JP2006341814A - Steering device for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a steering device for a vehicle capable of ensuring good steering feeling even in an environment wherein a steer characteristic is continuously varied. <P>SOLUTION: When a determination result in a control-on/off determination part shows continuously understeer control, in the case that an absolute value of an ACT instruction angle θus* at US control is smaller than an absolute value of a value (IFS retaining instruction angle θifs-m*) of an IFS-ACT instruction angle θifs* outputted at a former period and an absolute value of a differential value of a yaw rate (yaw rate differential value αRy) is larger than a predetermined threshold value β (step 305: NO, step 308: YES and step 309: YES), an IFS-ATC instruction angle operation part retains the outputted value of the IFS-ACT instruction angle θifs* to a value of the IFS retaining instruction angle θifs-m* (θifs*=θifs-m*, step 314). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a vehicle steering apparatus.

  In recent years, the steering angle of the steered wheels (steering angle) to control the yaw moment of the vehicle based on the vehicle model (vehicle motion model) that models the relationship between the vehicle state quantity such as the vehicle speed and the yaw rate and the motion state of the vehicle. There has been proposed a steering control system having a so-called active steering function for controlling the vehicle (for example, see Patent Document 1).

Specifically, for example, when the vehicle is in an oversteer state, the steering angle is controlled so as to apply a steering angle opposite to the direction of the yaw moment, that is, counter steer (oversteer control), and understeering. When in a state, control is performed to reduce the turning angle of the steered wheels (understeer control). As a result, the vehicle posture can be stabilized even on a low μ road such as a frozen road where the vehicle posture tends to become unstable.
JP 2002-254964 A

  By the way, on the low μ road, the stable region where the vehicle posture can be kept stable, that is, the range of the yaw rate changing speed (yaw angular acceleration) capable of stably controlling the yaw moment of the vehicle is extremely narrow. Therefore, in such an environment, for example, when the so-called double lane change or slalom driving, the yaw moment changes alternately, the steering characteristic (steering characteristic) is constant from understeer to oversteer, or from oversteer to understeer. In some cases, the state changes continuously without interposing the neutral steer state. In such a case, the next active steer control corresponding to the change in the steer characteristic is started immediately before the existing control completely converges.

  However, normally, the OS control component for oversteer control and the US control component for understeer control are calculated by different methods, and the active steer control uses the active control command for the same control. As appropriate. For this reason, when the steering characteristic continuously changes as described above, the value of the active control command may become discontinuous when the active steer control is switched (see FIGS. 14 and 15). Further, the steering reaction force transmitted to the steering is greatly fluctuated by the operation of the actuator, and there is a possibility that the steering feeling is deteriorated.

  In particular, when switching from understeer control to oversteer control, the generation direction of the US control component and the OS control component are the same, and the decreasing US control component and the increasing OS control component are combined, thereby active control. The command changes so that its value undulates (see FIG. 14). As a result, the driver feels the fluctuation of the steering reaction force more strongly and feels uncomfortable, and there is a problem that the tendency to deteriorate the steering feeling becomes more remarkable.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a vehicle steering apparatus capable of ensuring a good steering feeling even in an environment where the steering characteristic continuously changes. It is to provide.

  In order to solve the above-described problems, the invention described in claim 1 includes drive means capable of changing the turning angle of the steered wheels, and control means for controlling the operation of the drive means. A vehicle steering apparatus having an active steering function for controlling the turning angle so as to control a yaw moment of a vehicle based on a vehicle model, wherein the control means is configured to control the yaw when the vehicle is in an oversteer state. Active steer control, either oversteer control for controlling the steering angle to change in the direction opposite to the moment direction, or understeer control for controlling the steering angle to be small when the vehicle is in an understeer state Control determination means for determining whether to execute the control, OS control calculation means for calculating an OS control component for the oversteer control, and the understeer US control calculation means for calculating a US control component for control, and either the OS control component or the US control component is output as an active control command for performing active steer control according to the determination result of the control determination means Active steer control calculating means for calculating whether or not the active steer control calculating means performs the calculation at a predetermined cycle, and when the determination result is understeer control continuously, the US When the absolute value of the control component is smaller than the absolute value of the active control command at the time of the previous calculation and the differential value of the vehicle state quantity related to the yaw moment of the vehicle is larger than a predetermined threshold value, the value of the active control command Is maintained at the value at the time of the previous calculation.

  In other words, the continuous change in the steering characteristic from understeer to oversteer occurs when the yaw angular velocity at the time of understeer control convergence, that is, the absolute value of the yaw rate differential value exceeds the range in which the yaw moment of the vehicle can be stably controlled. To do. If the absolute value of the US control component is smaller than the absolute value of the active control command at the previous calculation when continuously understeering, it is considered that the US control component is decreasing, that is, the understeer control has converged. Can do. In such a case, when the absolute value of the yaw rate differential value exceeds a predetermined threshold value, it can be estimated that the steer characteristic continuously changes from understeer to oversteer.

  Therefore, according to the above configuration, when there is a possibility that the steer characteristic continuously changes from understeer to oversteer during understeer control, the calculation is performed even in a situation where the absolute value of the US control component starts to decrease. It is possible to keep the value of the active control command to be kept constant and to prevent the value from changing so as to wave. As a result, it is possible to alleviate the uncomfortable feeling felt by the driver due to fluctuations in the steering reaction force, and to secure a better steering feeling.

  According to a second aspect of the present invention, the active steer control calculating means is configured to output the absolute value of the OS control component when the determination result is oversteer control and the determination result at the previous calculation is understeer control. Is smaller than the absolute value of the active control command at the previous calculation, the value of the active control command is set until the absolute value of the OS control component is equal to or greater than the absolute value of the active control command at the previous calculation. The gist is to maintain the value at the time of the previous calculation.

  According to the above configuration, when switching from understeer control to oversteer control, if the absolute value of the OS control component is smaller than the absolute value of the active control command at the previous calculation, the absolute value of the OS control component is calculated the previous time. The value of the calculated active control command is kept constant until the absolute value of the current active control command becomes equal to or greater. Therefore, the value of the active control command can be suppressed from undulating. In particular, when the value is maintained from the time of understeer control according to the configuration of claim 1, a series of active steering commands The value of the active control command in the control becomes continuous, and the fluctuation thereof becomes gradual. As a result, a better steering feeling can be ensured.

The gist of the invention described in claim 3 is that the active steering control calculating means ends the holding after a predetermined time has elapsed from the start of the holding.
According to the above configuration, although the steer characteristic does not actually change continuously from understeer to oversteer, or the absolute value of the OS control component does not exceed the absolute value of the active control command at the previous calculation. Accordingly, the value of the active control command can be kept constant, thereby preventing the end of the active steering control from being delayed.

  According to a fourth aspect of the present invention, after the holding, the absolute value of the US control component is not less than the absolute value of the active control command at the time of the previous calculation, or the differential value of the vehicle state quantity is not more than a predetermined threshold value. In this case, the gist is to end the holding and perform filter processing on the calculated active control command.

  According to the above configuration, the value of the active control command continues to be held constant even though the steering characteristic does not continuously change from the understeer to the oversteer after the holding. It is possible to prevent the end of the steering control from being delayed. Even when there is a divergence between the absolute value of the US control component at the end of the holding and the absolute value of the active control command at the previous calculation, the value of the active control command changes abruptly. It can suppress and can ensure a favorable steering feeling.

  According to a fifth aspect of the present invention, the active steer control calculating means is configured to output the absolute value of the OS control component when the determination result is oversteer control and the determination result at the previous calculation is understeer control. Is greater than the absolute value of the active control command at the time of the previous calculation, the filter processing is performed on the calculated active control command.

  According to the above configuration, when switching from understeer control to oversteer control, the absolute value of the OS control component is larger than the absolute value of the active control command at the previous calculation, and there is a difference between the two. Therefore, it is possible to suppress a sudden change in the value of the calculated active control command and to ensure a good steering feeling.

  The gist of the invention described in claim 6 is that the active steering control calculating means performs a filtering process on the calculated active control command after the end of the holding due to the elapse of the predetermined time.

  According to the above configuration, after the end of holding after the elapse of a predetermined time, the calculation is performed even when there is a difference between the value of the US control component or the OS control component and the value of the active control command at the previous calculation. It is possible to suppress a sharp change in the value of the active control command to ensure a good steering feeling.

  The invention according to claim 7 comprises drive means capable of changing the turning angle of the steered wheels, and control means for controlling the operation of the drive means, wherein the control means is based on a vehicle model. The vehicle steering device having an active steering function for controlling the turning angle to control the steering angle, wherein the control means rotates the steering wheel in a direction opposite to the direction of the yaw moment when the vehicle is in an oversteer state. Control determining means for determining which active steer control is performed, such as over steer control for controlling the steering angle or under steer control for controlling the steer angle when the vehicle is in an under steer state An OS control calculation means for calculating an OS control component for the oversteer control, and a US control component for the understeer control. US control calculation means for calculating, and active steer control calculation for calculating which of the OS control component or the US control component is output as an active control command for performing active steer control according to the determination result of the control determination means The active steer control calculating means performs the calculation every predetermined cycle, the determination result is understeer control, and the determination result at the previous calculation is oversteer control The gist of the present invention is to perform a filtering process on the calculated active control command.

