JP2014054885A - Electric power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric power steering device that facilitates tuning, can prevent brake judder or brake shimmy to obtain safe and comfortable steering performance, and in an automatic steering mode, enables proper steering according to a calculated target steering angle and enables smooth steering even at a steep target steering angle, and even at slow vehicle speed enables steering according to the target steering angle by increasing responsiveness or steady state deviation.SOLUTION: An electric power steering device comprises: a steering angle control portion 200 for calculating a motor-current command value; and a switched portion 142. The steering angle control portion 200 is composed of: a feed back control portion for producing a feed back control-current command value; a SAT compensation portion for producing a SAT compensation-current command value; and an output portion for producing the motor-current command value on the basis of the feed back control-current command value and the SAT compensation-current command value. The switched portion is switched responding to switching command in an automatic steering mode and in a manual steering mode, and in the automatic steering mode, a motor is driven and controlled based on the motor-current command value.

Description

  The present invention relates to an electric power steering apparatus having functions of an automatic steering mode (parking assist mode) and a manual steering mode, and applying an assist force by a motor to a steering system of a vehicle. The present invention relates to an electric power steering apparatus that further improves the followability of a rudder angle to a target steering angle.

  An electric power steering device that applies a steering assist force (assist force) to a steering mechanism of a vehicle by a rotational force of a motor, a steering shaft or a rack shaft by a transmission mechanism such as a gear or a belt via a speed reducer. A steering assist force is applied to the vehicle. Such a conventional electric power steering device (EPS) performs feedback control of the motor current in order to accurately generate the torque of the steering assist force. In feedback control, the motor applied voltage is adjusted so that the difference between the steering assist command value (current command value) and the motor current detection value is small. The adjustment of the motor applied voltage is generally performed by PWM (pulse width). This is done by adjusting the duty of modulation) control.

  The general configuration of the electric power steering apparatus will be described with reference to FIG. 1. A column shaft (steering shaft) 2 of the handle 1 is passed through a reduction gear 3, universal joints 4a and 4b, a pinion rack mechanism 5, and tie rods 6a and 6b. Furthermore, it is connected to the steering wheels 8L and 8R via the hub units 7a and 7b. The column shaft 2 is provided with a torque sensor 10 that detects the steering torque of the handle 1, and a motor 20 that assists the steering force of the handle 1 is connected to the column shaft 2 via the reduction gear 3. . The control unit (ECU) 100 that controls the electric power steering apparatus is supplied with electric power from the battery 13 and also receives an ignition key signal via the ignition key 11. The control unit 100 calculates a steering assist command value of an assist (steering assist) command based on the steering torque Th detected by the torque sensor 10 and the vehicle speed Vel detected by the vehicle speed sensor 12, and obtains the steering assist command value. The current supplied to the motor 20 is controlled by the current control value E subjected to compensation or the like. The vehicle speed Vel can also be received from a CAN (Controller Area Network) or the like.

  In such an electric power steering apparatus, conventionally, as shown in, for example, Japanese Patent Application Laid-Open No. 8-290778 (Patent Document 1), the robust stabilization compensator in the control unit 100 provides system stability, road surface information, and disturbance. Information sensitivity characteristics are designed at the same time.

  However, in such a conventional control device, since the reaction force at the time of steering near the steering neutral point is small, it is difficult to accurately convey road surface information to the driver due to the influence of friction. Further, in the conventional electric power steering apparatus, it is difficult to make the hysteresis characteristic between the steering angle and the steering force equal to that of the hydraulic power steering.

  As an apparatus for solving such a problem, there is an apparatus disclosed in Japanese Patent Laid-Open No. 2002-369565 (Patent Document 2).

  The outline of the apparatus disclosed in Patent Document 2 will be described with reference to FIG. 2 corresponding to FIG. A motor 20 that generates an auxiliary steering force of the steering device is driven by a motor drive unit 21, and the motor drive unit 21 is controlled by a control unit 100 indicated by a two-dot chain line. The control unit 100 includes a steering torque Th from a torque sensor and The vehicle speed Vel from the vehicle speed detection system is input. In the motor 20, the motor terminal voltage Vm and the motor current value i are measured and output.

  The control unit 100 includes a torque system control unit 110 indicated by a broken line that performs control using the steering torque Th, and a motor system control unit 120 indicated by an alternate long and short dash line that performs control related to driving of the motor 20. The torque system control unit 110 includes an assist amount calculation unit 111, a differential control unit 112, a yaw rate convergence control unit 113, a robust stabilization compensation unit 114, and a self-aligning torque (SAT) estimation feedback unit 115. 116B and a subtracting unit 116C. The motor system control unit 120 includes a compensation unit 121, a disturbance estimation unit 122, a motor angular velocity calculation unit 123, a motor angular acceleration calculation unit 124, and a motor characteristic compensation unit 125, and includes addition units 126A and 126B.

  The steering torque Th is input to the assist amount calculation unit 111, the differential control unit 112, the yaw rate convergence control unit 113, and the SAT estimation feedback unit 115, and all use the vehicle speed Vel as a parameter input. The assist amount calculation unit 111 calculates the assist torque amount based on the steering torque Th, and the yaw rate convergence control unit 113 receives the steering torque Th and the motor angular velocity ω, and controls the steering wheel in order to improve the yaw convergence of the vehicle. The brakes are applied to the movement of the swaying. Further, the differential control unit 112 enhances control responsiveness near the neutral point of the steering and realizes smooth and smooth steering. The SAT estimation feedback unit 115 includes a steering torque Th and an assist amount calculation unit 111. The signal obtained by adding the output of the differentiation control unit 112 to the output of the addition unit 116A, the angular velocity ω calculated by the motor angular velocity calculation unit 123, and the angular acceleration α from the motor angular acceleration calculation unit 124 are input, and SAT is calculated. The estimated SAT is signal-processed using a feedback filter, and appropriate road surface information is given to the steering wheel as a reaction force.

