JP2020006832A - Steering control device - Google Patents

Abstract

To provide a steering control device that can mitigate an impact caused by an end contact depending on road surface conditions and that can inhibit steering feeling from deteriorating.SOLUTION: When an absolute value of a control steering angle θs exceeds a steering angle at a location near an end, a microcomputer 41 performs an end contact mitigation control to reduce an absolute value of a q axial current command value Iq* based on an increase of the control steering angle θs. In addition, the microcomputer 41 includes an axial force estimation unit 54 configured to calculate an estimated axial force Fb, which is an estimated value of an axial force acting on a rack shaft connected to a steering wheel and a mode selection unit 55 configured to select one of plural modes set such that values are different from one another when being used at the time of calculation of the q axial current command value Iq* based on the estimated axial force Fb during the end contact mitigation control. Then, the selected mode is held during the end contact mitigation control.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a steering control device.

  2. Description of the Related Art Conventionally, as a vehicle steering device, an electric power steering device (EPS) including an actuator using a motor as a driving source has been known. Some of such EPSs obtain a steering angle of a steering wheel (steering angle of a steered wheel) as an absolute angle including a range exceeding 360 °, and perform various controls based on the steering angle. For example, in Patent Document 1, before a rack end, which is an end of a rack shaft, hits a rack housing, a current command value corresponding to a target value of a motor torque generated by a motor is reduced based on a steering angle. A technique for executing end reliance mitigation control for alleviating a lash impact is disclosed.

  By the way, the torque (easiness of turning) required for turning the steered wheels changes according to the road surface condition such as the low μ road or the high μ road. It is desirable to change the current command value (torque command value) according to the road surface condition. Based on these points, the steering control device described in Patent Literature 2 changes the spring constant of the reference model (viscoelastic model) based on the axial force acting on the rack shaft to which the steered wheels are connected, so that various road surfaces can be controlled. Reduce the impact on the end depending on the situation.

JP 2015-20506 A JP 2017-165306 A

  By the way, in the configuration of Patent Document 2, when the road surface condition changes along with the running of the vehicle at the time of executing the end contact mitigation control, the motor is generated by changing the spring constant of the reference model according to the change in the axial force. There is a possibility that a sudden change in the motor torque will cause a decrease in the steering feeling.

  An object of the present invention is to provide a steering control device that can reduce an impact applied to an end according to a road surface condition and can suppress a decrease in steering feeling.

  A steering control device for solving the above-mentioned problem is a steering device to which a motor torque for reciprocating a steered shaft connected to steered wheels by an actuator using a motor as a drive source is to be controlled, and a motor output by the motor. A torque command value calculation unit that calculates a torque command value that is a target value of torque; and a control unit that controls driving of the motor so that the motor torque follows the torque command value. When the absolute value of the rotation angle of the rotating shaft that can be converted to the steered angle of the steered wheel exceeds a steering angle threshold value corresponding to the steering device, the absolute value of the rotation angle is increased based on the absolute value of the steering angle. An end contact mitigation control for reducing the absolute value of the torque command value is executed. Based on an axial force acting on a steered shaft connected to the steered wheels, the end contact mitigation control at the time of executing the end contact mitigation control is performed. A mode selection unit that selects one of a plurality of modes in which values used when calculating the lock command value are set to be different from each other. In the selected one of the modes, the end hitting mitigation control is executed. While being held.

  According to the above configuration, one of the plurality of modes is selected based on the axial force acting on the steered shaft, and the torque command value at the time of executing the end mitigation control is calculated according to the selected one mode. Therefore, the impact on the end can be reduced according to the road surface condition. Since the selected one mode is held while the end reliance mitigation control is being executed, even if the road surface state changes during the execution of the end reliance mitigation control, it is possible to suppress a sudden change in the motor torque. .

In the steering control device, it is preferable that the mode selection unit selects one of the plurality of modes based on the axial force and the vehicle speed.
According to the above configuration, by considering the vehicle speed in addition to the axial force, an optimal mode can be selected from a plurality of subdivided modes, and the impact of the end contact can be appropriately mitigated.

  In the steering control device, the mode selection unit selects one of the plurality of modes when the rotation angle exceeds a mode selection angle on the neutral position side than the steering angle threshold value toward the end side, and is selected. The one mode is held until the mode release angle on the neutral position side exceeds the mode selection angle to the neutral position side, and the angle range between the mode release angle and the mode selection angle is Preferably, the angle is set to be larger than an angle range between the steering angle threshold and the mode selection angle.

  According to the above configuration, for example, even if the steering operation is repeatedly performed in the vicinity of the mode selection angle, it is difficult to cancel the once set mode. Thereby, it is possible to prevent the mode from being repeatedly selected and released.

  ADVANTAGE OF THE INVENTION According to this invention, while being able to alleviate the impact of an end contact according to a road surface condition, a fall of a steering feeling can be suppressed.

FIG. 1 is a schematic configuration diagram of an electric power steering device according to a first embodiment. FIG. 2 is a block diagram of the steering control device according to the first embodiment. 6 is a graph illustrating a relationship among a rack end position, a steering angle near the end, a mode selection angle, and a mode release angle according to the first embodiment. FIG. 3 is a block diagram of a damping control amount calculation unit according to the first embodiment. FIG. 3 is a block diagram of a first excess angular velocity calculation unit according to the first embodiment. FIG. 3 is a block diagram of a limit value setting unit according to the first embodiment. FIG. 3 is a block diagram of an angle limit component calculation unit according to the first embodiment. FIG. 3 is a block diagram of a second excess angular velocity calculation unit of the first embodiment. FIG. 10 is a block diagram of a damping control amount calculation unit according to a second embodiment. FIG. 9 is a block diagram of an arithmetic processing unit according to the second embodiment. FIG. 10 is a block diagram of a limit value setting unit according to the second embodiment.

(1st Embodiment)
Hereinafter, a first embodiment of a steering control device will be described with reference to the drawings.
As shown in FIG. 1, an electric power steering device (EPS) 1 as a steering device to be controlled includes a steering mechanism 4 that turns a steered wheel 3 based on an operation of a steering wheel 2 by a driver. . The EPS 1 also includes an EPS actuator 5 as an actuator that applies an assist force to the steering mechanism 4 to assist the steering operation, and a steering control device 6 that controls the operation of the EPS actuator 5.

  The steering mechanism 4 includes a steering shaft 11 to which the steering wheel 2 is fixed, a rack shaft 12 as a steering shaft that reciprocates in the axial direction in accordance with the rotation of the steering shaft 11, and a rack shaft 12 that is reciprocally inserted. And a substantially cylindrical rack housing 13. The steering shaft 11 is configured by connecting a column shaft 14, an intermediate shaft 15, and a pinion shaft 16 in this order from the steering wheel 2 side.

  The rack shaft 12 and the pinion shaft 16 are arranged at a predetermined intersection angle in the rack housing 13, and the rack teeth 12 a formed on the rack shaft 12 and the pinion teeth 16 a formed on the pinion shaft 16 mesh with each other. Thus, the rack and pinion mechanism 17 is configured. Tie rods 19 are rotatably connected to both ends of the rack shaft 12 via rack ends 18 formed of ball joints provided at the shaft ends. The tip of the tie rod 19 is connected to a knuckle (not shown) to which the steered wheels 3 are attached. Therefore, in the EPS 1, the rotation of the steering shaft 11 accompanying the steering operation is converted into the axial movement of the rack shaft 12 by the rack and pinion mechanism 17, and this axial movement is transmitted to the knuckle via the tie rod 19, The steered angle of the steered wheels 3, that is, the traveling direction of the vehicle is changed.