  According to the above configuration, when the steer characteristic continuously changes from oversteer to understeer, and when switching from oversteer control to understeer control, there is a discrepancy between the value of the US control component and the value of the OS control component. Even in the case where there is, it is possible to suppress a sudden change in the value of the calculated active control command and to ensure a good steering feeling.

The gist of the invention described in claim 8 is that the active steering control calculating means continues the filtering process until a predetermined time elapses.
According to the above configuration, it is possible to prevent the change rate of the active control command caused by the continuation of the filter processing from slowing down and the accompanying decrease in the active steering function.

  According to a ninth aspect of the present invention, the OS control calculation means calculates the OS control component by a feedback control calculation of a target value and an actual value of the vehicle state quantity calculated based on a vehicle model, and the US control The gist of the computing means is to compute the US control component based on an analog value that continuously changes in accordance with the steering characteristic of the vehicle.

The gist of the invention described in claim 10 is that the vehicle state quantity is at least one of a yaw rate or a slip angle of the vehicle.
The invention according to claim 11 comprises drive means capable of changing the turning angle of the steered wheels, and control means for controlling the operation of the drive means, wherein the control means is based on a vehicle model. The vehicle steering device having an active steering function for controlling the turning angle to control the steering angle, wherein the control means rotates the steering wheel in a direction opposite to the direction of the yaw moment when the vehicle is in an oversteer state. Control determining means for determining which active steer control is performed, such as over steer control for controlling the steering angle or under steer control for controlling the steer angle when the vehicle is in an under steer state An OS control calculating means for calculating an OS control component for the oversteer control, and a US control component for the understeer control US control calculation means for calculating, and active steer control calculation means for calculating the OS control component or the US control component as an active control command for performing active steer control according to the determination result of the control determination means, The active steer control calculating means performs the calculation every predetermined period, and includes an estimating means for estimating a continuous change in the vehicle steering characteristic from the understeer state to the oversteer state, and the understeer state When it is estimated that the state changes continuously from the state to the oversteer state, the gist is to keep the value of the active control command at the value at the time of the previous calculation.

  According to the above configuration, when there is a possibility that the steer characteristic continuously changes from understeer to oversteer during understeer control, the calculation is performed even in a situation where the absolute value of the US control component starts to decrease. It is possible to keep the value of the active control command constant and prevent the value from changing so as to wave. As a result, it is possible to alleviate the uncomfortable feeling felt by the driver due to fluctuations in the steering reaction force, and to secure a better steering feeling.

  ADVANTAGE OF THE INVENTION According to this invention, the steering apparatus for vehicles which can ensure a favorable steering feeling also in the environment where a steering characteristic changes continuously can be provided.

Hereinafter, an embodiment in which the present invention is embodied in a vehicle steering apparatus (steering apparatus) including a gear ratio variable system will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram of a steering apparatus 1 according to the present embodiment. As shown in the figure, a steering shaft 3 to which a steering (handle) 2 is fixed is connected to a rack 5 via a rack and pinion mechanism 4, and the rotation of the steering shaft 3 in response to a steering operation is The pinion mechanism 4 converts the rack 5 into a reciprocating linear motion. Then, by changing the rudder angle of the steered wheels 6, that is, the steered angle, by the reciprocating linear motion of the rack 5, the traveling direction of the vehicle is changed.

  The steering device 1 of the present embodiment includes a gear ratio variable actuator 7 as a transmission ratio variable device that varies the transmission ratio (gear ratio) of the steered wheels 6 with respect to the steering angle (steering angle) of the steering 2, and the gear ratio variable actuator. And IFSECU 8 as a control means for controlling the operation of 7.

  More specifically, the steering shaft 3 includes a first shaft 9 to which the steering 2 is connected and a second shaft 10 to be connected to the rack and pinion mechanism 4. The variable gear ratio actuator 7 includes the first shaft 9 and the first shaft 9. A differential mechanism 11 that couples the two shafts 10 and a motor 12 that drives the differential mechanism 11 are provided. The gear ratio variable actuator 7 adds the rotation driven by the motor to the rotation of the first shaft 9 associated with the steering operation and transmits it to the second shaft 10, thereby inputting the steering shaft to the rack and pinion mechanism 4. The rotation of 3 is increased (or decelerated).

  That is, as shown in FIGS. 2 and 3, the gear ratio variable actuator 7 has the steered angle (ACT angle θta) of the steered wheels based on the motor drive to the steered angle (steer steered angle θts) of the steered wheels 6 based on the steering operation. ) Is added, the ratio of the turning angle θt of the steered wheels 6 to the steering angle θs, that is, the transmission ratio (gear ratio) is varied. The IFSECU 8 controls the control of the gear ratio variable actuator 7 through the supply of driving power to the motor 12, thereby controlling the transmission ratio (gear ratio) between the steering angle θs and the turning angle θt (gear ratio). Variable control).

  In this case, “addition” is defined to include not only addition but also subtraction, and so on. Further, when the “gear ratio of the steering angle θt to the steering angle θs” is expressed as an overall gear ratio (steering angle θs / steering angle θt), the ACT angle θta in the same direction as the steering angle θts should be added. Thus, the overall gear ratio becomes small (large turning angle θt, see FIG. 2). Then, the overall gear ratio is increased by adding the ACT angle θta in the reverse direction (small turning angle θt, see FIG. 3). In this embodiment, the steer turning angle θts constitutes the first rudder angle, and the ACT angle θta constitutes the second rudder angle.

  As shown in FIG. 1, the steering device 1 includes an EPS actuator 17 that applies an assist force for assisting a steering operation to the steering system, and an EPS ECU 18 that controls the operation of the EPS actuator 17.

  The EPS actuator 17 of the present embodiment is a so-called rack-type EPS actuator in which a motor 22 as a driving source thereof is arranged coaxially with the rack 5, and an assist torque generated by the motor 22 is a ball feed mechanism (not shown). Is transmitted to the rack 5 via. The EPS ECU 18 controls the assist force applied to the steering system by controlling the assist torque generated by the motor 22 (power assist control).

  In the present embodiment, the IFSECU 8 that controls the gear ratio variable actuator 7 and the EPSECU 18 that controls the EPS actuator 17 are connected via an in-vehicle network (CAN: Controller Area Network) 23. Are connected to a plurality of sensors for detecting the vehicle state quantity. Specifically, a steering angle sensor 24, a torque sensor 25, wheel speed sensors 26a and 26b, a lateral G sensor 28, a vehicle speed sensor 29, a brake sensor 30, and a yaw rate sensor 31 are connected to the in-vehicle network 23. A plurality of vehicle state quantities detected by the sensors, that is, steering angle θs, steering torque τ, wheel speed Vtr, Vtl, turning angle θt, slip angle θsp, vehicle speed V, brake signal Sbk, and yaw rate Ry are as follows: The data is input to the IFSECU 8 and the EPSECU 18 via the in-vehicle network 23. In this embodiment, the turning angle θt is obtained by multiplying the steering angle θs by the base gear ratio of the rack and pinion mechanism 4, that is, by adding the ACT angle θta to the steering angle θts, and the slip angle θsp is obtained based on the lateral acceleration detected by the lateral G sensor 28 and the yaw rate Ry. The IFSECU 8 and EPSECU 18 transmit and receive control signals by mutual communication via the in-vehicle network 23. The IFSECU 8 and EPSECU 18 perform the gear ratio variable control and the power assist control in an integrated manner based on the vehicle state quantities and control signals input via the in-vehicle network 23.

Next, the electrical configuration and control mode of the steering apparatus according to the present embodiment will be described.
FIG. 4 is a control block diagram of the steering device 1 of the present embodiment. As shown in the figure, the IFSECU 8 includes a microcomputer 33 that outputs a motor control signal and a drive circuit 34 that supplies drive power to the motor 12 based on the motor control signal.

  In the present embodiment, the motors 12 and 22 that are drive sources of the gear ratio variable actuator 7 and the EPS actuator 17 are both brushless motors, and the drive circuit 34 and the drive circuit 44 of the EPS ECU 18 described later are input. Based on the motor control signal, three-phase (U, V, W) driving power is supplied to the corresponding motors 12, 22 respectively. Each control block shown below is realized by a computer program executed by the microcomputer 33 (43).

  The microcomputer 33 includes an IFS control calculation unit 35, a gear ratio variable control calculation unit 36, and a Lead Steer control calculation unit 37. Each of these control calculation units is a control target component of the ACT angle θta based on the input vehicle state quantity. (And control signal) is calculated.

  More specifically, the steering angle θs, the turning angle θt, the vehicle speed V, the wheel speeds Vtr and Vtl, the brake signal Sbk, the yaw rate Ry, and the slip angle θsp are input to the IFS control calculation unit 35. The IFS control calculation unit 35 calculates the control target component of the ACT angle θta for controlling the yaw moment of the vehicle based on the so-called active steering function, that is, the vehicle model, based on these vehicle state quantities, and related items. Perform control signal calculations. Specifically, the IFS control calculation unit 35 calculates the IFS_ACT command angle θifs * as a control target component of the ACT angle θta for realizing the active steering function. Then, an OS / US characteristic value Val_st indicating a vehicle steering characteristic is calculated as a control signal (IFS control calculation).