  Further, robust stabilization is achieved by using the signal obtained by adding the output of the differentiation control unit 112 to the output of the assist amount calculation unit 111 by the addition unit 116A and the output of the yaw rate convergence control unit 113 by the addition unit 116B7 as the assist amount AQ. This is input to the compensation unit 114. The robust stabilization compensator 114 is a compensator disclosed in, for example, Japanese Patent Laid-Open No. 8-290778, and removes the peak value at the resonance frequency of the resonance system including the inertia element and the spring element included in the detected torque, and performs control. It compensates for the phase shift of the resonance frequency that hinders the responsiveness and stability of the system. By adding the output of the SAT estimation feedback unit 115 from the output of the robust stabilization compensator 114 by the adder 116C, an assist amount Ia that can transmit road surface information to the steering wheel as a reaction force is obtained.

  Further, the motor angular velocity calculation unit 123 calculates the motor angular velocity ω based on the motor terminal voltage Vm and the motor current value i. The motor angular velocity ω is calculated by the motor angular acceleration calculation unit 124, the yaw rate convergence control unit 113, and the SAT. Input to the estimation feedback unit 115. The motor angular acceleration calculation unit 124 calculates the motor angular acceleration α based on the input motor angular velocity ω, and the calculated motor angular acceleration α is input to the motor characteristic compensation unit 125. The assist amount Ia obtained by subtracting the output of the SAT estimation feedback unit 115 from the output of the robust stabilization compensation unit 114 is added to the output Ic of the motor characteristic compensation unit 125 by the addition unit 126A, and the addition signal is differentiated as the current command value Ir. The data is input to the compensation unit 121 including a compensation unit. A signal obtained by adding the output of the disturbance estimation unit 122 to the current command value Ira compensated by the compensation unit 121 by the addition unit 126B is input to the motor driving unit 21 and the disturbance estimation unit 122. The disturbance estimation unit 122 is a device as disclosed in JP-A-8-310417, and is a signal obtained by adding the output of the disturbance estimation unit 122 to the current command value Ira compensated by the compensation unit 121 that is a control target of the motor output. Based on the motor current value i, the desired motor control characteristic in the output reference of the control system can be maintained, and the stability of the control system is not lost.

Here, the state of the torque generated between the road surface and the steering will be described with reference to FIG. A steering torque Th is generated when the driver steers the handle 1, and the motor 20 generates an assist torque Tm according to the steering torque Th. As a result, the wheels are steered and SAT is generated as a reaction force. Further, at that time, torque serving as steering steering resistance is generated by the inertia J and friction (static friction) Fr of the motor 20. Considering the balance of these forces, the following equation of motion is obtained using sign () as a sign function.
(Equation 1)
J ・ α + Fr ・ sign (ω) + SAT = Tm + Th

Here, when the above equation 1 is Laplace transformed with an initial value of zero and the SAT is solved, the following equation 2 is obtained.
(Equation 2)
SAT (s) = Tm (s) + Th (s) −J ・ α (s) −Fr ・ sign (ω (s))

As can be seen from Equation 2, the SAT is estimated from the motor angular velocity ω, the motor angular acceleration α, the steering assist force Tm, and the steering torque Th by previously obtaining the inertia J and the static friction Fr of the motor 20 as constants. Can do. For this reason, the steering torque Th, the motor angular velocity ω, the motor angular acceleration α, and the output of the assist amount calculation unit 111 are input to the SAT estimation feedback unit 115, respectively.

  Further, when the SAT estimated current value * SAT estimated by the SAT estimation feedback unit 115 is fed back as it is, the steering becomes too heavy, and thus the steering feeling cannot be improved. Therefore, as shown in FIG. 4, the SAT estimated current value * SAT is signal-processed using a feedback filter 115A having a vehicle speed sensitivity gain and a frequency characteristic, and only necessary and sufficient information for improving the steering feeling is fed back. . The feedback filter used here has a Q filter (phase delay) 115B having a gain that reduces the estimated SAT size to a necessary and sufficient value as a static characteristic gain, and a gain unit that is sensitive to the vehicle speed Vel as shown in FIG. When the road surface information such as stationary driving and low-speed traveling is relatively low, the road surface information to be fed back is reduced.

  In the device described in Patent Document 2 described above, the feedback of the SAT estimation is configured so that the frequency band in which the disturbance to be suppressed exists and the frequency band in which the disturbance to be transmitted exist are compatible. There is no function of aggressive cancellation.

  On the other hand, in a vehicle, brake judder and shimmy that cause discomfort to the occupant occur during normal braking and steady running. Brake judder is floor pedal vibration that occurs during braking of a vehicle, and may be accompanied by vibration in the direction of steering rotation. Brake torque fluctuation generated by DTV (Disk Thickness Variation) of the brake disk is a vibration source, and has a primary component and a high-order component of wheel rotation. This is amplified by resonance before and after the suspension, etc., and transmitted to the vehicle body and the steering system to become floor pedal vibration and steering vibration. Shimmy is vibration that occurs in the direction of steering rotation when the vehicle is running. Unbalanced and non-uniformity of rotating parts such as tires and wheels is the source of vibration, and is amplified by suspension resonance. Vibration in the direction of rotation.