  The position where the rack end 18 abuts on the left end of the rack housing 13 is a position where steering can be performed to the right as much as possible, and this position corresponds to a rack end position as a right end position. The position where the rack end 18 abuts on the right end of the rack housing 13 is a position where steering can be performed to the left as much as possible, and this position corresponds to a rack end position as a left end position.

  The EPS actuator 5 includes a motor 21 as a drive source, and a speed reduction mechanism 22 such as a worm and wheel connected to the motor 21 and to the column shaft 14. Then, the EPS actuator 5 applies the motor torque to the steering mechanism 4 as an assist force by transmitting the rotation of the motor 21 to the column shaft 14 by reducing the rotation of the motor 21 by the reduction mechanism 22. Note that a three-phase brushless motor is used as the motor 21 of the present embodiment.

  The steering control device 6 is connected to a vehicle speed sensor 31 for detecting a vehicle speed SPD of the vehicle, and a torque sensor 32 for detecting a steering torque Ts applied to the steering shaft 11 by the driver's steering. In addition, a rotation sensor 33 that detects the motor angle θm of the motor 21 with a relative angle within a range of 360 ° is connected to the steering control device 6. The steering torque Ts and the motor angle θm are detected as positive values when steering in one direction (right in the present embodiment) and negative values when steering in the other direction (left in the present embodiment). I do. The steering control device 6 supplies drive power to the motor 21 based on a signal indicating each state amount input from each of the sensors and a signal indicating the state amount of the motor 21, thereby operating the EPS actuator 5. That is, the assist force applied to the steering mechanism 4 to reciprocate the rack shaft 12 is controlled.

Next, the configuration of the steering control device 6 will be described.
As shown in FIG. 2, the steering control device 6 includes a microcomputer 41 as a control unit that outputs a control signal, and a drive circuit 42 that supplies driving power to the motor 21 based on the control signal. The drive circuit 42 of the present embodiment employs a known PWM inverter having a plurality of switching elements (for example, FETs). The control signal output from the microcomputer 41 specifies the on / off state of each switching element. Thereby, each switching element is turned on / off in response to the control signal, and the energization pattern to the motor coil of each phase is switched, so that the DC power of the vehicle-mounted power supply 43 is converted into three-phase drive power and is transmitted to the motor 21. Is output. Each control block shown below is realized by a computer program executed by the microcomputer 41, detects each state quantity at a predetermined sampling period (detection period), and performs the following operation every predetermined operation period. Each operation shown in the control block is executed.

  The microcomputer 41 receives the vehicle speed SPD, the steering torque Ts, and the motor angle θm of the motor 21. Further, the microcomputer 41 receives the respective phase current values Iu, Iv, Iw of the motor 21 detected by the current sensor 45 provided on the connection line 44 between the drive circuit 42 and the motor coil of each phase. . In FIG. 2, the connection wires of each phase and the current sensor 45 of each phase are collectively shown as one for convenience of explanation. The microcomputer 41 is connected to a voltage sensor 46 for detecting a power supply voltage Vb of the vehicle-mounted power supply 43. Then, the microcomputer 41 outputs a control signal based on each of these state quantities.

  More specifically, the microcomputer 41 includes a current command value calculator 51 that calculates a target value of power supply to the motor 21, that is, current command values Id * and Iq * corresponding to the target assist force, and current command values Id * and Iq *. And a control signal output unit 52 that outputs a control signal based on the control signal. The current command values Id * and Iq * are target values of the current to be supplied to the motor 21, and indicate a current command value on the d-axis and a current command value on the q-axis in the d / q coordinate system, respectively. Among them, the q-axis current command value Iq * corresponds to a torque command value that is a target value of the output torque of the motor 21, and the current command value calculation unit 51 corresponds to a torque command value calculation unit. In this embodiment, the d-axis current command value Id * is basically fixed to zero. Similarly to the motor angle θm of the motor 21, the current command values Id * and Iq * are positive values when assisting steering in one direction, and negative values when assisting steering in the other direction. I do.

  Further, the microcomputer 41 includes a control steering angle calculation unit 53 that calculates a control steering angle θs indicating a rotation angle (steering angle) of the steering shaft 11, which is a rotation axis that can be converted into a turning angle of the steered wheels 3. . Further, the microcomputer 41 selects an axial force estimating unit 54 that calculates an estimated axial force Fb, which is an estimated value of the axial force acting on the rack shaft 12, and selects a mode according to the road surface condition and the vehicle speed SPD based on the estimated axial force Fb. And a mode selection unit 55 for performing the operation. Further, the microcomputer 41 includes a limit value setting unit 56 for setting a limit value Ig that is an upper limit of the q-axis current command value Iq *, and a memory 57. The memory 57 stores a rated current Ir corresponding to a preset rated torque as a motor torque that can be output by the motor 21 and the like.

  More specifically, the control steering angle calculation unit 53 receives the motor angle θm. Then, the control steering angle calculation unit 53 integrates (counts) the number of revolutions of the motor 21 with the control steering angle θs when the rack shaft 12 is at the neutral position where the vehicle goes straight ahead as the origin (zero degree), for example. Based on the rotation speed and the motor angle θm, the control steering angle θs is calculated as an absolute angle including a range exceeding 360 °. Note that, similarly to the motor angle θm of the motor 21, the control steering angle θs is a positive value when the rotation angle is in one direction from the neutral position, and is a negative value when the rotation angle is in the other direction.

  The steering torque Ts, the phase current values Iu, Iv, Iw and the motor angle θm are input to the axial force estimating unit 54. The axial force estimating unit 54 calculates a q-axis current value which is an actual current value on the q-axis based on the phase current values Iu, Iv, Iw and the motor angle θm, and calculates the motor 21 based on the q-axis current value. Calculate the motor torque output by. Then, the axial force estimating unit 54 calculates the axial force obtained by multiplying the motor torque by a conversion coefficient based on the reduction ratio of the reduction mechanism 22 and the gear ratio of the rack and pinion mechanism 17 and the steering torque Ts by the rack and pinion mechanism 17. The estimated axial force Fb acting on the rack shaft 12 is calculated by adding the axial force obtained by multiplying by the conversion coefficient based on the gear ratio.

  The estimated axial force Fb, the vehicle speed SPD, and the control steering angle θs are input to the mode selection unit 55. The mode selection unit 55 of the present embodiment includes a high μ road mode indicating that the road μ is a high μ road, a low μ road stop mode in which the road μ is a low μ road and the vehicle is in a stopped state, a road μ One is selected from a low μ road traveling mode in which the vehicle is traveling on a low μ road and a middle μ road mode in which the road surface μ is lower than the high μ road and higher than the low μ road. Specifically, the mode selecting unit 55 selects the high μ road mode when the estimated axial force Fb is equal to or higher than the high axial force threshold Fthh, and when the estimated axial force Fb is less than the high axial force threshold Fthh and the low axial force threshold If it is larger than Fthl, the middle μ road mode is selected. In addition, when the estimated axial force Fb is equal to or less than the low axial force threshold Fthl, the mode selecting unit 55 selects the low μ road stop mode when the vehicle speed SPD is equal to or less than the vehicle speed threshold SPDth, and the vehicle speed SPD is equal to or smaller than the vehicle speed threshold SPDth. If it is larger, the low μ road running mode is selected. Note that the high axial force threshold Fthh is an axial force acting on the rack shaft 12 when the road surface is a high μ road, and is set in advance by an experiment or the like. The low axial force threshold Fthl is an axial force acting on the rack shaft 12 when the road surface is a low μ road, is smaller than the high axial force threshold Fthh, and is set in advance by experiments or the like. The vehicle speed threshold value SPDth is a speed indicating that the vehicle is stopped, and is set to a small value near zero.