  Here, the vehicle posture in the yaw direction is expressed as “steer characteristic (steering characteristic)”. The steer characteristic is a characteristic regarding a difference between a vehicle turning speed assumed by the driver and an actual vehicle turning speed when the driver performs a steering operation. The case where the actual vehicle turning speed is larger than the assumed vehicle turning speed is referred to as oversteer (OS), the case where the actual vehicle turning speed is small is referred to as understeer (US), and the case where there is no difference is referred to as neutral steer (NS). This “vehicle turning speed assumed by the driver” can be replaced with the target yaw rate in the vehicle model. When the vehicle is in a steady turning state and the steering characteristic is neutral steering, the turning direction is changed. In other words, the vehicle traveling direction.

  In the present embodiment, the IFS control calculation unit 35 reduces the turning angle of the steered wheel 6 when the steer characteristic is understeer, and when the steer characteristic is oversteer, The IFS_ACT command angle θifs * is calculated as a control target component of the ACT angle θta for giving the reverse steering angle (counter steer). The OS / US characteristic value Val_st is used for internal calculation processing in the IFS control calculation unit 35 and is transmitted to the EPS ECU 18 via the in-vehicle network 23 (see FIG. 1). And it is used for power assist control by EPSECU18.

  A steering angle θs, a turning angle θt, and a vehicle speed V are input to the gear ratio variable control calculation unit 36. Then, the gear ratio variable control calculation unit 36 uses the gear ratio variable ACT command angle θgr * as a control target component for varying the gear ratio according to the vehicle speed V based on these vehicle state quantities (and control signals). Calculate (gear ratio variable control calculation).

  The vehicle speed V and the steering speed ωs are input to the lead steer control calculation unit 37. The steering speed ωs is calculated by differentiating the steering angle θs (the same applies hereinafter). Then, the Lead Steer control calculation unit 37 calculates the LS_ACT command angle θ ls * as a control target component for improving the responsiveness of the vehicle based on the vehicle speed V and the steering speed ω s (Lead Steer control calculation). ).

  The IFS control calculation unit 35, the gear ratio variable control calculation unit 36, and the Lead Steer control calculation unit 37 are each control target component calculated by the above calculation, that is, IFS_ACT command angle θifs *, gear ratio variable ACT command angle θgr *, and The LS_ACT command angle θls * is output to the adder 38a. In the adder 38a, the IFS_ACT command angle θifs *, the gear ratio variable ACT command angle θgr *, and the LS_ACT command angle θls * are superimposed, whereby the ACT command angle θta * that is the control target of the ACT angle θta is obtained. Calculated.

  The ACT command angle θta * calculated by the adder 38 a is input to the F / F control calculation unit 39 and the F / B control calculation unit 40. Further, the ACT angle θta detected by the rotation angle sensor 41 provided in the motor 12 is input to the F / B control calculation unit 40. The F / F control calculation unit 39 calculates the control amount εff by feedforward calculation based on the input ACT command angle θta *, and the F / B control calculation unit 40 calculates the ACT command angle θta * and the ACT angle θta. The control amount εfb is calculated by feedback calculation based on the above.

  The F / F control calculation unit 39 and the F / B control calculation unit 40 output the calculated control amount εff and control amount εfb to the adder 38b. Then, the control amount εff and the control amount εfb are superimposed in the adder 38b and input to the motor control signal output unit 42 as a current command. The motor control signal output unit 42 generates a motor control signal based on the input current command and outputs it to the drive circuit 34.

  That is, as shown in the flowchart of FIG. 5, when the microcomputer 33 fetches sensor values from the respective sensors as vehicle state quantities (step 101), first, IFS control calculation is performed (step 102), and then gear ratio variable control is performed. An operation (step 103) and a lead steer control operation are performed (step 104). Then, the microcomputer 33 superimposes the IFS_ACT command angle θifs *, the gear ratio variable ACT command angle θgr *, and the LS_ACT command angle θls *, which are calculated by executing the calculation processes of the above steps 102 to 104, To calculate the ACT command angle θta * which is the control target. The microcomputer 33 calculates a current command by performing a feedforward calculation (step 105) and a feedback calculation (step 106) based on the calculated ACT command angle θta *, and performs motor control based on the current command. A signal is output (step 107).

  On the other hand, as shown in FIG. 4, the EPS ECU 18 includes a microcomputer 43 and a drive circuit 44 in the same manner as the IFSECU 8. The microcomputer 43 includes an assist control unit 45, a torque inertia compensation control unit 46, a steering return control unit 47, and a damper compensation control unit 48, and each of these control units has the motor 22 based on the input vehicle state quantity. A control target component of the generated assist torque is calculated.

  More specifically, the vehicle speed V and the steering torque τ are input to the assist control unit 45 and the torque inertia compensation control unit 46, respectively. The assist control unit 45 calculates a basic assist current command Ias * as a base control target component, and the torque inertia compensation control unit 46 is an inertia compensation current command Iti that is a control target component for compensating the inertia of the motor 22. Calculate *. The vehicle speed V, the steering torque τ, and the turning angle θt are input to the steering return control unit 47, and the vehicle speed V and the steering speed ωs are input to the damper compensation control unit 48. The steering return control unit 47 calculates a steering return current command Isb *, which is a control target component for improving the return characteristic of the steering 2, and the damper compensation control unit 48 improves the power assist characteristic during high speed running. A damper compensation current command Idp *, which is a control target component for the calculation, is calculated.

  The microcomputer 43 includes an IFS torque compensation control unit 49 that calculates an IFS torque compensation gain Kifs for improving the steering feel during IFS control, in addition to the control units described above. In the present embodiment, the IFS torque compensation control unit 49 includes the steering torque τ, the steering angle θs, and the steering speed ωs, the IFS_ACT command angle θifs * calculated by the IFS control calculation unit 35, and the OS / US characteristic value Val_st. Is entered. Then, the IFS torque compensation controller 49 calculates the IFS torque compensation gain Kifs based on each vehicle state quantity, the IFS_ACT command angle θifs *, and the OS / US characteristic value Val_st.

  In the present embodiment, the IFS torque compensation gain Kifs is multiplied by the basic assist current command Ias * calculated by the assist control unit 45, and the corrected basic assist current command Ias ** is the inertia compensation current command Iti. *, The steering return current command Isb *, and the damper compensation current command Idp * are input to the adder 50. Then, by superimposing these control target components, a current command that is a control target of the assist torque generated by the motor 22 is calculated.

  The current command calculated by the adder 50 is input to the motor control signal output unit 51. In addition, the motor control signal output unit 51 receives an actual current and a rotation angle detected by a current sensor 52 and a rotation sensor 53 provided in the motor 22. The motor control signal output unit 51 generates a motor control signal by performing feedback control based on the current command, the actual current, and the rotation angle, and outputs the motor control signal to the drive circuit 44.

Next, IFS control calculation processing in the IFS control calculation unit will be described in detail.
FIG. 6 is a control block diagram of the IFS control calculation unit. As shown in the figure, the IFS control calculation unit 35 includes a vehicle model calculation unit 61, a crossing road determination unit 62, a steer characteristic calculation unit 63, an OS control calculation unit 65, a US control calculation unit 66, and a control ON / OFF determination unit. 67, and an IFS_ACT command angle calculation unit 68.

  The turning angle θt and the vehicle speed V are input to the vehicle model calculation unit 61. Then, the vehicle model calculation unit 61 performs vehicle model calculation based on the turning angle θt and the vehicle speed V, and the target value of the vehicle state quantity related to the yaw moment of the vehicle, that is, the target yaw rate Ry0 as the target state quantity and The target slip angle θsp0 is calculated. Note that the vehicle model calculation in the vehicle model calculation unit 61 of the present embodiment, that is, a method of calculating the target yaw rate Ry0 and the target slip angle θsp0 from the turning angle θt and the vehicle speed V based on the vehicle model is described in, for example, Patent Document 1 described above Please refer to.

  Wheel speeds Vtr and Vtl, a turning angle θt, a vehicle speed V, and a brake signal Sbk are input to the crossing road determination unit 62. Based on these vehicle state quantities, the crossing road determination unit 62 determines whether or not the vehicle is on a crossing road, that is, whether the left and right wheels of the vehicle are on two road surfaces (μ split road surfaces) with significantly different road resistances. Judgment is made. Specifically, it is determined whether braking is in the μ split state, that is, whether the vehicle is in the μ split braking state (crossing road determination).

  The steering characteristic calculator 63 receives the steering angle θs, the vehicle speed V, the yaw rate Ry, and the target yaw rate Ry0 calculated by the vehicle model calculator 61. Based on these vehicle state quantities, the steer characteristic calculation unit 63 calculates the steer characteristic of the vehicle, that is, whether the vehicle is in oversteer, understeer, or neutral steer, and indicates the characteristic. An OS / US characteristic value Val_st is calculated (steer characteristic calculation). In the present embodiment, the OS / US characteristic value Val_st is calculated based on the following equation, Val_st = (L × Ry / V−θt) × Ry, L: wheelbase, and continuously according to the steering characteristic of the vehicle. Is output as an analog value.