  Such a brake judder and shimmy are not considered at all in the device of Patent Document 2, and Japanese Patent Application Laid-Open No. 2002-145075 (Patent Document 3) and Japanese Patent Application Laid-Open No. 2002-161969 (Patent Document 4) describe the brake judder and shimmy. Although devices for attenuating vibration are disclosed, there are problems that all of them are mechanical measures, increase costs, and cannot be finely controlled such as sensitivity to vehicle speed.

  Further, when the inertia and friction of the steering system are large, the vibration caused by the brake judder is not transmitted to the steering wheel, but it is desirable for the inertia and friction of the steering system to be as small as possible for good steering feeling and vehicle stability.

  In such an electric power steering apparatus, in recent years, a vehicle having a parking assist function (parking assist) and switching between an automatic steering mode and a manual steering mode has emerged. Sets a target steering angle based on data such as a camera (image) and a distance sensor, and automatic control is performed according to the target steering angle.

  In WO 2008/146372 (Patent Document 5), a target sub steering angle or target steering angle added by a sub steering angle superimposing mechanism is generated based on a steering wheel angle detection value and a transmission characteristic from a steering wheel angle detection unit. Thus, the target sub steering angle and the sub steering angle detection value from the sub steering angle detection means match, or the target sub steering angle and the sub steering angle detection value from the sub steering angle detection means match, Target drive amount calculation means for calculating the target drive amount of the motor and motor drive means for driving the motor according to the target drive amount are provided, and the steered wheels are steered according to the steering of the driver's steering wheel.

JP-A-8-290778 JP 2002-369565 A JP 2002-145075 A Japanese Patent Laid-Open No. 2002-161969 WO 2008/146372

  However, in the electric power steering device described in Patent Document 5, since the rate limiting process is not performed on the target steering angle, the driver's steering feeling is impaired when the target steering angle changes abruptly. turn into. In addition, since gain control according to the vehicle speed is not performed, there is a problem that precise control corresponding to the vehicle speed cannot be performed.

  In addition, steering angle control of the steering wheel is performed in automatic steering modes such as parking assistance and automatic driving, but the friction (SAT) that the tire receives from the road surface changes due to the influence of vehicle speed, road surface conditions (tilt, humidity, etc.) Thus, there is a problem that the followability of the actual steering angle with respect to the target steering angle of the column shaft angle changes, and there is a demand for a solution to such a problem.

  The present invention has been made under the circumstances described above, and the object of the present invention is to facilitate tuning by performing signal processing such as road surface information in a high frequency region, and to suppress brake judder and shimmy. Safe and comfortable steering performance can be obtained, and in the automatic steering mode (parking assist function), the steering can be accurately performed according to the calculated target steering angle, and even if the target steering angle is abrupt steering, the steering can be smoothly performed. It is another object of the present invention to provide an electric power steering device that can always follow the target steering angle by increasing the responsiveness or steady deviation.

  The present invention calculates a motor current command value 1 based on the steering torque and the vehicle speed, drives the motor based on the motor current command value 1 to perform assist control of the steering system, and includes an automatic steering mode and a manual steering mode. The object of the present invention is to provide a motor current command based on the target steering angle, the actual steering angle, the motor angular velocity and motor angular acceleration of the motor, the steering torque, and the previous current command value. A steering angle control unit that calculates a value 2; and a switching unit that inputs and switches the motor current command value 1 and the motor current command value 2, and the steering angle control unit includes the target steering angle and the actual steering. A feedback control unit that generates a feedback control current command value based on the angle, the motor angular velocity, and the steering torque; the motor angular velocity; A SAT compensation unit that generates an SAT compensation current command value based on angular acceleration, the steering torque, and the previous current command value; and generates the motor current command value 2 from the feedback control current command value and the SAT compensation current command value An output unit that switches the switching unit according to a switching command between the automatic steering mode and the manual steering mode, and drives and controls the motor based on the motor current command value 2 in the automatic steering mode. Is achieved.

  The object of the present invention is to provide a rate limiter for smoothing the target steering angle by the feedback control unit, an LPF connected to the output of the rate limiter, and an angular deviation between the output of the LPF and the actual steering angle. A proportional gain, a first proportional gain section, an integral gain section that integrates the speed deviation between the error speed from the first proportional gain section and the motor angular speed, and multiplies the integral gain, and the speed deviation is multiplied by the proportional gain. A differential gain unit that differentiates the steering torque and multiplies the differential gain, and an output value of the differential gain unit is a deviation value between an output of the integral gain unit and an output of the second proportional gain unit. Or an output unit that limits the upper and lower limit values and outputs the feedback control current command value, or the SAT compensation unit includes the steering torque, The SAT estimation unit calculates a SAT estimated current value based on the motor angular velocity, the motor angular acceleration, and the previous current command value, and inputs the SAT estimated current value, and has a cutoff frequency characteristic higher than the angular response frequency. An LPF and a vehicle speed sensitive gain unit that multiplies the output of the LPF by a vehicle speed variable gain and outputs the SAT compensation current command value, or the SAT estimation unit performs viscous friction on the motor angular velocity. A viscous friction coefficient part that multiplies a coefficient; an encoded Coulomb friction part that encodes the motor angular velocity and multiplies Coulomb friction; a total inertia moment part that multiplies the motor angular acceleration by a total inertia moment; and the viscous friction coefficient The steering torque is subtracted from an added value of the output of the encoder and the output of the encoded coulomb friction unit, and the total moment of inertia part An output coefficient unit that adds the output and multiplies the coefficient, or the SAT estimation unit adds the current command value corresponding to the assist torque and the steering torque, and the motor angle A first subtraction unit that subtracts a value obtained by multiplying the acceleration by inertia from the addition result of the addition unit, and a value obtained by encoding the motor angular velocity and multiplying the friction is subtracted from the subtraction result of the first subtraction unit. By being configured with a second subtracting unit that outputs the SAT estimated current value, or by connecting a limiter that limits upper and lower limit values downstream of the vehicle speed sensitive gain unit, it is more effective. Achieved.