  As shown in FIG. 3, when the absolute value of the control steering angle θs exceeds the mode selection angle θsl set to the neutral position side from the near-end steering angle θne toward the rack end side, the mode selection unit 55 A mode selection signal Ssl indicating one mode selected from the plurality of modes based on the force Fb and the vehicle speed SPD is output to the current command value calculation unit 51 and the limit value setting unit 56. In addition, the mode selection unit 55 releases a mode selection signal for releasing the selected mode when the absolute value of the control steering angle θs exceeds the mode release angle θre set to the neutral position side from the mode selection angle θsl toward the neutral side. Output Ssl. That is, the selected mode is maintained from the time when the absolute value of the control steering angle θs exceeds the mode selection angle θsl to the rack end side until the time when the mode release angle θre exceeds the neutral position. Further, when the absolute value of the control steering angle θs is smaller than the mode release angle θre, the mode is not selected. In the present embodiment, as shown in the figure, the angle range between the mode release angle θre and the mode selection angle θsl is larger than the angle range between the near-end steering angle θne and the mode selection angle θsl. Is set.

  As shown in FIG. 2, the current command value calculation unit 51 calculates a basic assist command unit 61 that calculates a basic current command value Ias *, which is a basic component of the q-axis current command value Iq *, and a basic current command value Ias *. A damping control amount calculation unit 62 for calculating a damping control amount Ida, which is a component to be corrected. Further, the current command value calculation unit 51 includes a guard processing unit 63 that limits the absolute value of the corrected current command value Ias ** obtained by correcting the basic current command value Ias * with the damping control amount Ida to a limit value Ig or less. I have.

  The steering torque Ts and the vehicle speed SPD are input to the basic assist calculation unit 61. Then, the basic assist calculation unit 61 calculates a basic current command value Ias * based on the steering torque Ts and the vehicle speed SPD. Specifically, the basic assist calculation unit 61 calculates the basic current command value Ias * having a larger value (absolute value) as the absolute value of the steering torque Ts is larger and the vehicle speed SPD is slower. The basic current command value Ias * calculated in this manner is output to the subtractor 64.

  The damping control amount Ida output from the damping control amount calculation unit 62 is input to the subtracter 64 together with the basic current command value Ias * as described later. Then, the current command value calculator 51 calculates the corrected current command value Ias ** by subtracting the damping control amount Ida from the basic current command value Ias * in the subtractor 64. The corrected current command value Ias ** calculated in this way is output to the guard processing unit 63.

  The limit value Ig set by the limit value setting unit 56 as described later is input to the guard processing unit 63 in addition to the corrected current command value Ias **. When the absolute value of the corrected current command value Ias ** input is equal to or smaller than the limit value Ig, the guard processing unit 63 sets the value of the corrected current command value Ias ** as the q-axis current command value Iq * as it is. The signal is output to the control signal output unit 52. On the other hand, when the absolute value of the input corrected current command value Ias ** is larger than the limit value Ig, the value obtained by limiting the absolute value of the corrected current command value Ias ** to the limit value Ig is q It is output to the control signal output unit 52 as the shaft current command value Iq *.

  The control signal output unit 52 performs current feedback control in the d / q coordinate system based on the current command values Id *, Iq *, the phase current values Iu, Iv, Iw, and the motor angle θm of the motor 21. , Generate a control signal. Specifically, the control signal output unit 52 maps each phase current value Iu, Iv, Iw on the d / q coordinate based on the motor angle θm, thereby obtaining the actual current of the motor 21 in the d / q coordinate system. A d-axis current value and a q-axis current value are calculated. Then, the control signal output unit 52 performs current feedback control so that the d-axis current value follows the d-axis current command value Id * and the q-axis current value follows the q-axis current command value Iq *. Thus, a control signal is generated. When this control signal is output to the drive circuit 42, drive power according to the control signal is supplied to the motor 21. Thereby, the drive of the motor 21 is controlled such that the motor torque output by the motor 21 follows the torque command value corresponding to the q-axis current command value Iq *.

Next, the configuration of the damping control amount calculation unit 62 will be described.
The vehicle speed SPD, the control steering angle θs, and the mode selection signal Ssl are input to the damping control amount calculation unit 62. When the absolute value of the control steering angle θs exceeds the near-end steering angle θne as the steering angle threshold, the damping control amount calculation unit 62 differentiates the control steering angle θs based on these state quantities. Then, a damping control amount Ida having a larger absolute value is calculated based on the increase in the absolute value of the control angular velocity ωs (steering speed) obtained by the control. The damping control amount Ida is a component that reduces the absolute value of the basic current command value Ias * by being subtracted from the basic current command value Ias *. Note that the near-end steering angle θne is set to a value indicating an angle whose absolute value is smaller by a predetermined angle θ1 than the control steering angle θs at the rack end position. The predetermined angle θ1 is a relatively small angle such that the near-end steering angle θne is not too far from the rack end position.

  Specifically, as shown in FIG. 4, the damping control amount calculation unit 62 is a difference between the control steering angle θs in the latest calculation cycle and the control steering angle θs at one of the left and right rack end positions. An end separation angle calculator 71 for calculating the end separation angle Δθ is provided. Further, the damping control amount calculation unit 62 calculates a first excess angular velocity ωo1 which is an excess of the control angular velocity ωs with respect to the first upper limit angular velocity ωlim1 determined according to the end separation angle Δθ and the mode selection signal Ssl. And a processing unit 73 for calculating the damping control amount Ida based on the first excess angular velocity ωo1.

  The control steering angle θs is input to the end separation angle calculation unit 71. The end separation angle calculation unit 71 calculates the difference between the control steering angle θs at the latest calculation cycle and the control steering angle θs at the left rack end position, and the control steering angle θs at the latest calculation cycle and the right The difference from the control steering angle θs at the rack end position is calculated. Then, the end separation angle calculation unit 71 outputs the smaller absolute value of the calculated differences to the first excess angular velocity calculation unit 72 as the end separation angle Δθ.

  The first excess angular velocity calculator 72 receives the end separation angle Δθ, the control angular velocity ωs obtained by differentiating the control steering angle θs, and the mode selection signal Ssl. Then, the first excess angular velocity calculation unit 72 calculates the first excess angular velocity ωo1 corresponding to the mode indicated by the mode selection signal Ssl.

  Specifically, as shown in FIG. 5, the first excess angular velocity calculating section 72 includes a first upper limit angular velocity calculating section 81 to which the end separation angle Δθ and the mode selection signal Ssl are input. The first upper limit angular velocity calculation unit 81 determines the relationship between the end separation angle Δθ and the first upper limit angular velocity ωlim1 in the high μ road mode, the middle μ road mode, the low μ road stop mode, and the low μ road traveling mode, respectively. A μ road upper limit angular velocity map 82, a medium μ road upper limit angular velocity map 83, a low μ road stopping upper limit angular velocity map 84, and a low μ road traveling upper limit angular velocity map 85 are provided. Then, the first upper limit angular velocity calculation unit 81 calculates the first upper limit angular velocity ωlim1 corresponding to each mode based on the end separation angle Δθ by referring to each map. In each of the maps 82 to 85, the first upper limit angular velocity ωlim1 is the smallest when the end separation angle Δθ is zero, and the first upper limit angular velocity ωlim1 increases in proportion to the increase in the end separation angle Δθ. It is set to be. The first upper limit angular velocity ωlim1 is set to be constant at a value set in advance as the maximum angular velocity at which the motor 21 can rotate when the end separation angle Δθ is larger than the predetermined angle θ2. The first upper limit angular velocity ωlim1 when the end separation angle Δθ is zero is the upper limit angular velocity map 82 for high μ road, the upper limit angular velocity map 83 for middle μ road, the upper limit angular velocity map 84 for stopping on low μ road, and the lower μ road The upper limit angular velocity map 85 for traveling is set so as to be smaller in the order. In other words, the first excess angular velocity calculation unit 72 determines that the smaller the torque required to steer the steered wheels 3 according to the road surface condition (the easier the steering is), the smaller the first upper limit angular velocity ωlim1 and the first excess angular velocity ωo1 Is calculated so as to increase. The first upper limit angular velocity ωlim1 when the end separation angle Δθ is larger than the predetermined angle θ2 is set to be the same in each of the maps 82 to 85. The predetermined angle θ2 is set to be larger than the predetermined angle θ1 and smaller than the angle between the mode selection angle θsl and the rack end position. That is, any mode is selected before the first upper limit angular velocity ωlim1 decreases as the end separation angle Δθ decreases. Further, the damping control amount calculation unit 62 of the present embodiment calculates a damping control amount Ida having an absolute value larger than zero from a situation before the absolute value of the control steering angle θs exceeds the near-end steering angle θne, When the absolute value of the control steering angle θs exceeds the near-end steering angle θne, a damping control amount Ida having an absolute value larger than zero is calculated.