  The OS control calculation unit 65 includes a yaw rate F / B calculation unit 71 and a slip angle F / B calculation unit 72. The yaw rate F / B calculation unit 71 and the slip angle F / B calculation unit 72 correspond to each other. A feedback calculation is performed so that the actual value of the vehicle state quantity follows the target value. Based on the feedback calculation in each of these F / B calculation units, the OS control calculation unit 65 controls the control target component of the ACT angle θta when the steer characteristic is oversteer, that is, the steering angle in the direction opposite to the yaw moment ( As an OS control component for generating counter steer), an OS control ACT command angle θos * is calculated (OS control calculation).

  More specifically, the yaw rate Ry and the target yaw rate Ry0 calculated by the vehicle model calculation unit 61 are input to the yaw rate F / B calculation unit 71, and the yaw rate F / B calculation unit 71 performs feedback based on the deviation ΔRy. Perform the operation. Specifically, the yaw rate F / B calculating unit 71 calculates the yaw rate proportional F / B command angle θRyp * by multiplying the deviation ΔRy by the proportional F / B gain KP, and calculates the derivative F / B as the differential amount of the deviation ΔRy ′. The yaw rate differential F / B command angle θRyd * is calculated by multiplying by the B gain KD (yaw rate F / B calculation). Similarly, the slip angle F / B calculation unit 72 receives the slip angle θsp and the target slip angle θsp0 calculated by the vehicle model calculation unit 61, and the slip angle F / B calculation unit 72 adds the deviation Δθsp to the slip angle F / B calculation unit 72. By multiplying the slip angle F / B gain Kslip, the slip angle F / B command angle θsp * is calculated (slip angle F / B calculation).

  The yaw rate proportional F / B command angle θRyp * and yaw rate differential F / B command angle θRyd * calculated by the yaw rate F / B calculation unit 71 and the slip angle F / B calculated by the slip angle F / B calculation unit 72 are calculated. The command angle θsp * is input to the adder 73. Then, the OS control calculation unit 65 calculates the OS control ACT command angle θos * by superimposing these control target components in the adder 73 (OS control calculation).

  Note that the OS control calculation unit 65 of this embodiment includes a yaw angle F / B calculation unit 74 in addition to the yaw rate F / B calculation unit 71 and the slip angle F / B calculation unit 72, and the yaw angle F / B The B calculation unit 74 executes a yaw angle F / B calculation based on the target yaw angle θy0 and the yaw angle θy using the determination result in the crossing road determination unit 62 as a trigger. Then, the OS control calculation unit 65 determines that the yaw angle F / B command angle θy * calculated by the yaw angle F / B calculation unit 74 for ensuring the stability during so-called μ split braking is the control target component. Is output as an ACT command angle θos * during OS control.

  The US control calculation unit 66 receives the steering angle θs, the steering speed ωs, and the OS / US characteristic value Val_st calculated by the steering characteristic calculation unit 63. Then, the US control calculation unit 66 calculates the ACT command angle θus * during US control as a US control component for understeer control based on these vehicle state quantities (US control calculation).

  The vehicle speed V, the steering angle θs, the yaw rate Ry, and the OS / US characteristic value Val_st are input to the control ON / OFF determination unit 67 serving as a control determination unit. Then, the control ON / OFF determination unit 67 performs oversteer control or steer for controlling the steered wheels 6 to give a steered angle (counter steer) in a direction opposite to the yaw moment when the steer characteristic is oversteer. When the characteristic is understeer, it is determined which active steer control of the understeer control for controlling the turning angle of the steered wheels 6 to be reduced, and the determination result is output as a control ON / OFF signal Sc (control) ON / OFF judgment).

  The IFS_ACT command angle calculation unit 68 as the active steer control calculation unit and the estimation unit includes an OS control time ACT command angle θos * calculated by the OS control calculation unit 65 and a US control time ACT calculated by the US control calculation unit 66. The command angle θus *, the control ON / OFF signal Sc output from the control ON / OFF determination unit 67, and the yaw rate Ry are input. Based on the control ON / OFF signal Sc and the yaw rate Ry, the IFS_ACT command angle calculation unit 68 outputs either the ACT command angle θos * during OS control or the ACT command angle θus * during US control as an IFS_ACT command angle θifs *. Or calculate (IFS_ACT command angle calculation). In the present embodiment, if the control ON / OFF signal Sc indicates “control OFF”, that is, indicates neutral steering, the IFS_ACT command angle calculator 68 sets the IFS_ACT command angle θifs * to “0”. "

  That is, as shown in the flowchart of FIG. 7, the IFS control calculation unit 35 first executes vehicle model calculation (step 201), and then executes crossover determination (step 202). Then, a steer characteristic calculation is executed (step 203).

  Next, the IFS control calculation unit 35 calculates the yaw rate F / B and the slip angle F / B based on the target state quantities calculated in the vehicle model calculation in step 201, that is, the target yaw rate Ry0 and the target slip angle θsp0. Is executed to calculate the OS control ACT command angle θos * (OS control calculation, step 204). If it is determined in step 202 that the μ split braking state is in effect, the yaw angle F / B calculation is executed using the determination result as a trigger.

  Next, the IFS control calculation unit 35 calculates a US control ACT command angle θus * by executing a US control calculation (step 205), and then executes a control ON / OFF determination (step 206). Then, based on the determination result of step 206, either the OS control ACT command angle θos * or the US control ACT command angle θus * (or 0) is a control target component for realizing the active steering function, that is, an IFS_ACT command. It is calculated whether the angle θifs * is output (IFS_ACT command angle calculation, step 207).

  As described above, the IFS control calculation unit 35 outputs the IFS_ACT command angle θifs * by executing the processing of Step 201 to Step 207 at every predetermined cycle (sampling cycle). Then, by controlling the operation of the gear ratio variable actuator 7 based on the IFS_ACT command angle θifs * (including the ACT command angle θta *), the above-described active steering control (oversteer control or understeer control) is executed. It is like that.

(IFS_ACT command angle calculation)
Next, an aspect of IFS_ACT command angle calculation in the IFS_ACT command angle calculation unit and a processing procedure thereof will be described.

[Processing procedure of IFS_ACT command angle calculation]
First, the processing procedure of the IFS_ACT command angle calculation in the IFS_ACT command angle calculation unit 68 will be described.

8 to 10 are flowcharts showing the processing procedure of the IFS_ACT command angle calculation.
As shown in FIG. 8, the IFS_ACT command angle calculation unit 68 first determines whether or not the control ON / OFF signal Sc output from the control ON / OFF determination unit 67 is “control OFF” (step 301). When the control ON / OFF signal Sc is “control OFF” (step 301: YES), the output IFS_ACT command angle θifs * is determined to be “0” (no output: θifs * = 0, step 302). ).

  On the other hand, when it is determined in step 301 that the control ON / OFF signal Sc is not “control OFF” (step 301: NO), the IFS_ACT command angle calculation unit 68 subsequently sets the control ON / OFF signal Sc to “US control ON”. Is determined (US control ?, step 303). When the control ON / OFF signal Sc is “US control ON” (step 303: YES), it is subsequently determined whether or not a US shift flag for executing a filter process described later is set. (Step 304) If the US shift flag is not set (Step 304: NO), it is determined whether or not the control ON / OFF signal Sc in the previous calculation cycle (previous cycle) is “OS control ON”. Determine (previous OS control ?, step 305). When it is determined in step 305 that the control ON / OFF signal Sc in the previous cycle is “OS control ON” (step 305: YES), that is, when switching from oversteer control to understeer control, the US transition flag And the US transition timer for measuring the elapsed time tf_us from the start of the filtering process is reset (tf_us = 0, step 306), and the ACT command angle θus * during US control is output as the IFS_ACT command angle θifs *. Is determined (θifs * = θus *, step 307).

  If it is determined in step 304 that the US transition flag has already been set (step 304: YES), that is, if filter processing has already been performed, the IFS_ACT command angle calculation unit 68 performs the above step. Step 307 is executed without executing steps 305 and 306, and steps 308 to 314 described below. Then, it is determined to output the ACT command angle θus * during US control as the IFS_ACT command angle θifs * (θifs * = θus *).

  If it is determined in step 305 that the control ON / OFF signal Sc in the previous cycle is not “OS control ON” (step 305: NO), the IFS_ACT command angle calculation unit 68 first determines the ACT command during US control. It is determined whether or not the absolute value of the angle θus * is smaller than the absolute value of the value of the IFS_ACT command angle θifs * (IFS holding command angle θifs_m *) output in the previous cycle (step 308). When the absolute value of the ACT command angle θus * during US control is smaller than the absolute value of the IFS hold command angle θifs_m * (| θus * | <| θifs_m * |, step 308: YES), the yaw rate differentiation is subsequently performed. It is determined whether or not the absolute value of the value αRy is larger than a predetermined threshold value β (step 309). In the present embodiment, the threshold value β is set to the yaw rate differential value αRy that can stably control the yaw moment of the vehicle on the low μ road, that is, the upper limit value of the yaw angular velocity.