  According to the electric power steering apparatus of the present invention, in a vehicle having an automatic steering mode (parking support function) and a manual steering mode, a target steering angle calculated from data such as a camera (image) and a distance sensor is taken into consideration for the vehicle speed. Therefore, the steering can be accurately performed with respect to the target steering angle, and the driver does not feel uncomfortable. In addition, since the abrupt target steering angle is controlled in a smooth manner, the driver will not feel uneasy even in automatic driving.

  Furthermore, the control gain is increased at low vehicle speeds to increase responsiveness or steady state deviation, and the target steering angle can be approached even at low vehicle speeds.

  Furthermore, the SAT is estimated, the estimated SAT is filtered with an LPF set to a cutoff frequency higher than the angular response frequency, and the value after filtering is multiplied by a vehicle speed gain set according to the vehicle speed, as a compensation value. Since the addition is performed, the followability of the actual steering angle to the target steering angle can be further improved.

It is a lineblock diagram showing an outline of an electric power steering device. It is a block diagram which shows the structural example of the control system of an electric power steering apparatus. It is a schematic diagram which shows the mode of the torque generate | occur | produced between a road surface and a steering system. It is a block diagram which shows the structural example of a feedback part. It is a figure which shows the example of a characteristic of a feedback filter. It is a characteristic view for demonstrating the principle of this invention. It is a block diagram which shows the structural example of this invention. It is a block diagram which shows the structural example of a steering angle control part. It is a block diagram which shows the structural example of a feedback control part. It is a block block diagram which shows an example of a rate limiter. It is a block diagram which shows the structural example of a variation setting part. It is a block diagram which shows the structural example of a SAT compensation part. It is a characteristic view which shows the example of a characteristic of a vehicle speed sensitive gain part. It is a flowchart which shows the operation example of this invention. It is a flowchart which shows the operation example of a steering angle control part. It is a flowchart which shows the operation example of a feedback control part. It is a flowchart which shows the operation example of a SAT compensation part. It is a block diagram which shows the other structural example of a SAT compensation part.

  Steering angle control of the steering wheel is performed in automatic steering modes such as parking assistance and automatic driving, but the friction (SAT) that the tire receives from the road surface changes due to the effects of vehicle speed, road surface conditions (tilt, moisture, etc.), etc. There is a problem that the followability of the actual steering angle with respect to the target steering angle of the shaft angle changes. To solve this problem, the present invention estimates the SAT, filters the estimated SAT with an LPF set to a cutoff frequency higher than the angle response frequency, and sets the filtered SAT value according to the vehicle speed. Is added to the current command value as a compensation value, thereby improving the followability of the actual steering angle to the target steering angle.

  In the present invention, by adding the feedback control current command value generated by the feedback control unit to the SAT compensation current command value generated by the SAT compensation unit, the direction to cancel the influence of the reaction force (SAT) that the tire receives from the road surface The motor torque is generated. Thereby, the influence of the SAT disturbance generated during the steering angle control can be suppressed, and the followability of the steering angle control with respect to the target steering angle can be improved. For example, in the parking assist operation, the SAT varies according to the friction μ between the tire and the road surface, and the response of the rudder angle changes accordingly. As another example, when the road surface tilts in the left-right direction during automatic driving, the SAT is applied in a certain direction. Therefore, the steering angle temporarily deviates from the target steering angle due to this effect. Will occur. As means for solving these problems, the steering angle control with better followability is made possible by subtracting the SAT compensation current command value from the feedback control current command value.

  FIG. 6A shows an example of a steering angle response waveform, and FIG. 6B shows an example of a SAT estimated value waveform. 6A and 6B show respective response waveforms when the SAT disturbance step as shown in FIG. 6C is input after 1 second from time (second). In the present invention, an LPF (low-pass filter) that cuts high-frequency components of disturbance is used for a compensation path of a SAT estimated value that has a function of extracting and canceling disturbance components, and depending on the magnitude of the cutoff frequency Fc of the LPF. The steering angle response waveform and the SAT estimated value waveform change. When a SAT disturbance step as shown in FIG. 6C is input, the SAT estimated value waveform shown in FIG. 6B rises as indicated by an arrow B as the cutoff frequency Fc of the LPF increases. It becomes large and can cancel disturbances at high speed. As a result, the rudder angle fluctuates as shown by arrow A from no SAT estimation as shown in FIG. 6A, and the rudder angle response can be improved as the cut-off frequency Fc is increased. Therefore, it is possible to prevent the handle from rotating suddenly.

  Even in a vehicle having an automatic steering mode and a manual steering mode, the road surface reaction force (SAT) transmitted to the steering system through the tire varies depending on the vehicle speed. Therefore, when the steering is automatically controlled to the calculated target steering angle in the automatic steering mode, the response of the steering angle varies depending on the vehicle speed. Therefore, in the present invention, the motor current command value for automatic control is adjusted according to the vehicle speed so as to reduce the influence of the road surface reaction force that the tire receives from the road surface. Furthermore, in the present invention, the target steering angle is smoothed by a rate limiter, and the response of the steering wheel steering angle can be reduced even when the target steering angle changes suddenly. Regardless of the vehicle speed, the vehicle can be moved accurately with respect to the target steering angle, which is safer for the driver.