  Further, the first upper limit angular velocity calculating section 81 includes a mode switching section 86 to which the first upper limit angular velocity ωlim1 calculated based on each of the maps 82 to 85 and the mode selection signal Ssl are input. The mode switching unit 86 switches an internal switch so that the first upper-limit angular velocity ωlim1 calculated based on the map corresponding to the mode indicated by the mode selection signal Ssl is output. As a result, the first upper limit angular velocity ωlim1 corresponding to the selected mode is output.

  When the absolute value of the control angular velocity ωs is larger than the first upper limit angular velocity ωlim1 calculated by the first upper limit angular velocity calculator 81, the first excess angular velocity calculation unit 72 determines that the control angular velocity ωs exceeds the first upper limit angular velocity ωlim1. The minute is output to the arithmetic processing unit 73 (see FIG. 3) as the first excess angular velocity ωo1. On the other hand, when the absolute value of the control angular velocity ωs is equal to or smaller than the first upper limit angular velocity ωlim1, the first excess angular velocity calculation section 72 outputs the first excess angular velocity ωo1 indicating zero to the calculation processing section 73.

  Specifically, the first excess angular velocity calculation section 72 includes a minimum value selection section 87 to which the first upper limit angular velocity ωlim1 and the control angular velocity ωs are input. The minimum value selector 87 selects the smaller one of the absolute values of the first upper limit angular velocity ωlim1 and the control angular velocity ωs, and outputs the selected one to the subtracter 88. Then, the first excess angular velocity calculator 72 calculates the first excess angular velocity ωo1 by subtracting the output value of the minimum value selector 87 from the absolute value of the control angular velocity ωs in the subtractor 88. As described above, by selecting the smaller one of the absolute values of the first upper limit angular velocity ωlim1 and the control angular velocity ωs in the minimum value selector 87, when the control angular velocity ωs is equal to or less than the first upper limit angular velocity ωlim1, the subtracter 88 is used. In, the control angular velocity ωs is subtracted from the control angular velocity ωs, and the first excess angular velocity ωo1 becomes zero. On the other hand, when the control angular velocity ωs is higher than the first upper limit angular velocity ωlim1, the first upper limit angular velocity ωlim1 is subtracted from the absolute value of the control angular velocity ωs in the subtractor 88, and the first excess angular velocity ωo1 is This is an excess of the first upper limit angular velocity ωlim1.

  As shown in FIG. 4, the first excess angular velocity ωo1, the vehicle speed SPD, and the control angular velocity ωs are input to the arithmetic processing unit 73. The arithmetic processing unit 73 includes a map that defines the relationship between the first excess angular velocity ωo1 and the vehicle speed SPD and the damping control amount Ida, and refers to the map to refer to the first excess angular velocity ωo1 and the damping corresponding to the vehicle speed SPD. The control amount Ida is calculated. The arithmetic processing unit 73 sets the sign (direction) of the damping control amount Ida to the sign (direction) indicated by the control angular velocity ωs. In this map, the damping control amount Ida is set such that the speed limiting component Igs becomes the smallest when the first excess angular velocity ωo1 is zero, and the damping control amount Ida increases in proportion to the increase of the first excess angular velocity ωo1. Have been. This map is set such that the damping control amount Ida decreases in proportion to the increase in the vehicle speed SPD. As described above, the smaller the torque required to steer the steered wheels 3 according to the road surface condition, the larger the first excess angular velocity ωo1 becomes. Therefore, the smaller the torque required to steer the steered wheels 3, the smaller the damping control amount. Ida also increases. The damping control amount Ida calculated in this manner is output to the subtractor 64 (see FIG. 2).

Next, the configuration of the limit value setting unit 56 will be described.
As shown in FIG. 2, the control value setting unit 56 receives the control steering angle θs, the vehicle speed SPD, the mode selection signal Ssl, the power supply voltage Vb, and the rated current Ir stored in the memory 57. Then, the limit value setting unit 56 sets the limit value Ig based on these state quantities.

  Specifically, as shown in FIG. 6, the limit value setting unit 56 includes a steering angle limit value calculating unit 91 that calculates a steering angle limit value Ien based on the control steering angle θs, and a voltage limit value Ivb based on the power supply voltage Vb. A voltage limit value calculating unit 92 for calculating and a minimum value selecting unit 93 for selecting the smaller one of the steering angle limit value Ien and the voltage limit value Ivb are provided.

  The steering angle limit value calculation unit 91 receives the control steering angle θs, the vehicle speed SPD, the mode selection signal Ssl, and the rated current Ir. Based on these state quantities, the steering angle limit value calculation unit 91 determines the absolute value of the control steering angle θs and the absolute value of the control steering angle θs when the absolute value of the control steering angle θs exceeds the near-end steering angle θne as described later. A steering angle limit value Ien that is reduced based on an increase in the absolute value of the control angular speed ωs (steering speed) is calculated. The steering angle limit value Ien calculated in this manner is output to the minimum value selection unit 93.

  The power supply voltage Vb is input to the voltage limit value calculator 92. The voltage limit value calculator 92 calculates a voltage limit value Ivb smaller than the rated voltage for supplying the rated current Ir when the absolute value of the power supply voltage Vb becomes equal to or less than the preset voltage threshold Vth. Specifically, when the absolute value of the power supply voltage Vb becomes equal to or less than the voltage threshold Vth, the voltage limit value calculating unit 92 determines that the voltage limit value having a smaller absolute value is based on the decrease in the absolute value of the power supply voltage Vb. Calculate Ivb. The voltage limit value Ivb calculated in this way is output to the minimum value selection unit 93.

Then, the minimum value selection unit 93 selects the smaller one of the input steering angle limit value Ien and voltage limit value Ivb as the limit value Ig, and outputs it to the guard processing unit 63 (see FIG. 2).
Next, the configuration of the steering angle limit value calculation unit 91 will be described.

  The steering angle limit value calculating section 91 calculates an end separation angle calculating section 101 for calculating the end separation angle Δθ, and an angle limiting component for calculating an angle limiting component Iga which is a current (torque) limiting amount determined according to the end separation angle Δθ. And an operation unit 102. Further, the steering angle limit value calculating section 91 calculates a second excess angular velocity ωo2 which is an excess of the control angular velocity ωs with respect to the second upper limit angular velocity ωlim2 determined according to the end separation angle Δθ; A speed limiting component calculator 104 for calculating a speed limiting component Igs that is a current (torque) limiting amount determined according to the second excess angular speed ωo2. Further, the steering angle limit value calculation unit 91 includes an angle limit execution determination unit 105 that determines whether the steering angle limit value Ien is limited by calculating an angle limit component Iga greater than zero, A speed limiting component attenuator for gradually attenuating the speed limiting component Igs when the speed is limited. The end separation angle calculation unit 101 calculates the end separation angle Δθ in the same manner as the end separation angle calculation unit 71 of the damping control amount calculation unit 62, and sends the calculated information to the angle limit component calculation unit 102 and the second excess angular velocity calculation unit 103. Output.