  Next, the IFS_ACT command angle calculation unit 68 determines that the absolute value of the ACT command angle θus * during US control is greater than or equal to the absolute value of the IFS hold command angle θifs_m * in step 308 (| θus * | ≧ | θifs_m * | : NO), or when it is determined in step 309 that the absolute value of the yaw rate differential value αRy is equal to or smaller than a predetermined threshold value β (| αRy | ≦ β, step 309: NO), subsequently, US holding control described later is executed. It is determined whether or not the US holding flag for setting is set (step 310). If the same US holding flag is not set (step 310: NO), that is, if the US holding control is not being executed, the process of step 307 is executed without executing the process of step 306, and the US It is determined to output the ACT command angle θus * during control as the IFS_ACT command angle θifs * (θifs * = θus *).

  In step 310, if the US holding flag is already set (step 310: YES), that is, if the continuation condition is not satisfied during the US holding control, the processing in step 306 is executed. Thus, the US transition flag is set and the US transition timer is reset (tf_us = 0). Then, by executing the processing of step 307, it is determined that the ACT command angle θus * during US control is output as the IFS_ACT command angle θifs * (θifs * = θus *).

  On the other hand, if it is determined in step 309 that the absolute value of the yaw rate differential value αRy is greater than the predetermined threshold value β (| αRy |> β, step 309: YES), the IFS_ACT command angle calculation unit 68 similarly uses the US It is determined whether or not a holding flag is set (step 311). If the US holding flag is not set (step 311: NO), the US holding flag is set and the US holding timer for measuring the elapsed time th_us from the start of holding is reset (th_us = 0, step 312). If it is determined in step 311 that the US holding flag has already been set (step 311: YES), that is, if the US holding control is already being executed, the processing in step 312 is not executed.

  Next, the IFS_ACT command angle calculator 68 determines whether or not the elapsed time th_us has passed the predetermined time t1 (step 313). If the elapsed time th_us has not reached the predetermined time t1 (th_us ≦ t1, step 313: NO), the value of the IFS_ACT command angle θifs * output in the previous cycle, that is, the IFS holding command angle θifs_m * is set to the IFS_ACT command. The output is determined as the angle θifs * (θifs * = θifs_m *, step 314).

  If it is determined in step 313 that the elapsed time th_us has passed the predetermined time t1 (th_us> t1, step 313: YES), the process of step 306 is executed to set the US transition flag. , And reset the US transition timer (tf_us = 0). Then, by executing the processing of step 307, it is determined that the ACT command angle θus * during US control is output as the IFS_ACT command angle θifs * (θifs * = θus *).

  As shown in FIG. 9, when it is determined in step 303 that the control ON / OFF signal Sc is not “US control ON”, that is, the control ON / OFF signal Sc is “OS control ON” (FIG. 9). 8 (step 303: NO), the IFS_ACT command angle calculation unit 68 first determines whether or not an OS transition flag for executing a filtering process to be described later is set (step 315). If it is not set (step 315: NO), it is subsequently determined whether or not an OS holding flag for executing OS holding control described later is set (step 316). If the OS holding flag is not set (step 316: NO), it is determined whether or not the control ON / OFF signal Sc in the previous cycle is “US control ON” (previous US control ?, step 317) If it is not “US control ON”, that is, not when switching from understeer control to oversteer control, it is determined to output the ACT command angle θos * during OS control as the IFS_ACT command angle θifs * ( θifs * = θos *, step 318).

  If it is determined in step 315 that the OS transition flag has already been set (step 315: YES), that is, if it is determined that filtering has already been performed, the IFS_ACT command angle calculation unit 68 The processing of step 318 is executed without executing the processing of step 316 and step 317 and the processing of step 319 to step 325 described below. Then, it is determined to output the ACT command angle θos * during OS control as the IFS_ACT command angle θifs * (θifs * = θos *).

  Next, the IFS_ACT command angle calculation unit 68 determines in step 317 that the control ON / OFF signal Sc in the previous cycle is “US control ON” (step 317: YES), that is, the control ON / OFF signal. If Sc is “OS control ON” and the control ON / OFF signal Sc of the previous cycle is “US control ON”, then the absolute value of the ACT command angle θos * during OS control is the IFS hold command. It is determined whether or not the angle θifs_m * is smaller than the absolute value (step 319).

  If it is determined in step 316 that the OS retention flag has already been set (step 316: YES), that is, if the OS retention control is already in progress, the IFS_ACT command angle calculation unit 68 performs the above step 317. The process of step 319 is executed without executing the process. If it is determined in step 317 that the control ON / OFF signal Sc in the previous cycle is not “US control ON” (step 317: NO), the processing in step 319 and steps 320 to 325 described below is performed. The process of step 318 is executed without executing it. Then, it is determined to output the ACT command angle θos * during OS control as the IFS_ACT command angle θifs * (θifs * = θos *).

  Next, when the IFS_ACT command angle calculation unit 68 determines in step 319 that the absolute value of the ACT command angle θos * during OS control is greater than or equal to the absolute value of the IFS hold command angle θifs_m * (| θos * | ≧ | Next, it is determined whether or not the absolute value of the OS control ACT command angle θos * is larger than the absolute value of the IFS hold command angle θifs_m * (step 320). When it is determined that the absolute value of the ACT command angle θos * during OS control is larger than the absolute value of the IFS hold command angle θifs_m * (| θos * |> | θifs_m * |, step 320: YES), the OS The OS transition timer for measuring the transition flag setting and the elapsed time tf_os from the start of the filter process is reset (tf_os = 0, step 321). Then, by executing the processing of step 318, it is determined that the OS control ACT command angle θos * is output as the IFS_ACT command angle θifs * (θifs * = θos *).

  In step 320, the absolute value of the ACT command angle θos * during OS control is not larger than the absolute value of the IFS hold command angle θifs_m *, that is, the absolute value of the ACT command angle θos * during OS control and the IFS hold command angle. If it is determined that the absolute value of θifs_m * is equal (| θos * | = | θifs_m * |, step 320: NO), the IFS_ACT command angle calculation unit 68 does not execute the processing of step 321 described above. The process of step 318 is executed. Then, it is determined to output the ACT command angle θos * during OS control as the IFS_ACT command angle θifs * (θifs * = θos *).

  On the other hand, when it is determined in step 319 that the absolute value of the OS control ACT command angle θos * is smaller than the absolute value of the IFS hold command angle θifs_m * (| θos * | <| θifs_m * |, step 319: YES) ), The IFS_ACT command angle calculation unit 68 determines whether or not the OS holding flag is set (step 322). When the OS holding flag is not set (step 322: NO), the OS holding flag is set and the OS holding timer for measuring the elapsed time th_os from the start of the OS holding control is reset (th_os = 0, step 323). If it is determined in step 322 that the OS retention flag is set (step 322: YES), that is, if the OS retention control is already being executed, the processing in step 323 is not performed.

  Next, the IFS_ACT command angle calculation unit 68 determines whether or not the elapsed time th_os has passed the predetermined time t2 (step 324). If the elapsed time th_os does not reach the predetermined time t2 (th_os ≦ t2, step 324: NO), the value of the IFS_ACT command angle θifs * output in the previous cycle, that is, the IFS holding command angle θifs_m * is set as the IFS_ACT command. The output is determined as the angle θifs * (θifs * = θifs_m *, step 325).

  If it is determined in step 324 that the elapsed time th_os has passed the predetermined time t2 (th_os> t2, step 324: YES), the process of step 321 is executed to set the OS transition flag. And the OS transition timer is reset (tf_os = 0). Then, by executing the processing of step 318, it is determined that the ACT command angle θos * during OS control is output as the IFS_ACT command angle θifs * (θifs * = θos *).

  As shown in FIG. 10, the IFS_ACT command angle calculation unit 68 outputs the value of the IFS_ACT command angle θifs * to be output in step 307, step 314 (see FIG. 8), step 318, or step 325 (see FIG. 9). If determined, the time-over process of each elapsed time (th_us, th_os, tf_us, tf_os) is executed (steps 326 to 333).

  Specifically, the IFS_ACT command angle calculation unit 68 first determines whether or not the elapsed time th_us from the start of the US holding control has passed the predetermined time t1 (step 326). If it is determined that the elapsed time th_us has passed the predetermined time t1 (th_us> t1, step 326: YES), the US holding flag is reset (step 327). When it is determined in step 326 that the elapsed time th_us has not reached the predetermined time t1 (th_us ≦ t1, step 326: NO), the process of step 327 is not executed.

  Subsequently, the IFS_ACT command angle calculation unit 68 determines whether or not the elapsed time th_os from the start of the OS holding control has passed the predetermined time t2 (step 328). When it is determined that the elapsed time th_os has passed the predetermined time t2 (th_os> t2, step 328: YES), the OS holding flag is reset (step 329). If it is determined in step 328 that the elapsed time th_os has not reached the predetermined time t2 (th_os ≦ t2, step 328: NO), the processing in step 329 is not executed.

  Next, the IFS_ACT command angle calculation unit 68 determines whether or not the elapsed time tf_us from the start of the filter processing at the time of US control has passed the predetermined time t3 (step 330). If it is determined that the elapsed time tf_us has passed the predetermined time t3 (tf_us> t3, step 330: YES), the US holding flag is reset (step 331). If it is determined in step 330 that the elapsed time tf_us has not reached the predetermined time t3 (tf_us ≦ t3, step 330: NO), the process of step 331 is not executed.