  Embodiments of the present invention will be described below in detail with reference to the drawings.

  FIG. 7 shows a configuration example of the present invention. A rotation sensor 151 such as a resolver for detecting a motor rotation angle θs is connected to the motor 150. The motor 150 includes an ECU 130 and an EPS (electric power) on the vehicle side. The drive is controlled via the ECU 140 on the steering device side.

The ECU 130 on the vehicle side, based on a button, switch or the like indicating the driver's intention, outputs a switching command unit 131 that outputs a switching command SW for the automatic steering mode or the manual steering mode, and signals from a camera (image) and a distance sensor. And a target steering angle generator 132 that generates a target steering angle θt based on the above. The actual steering angle θr detected by the steering angle sensor 152 provided on the column shaft and the vehicle speed Vel from the vehicle speed sensor 153 are input to the steering angle control unit 200 in the ECU 140 on the EPS side via the ECU 130. The rudder angle sensor 152 may be a column angle (including intermediate and pinion shafts), a rack and pinion rack displacement, and a rudder angle estimated value based on wheel speed. The vehicle speed Vel can also be received from CAN or the like. The switching command unit 131 is a signal for identifying that the vehicle enters the automatic steering mode, for example, a button or a switch provided on the dashboard or around the steering wheel. Alternatively, a switching command SW is output based on a vehicle state signal based on a parking mode provided in the shift, and the switching command SW is input to the switching unit 142 in the ECU 140 on the EPS side. The target steering angle generation unit 132 generates a target steering angle θt by a known method based on data such as a camera (image) and a distance sensor, and the generated target steering angle θt is steered in the ECU 140 on the EPS side. Input to the angle controller 200.

  The ECU 140 on the EPS side outputs a motor current command value Itref calculated as described above based on the steering torque Th and the vehicle speed Vel, the target steering angle θt, the actual steering angle θr, the vehicle speed Vel, the torque A steering angle control unit 200 that calculates and outputs a motor current command value Imref for steering angle automatic control based on the steering torque Th, the motor angular velocity ω, and the motor angular acceleration α from the sensor 154, and the motor current by the switching command SW. A switching unit 142 that switches between the command values Itref and Imref, a current control / drive unit 143 that drives and controls the motor 150 based on a motor current command value (Itref or Imref) from the switching unit 142, and a motor rotation from the rotation sensor 151 A motor angular speed calculator 144 that calculates a motor angular speed ω based on the angle θs; It has and a motor angular acceleration calculation unit 145 for calculating the motor angular acceleration α based on the speed omega. The switching unit 142 switches between a torque control mode (manual steering mode) by the torque control unit 141 and an automatic steering mode by the rudder angle control unit 200 based on a switching command SW from the switching command unit 131 of the ECU 130, and torque control. The motor current command value Itref is output in the mode, and the motor current command value Imref is output in the automatic steering mode. The current control / driving unit 143 includes a PI current control unit, a PWM control unit, an inverter, and the like.

The configuration of the steering angle control unit 200 is as shown in FIG. 8, and the target steering angle θt, the actual steering angle θr, the motor angular velocity ω, and the steering torque Th are input to calculate the feedback control current command value Ifref. SAT compensation that outputs the SAT compensation current command value Isref by inputting the feedback control unit 210, the motor angular velocity ω, the steering torque Th, the motor angular acceleration α, and the previous current command value Iref (Z ⁻¹ ). Unit 230, addition unit 201 for adding SAT compensation current command value Isref to feedback control current command value Ifref and outputting motor current command value Imo, and adding motor current command value Imo to current command value for motor current command And an adder 202 that outputs the value Imref.

  The feedback control unit 210 has a function of suppressing torsional vibration generated by a torsion bar and steering inertia. Further, the adder 201 and the adder 202 constitute an output unit.

  The feedback control unit 210 has a configuration as shown in FIG. 9 and is a position control system in which the speed control loop system is a minor loop. Smoothing when the target steering angle θt changes abruptly, that is, a predetermined time. The target steering angle θt is input to the rate limiter 211 that smoothly changes within the range of the change rate, and the target steering angle θta that has passed through the LPF 212 that removes high-frequency disturbances is input to the subtraction unit 213A. The actual steering angle θr is subtracted and input to the subtracting unit 213A, the angular deviation from the smoothed target steering angle θta is multiplied by the gain Kpp by the proportional gain (Kpp) unit 214, and added to the subtracting unit 213B as the error speed ωe. The The motor angular speed ω is subtracted and input from the motor angular speed calculation unit 144 to the subtraction unit 213B, and the calculated speed deviation Df is multiplied by the gain Kvi by the integration gain (Kvi) unit 216B via the integration unit 216A and added to the subtraction unit 213C. At the same time, the speed deviation Df is multiplied by the gain Kvp by the proportional gain (Kvp) unit 216C and is subtracted and input to the subtraction unit 213C. The subtraction result in the subtraction unit 213C is input to the addition unit 213D.

  The steering torque Th from the torque sensor 154 passes through the differentiating unit 215A, is multiplied by the gain Kc by the differential gain (Kc) unit 215B, and is input to the adding unit 213D. And output as a feedback control current command value Ifref. The subtracting unit 213C, the adding unit 213D, and the limiter 217 constitute an output unit.

