualitatively explaining the present disclosure, and are not limited to these. In addition, although the above-described embodiment is an example of the preferred implementation of the present disclosure, it is not limited to this, and various modifications can be implemented without departing from the gist of the present disclosure.

Reference Signs List 1 steering wheel 2 column shaft 3 speed reduction mechanism 5 pinion rack mechanism 6a, 6b tie rod 7a, 7b hub unit 8L, 8R steering wheel 10 torque sensor 11 ignition key 12 vehicle speed sensor 13 battery 14 steering angle sensor 50 control unit (ECU)
60 reaction force device 61 reaction force motor 70 drive device 71 drive motor 72 gear 73 angle sensor 130 current control section 140 motor current detector 200 target steering torque generation section 210 basic map section 211 multiplication section 213 sign extraction section 220 differentiation section 230 damper gain map unit 240 hysteresis correction unit 260 multiplication unit 261, 262, 263 addition unit 300 torsion angle control unit 310 torsion angle feedback (FB) compensation unit 320 torsion angular velocity calculation unit 330 speed control unit 331 integration unit 332 proportional unit 333, 334 subtractor 340 stabilization compensator 350 output limiter 361 subtracter 362 adder 500 converter 900, 900a, 900b, 900c steering end controller 901 end target steering torque generator 904, 904a, 904b end steering angle setting unit 905 Turning ratio gain calculation unit 906, 906a End steering angle map 907, 907a End steering angle calculation unit 908 Change amount limiting unit 910 Target turning angle generation unit 920 Turning angle control unit 921 Turning angle feedback (FB) compensation unit 922 Steering angular velocity calculator 923 Speed controller 926 Output limiter 927 Subtractor 930 Current controller 931 Limiter 932 Rate limiter 933 Corrector 940 Motor current detector 1001 CPU
1005 interface 1006 A/D converter 1007 PWM controller 1100 control computer (MCU)

Claims (13)