  Then, the IFS_ACT command angle calculation unit 68 determines whether or not the elapsed time tf_os from the start of the filter processing during OS control has passed the predetermined time t4 (step 332). When it is determined that the elapsed time tf_os has passed the predetermined time t4 (tf_os> t4, step 332: YES), the OS holding flag is reset (step 333). If it is determined in step 332 that the elapsed time tf_os has not reached the predetermined time t4 (tf_os ≦ t4, step 332: NO), the process of step 333 is not executed.

  After executing the time-over process from step 326 to step 333, the IFS_ACT command angle calculation unit 68 next determines whether or not the US shift flag is set (step 334), and the US shift flag is set. If not (step 334: NO), it is then determined whether the OS migration flag is set (step 335). If either the US transition flag or the OS transition flag is set (step 334: YES or step 335: YES), the IFS_ACT command angle θifs * determined in step 307 or step 318 is determined. Filter processing is executed (step 336). If it is determined that neither the US transition flag nor the OS transition flag is set (step 334: NO and step 335: NO), the process of step 336 is not executed, and the filter process is executed. Not.

  Then, the IFS_ACT command angle calculation unit 68 receives the IFS_ACT command angle θifs * determined in the above step 307, step 314, step 318, or step 325, or the IFS_ACT after the filter processing in which the filter processing is performed in the above step 336. The command angle θifs ** is output (step 337).

  Then, the IFS_ACT command angle calculation unit 68 updates the IFS hold command angle θifs_m * (θifs_m * = θifs * (θifs **), step 338), and increments each measurement timer (tx = tx + 1, step 339). By doing so, the IFS_ACT command angle calculation in the cycle is completed. Note that “tx” indicates th_us, th_os, tf_us, or tf_os.

[IFS_ACT command angle calculation mode]
Next, an aspect of IFS_ACT command angle calculation will be described in detail.
As described above, the IFS_ACT command angle calculation unit 68 executes the IFS_ACT command angle calculation according to the following modes (1) to (8) by executing the processes in steps 301 to 339 at predetermined intervals. To do.

  (1) When the determination result in the control ON / OFF determination unit 67 is “understeer control” continuously, the absolute value of the ACT command angle θus * during US control is output in the previous calculation cycle (previous cycle). The absolute value of the differential value of yaw rate Ry (yaw rate differential value αRy) is smaller than the absolute value of IFS_ACT command angle θifs * (IFS holding command angle θifs_m *) (| θus * | <| θifs_m * |) Is larger than the threshold value β (| αRy |> β), the output value of the IFS_ACT command angle θifs * is held at the value of the IFS hold command angle θifs_m * (US holding control).

  That is, the control ON / OFF signal Sc is “US control ON” (step 303: YES), the control ON / OFF signal Sc in the previous cycle is not “OS control ON” (step 305: NO), and US control is performed. When the absolute value of the hour ACT command angle θus * is smaller than the absolute value of the IFS hold command angle θifs_m * (| θus * | <| θifs_m * |, step 308: YES), the above determination result is “continuously Can be regarded as “understeer control” (since θifs_m * = 0 in the case of the previous cycle “control OFF”). Then, in such a case, if the absolute value of the yaw rate differential value αRy is larger than the predetermined threshold β (| αRy |> β, step 309: YES), the IFS_ACT command angle calculation unit 68 uses the US holding flag. Is set (step 312), and it is determined that the IFS holding command angle θifs_m * is output as the IFS_ACT command angle θifs * (θifs * = θifs_m *, step 314). That is, the IFS holding command angle θifs_m * that is first output as the IFS_ACT command angle θifs * is the US control time ACT command angle θus * in the previous cycle. While the US holding flag is set, the IFS holding command angle θifs_m * is output as the IFS_ACT command angle θifs * (step 314), and the output IFS_ACT command angle θifs * (that is, the US control in the previous cycle). The IFS hold command angle θifs_m * is updated with the hour ACT command angle θus *) (step 338). Accordingly, the value of the IFS_ACT command angle θifs * is held until any one of the continuation conditions (step 303: YES, step 305: NO, step 308: YES, and step 309: YES) is not satisfied.

  (2) The absolute value of the ACT command angle θos * during OS control when the determination result in the control ON / OFF determination unit 67 is “oversteer control” and the determination result in the previous cycle is “understeer control” Is smaller than the absolute value of the IFS retention command angle θifs_m * (| θos * | <| θifs_m * |), the absolute value of the ACT command angle θos * during OS control is greater than or equal to the absolute value of the IFS retention command angle θifs_m * Until this time, the value of the output IFS_ACT command angle θifs * is held at the value of the IFS hold command angle θifs_m * (OS holding control).

  That is, in the IFS_ACT command angle calculation unit 68, the control ON / OFF signal Sc is “OS control ON” (step 303: NO), and the control ON / OFF signal Sc of the previous cycle is “US control ON” (step 317: YES), and when the absolute value of the ACT command angle θos * during OS control is smaller than the absolute value of the IFS hold command angle θifs_m * (step 319: YES), the OS hold flag is set (step 323), and the IFS It is determined that the holding command angle θifs_m * is output as the IFS_ACT command angle θifs * (θifs * = θifs_m *, step 325). Thus, while the OS holding flag is set, the IFS holding command angle θifs_m * is output as the IFS_ACT command angle θifs * (step 325), and the IFS holding command angle θifs_m * is output based on the output IFS_ACT command angle θifs *. Is updated (step 338). Thus, the value of the IFS_ACT command angle θifs * is held until any one of the continuation conditions (step 303: NO, step 319: YES) is not satisfied. Step 317 is not a “continuation condition” but a “start condition”.

  (3) After a predetermined time (t1, t2) has elapsed from the start of holding of (1) and (2), the holding ends. That is, when setting the US holding flag, the IFS_ACT command angle calculation unit 68 also resets the US holding timer for measuring the elapsed time th_us from the start of the US holding control (th_us = 0, step 312). Further, when the OS holding flag is set, the OS holding timer for measuring the elapsed time th_os from the start of the OS holding control is also reset (th_os = 0, step 323). If the elapsed time th_us has passed the predetermined time t1 (th_us> t1, step 313: YES), the ACT command angle θus * during US control is changed to the IFS_ACT command angle θifs without executing the processing of step 314. * Is determined to be output (θifs * = θus *, step 307), and the US holding flag is reset (step 327 (step 326: YES)). Similarly, when the elapsed time th_os has passed the predetermined time t2 (th_os> t2, step 324: YES), the OS control ACT command angle θos * is changed to the IFS_ACT command angle without executing the processing of step 325. The output is determined as θifs * (θifs * = θos *, step 318), and the OS holding flag is reset (step 329 (step 328: YES)). Thereby, the US holding control (1) or the OS holding control (2) is completed.

  (4) After holding in (1) above, the absolute value of the ACT command angle θus * during US control is greater than or equal to the absolute value of the IFS hold command angle θifs_m *, or the absolute value of the yaw rate differential value αRy is less than or equal to the threshold value β. In such a case, the holding is ended, the calculated IFS_ACT command angle θifs * is filtered (primary filter, the same applies hereinafter), and the filtered IFS_ACT command angle θifs ** is output.

  That is, the IFS_ACT command angle calculator 68 determines that the absolute value of the ACT command angle θus * during US control is equal to or greater than the absolute value of the IFS hold command angle θifs_m * (| θus * | ≧ | θifs_m * |, Step 308: NO), or If the absolute value of the yaw rate differential value αRy is less than or equal to the predetermined threshold β (| αRy | ≦ β, step 309: NO), the US transition flag is set (step 306). When the US control time ACT command angle θus * is determined to be output as the IFS_ACT command angle θifs * (θifs * = θus *, step 307), the US holding control ends. Thereafter, while the US shift flag is set, the filter process for the IFS_ACT command angle θifs * is executed (step 336), and the IFS_ACT command angle θifs ** after the filter process is output (step 337). ).

  (5) The absolute value of the ACT command angle θos * during OS control when the determination result in the control ON / OFF determination unit 67 is “oversteer control” and the determination result in the previous cycle is “understeer control” Is larger than the absolute value of the IFS hold command angle θifs_m * (| θos * |> | θifs_m * |), the calculated IFS_ACT command angle θifs * is filtered, and the IFS_ACT command after the filter processing is performed. Outputs the angle θifs **.

  That is, in the IFS_ACT command angle calculation unit 68, the control ON / OFF signal Sc is “OS control ON” (step 303: NO), and the control ON / OFF signal Sc of the previous cycle is “US control ON” (step 317: If the absolute value of the OS control ACT command angle θos * is larger than the absolute value of the IFS hold command angle θifs_m * (step 320: YES), the OS transition flag is set (step 321). Thus, thereafter, while the OS shift flag is set, the filter process is executed for the IFS_ACT command angle θifs * (step 336), and the IFS_ACT command angle θifs ** after the filter process is output. (Step 337).

  (6) After the end of the retention after the elapse of the predetermined time in (3) above, the calculated IFS_ACT command angle θifs * is filtered, and the filtered IFS_ACT command angle θifs ** is output.