The rate limiter 211 smoothes and outputs when the target steering angle θt changes suddenly. For example, the rate limiter 211 is configured as shown in FIG. That is, the target steering angle θt is added and input to the subtracting unit 211-1, and the steering angle θt1, which is a result of subtraction from the past value, is set by the variation setting unit 211-2 as the variation θt2. The change setting unit 211-2 sets a difference θt1 between the past value from the holding unit (Z ⁻¹ ) 211-4 and the input (θt), and the change θt2 in the addition unit 211-3 and the past value are set. The addition result is output as a new target steering angle θt3. The change setting unit 211-2 prevents the change from exceeding the set upper limit and lower limit, and its characteristics are obtained by obtaining a difference from the input (target steering angle) θt for each calculation cycle T and changing. When the value is outside the upper and lower limits of the minute setting unit 211-2, the output θt 3 is changed in a stepwise manner as shown in FIG. The output θt3 is made to coincide with the target steering angle θt. When the difference from the input (target steering angle) θt is within the upper and lower limits of the change setting unit 211-2, the change θt2 = the difference θt1 is output and added to the past value. The result output θt3 matches the input (target steering angle) θt. As a result, even if the target steering angle θt changes abruptly, the target steering angle θt that changes abruptly can be changed smoothly, preventing sudden current changes (= rapid steering) and It plays a function to reduce the anxiety of autonomous driving.

The SAT compensation unit 230 obtains the SAT torque (converted to the column axis) from the equation of motion around the column axis, and obtains a SAT estimated current value I _SAT that is a motor current corresponding to the SAT torque. Then, the SAT estimated current value I _SAT is passed through the LPF set to a cutoff frequency higher than the angle response frequency, and further multiplied by the vehicle speed sensitivity gain set at the vehicle speed to obtain the SAT compensation current command value Isref.

When the SAT torque (converted to the column axis) is obtained from the equation of motion around the column axis, and the SAT estimated current value I _SAT corresponding to the SAT torque is obtained, the following equation 3 is obtained.

ただし、Ｉｃはコラム軸に換算したコラム、ピニオンラック機構、タイヤの全慣性モーメント、ω_ｃはコラム軸角速度、Ｔｈは操舵トルク（トーションバーの捩りトルク）、Ｔ_Ｆｒｃはコラム軸に作用するクーロン摩擦、ｃはコラム軸粘性摩擦係数、Ｋｔは電流値からコラム軸のトルクに変換する係数（モータトルク定数×減速比）である。

上記数３に基づくＳＡＴ補償部２３０は図１２のような構成となっており、モータ角速度ωは粘性摩擦係数（ｃ）部２３１に入力され、粘性摩擦係数ｃを乗算されて加減算部２３２Ａに加算入力されると共に、符号（ｓｉｇｎ）部２３３で符号化され、クーロン摩擦（Ｔ_Ｆｒｃ）部２３４でをクーロン摩擦Ｔ_Ｆｒｃを乗算されて加減算部２３２Ａに加算入力される。符号部２３３及びクーロン摩擦部２３４で符号化クーロン摩擦部を構成している。また、加減算部２３２Ａには操舵トルクＴｈが減算入力され、その加減算結果が加算部２３２Ｂに加算入力される。モータ角加速度α（ここでは、モータ角加速度αはコラム軸角加速度と等しいとしている）は全慣性モーメント（Ｉｃ）部２３５に入力され、全慣性モーメントＩｃを乗算されて加算部２３２Ｂに入力され、その加算結果が係数（１／Ｋｔ）部２３６に入力され、１／Ｋｔ倍されて減算部２３２Ｃに加算入力される。減算部２３２Ｃには前回電流指令値Ｉｒｅｆ（Ｚ^−１）が減算入力され、その差が、ＳＡＴに相当するモータトルクを発生するＳＡＴ推定電流値Ｉ_ＳＡＴとして出力される。加算部２３２Ｂ、係数部２３６及び減算部２３２Ｃで出力係数部を構成している。

Where Ic is the column converted to the column shaft, pinion rack mechanism, total moment of inertia of the tire, ω _c is the column shaft angular velocity, Th is the steering torque (torsion torque of the torsion bar), and T _Frc is the Coulomb friction acting on the column shaft. , C is a column shaft viscous friction coefficient, and Kt is a coefficient (motor torque constant × reduction ratio) for converting the current value into the column shaft torque.

The SAT compensation unit 230 based on Equation 3 is configured as shown in FIG. 12, and the motor angular velocity ω is input to the viscous friction coefficient (c) unit 231, multiplied by the viscous friction coefficient c, and added to the addition / subtraction unit 232A. At the same time, it is encoded by the sign unit 233, multiplied by the Coulomb friction T _Frc by the Coulomb friction (T _Frc ) unit 234, and added to the addition / subtraction unit 232A. The encoding part 233 and the coulomb friction part 234 constitute an encoding coulomb friction part. Further, the steering torque Th is input to the addition / subtraction unit 232A, and the addition / subtraction result is input to the addition unit 232B. Motor angular acceleration α (here, motor angular acceleration α is equal to column axis angular acceleration) is input to total inertia moment (Ic) unit 235, multiplied by total inertia moment Ic, and input to addition unit 232B. The addition result is input to the coefficient (1 / Kt) unit 236, multiplied by 1 / Kt, and added to the subtraction unit 232C. The subtraction unit 232C receives the previous current command value Iref (Z ⁻¹ ) and inputs the difference as a SAT estimated current value I _SAT that generates motor torque corresponding to SAT. The addition unit 232B, the coefficient unit 236, and the subtraction unit 232C constitute an output coefficient unit.