a reaction force device that applies a steering reaction force to the steering wheel;
a driving device that steers tires in response to steering of the steering wheel;
a control unit that controls the reaction force device and the driving device;
with
The control unit
a target steering torque generator that generates a target steering torque that is a target value of the steering torque;
Based on the steering angle of the steering wheel and the end steering angle corresponding to the maximum steering angle, the absolute value of the steering angle of the steering wheel becomes zero in a region where the steering angle is less than the end steering angle, and the absolute value of the steering angle an end target steering torque generator that generates a first torque signal that increases from zero at a predetermined rate of change in a region equal to or greater than the end steering angle;
an end steering angle setting unit that sets the end steering angle according to at least the vehicle speed of the vehicle;
a steering ratio gain calculation unit that calculates a steering ratio gain by which the steering angle is multiplied when generating a target steering angle of the tire based on the end steering angle;
with
The target steering torque generation unit
A second torque signal is generated based on a predetermined basic map corresponding to at least the vehicle speed and the steering angle, and the first torque signal is added to the second torque signal to generate the target steering torque. Steering device for the second torque signal increases along a curve whose rate of change gradually decreases at least as the absolute value of the steering angle increases;
2. The vehicle steering system according to claim 1, wherein a rate of change of said first torque signal in a region where the absolute value of said steering angle is equal to or greater than said end steering angle is greater than a maximum rate of change of said second torque signal. The end target steering torque generation unit
Tref_e is the first torque signal, θh is the steering angle, θh_e is the end steering angle, and a coefficient that determines the slope of the first torque signal in a region where the absolute value of the steering angle is equal to or greater than the end steering angle is 3. The steering system for a vehicle according to claim 1, wherein the first torque signal is generated using the following equation (1), where Ke.
Tref_e=Ke×max(0, (|θh|−θh_e))×sign(θh)
... (1) a reaction force device that applies a steering reaction force to the steering wheel;
a driving device that steers tires in response to steering of the steering wheel;
a control unit that controls the reaction force device and the driving device;
with
The control unit
a target steering torque generator that generates a target steering torque that is a target value of the steering torque;
Based on the steering angle of the steering wheel and the end steering angle corresponding to the maximum steering angle, the absolute value of the steering angle of the steering wheel becomes zero in a region where the steering angle is less than the end steering angle, and the absolute value of the steering angle an end target steering torque generator that generates a first torque signal that increases from zero at a predetermined rate of change in a region equal to or greater than the end steering angle;
with
The target steering torque generation unit
A second torque signal is generated based on a predetermined basic map corresponding to at least the vehicle speed and the steering angle, and the first torque signal is added to the second torque signal to generate the target steering torque. ,
The end target steering torque generation unit
Tref_e is the first torque signal, θh is the steering angle, θh_e is the end steering angle, and a coefficient that determines the slope of the first torque signal in a region where the absolute value of the steering angle is equal to or greater than the end steering angle is When Ke is used, the first torque signal is generated using the following equation (2)
Vehicle steering system.
Tref_e=Ke×max(0, (|θh|−θh_e))×sign(θh)
... (2) The control unit
an end steering angle setting unit that sets the end steering angle according to at least the vehicle speed;
a steering ratio gain calculation unit that calculates a steering ratio gain by which the steering angle is multiplied when generating a target steering angle of the tire based on the end steering angle;
The steering system for a vehicle according to claim 4 , comprising: The steering ratio gain calculation unit is
When the steering ratio gain is G, the steering angle is θh, the end steering angle is θh_e, the maximum steering angle is θt_max, and the reference value of the steering ratio gain is Kt, the following equation (3) is used. 6. The vehicle steering system according to any one of claims 1 to 3 and 5, wherein the steering ratio gain is generated by
G=(θt_max/Kt)/θh_e (3) The end steering angle setting unit
a first region is a region where the vehicle speed is equal to or higher than a first vehicle speed;
A second region is a region where the vehicle speed is equal to or higher than a third vehicle speed lower than the first vehicle speed and less than the first vehicle speed,
a third region in which the vehicle speed is 0 or more and less than the third vehicle speed;
When
7. The vehicle steering system according to claim 1, wherein the end steering angle in the third region is set to a smaller value than the end steering angle in the first region. The end steering angle setting unit
setting the end steering angle in the first region to a constant value;
setting the end steering angle in the third region to a constant value different from the end steering angle in the first region;
8. The vehicle according to claim 7 , wherein the end steering angle in the second region is set to gradually decrease within a range from the end steering angle in the first region to the end steering angle in the third region. Steering device for The end steering angle setting unit
an end steering angle map in which a basic end steering angle according to the vehicle speed of the vehicle is set;
an end steering angle calculator that calculates the end steering angle based on the steering angle and the basic end steering angle;
A vehicle steering system according to any one of claims 1 to 3 and 5 to 8 . The end steering angle calculator,
outputting the basic end steering angle when the absolute value of the steering angle is less than a predetermined first threshold;
10. The vehicle steering system according to claim 9, wherein the previous value of the end steering angle is output when the absolute value of the steering angle is greater than or equal to the first threshold value. The end steering angle calculator,
outputting the basic end steering angle when the absolute value of the steering angle is less than the basic end steering angle;
outputting the absolute value of the steering angle when the absolute value of the steering angle is greater than or equal to the basic end steering angle and the absolute value of the steering angle is less than the previous value of the end steering angle;
The previous value of the end steering angle is output when the absolute value of the steering angle is greater than or equal to the basic end steering angle and the absolute value of the steering angle is greater than or equal to the previous value of the end steering angle. 9. The vehicle steering system according to 9 . The end steering angle setting unit
further comprising a change amount limiting unit that limits the amount of change in the end steering angle;
The end steering angle calculator,
outputting the basic end steering angle when the absolute value of the steering angle is less than a predetermined first threshold;
outputting the previous value of the end steering angle when the absolute value of the steering angle is greater than or equal to the first threshold;
The variation limiter is
outputting the end steering angle when an absolute value of a difference value between the end steering angle and a previous value of the end steering angle is less than a predetermined second threshold;
The absolute value of the difference between the end steering angle and the previous value of the end steering angle is equal to or greater than the second threshold, and the value obtained by subtracting the previous value of the end steering angle from the end steering angle is the second threshold. if it is equal to or greater than the threshold, adding the second threshold to the previous value of the end steering angle and outputting the result;
The absolute value of the difference between the end steering angle and the previous value of the end steering angle is equal to or greater than the second threshold, and the value obtained by subtracting the previous value of the end steering angle from the end steering angle is the second threshold. 10. The steering system for a vehicle according to claim 9 , wherein the second threshold value is subtracted from the previous value of the end steering angle and output when the value is less than the threshold value. The end steering angle setting unit
further comprising a change amount limiting unit that limits the amount of change in the end steering angle;
The end steering angle calculator,
outputting the basic end steering angle when the absolute value of the steering angle is less than the basic end steering angle;
outputting the absolute value of the steering angle when the absolute value of the steering angle is greater than or equal to the basic end steering angle and the absolute value of the steering angle is less than the previous value of the end steering angle;
outputting the previous value of the end steering angle when the absolute value of the steering angle is greater than or equal to the basic end steering angle and the absolute value of the steering angle is greater than or equal to the previous value of the end steering angle;
The variation limiter is
outputting the end steering angle when an absolute value of a difference value between the end steering angle and a previous value of the end steering angle is less than a predetermined second threshold;
The absolute value of the difference between the end steering angle and the previous value of the end steering angle is equal to or greater than the second threshold, and the value obtained by subtracting the previous value of the end steering angle from the end steering angle is the second threshold. if it is equal to or greater than the threshold, adding the second threshold to the previous value of the end steering angle and outputting the result;
The absolute value of the difference between the end steering angle and the previous value of the end steering angle is equal to or greater than the second threshold, and the value obtained by subtracting the previous value of the end steering angle from the end steering angle is the second threshold. 10. The steering system for a vehicle according to claim 9 , wherein the second threshold value is subtracted from the previous value of the end steering angle and output when the value is less than the threshold value.

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