  That is, the IFS_ACT command angle calculation unit 68 sets the US transition flag when the predetermined time t1 has elapsed since the start of the US holding control (th_us> t1, step 313: YES) (step 306), If the elapsed time th_os from the start of OS holding control has passed the predetermined time t2 (th_os> t2, step 324: YES), the OS transition flag is set (step 321). As a result, while the US transition flag or the OS transition flag is set, the filter process for the IFS_ACT command angle θifs * is executed (step 336), and the IFS_ACT command angle θifs ** after the filter process is output. (Step 337).

  (7) When the determination result in the control ON / OFF determination unit 67 is “understeer control” and the determination result in the previous cycle is “oversteer control”, the calculated IFS_ACT command angle θifs * The filter process is performed, and the IFS_ACT command angle θifs ** after the filter process is output.

  That is, the IFS_ACT command angle calculation unit 68 determines that the control ON / OFF signal Sc is “US control ON” (step 303: YES) and the control ON / OFF signal Sc in the previous cycle is “OS control ON”. In (Step 305: YES), a US transition flag is set (Step 306). Thus, thereafter, while the US shift flag is set, the filter process for the IFS_ACT command angle θifs * is executed (step 336), and the IFS_ACT command angle θifs ** after the filter process is output. (Step 337).

(8) The filtering processes (4) to (6) are continued until a predetermined time (t3, t4) elapses.
That is, when setting the US transition flag, the IFS_ACT command angle calculation unit 68 also resets the US transition timer for measuring the elapsed time tf_us from the start of the filter processing during the understeer control (tf_us = 0, Step 306). Similarly, when setting the OS transition flag, the OS transition timer for measuring the elapsed time tf_os from the start of the filter processing at the time of oversteer control is reset (tf_os = 0, step 321). If it is determined that the elapsed time tf_us has passed the predetermined time t3 (tf_us> t3, step 330: YES), the US transition flag is reset (step 331), and the elapsed time tf_os has passed the predetermined time t4. Is determined (tf_os> t4, step 332: YES), the OS migration flag is reset (step 333). Thus, each filter process is completed.

(Action / Effect)
Next, the operation and effect of the steering apparatus of the present embodiment configured as described above will be described. 11-13 is explanatory drawing which shows the effect | action of the steering apparatus of this embodiment.

  As described above, the OS control ACT command angle θos * for oversteer control and the US control ACT command angle θus * for understeer control are calculated by different methods. For this reason, when the steer characteristic continuously changes without sandwiching a constant neutral steer state, the IFS_ACT command angle θifs * may become discontinuous when the active steer control is switched (see FIGS. 14 and 15). Further, the steering reaction force transmitted to the steering is greatly fluctuated by the operation of the actuator corresponding to the actuator, and there is a possibility that the steering feeling is deteriorated.

  In particular, when switching from understeer control to oversteer control, the generation direction of the ACT command angle θus * during US control and the ACT command angle θos * during OS control is the same, and increases with the decreasing ACT command angle θus * during US control. By combining the ACT command angle θos * during OS control, the IFS_ACT command angle θifs * changes so that its value undulates (see FIG. 14). As a result, the driver feels that the steering reaction force fluctuates more strongly and feels uncomfortable, thereby causing a problem that the tendency of deterioration of the steering feeling becomes more prominent.

  In consideration of this point, in the present embodiment, the IFS_ACT command angle calculation unit 68, when the determination result in the control ON / OFF determination unit 67 is continuously “understeer control” according to the aspect (1), The absolute value of the ACT command angle θus * during US control is smaller than the absolute value of the IFS_ACT command angle θifs * (IFS holding command angle θifs_m *) in the previous cycle (| θus * | <| θifs_m * |) and the yaw rate When the absolute value of the differential value of Ry (the yaw rate differential value αRy) is larger than the predetermined threshold β (| αRy |> β), the value of the output IFS_ACT command angle θifs * is set to the IFS holding command angle θifs_m *. Hold on value.

  That is, the continuous change in the steering characteristic from understeer to oversteer is caused by the fact that the yaw angular velocity at the time of understeer control convergence, that is, the absolute value of the yaw rate differential value αRy exceeds the range in which the vehicle yaw moment can be stably controlled. appear. When the absolute value of the US control ACT command angle θus * is smaller than the absolute value of the IFS holding command angle θifs_m * (US control time ACT command angle θus * in the previous cycle) when continuously understeering. Can be considered that the ACT command angle θus * during the US control is decreasing, that is, when the understeer control converges. In such a case, when the absolute value of the yaw rate differential value αRy exceeds a predetermined threshold value β, it can be estimated that the steering characteristic continuously changes from understeer to oversteer.

  Therefore, as shown in FIG. 11, when the steer characteristic may change continuously from understeer to oversteer during understeer control, the absolute value of the ACT command angle θus * during US control starts to decrease. Also in the situation, it is possible to keep the value of the output IFS_ACT command angle θifs * constant and to suppress the value from changing so as to wave. As a result, it is possible to alleviate the uncomfortable feeling felt by the driver due to fluctuations in the steering reaction force, and to secure a better steering feeling.

  Further, the IFS_ACT command angle calculation unit 68 determines that the determination result in the control ON / OFF determination unit 67 is “oversteer control” and the determination result in the previous cycle is “understeer control” according to the aspect (2). In some cases, when the absolute value of the ACT command angle θos * during OS control is smaller than the absolute value of the IFS hold command angle θifs_m * (| θus * | <| θifs_m * |), the ACT command angle θos during OS control Until the absolute value of * becomes equal to or greater than the absolute value of the IFS holding command angle θifs_m *, or until the predetermined time t2 has elapsed from the start, the value of the output IFS_ACT command angle θifs * is the value of the IFS holding command angle θifs_m * Hold on.

  That is, as shown in FIG. 11, when switching from understeer control to oversteer control, when the absolute value of the ACT command angle θos * during OS control is smaller than the absolute value of the IFS hold command angle θifs_m *, OS control is performed. Until the absolute value of the hour ACT command angle θos * becomes equal to or greater than the absolute value of the IFS hold command angle θifs_m *, the output IFS_ACT command angle θifs * is held constant. Therefore, a wavy change in the IFS_ACT command angle θifs * can be suppressed. In particular, when executed successively from the above mode (1), the value of the IFS_ACT command angle θifs * in the series of active steering controls becomes continuous, and the fluctuation thereof becomes gradual. As a result, a better steering feeling can be ensured.

  Further, the IFS_ACT command angle calculation unit 68 ends the holding after a predetermined time (t1, t2) has elapsed from the start of holding according to the mode of (3) above. As a result, the steering characteristic does not actually change continuously from understeer to oversteer, or the absolute value of the ACT command angle θos * during OS control does not exceed the absolute value of the IFS hold command angle θifs_m *. Nevertheless, the value of the IFS_ACT command angle θifs * can be kept constant, thereby preventing the end of the active steering control from being delayed.

  Further, the IFS_ACT command angle calculation unit 68, according to the mode of (4) above, after the holding of (1) is started, the absolute value of the ACT command angle θus * during US control is greater than or equal to the absolute value of the IFS holding command angle θifs_m *, Alternatively, when the absolute value of the yaw rate differential value αRy becomes equal to or less than the threshold value β, the holding is ended, the calculated IFS_ACT command angle θifs * is filtered, and the filtered IFS_ACT command angle θifs ** Is output.

  As a result, the value of the IFS_ACT command angle θifs * continues to be held even though the steering characteristic does not continuously change from understeer to oversteer after the hold, thereby ending the active steer control. Can be prevented from being delayed. Even when there is a divergence between the absolute value of the ACT command angle θus * during US control and the absolute value of the IFS hold command angle θifs_m * at the end of the US hold control, the IFS_ACT command angle θifs * It is possible to secure a good steering feeling by suppressing the value from changing sharply.

  In addition, the IFS_ACT command angle calculation unit 68, according to the mode (5), the determination result in the control ON / OFF determination unit 67 is “oversteer control”, and the determination result in the previous cycle is “understeer control”. If the absolute value of the ACT command angle θos * during OS control is larger than the absolute value of the IFS hold command angle θifs_m * (| θos * |> | θifs_m * |), the calculated IFS_ACT command The filter process is performed on the angle θifs *, and the IFS_ACT command angle θifs ** after the filter process is output.

  Therefore, as shown in FIG. 12, when switching from understeer control to oversteer control, the absolute value of the ACT command angle θos * during OS control is larger than the absolute value of the IFS hold command angle θifs_m *, and there is a difference between the two. Even if there is, it is possible to suppress a steep change in the IFS_ACT command angle θifs * and to ensure a good steering feeling.

  Further, the IFS_ACT command angle calculation unit 68 performs the filter process on the calculated IFS_ACT command angle θifs * after the end of the predetermined time elapse in (3) according to the mode of (6), and performs the filter process. The subsequent IFS_ACT command angle θifs ** is output.

  Thus, there is a difference between the absolute value of the US control ACT command angle θus * or the OS control ACT command angle θos * and the IFS hold command angle θifs_m * at the end of the US hold control or the OS hold control due to time over. Even in this case, it is possible to suppress a steep change in the IFS_ACT command angle θifs * and to secure a good steering feeling.

  Further, the IFS_ACT command angle calculation unit 68 uses the aspect (7) above, the determination result in the control ON / OFF determination unit 67 is “understeer control”, and the determination result in the previous cycle is “oversteer control”. If there is, filter processing is performed on the calculated IFS_ACT command angle θifs *, and the filtered IFS_ACT command angle θifs ** is output.