If the estimated SAT current value I _SAT is directly added to the current command value, vibration and noise are likely to occur. Therefore, the cutoff frequency is filtered by the LPF 237 having characteristics higher than the response frequency (for example, 1 Hz) of the steering angle control. The filtering output of the LPF 237 is multiplied by a gain G by a gain (G) unit 238. The upper limit value of the current value command value multiplied by the gain G is limited by the limiter 239, and the SAT compensation current command value Isref is output from the limiter 239. The limiter 239 is not an essential element. The gain unit 238 may be vehicle speed sensitive, and the gain G characteristic of the vehicle speed sensitive gain may be any characteristic as long as the gain G gradually decreases as the vehicle speed Vel increases as shown in FIG.

  An example of the overall operation in such a configuration will be described with reference to the flowchart of FIG.

  When the operation of the steering system starts, torque control by the torque control unit 141 is performed (step S1), and the motor 150 is driven by the current control / drive unit 143 using the motor current command value Itref (step S2). The above operation is repeated until a switching command SW is output from the switching command unit 131 (step S3).

  When the automatic steering mode is entered, and the switching command SW is output from the switching command unit 131, the target steering angle θt is input from the target steering angle generation unit 132 (step S4), and the actual steering angle θr is input from the steering angle sensor 152. (Step S5), the steering torque Th is input from the torque sensor 154 (Step S6), the vehicle speed Vel is input from the vehicle speed sensor 153 (Step S7), and the motor angular speed ω is input from the motor angular speed calculation unit 144 (Step S8). Further, the motor angular acceleration α is input from the motor angular acceleration calculation unit 145 (step S9), and the motor current command value Imref is generated by the steering angle control unit 200 (step S100). The order of input of the target steering angle θt, the actual steering angle θr, the steering torque Th, the motor angular velocity ω, and the motor angular acceleration α is arbitrary.

  Thereafter, the switching unit 142 is switched by the switching command SW from the switching command unit 131 (step S10), and the motor 150 is driven by the current control / drive unit 143 using the motor current command value Imref from the steering angle control unit 200. (Step S11), the process returns to Step S3. The drive control based on the motor current command value Imref is repeated until the switching command SW is changed from the switching command unit 131.

  The generation of the motor current command value Imref is performed by the steering angle control unit 200, and the generation operation of the motor current command value Imref by the steering angle control unit 200 is as shown in the flowchart of FIG.

First, the feedback control unit 210 inputs the target steering angle θt, the actual steering angle θr, the motor angular velocity ω, and the steering torque Th (step S101), and generates a feedback control current command value Ifref (step S102). In parallel with this, the SAT compensation unit 230 receives the motor angular velocity ω, the steering torque Th, the motor angular acceleration α, and the previous current command value Iref (Z ⁻¹ ) (step S103), and generates the SAT compensation current command value Isref. (Step S104). The feedback control current command value Ifref is input to the adding unit 201, and the SAT compensation current command value Isref is input to the adding unit 201 (step s105), and the current command value Imo (= Ifref−Isref) as the addition result is input to the current command. The motor current command value Imref is output by adding the value (step S106).

  Next, the operation of the feedback control unit 210 will be described with reference to the flowchart of FIG.

  The target steering angle θt is input to the rate limiter 211 (step S110), the rate limiting operation as described above is executed by the rate limiter 211 (step S111), and the target steering angle θta that has passed through the LPF 212 is input to the subtraction unit 213A. . Further, the actual steering angle θr is input from the rudder angle sensor 152 (step S112), “θta−θr” is subtracted by the subtraction unit 213A (step S113), and the angular deviation θd as a subtraction value is proportional gain unit 214. The gain is multiplied by Kpp and added to the subtraction unit 213B (step S114). The motor angular speed ω is subtracted and input to the subtracting unit 213B, and a speed deviation from the angular speed multiplied by the gain Kpp is obtained (step S115). The speed deviation obtained by the subtracting unit 213B is integrated and gained Kvi times by the integrating unit 216A and the integrating gain unit 216B, added to the subtracting unit 213C (step S116), and proportional gain Kvp times by the proportional gain unit 216C. Then, subtraction is input to the subtraction unit 213C (step S117), and subtraction is performed by the subtraction unit 213C (step S118).

  Thereafter, the steering torque Th is input (step S120), the steering torque Th is differentiated by the differentiation unit 215A, multiplied by the differential gain Kc by the differential gain unit 215B, and input to the addition unit 213C (step S121). The addition unit 213D adds the value to the subtraction value from the subtraction unit 213C (step S122), the upper / lower limit value is limited by the limiter 217 (step S123), and is output as the feedback control current command value Ifref (step S124).

  Next, the operation of the SAT compensation unit 230 will be described with reference to the flowchart of FIG.

The motor angular velocity ω and the steering torque Th are input (step S130), the viscous friction coefficient portion 231 multiplies the motor angular velocity ω by the viscous friction coefficient c (step S131), the encoding portion 233 encodes the coulomb friction portion 234, and the coulomb friction portion 234. The friction _TFrc is multiplied (step S132), the output of the viscous friction coefficient unit 231 and the output of the coulomb friction unit 234 are added, and the steering torque Th is added / subtracted by the addition / subtraction unit 232A (step S133).