  The end separation angle Δθ and the mode selection signal Ssl are input to the angle limiting component calculation unit 102. Then, the angle limit component calculation unit 102 calculates the angle limit component Iga according to the mode indicated by the mode selection signal Ssl.

  As shown in FIG. 7, the angle limiting component calculation unit 102 determines the relationship between the end separation angle Δθ and the angle limiting component Iga in the high μ road mode, the middle μ road mode, the low μ road stop mode, and the low μ road traveling mode. , A high μ road angle restriction map 112, a medium μ road angle restriction map 112, a low μ road stopping angle restriction map 113, and a low μ road traveling angle restriction map 114. Then, the angle limit component calculation unit 102 calculates the angle limit component Iga corresponding to each mode based on the end separation angle Δθ by referring to each of the maps 111 to 114. In each of the maps 111 to 114, the angle limiting component Iga is set to be largest when the end separation angle Δθ is zero, and to decrease in proportion to an increase in the end separation angle Δθ. The angle limiting component Iga is set to be zero when the end separation angle Δθ is larger than the predetermined angle θ1 (when the absolute value of the control steering angle θs is smaller than the near-end steering angle θne). When the end separation angle Δθ is zero, the angle limiting component Iga includes the high μ road angle restriction map 111, the middle μ road angle restriction map 112, the low μ road stopping angle restriction map 113, and the low μ road traveling. It is set to increase in the order of the use angle restriction map 114. The angle limiting component Iga when the end separation angle Δθ is larger than the predetermined angle θ1 is set to be the same (zero) in each of the maps 111 to 114. That is, the angle limiting component calculation unit 102 calculates so that the smaller the torque required for turning the steered wheels 3 according to the road surface condition, the larger the angle limiting component Iga.

  Further, the angle limit component calculation unit 102 includes a mode switching unit 115 to which the angle limit component Iga calculated based on each of the maps 111 to 114 and the mode selection signal Ssl are input. The mode switching unit 115 switches an internal switch so that the angle limiting component Iga calculated based on the map corresponding to the mode indicated by the mode selection signal Ssl is output. As a result, as shown in FIG. 6, the angle limit component Iga corresponding to the selected mode is output to the angle limit execution determination unit 105 and the subtractor 107.

  The second excess angular velocity calculator 103 receives the end separation angle Δθ, the control angular velocity ωs obtained by differentiating the control steering angle θs, and the mode selection signal Ssl. Then, the second excess angular velocity calculation unit 103 calculates the second excess angular velocity ωo2 according to the mode indicated by the mode selection signal Ssl.

  Specifically, as shown in FIG. 8, the second excess angular velocity calculating section 103 includes a second upper limit angular velocity calculating section 121 to which the end separation angle Δθ and the mode selection signal Ssl are input. The second upper limit angular velocity calculation unit 121 determines the relationship between the end separation angle Δθ and the second upper limit angular velocity ωlim2 in the high μ road mode, the middle μ road mode, the low μ road stop mode, and the low μ road traveling mode, respectively. A μ road upper limit angular velocity map 122, a medium μ road upper limit angular velocity map 123, a low μ road stopping upper limit angular velocity map 124, and a low μ road traveling upper limit angular velocity map 125 are provided. Then, the second upper limit angular velocity calculation unit 121 calculates the second upper limit angular velocity ωlim2 corresponding to each mode based on the end separation angle Δθ by referring to each of the maps 122 to 125. Each of the maps 122 to 125 is set to have a similar tendency to the maps 82 to 85 of the first upper limit angular velocity calculation unit 81, respectively. More specifically, the second upper limit angular velocity ωlim2 in the region where the end separation angle Δθ in each of the maps 122 to 125 is equal to or less than the predetermined angle θ2 is greater than the first upper limit angular velocity ωlim1 in the corresponding region in the corresponding maps 82 to 85. It is set to be smaller with the same gradient as the first upper limit angular velocity ωlim1 as the end separation angle Δθ decreases. Further, the second upper limit angular velocity ωlim2 in a region where the end separation angle Δθ is larger than the predetermined angle θ2 in each of the maps 122 to 125 is set to be constant at a value smaller than the first upper limit angular velocity ωlim1. In other words, the second excess angular velocity calculation unit 103 calculates the second upper angular velocity ωlim2 to be smaller and the second excess angular velocity ωo2 to be larger as the torque required for turning the steered wheels 3 according to the road surface condition is smaller. I do.

  Further, the second upper limit angular velocity calculation unit 121 includes a mode switching unit 126 to which the second upper limit angular velocity ωlim2 calculated based on each of the maps 122 to 125 and the mode selection signal Ssl are input. The mode switching unit 126 switches an internal switch so that the second upper limit angular velocity ωlim2 calculated based on the map corresponding to the mode indicated by the mode selection signal Ssl is output. As a result, the second upper limit angular velocity ωlim2 corresponding to the selected mode is output.

  When the absolute value of the control angular velocity ωs is larger than the second upper limit angular velocity ωlim2 calculated by the second upper limit angular velocity calculator 121, the second excess angular velocity calculator 103 determines that the control angular velocity ωs exceeds the second upper limit angular velocity ωlim2. The minute is output as the second excess angular speed ωo2 to the speed limit component calculation unit 104 (see FIG. 6). On the other hand, when the absolute value of the control angular velocity ωs is equal to or smaller than the second upper limit angular velocity ωlim2, the second excess angular velocity calculation section 103 outputs the second excess angular velocity ωo2 indicating zero to the speed limit component calculation section 104. The second excess angular velocity calculator 103 has a minimum value selector 127 and a subtractor 128, and computes the second excess angular velocity ωo2 in the same manner as the first excess angular velocity calculator 72.

  As shown in FIG. 6, the second excess angular speed ωo2 and the vehicle speed SPD are input to the speed limit component calculation unit 104. The speed limiting component calculation unit 104 has a map that defines the relationship between the second excess angular speed ωo2 and the vehicle speed SPD and the speed limiting component Igs, and refers to the map to determine the relationship between the second excess angular speed ωo2 and the vehicle speed SPD. The calculated speed limiting component Igs is calculated. In this map, the speed limit component Igs is set such that the speed limit component Igs becomes the smallest when the second excess angular speed ωo2 is zero, and the speed limit component Igs increases in proportion to the increase of the second excess angular speed ωo2. Have been. This map is set so that the speed limit component Igs becomes smaller based on the increase in the vehicle speed SPD. That is, the map of the speed limit component calculation unit 104 of the present embodiment is set in the same manner as the map of the calculation processing unit 73 of the damping control amount calculation unit 62. Further, as the torque required for turning the steered wheels 3 according to the road surface condition as described above becomes smaller, the second excess angular velocity ωo2 becomes larger. The limiting component Igs also increases. This map is set so that the speed limit component Igs has a smaller value than the angle limit component Iga. The speed limiting component Igs calculated in this way is output to the speed limiting component attenuator 106.

  The angle restriction component determination unit 105 receives the angle restriction component Iga and the rated current Ir. The angle limit execution determination unit 105 determines whether a value obtained by subtracting the angle limit component Iga from the rated current Ir is equal to the rated current Ir. If the same value is equal to the rated current Ir, a determination signal Sde indicating that the angle restriction is being performed is output to the speed limiting component attenuating unit 106. If the same value is different from the rated current Ir, the angle restriction is performed. The determination signal Sde indicating that the operation is not performed is output to the speed limiting component attenuating unit 106.