  Therefore, as shown in FIG. 13, the steer characteristic continuously changes from oversteer to understeer, and at the time of switching from oversteer control to understeer control, US control ACT command angle θus * and OS control ACT Even when there is a deviation from the command angle θos *, it is possible to suppress a steep change in the IFS_ACT command angle θifs * and to ensure a good steering feeling.

  In addition, the IFS_ACT command angle calculation unit 68 continues the filtering processes (4) to (7) until a predetermined time (t3, t4) elapses according to the aspect (8). As a result, it is possible to prevent the change rate of the IFS_ACT command angle θifs * caused by the continuation of the filter process from slowing and the accompanying decrease in the active steering function.

In addition, you may change this embodiment as follows.
In the present embodiment, the present invention is embodied in the steering device 1 having the variable gear ratio system, and the active steering control is performed by controlling the ACT angle θta based on the operation of the variable gear ratio actuator 7. . However, the present invention is not limited to this, and a drive unit that can change the turning angle θt other than the gear ratio variable actuator 7 may be used to implement active steering control.

  In the present embodiment, the IFS_ACT command angle calculation unit 68 uses the yaw rate Ry as the vehicle state quantity related to the yaw moment of the vehicle. However, the present invention is not limited to this, and the slip angle θsp may be used, and both the yaw rate Ry and the slip angle θsp may be used.

  In the present embodiment, the steering device 1 includes the EPS actuator 17 that uses the motor 22 as a drive source, but the power assist device may be hydraulic. Further, the present invention may be embodied in a vehicle steering device that does not include a power assist device.

The schematic block diagram of a steering device. Explanatory drawing of gear ratio variable control. Explanatory drawing of gear ratio variable control. The control block diagram of a steering device. The flowchart which shows the aspect of the arithmetic processing in IFSECU. The control block diagram of an IFS control calculating part. The flowchart which shows the aspect of the IFS control calculation process in an IFS control calculation part. The flowchart which shows the process sequence of IFS_ACT command angle calculation. The flowchart which similarly shows the process sequence of IFS_ACT command angle calculation. The flowchart which similarly shows the process sequence of IFS_ACT command angle calculation. Explanatory drawing which shows the effect | action of the IFS_ACT command angle calculation of this embodiment. Explanatory drawing which similarly shows the effect | action of IFS_ACT command angle calculation of this embodiment. Explanatory drawing which similarly shows the effect | action of IFS_ACT command angle calculation of this embodiment. The wave form diagram which shows transition of the US control component, OS control component, and active control command at the time of shifting continuously from understeer control to oversteer control. The wave form diagram which shows transition of OS control component, US control component, and active control command at the time of transfering continuously from oversteer control to understeer control control.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Steering device, 2 ... Steering, 6 ... Steered wheel, 7 ... Gear ratio variable actuator, 8 ... IFSECU, 35 ... IFS control calculating part, 61 ... Vehicle model calculating part, 63 ... Steer characteristic calculating part, 65 ... OS control Calculation unit 66 ... US control calculation unit 67 ... Control ON / OFF determination unit 68 ... IFS_ACT command angle calculation unit Ry ... Yaw rate, αRy ... Yaw rate differential value, θsp ... Slip angle, θt ... Steering angle, θts ... Steer turning angle, θta: ACT angle, θifs *, θifs **: IFS_ACT command angle, θos *: ACT command angle during OS control, θus *: ACT command angle during US control, Val_st: OS / US characteristic value, Sc ... control ON / OFF signal, θifs_m * ... IFS hold command angle, β ... threshold value, th_us, th_os, tf_us, tf_os, tx ... elapsed time, t1, t2, t3, t4 ... predetermined time.

Claims (11)

Drive means capable of changing the turning angle of the steered wheels, and control means for controlling the operation of the drive means, wherein the control means sets the turning angle to control the yaw moment of the vehicle based on the vehicle model. A vehicle steering apparatus having an active steering function to control,
The control means includes
Oversteer control for controlling the turning angle to change in the direction opposite to the yaw moment when the vehicle is in an oversteer state, or the turning angle is reduced when the vehicle is in an understeer state. Control determining means for determining which active steer control of under steer control to be controlled is executed,
OS control calculation means for calculating an OS control component for the oversteer control;
US control calculation means for calculating a US control component for the understeer control;
Active steer control calculating means for calculating which of the OS control component or the US control component is output as an active control command for performing active steer control according to the determination result of the control determining means;
The active steer control calculating means performs the calculation every predetermined cycle,
When the determination result is continuously understeer control, the absolute value of the US control component is smaller than the absolute value of the active control command at the previous calculation, and the differential value of the vehicle state quantity related to the yaw moment of the vehicle is A vehicle steering apparatus characterized by holding the value of the active control command at the value at the time of the previous calculation when it is larger than a predetermined threshold. The vehicle steering apparatus according to claim 1,
The active steer control calculation means is configured such that when the determination result is oversteer control and the determination result at the previous calculation is understeer control, the absolute value of the OS control component is the active control command at the previous calculation. If the absolute value of the OS control component is smaller than the absolute value of the active control command, the value of the active control command is held at the value of the previous calculation until the absolute value of the OS control component becomes equal to or greater than the absolute value of the active control command at the previous calculation. thing,
A vehicle steering apparatus characterized by the above. In the vehicle steering device according to claim 1 or 2,
The vehicle steering apparatus according to claim 1, wherein the active steering control calculating means ends the holding after a predetermined time has elapsed from the start of the holding. In the steering device for vehicles according to any one of claims 1 to 3,
After the holding, if the absolute value of the US control component is equal to or greater than the absolute value of the active control command at the time of the previous calculation or the differential value of the vehicle state quantity is equal to or less than a predetermined threshold, the holding is terminated. Filtering the calculated active control command;
A vehicle steering apparatus characterized by the above. In the vehicle steering device according to any one of claims 1 to 4,
The active steer control calculation means is configured such that when the determination result is oversteer control and the determination result at the previous calculation is understeer control, the absolute value of the OS control component is the active control command at the previous calculation. When the absolute value of the vehicle is larger than the absolute value of the vehicle, the vehicle steering apparatus is characterized in that the calculated active control command is filtered. In the steering device for vehicles according to any one of claims 1 to 5,
The active steer control calculating means performs a filtering process on the calculated active control command after completion of the holding due to the elapse of the predetermined time;
A vehicle steering apparatus characterized by the above. Drive means capable of changing the turning angle of the steered wheels, and control means for controlling the operation of the drive means, wherein the control means sets the turning angle to control the yaw moment of the vehicle based on the vehicle model. A vehicle steering apparatus having an active steering function to control,
The control means includes
Oversteer control for controlling the turning angle to change in the direction opposite to the yaw moment when the vehicle is in an oversteer state, or the turning angle is reduced when the vehicle is in an understeer state. Control determining means for determining which active steer control of under steer control to be controlled is executed,
OS control calculation means for calculating an OS control component for the oversteer control;
US control calculation means for calculating a US control component for the understeer control;
Active steer control calculating means for calculating which of the OS control component or the US control component is output as an active control command for performing active steer control according to the determination result of the control determining means;
The active steer control calculating means performs the calculation every predetermined cycle,
A vehicle steering apparatus, wherein when the determination result is understeer control and the determination result at the time of previous calculation is oversteer control, a filter process is performed on the calculated active control command. In the vehicle steering device according to any one of claims 4 to 7,
The vehicle steering apparatus, wherein the active steering control calculation means continues the filtering process until a predetermined time elapses. In the vehicle steering device according to any one of claims 1 to 8,
The OS control calculation means calculates the OS control component by feedback control calculation of a target value and an actual value of the vehicle state quantity calculated based on a vehicle model,
The vehicle steering apparatus according to claim 1, wherein the US control calculation means calculates the US control component based on an analog value that continuously changes in accordance with a steering characteristic of the vehicle. In the vehicle steering device according to any one of claims 1 to 9,
The vehicle state quantity is at least one of a yaw rate or a slip angle of the vehicle;
A vehicle steering apparatus characterized by the above. Drive means capable of changing the turning angle of the steered wheels, and control means for controlling the operation of the drive means, wherein the control means sets the turning angle to control the yaw moment of the vehicle based on the vehicle model. A vehicle steering apparatus having an active steering function to control,
The control means includes
Oversteer control for controlling the turning angle to change in the direction opposite to the yaw moment when the vehicle is in an oversteer state, or the turning angle is reduced when the vehicle is in an understeer state. Control determining means for determining which active steer control of under steer control to be controlled is executed,
OS control calculation means for calculating an OS control component for the oversteer control;
US control calculation means for calculating a US control component for the understeer control;
Active steer control calculating means for calculating the OS control component or the US control component as an active control command for performing active steer control according to the determination result of the control determining means,
The active steer control calculating means performs the calculation every predetermined cycle,
Comprising estimation means for estimating a continuous change in a vehicle steering characteristic from the understeer state to the oversteer state;
When it is estimated that the understeer state continuously changes to the oversteer state, the value of the active control command is held at the value at the previous calculation,
A vehicle steering apparatus characterized by the above.

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