Next, the total inertia moment unit 235 receives the motor angular acceleration α, multiplies the total inertia moment Ic (step S132), and adds it by the addition unit 232B (step S135). The addition result in the addition unit 232B is multiplied by 1 / Kt in the coefficient unit 236 and added to the subtraction unit 232C, and the previous current command value Iref (Z ⁻¹ ) separately input (stored) is subtracted in the subtraction unit 232C. (Step S137). The subtractor 232C outputs a SAT estimated current value I _SAT that generates a motor torque corresponding to SAT, and the SAT estimated current value I _SAT is filtered by the LPF 237 (step S140), and the vehicle speed Vel is input to gain (G). The unit 238 multiplies the gain G (step S141), further limits the upper and lower limit values by the limiter 239 (step S122), and outputs the SAT compensation current command value Isref from the limiter 239 (step S143).

The SAT compensation unit 230 in FIG. 12 is configured based on Equation 3, but the SAT estimation described in FIG. 4 can be configured in the same manner. FIG. 18 shows an example of the configuration, and the estimated SAT current value * SAT (= I _SAT ) is set to the LPF 230-1, the vehicle speed sensitive gain (G) section 230-2, and the limiter 230-3. Thus, the SAT compensation current command value Isref can be obtained.

1 Handle 2 Column shaft (steering shaft)
10, 154 Torque sensors 12, 153 Vehicle speed sensor 13 Battery 20, 150 Motor 21 Motor drive unit 100 Control unit (ECU)
110 Torque system control unit 120 Motor system control unit 151 Rotation sensor 152 Steering angle sensor 130 ECU on vehicle side
131 switching command section 132 target steering angle generation section 140 ECU on EPS side
141 torque control unit 142 switching unit 143 current control / drive unit 144 motor angular velocity calculation unit 145 motor angular acceleration calculation unit 200 rudder angle control unit 210 feedback control unit 211 rate limiter 211-2 change setting unit 211-4 holding unit 212, 230-1, 237 LPF
214 Proportional gain unit 215A Differentiation unit 215B Differential gain (Kc) unit 216A Integration unit 216B Integration gain (Kvi) unit 216C Proportional gain (Kvp) units 217, 239, 230-3 Limiter 230 SAT compensation unit 231 Viscous friction coefficient unit 233 Sign Part 234 Coulomb friction part 238 (vehicle speed sensitive) gain part

Claims (7)

A function of calculating a motor current command value 1 based on the steering torque and the vehicle speed, driving the motor based on the motor current command value 1 to assist control of the steering system, and switching between an automatic steering mode and a manual steering mode. In the electric power steering apparatus having
A steering angle control unit that calculates a motor current command value 2 based on a target steering angle, an actual steering angle, a motor angular velocity and motor angular acceleration of the motor, the steering torque, and a previous current command value; and the motor current command value 1 and A switching unit for inputting and switching the motor current command value 2;
The steering angle control unit generates a feedback control current command value based on the target steering angle, the actual steering angle, the motor angular velocity, and the steering torque, the motor angular velocity, the motor angular acceleration, A SAT compensation unit that generates a SAT compensation current command value based on the steering torque and the previous current command value; and an output unit that generates the motor current command value 2 from the feedback control current command value and the SAT compensation current command value; Consists of
The electric power steering apparatus characterized in that the switching unit is switched according to a switching command between the automatic steering mode and the manual steering mode, and the motor is driven and controlled based on the motor current command value 2 in the automatic steering mode. . The feedback control unit is
A rate limiter for smoothing the target steering angle; an LPF connected to the output of the rate limiter; a first proportional gain unit for multiplying an angular deviation between the output of the LPF and the actual steering angle by a proportional gain; An integral gain section that integrates the speed deviation between the error speed from the first proportional gain section and the motor angular speed to multiply the integral gain, a second proportional gain section that multiplies the speed deviation by a proportional gain, and a derivative of the steering torque. A differential gain unit that doubles the differential gain, and the output of the differential gain unit is added to the deviation value between the output of the integral gain unit and the output of the second proportional gain unit to limit the upper and lower limit values, and the feedback The electric power tearing device according to claim 1, comprising an output unit that outputs a control current command value. The SAT compensator is
A SAT estimation unit that calculates a SAT estimated current value based on the steering torque, the motor angular velocity, the motor angular acceleration, and the previous current command value, and inputs the SAT estimated current value and has a cutoff higher than the angular response frequency. 3. The electric power steering apparatus according to claim 1, comprising: an LPF having frequency characteristics; and a vehicle speed sensitive gain unit that outputs the SAT compensation current command value by multiplying an output of the LPF by a vehicle speed variable gain. . The SAT estimation unit is
A viscous friction coefficient portion that multiplies the motor angular velocity by a viscous friction coefficient; an encoded Coulomb friction portion that encodes the motor angular velocity and multiplies Coulomb friction; and a total inertia moment portion that multiplies the motor angular acceleration by a total inertia moment. And an output coefficient unit that subtracts the steering torque from the added value of the output of the viscous friction coefficient part and the output of the coded Coulomb friction part, adds the output of the total moment of inertia part, and multiplies the coefficient. The electric power steering apparatus according to claim 3. The electric power steering apparatus according to claim 3 or 4, wherein a limiter for limiting upper and lower limit values is connected to a subsequent stage of the vehicle speed sensitive gain unit. The SAT estimation unit is
An addition unit for adding the current command value corresponding to the assist torque and the steering torque, a first subtraction unit for subtracting a value obtained by multiplying the motor angular acceleration by inertia from the addition result of the addition unit, and the motor angular velocity. The electric power steering apparatus according to claim 3, further comprising: a second subtraction unit that subtracts a value obtained by encoding and multiplying friction from a subtraction result of the first subtraction unit and outputs the estimated SAT current value. . The electric power steering apparatus according to claim 6, wherein a limiter for limiting upper and lower limit values is connected to a subsequent stage of the vehicle speed sensitive gain unit.

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