  The speed limit component attenuator 106 receives the speed limit component Igs and the determination signal Sde. When the determination signal Sde indicating that the angle limitation is not performed is input, the speed limiting component attenuator 106 outputs the speed limiting component Igs to the subtractor 108 as it is. On the other hand, when the determination signal Sde indicating that the angle limitation is being performed is input, the speed limiting component attenuating unit 106 determines 1 / N (N is an arbitrary value) of the speed limiting component Igs input in the same operation cycle. ), And outputs a value obtained by subtracting the attenuation value from the speed limiting component Igs to the subtractor 108 as a speed limiting component Igs'. Then, in the subsequent calculation cycle, the speed limiting component attenuating unit 106 outputs a value obtained by subtracting the attenuation value from the speed limiting component Igs 'to the subtractor 108 as a new speed limiting component Igs'. Note that the speed limiting component attenuating unit 106 continuously keeps zero after the speed limiting component Igs' becomes zero in the Nth calculation cycle after the determination signal Sde indicating that the angle limiting is being performed. Is output. When the determination signal Sde indicating that the angle restriction is not performed is input while the speed limiting component attenuating unit 106 outputs the attenuated speed limiting component Igs ′, the stored attenuation value is reset. I do.

  The rated current Ir is input to the subtractor 107 to which the angle limiting component Iga is input. The steering angle limit value calculator 91 outputs a value obtained by subtracting the angle limiting component Iga from the rated current Ir in the subtractor 107 to the subtractor 108 to which the speed limiting component Igs' is input. Then, the steering angle limit value calculating section 91 subtracts the angle limit component Iga and the speed limit component Igs 'from the output value of the subtracter 107 by subtracting the speed limit component Igs', that is, the rated current Ir. The output value is output to the minimum value selection unit 93 as the steering angle limit value Ien.

Next, the mitigation of the impact applied to the end by the steering control device 6 of the present embodiment will be described.
When steering is performed near the rack end, the limit value Ig is set to a steering angle limit value Ien smaller than the rated current Ir, and the absolute value of the q-axis current command value Iq * (corrected current command value Ias **) is set. It is assumed that the value is set to the limit value Ig. As described above, the steering angle limit value Ien is a value obtained by subtracting the angle limiting component Iga and the speed limiting component Igs ′ from the rated current Ir, and the motor torque is determined by the angle limiting component Iga according to the magnitude of the end separation angle Δθ. And the speed limiting component Igs' is limited in accordance with the second excess angular speed ωo2. This not only prevents the end separation angle Δθ from decreasing further when the end separation angle Δθ is equal to or smaller than the predetermined angle θ1, but also controls the control angular velocity ωs when the end separation angle Δθ is equal to or smaller than the predetermined angle θ2. To reduce the impact of the end contact. Since the angle limiting component Iga and the speed limiting component Igs' are values corresponding to the mode selected based on the estimated axial force Fb and the vehicle speed SPD, the impact applied to the end according to the road surface condition and the vehicle speed SPD is determined. Is alleviated.

  Further, in the present embodiment, the predetermined angle θ2 at which the second upper limit angular velocity ωlim2 starts to decrease is set closer to the neutral position than the predetermined angle θ1 at which the angle restriction component Iga starts to increase. The value becomes larger than zero earlier than the angle limiting component Iga. As a result, when steering to the rack end, the steering angle limit value Ien initially becomes a value limited only by the speed limiting component Igs ', and then the steering angle limit value Ien is changed to the speed limiting component Igs' and the angle limiting component Iga. The value is limited by When the limitation of the steering angle limit value Ien by the angle limitation component Iga is started as described above, the speed limitation component Igs' is gradually attenuated, so that the steering angle limitation value Ien is limited by the large angle limitation component Iga. Even if this is done, the sudden change of the steering angle limit value Ien is suppressed, and it becomes difficult for the driver to feel uncomfortable.

  Here, it is assumed that the steering to the vicinity of the rack end is performed on a low μ road as described above. In this case, even if the absolute value of the q-axis current command value Iq * is limited to the limit value Ig, the control angular velocity ωs may become a large value. In this regard, in this embodiment, the corrected current command value Ias ** is calculated by subtracting the damping control amount Ida from the basic current command value Ias *, and the damping control amount Ida is the first upper limit of the control angular velocity ωs. It increases based on an increase in the first excess angular velocity ωo1 with respect to the angular velocity ωlim1. Thus, when the control angular velocity ωs increases on a low μ road or the like, the absolute value of the corrected current command value Ias ** decreases, so that the impact on the end contact is reduced. Since the damping control amount Ida has a value corresponding to the mode selected based on the estimated axial force Fb and the vehicle speed SPD, the impact applied to the end is reduced according to the road surface condition and the vehicle speed SPD.

  Also, as described above, the gradient of the first upper limit angular velocity ωlim1 at a predetermined angle θ2 or less in each of the maps 82 to 85 of the first excess angular velocity calculation unit 72 and the predetermined value in each of the maps 122 to 125 of the second excess angular velocity calculation unit 103 The gradient of the second upper limit angular velocity ωlim2 at the angle θ2 or less is equal. Therefore, the change tendency of the first excessive angular velocity ωo1 and the second excessive angular velocity ωo2 when steering to the rack end becomes equal. As a result, the end contact mitigation based on the steering angle limit value Ien based on the speed limit component Igs and the end contact mitigation based on the damping control amount Ida are close to each other, and the driver is less likely to feel uncomfortable.

  Further, in the steering control device 6 of the present embodiment, a mode is selected before the absolute value of the control steering angle θs becomes equal to or more than the end separation angle Δθ, that is, before the end hitting relaxation control is executed, and the control steering angle θs is selected. While the absolute value is equal to or larger than the end separation angle Δθ, the selected mode is maintained. Therefore, even if the road surface condition changes during execution of the end contact mitigation control, a sudden change in the motor torque is suppressed.

The operation and effect of the present embodiment will be described.
(1) The steering control device 6 selects one of a plurality of modes, and calculates the q-axis current command value Iq * at the time of executing the end contact mitigation control according to the selected one of the modes. Can reduce the impact of the end contact. Then, since the selected one mode is maintained during the execution of the end mitigation control, even if the road surface condition changes during the execution of the end mitigation control, it is possible to suppress a sudden change in the motor torque. In addition, a decrease in steering feeling can be suppressed.

  (2) The steering control device 6 selects an optimal mode from a plurality of subdivided modes by taking into account the vehicle speed SPD in addition to the estimated axial force Fb. it can.

  (3) Since the angle range between the mode release angle θre and the mode selection angle θsl is set to be larger than the angle range between the near-end steering angle θne and the mode selection angle θsl, the steering is performed near the mode selection angle θsl. Is repeated, it is difficult to release the mode once set. Thereby, for example, it is possible to prevent the mode from being repeatedly selected and canceled, and it is possible to suppress, for example, an increase in the calculation load of the steering control device 6.

(2nd Embodiment)
Next, a second embodiment of the steering control device will be described with reference to the drawings. For convenience of description, the same components are denoted by the same reference numerals as in the first embodiment, and description thereof is omitted.

  As shown in FIG. 9, the damping control amount calculation unit 62 of the present embodiment calculates the first excess angular velocity ωo1 irrespective of the mode, and changes the processing in the calculation processing unit 73 according to the selected mode. Thus, the damping control amount Ida according to the mode is calculated.

  More specifically, the first upper angular velocity calculation unit 81 of the first excess angular velocity ωo1 includes a single map that defines the relationship between the end separation angle Δθ and the first upper angular velocity ωlim1, and refer to the map. Calculates the first upper limit angular velocity ωlim1 according to the end separation angle Δθ. This map is set in the same manner as the low-μ road running upper limit angular velocity map 85, and the first excess angular velocity calculation unit 72 calculates the first excess angular velocity ωo1 as in the first embodiment.

  The mode processing signal Ssl is input to the arithmetic processing unit 73 of the present embodiment in addition to the first excess angular velocity ωo1 and the control angular velocity ωs. Then, the arithmetic processing unit 73 calculates the damping control amount Ida according to the mode indicated by the mode selection signal Ssl.

  As shown in FIG. 10, the arithmetic processing unit 73 determines the relationship between the first excess angular velocity ωo1 and the damping control amount Ida in the high μ road mode, the middle μ road mode, the low μ road stop mode, and the low μ road traveling mode. A high-μ road operation processing map 131, a medium-μ road operation processing map 132, a low-μ road stop operation processing map 133, and a low-μ road traveling operation processing map 134 are provided. Then, the arithmetic processing unit 73 calculates the damping control amount Ida according to each of the maps 131 to 134 based on the first excess angular velocity ωo1 by referring to each of the maps 131 to 134. The arithmetic processing unit 73 sets the sign (direction) of the damping control amount Ida to the sign (direction) indicated by the control angular velocity ωs. In each of the maps 131 to 134, the damping control amount Ida is set to be smallest when the first excess angular velocity ωo1 is zero, and to increase in proportion to the increase of the first excess angular velocity ωo1. The gradient of the damping control amount Ida with respect to the first excess angular velocity ωo1 is as follows: the high μ road angle restriction map 131, the middle μ road angle restriction map 132, the low μ road stopping angle restriction map 133, and the low μ road traveling angle. It is set to increase in the order of the restriction map 134.

  Further, the arithmetic processing unit 73 includes a mode switching unit 135 to which the damping control amount Ida and the mode selection signal Ssl calculated based on each of the maps 131 to 134 are input. The mode switching unit 135 switches an internal switch so that the damping control amount Ida calculated based on the map corresponding to the mode indicated by the mode selection signal Ssl is output. As a result, the damping control amount Ida according to the selected mode is output to the subtractor 64 (see FIG. 2).

  As shown in FIG. 11, in the steering angle limit value calculator 91 of the present embodiment, the angle limit component calculator 102 calculates the angle limit component Iga irrespective of the mode. Specifically, the angle limiting component calculation unit 102 includes a single map that defines the relationship between the end limiting angle Δθ and the vehicle speed SPD and the angle limiting component Iga. An angle limiting component Iga corresponding to the angle Δθ and the vehicle speed SPD is calculated. This map is set in the same manner as the low μ road stopping angle limit map 113, and in the region where the end separation angle Δθ is equal to or smaller than the predetermined angle θ1, the angle limit component Iga is small based on the increase in the vehicle speed SPD. It is set to be.

  Further, the second excess angular velocity calculation unit 103 calculates the second excess angular velocity ωo2 irrespective of the mode, and changes the processing in the speed limit component calculation unit 104 according to the selected mode, thereby changing the mode according to the mode. The calculated speed limiting component Igs is calculated.

  Specifically, the second upper-limit angular velocity calculation unit 121 of the second excess angular velocity ωo2 includes a single map that defines the relationship between the end separation angle Δθ and the second upper-limit angular velocity ωlim2, and refers to the map. Calculates the second upper limit angular velocity ωlim2 according to the end separation angle Δθ. This map is set in the same manner as the low-μ road traveling upper limit angular velocity map 125, and the second excess angular velocity calculation unit 103 calculates the second excess angular velocity ωo2 in the same manner as in the first embodiment.

  The speed limit component calculator 104 receives the mode selection signal Ssl in addition to the second excess angular speed ωo2. Then, the speed limit component calculator 104 calculates the speed limit component calculator 104 according to the mode indicated by the mode selection signal Ssl. The speed limit component calculation unit 104 of the present embodiment calculates the relationship between the second excess angular velocity ωo2 and the speed limit component Igs in the high μ road mode, the middle μ road mode, the low μ road stop mode, and the low μ road traveling mode, respectively. A predetermined high μ road speed limit map, a middle μ road speed limit map, a low μ road stop speed limit map, and a low μ road traveling speed limit map are provided. In addition, each map of the speed limit component calculation unit 104 is set in the same manner as each of the maps 131 to 134, and the speed limit component calculation unit 104 responds to the selected mode similarly to the calculation processing unit 73. The speed limit component Igs is calculated and output to the speed limit component attenuator 106.

  In the steering control device 6 configured as described above, similarly to the first embodiment, the impact of the end contact is reduced according to the road surface condition and the vehicle speed SPD, and the road surface state is changed during the execution of the end contact relaxation control. Even if it changes, the sudden change of the motor torque is suppressed.

As described above, this embodiment has the same operations and effects as the operations and effects (1) to (3) of the first embodiment.
This embodiment can be implemented with the following modifications. The present embodiment and the following modifications can be implemented in combination with each other within a technically consistent range.

  In the above embodiments, at least one of the high μ road mode and the middle μ road mode may be subdivided based on the vehicle speed SPD. Further, the low μ road mode does not have to be subdivided based on the vehicle speed SPD. Further, the mode selection unit 55 may select one of the subdivided modes based on a state quantity other than the vehicle speed SPD in addition to the estimated axial force Fb.

  In the above embodiments, the angle range between the mode release angle θre and the mode selection angle θsl may be set to be equal to or less than the angle range between the near-end steering angle θne and the mode selection angle θsl. The angle θre and the mode selection angle θsl may be the same angle.

  In the above embodiments, the estimated axial force Fb acting on the rack shaft 12 is calculated based on the motor torque and the steering torque Ts. However, the present invention is not limited to this. For example, the estimated axial force Fb is estimated based on the steered angle of the steered wheels 3 and the like. The axial force Fb may be calculated. Further, for example, a pressure sensor or the like capable of detecting an axial force may be provided on the rack shaft 12, and the mode selection unit 55 may select a mode based on the detection result.

  In the above embodiments, the shapes of the maps 82 to 85 in the first excess angular velocity calculation unit 72 can be appropriately changed. For example, the angle at which the first upper limit angular velocity ωlim1 starts to decrease may be the predetermined angle θ1, or the angle at which the first upper limit angular velocity ωlim1 starts to decrease may differ between the maps 82 to 85. Further, the gradient of the first upper limit angular velocity ωlim1 in the area of the predetermined angle θ2 or less in each of the maps 82 to 85 and the second upper limit in the area of the predetermined angle θ2 or less of each of the maps 122 to 125 of the second excess angular velocity calculation unit 103. It may be different from the gradient of the angular velocity ωlim2. Further, the first upper angular velocity ωlim1 in a region larger than the predetermined angle θ2 in each of the maps 82 to 85 of the first excess angular velocity calculation unit 72 and the predetermined angle θ2 in each of the maps 122 to 125 of the second excess angular velocity calculation unit 103 May be equal to the second upper limit angular velocity ωlim2 in a region where the maximum is also large. Similarly, the shape of each of the maps 122 to 125 in the second excess angular velocity calculation unit 103 can be appropriately changed.

  In each of the above embodiments, the shapes of the maps 111 to 114 in the angle limiting component calculation unit 102 can be changed as appropriate. For example, the angle at which the angle limiting component Iga starts to increase may be the predetermined angle θ2. Further, the angle limiting component Iga may change non-linearly in a region of a predetermined angle θ1 or less in each of the maps 111 to 114. In the second embodiment, the angle limiting component Iga may not be changed according to the vehicle speed SPD.

  In the above embodiments, the shapes of the maps 131 to 134 of the arithmetic processing unit 73 can be changed as appropriate. For example, the damping control amount Ida may be set to increase nonlinearly based on an increase in the first excess angular velocity ωo1. In the first embodiment, the damping control amount Ida may not be changed according to the vehicle speed SPD. Similarly, the shape of each map in the speed limit component calculation unit 104 can be appropriately changed.

  In the above embodiments, the value obtained by subtracting the damping control amount Ida from the basic current command value Ias * is subjected to the guard process based on the limit value Ig. However, the present invention is not limited to this. For example, the steering wheel 2 may return to the neutral position. A guard processing may be performed based on the limit value Ig with a value obtained by further adding the control amounts and the like for assistance.

  In the above embodiments, the limit value setting unit 56 includes the voltage limit value calculation unit 92 that calculates the voltage limit value Ivb based on the power supply voltage Vb. However, the present invention is not limited to this. Additionally or alternatively, another calculation unit that calculates another limit value based on another state quantity may be provided. Alternatively, the limit value setting unit 56 may not include the voltage limit value calculation unit 92, and may set the steering angle limit value Ien as it is as the limit value Ig.

In the above embodiments, the steering angle limit value calculation unit 91 may not include the angle limit execution determination unit 105 and the speed limit component attenuation unit 106.
In the above embodiments, the steering angle limit value Ien may be calculated by subtracting only the angle limiting component Iga from the rated current Ir.

  In each of the above embodiments, the end command mitigation control may be performed by limiting the basic current command value Ias * to the limit value Ig or less without providing the current command value calculation unit 51 with the damping control amount calculation unit 62. . Further, the current command value calculation unit 51 may not include the guard processing unit 63, and may perform the end hitting mitigation control only by subtracting the damping control amount Ida from the basic current command value Ias *.

In the above embodiments, the steering angle threshold may be set to an angle other than the near-end steering angle θne.
In each of the above embodiments, the control steering angle calculation unit 53 integrates the rotation speed of the motor 21 with the control steering angle θs when the rack shaft 12 is in the steering neutral position as the origin, and calculates the rotation speed and the motor angle θm. The control steering angle θs was calculated based on However, the present invention is not limited to this, and the control steering angle calculation unit 53 calculates the control steering angle and the end separation angle based on the rotation angle and the motor angle θm with the control steering angle at the rack end position as the origin, for example. The limit value Ig may be calculated based on this. The origin of the control steering angle may be stored in advance, for example, at the time of manufacturing the vehicle, or may be set by learning through steering. Further, for example, a sensor for detecting the rotation angle of the steering shaft 11, which is a rotation shaft that can be converted into the steering angle of the steered wheels 3, is provided as an absolute angle, and the control steering angle calculation unit 53 performs the control based on the detection value of the sensor. The control steering angle θs may be calculated.

  In the above embodiments, the steering control device 6 controls the EPS 1 in which the EPS actuator 5 applies a motor torque to the column shaft 14. However, the present invention is not limited thereto. A control device may be a steering device that applies a motor torque to the steering wheel 12. In addition to the EPS, the steering control device 6 controls a steer-by-wire steering device in which power transmission between a steering unit operated by a driver and a steering unit that steers steered wheels is separated. As a target, the end contact mitigation control may be executed as in the present embodiment with respect to the torque command value (q-axis current command value) of the motor of the steering actuator provided in the steering unit.

Next, technical ideas that can be grasped from the above embodiments and modified examples will be additionally described below.
(A) The control unit is configured to, when the absolute value of the rotation angle of the rotating shaft that can be converted to the steered angle of the steered wheel exceeds a steering angle threshold value according to the steering device, to determine the absolute value of the rotation angle. A steering angle limit value calculating unit that calculates a steering angle limit value that decreases based on an increase in the value, and a limit value setting unit that sets a limit value that is an upper limit of the absolute value of the torque command value to be equal to or less than the angle limit value. A guard processing unit for limiting an absolute value of the torque command value to the limit value or less, and driving the motor so that the motor torque follows the torque command value limited by the guard processing unit. Wherein the end hitting mitigation control is executed, and the steering angle limit value calculation unit is configured to select the one mode selected from a value based on a rated torque preset as a motor torque that can be output by the motor. Angle according to The steering angle limit value is calculated based on a value obtained by subtracting the limit component and the speed limit component, and the angle limit component is used when the absolute value of the rotation angle exceeds the steering angle threshold. The calculation is performed so as to increase based on the increase in the absolute value of the rotation angle, and the speed limiting component is calculated so as to increase based on the increase in the excess of the angular speed with respect to the upper limit angular speed according to the absolute value of the rotation angle. Steering control device.

  (B) the torque command value calculating section includes a basic command value calculating section that calculates a basic command value based on a steering torque; A damping control amount calculation unit that calculates a damping control amount so as to increase based on an increase in the excess of the angular velocity with respect to the upper limit angular velocity according to the absolute value, wherein the absolute value of the basic command value is reduced. A steering control device that calculates the torque command value based on a value obtained by adding a damping control amount, wherein the damping control amount calculation unit calculates the damping control amount according to the selected one mode. .

  DESCRIPTION OF SYMBOLS 1 ... Electric power steering device (EPS), 2 ... Steering wheel, 3 ... Steering wheel, 4 ... Steering mechanism, 5 ... EPS actuator (actuator), 6 ... Steering control device, 11 ... Steering shaft, 12 ... Rack shaft, 18 ... Rack end, 21 ... Motor, 41 ... Microcomputer (control unit), 51 ... Current command value calculation unit, 54 ... Axial force estimation unit, 55 ... Mode selection unit, 56 ... Limit value setting unit, 61 ... Basic assist calculation unit , 62: damping control amount calculation unit, 63: guard processing unit, 86, 115, 126, 135: mode switching unit, 91: steering angle limit value calculation unit, 92: voltage limit value calculation unit, 102: angle limit component calculation Unit, 104: speed limit component calculation unit, Fb: estimated axial force, Ien: steering angle limit value, Iga: angle limit component, Igs: speed limit component, Ivb: voltage limit value, Ias *: basic power Command value, Ias **: corrected current command value, Id *: d-axis current command value, Ida: damping control amount, Ig: limit value, Iq *: q-axis current command value, Ir: rated current, SPD: vehicle speed Ssl: Mode selection signal, Ts: Steering torque, Vb: Power supply voltage, θs: Control steering angle, θne: End near steering angle (steering angle threshold), θre: Mode release angle, θsl: Mode selection angle, ωs: Control angular velocity.

Claims (3)

A steering device to which a motor torque for reciprocating a steered shaft connected to steered wheels by an actuator having a motor as a drive source is to be controlled,
A control unit that controls a drive of the motor so as to have a torque command value calculation unit that calculates a torque command value that is a target value of the motor torque output by the motor, and that the motor torque follows the torque command value. Prepared,
The control unit is configured to increase the absolute value of the rotation angle when the absolute value of the rotation angle of the rotation shaft that can be converted to the steered angle of the steered wheels exceeds a steering angle threshold value according to the steering device. Based on, to execute the end hit relaxation control to reduce the absolute value of the torque command value,
Based on an axial force acting on a steered shaft connected to the steered wheels, a plurality of modes in which values used when calculating the torque command value at the time of executing the end contact mitigation control are set to be different from each other. Equipped with a mode selection unit to select one of them,
The selected one mode is a steering control device that is held while the end hit mitigation control is being executed. The steering control device according to claim 1,
The steering control device, wherein the mode selection unit selects one of the plurality of modes based on the axial force and the vehicle speed. The steering control device according to claim 1 or 2,
The mode selection unit, when the rotation angle exceeds the mode selection angle on the neutral position side than the steering angle threshold to the end side, selects one of the plurality of modes,
The selected one mode is held until the mode selection angle exceeds the mode release angle to the neutral position side from the mode selection angle to the neutral position side,
A steering control device wherein an angle range between the mode release angle and the mode selection angle is set to be larger than an angle range between the steering angle threshold and the mode selection angle.