JP4730223B2 - Vehicle steering system - Google Patents

Description

  The present invention relates to a vehicle steering apparatus.

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

For example, in the vehicle steering device described in Patent Document 2, a target value of a vehicle state quantity (target state quantity, target yaw rate, target slip angle, etc.) related to the yaw moment of the vehicle is calculated based on the vehicle model, The steering characteristic (steer characteristic) of the vehicle is determined by comparing the value of the target state quantity with the actual value (actual value) detected by the sensor. When the vehicle is in the oversteer state, the steering angle is changed in the opposite direction to the yaw moment by feedback control based on the deviation between the value of the target state quantity calculated based on the vehicle model and the actual value. By controlling the turning angle so as to apply a so-called counter steer, the vehicle posture is stabilized.
JP 2002-254964 A JP 2005-88648 A

  By the way, when the vehicle is in an oversteer state, in many cases, the driver also performs a steering operation to apply the countersteer. As a result, the steer characteristic rapidly moves toward the stabilization direction. However, the counter-steer operation by such a driver often tends to delay its “return”, that is, return from the counter steering. For this reason, the counter amount tends to be excessive, and particularly in the case where the control is performed based on the vehicle model as in the conventional example, the control target value and the actual value are maintained by maintaining the counter steering by the driver. Is large, that is, the amount of control becomes large, and the excess of the counter amount is likely to become more remarkable. As a result, overshoot, that is, the situation where the vehicle posture stabilizes and then destabilizes in the reverse direction, especially on a low μ road with a narrow stable region that can keep the vehicle posture stable, such as a frozen road. There was a problem that it was easy to fall, and in this respect, there was still room for improvement.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to promptly stabilize the vehicle by suppressing the occurrence of overshoot caused by the counter steering return delay by the driver. An object of the present invention is to provide a vehicular steering apparatus.

In order to solve the above problems, the invention according to claim 1 is directed to steering by adding a second rudder angle of the steered wheel based on motor drive to a first rudder angle of the steered wheel based on a steering operation. A transmission ratio variable device that varies a transmission ratio between the steering wheel and the steered wheel, a control unit that controls the operation of the transmission ratio variable device, and a steering characteristic determination unit that determines a steering characteristic of the vehicle. The means controls the operation of the transmission ratio variable device to stabilize the vehicle posture based on a control target component for controlling the yaw moment of the vehicle, and when the vehicle is in an oversteer state , by calculating the over-steering control amount as the control target element, it actuates the variable transmission ratio device so as to change the second steering angle yaw moment and reverse direction of the vehicle A steering apparatus for a vehicle that performs oversteer control, comprising: a countersteering determination unit that determines whether or not countersteering is performed during the oversteer control, wherein the control unit includes the countersteering and the yaw moment is If the changes in the stable direction, to a value after correction in reducing the oversteer control amount and the control target components, and the gist.

  That is, when the yaw moment of the vehicle changes in a stable direction due to the counter steer, it is desirable to quickly reduce the counter amount and return to the normal steering state. Therefore, if the counter steering by the driver is still performed even though the yaw moment has changed in the stable direction, this means that a “return delay” has occurred. However, according to the above configuration, even in a situation in which the counter steering by the driver is delayed, the oversteer control amount, that is, the counter amount based on the oversteer control is reduced, thereby reducing the counter amount as a whole. It can be kept small. As a result, it is possible to quickly stabilize the vehicle while suppressing the occurrence of overshoot.

The gist of the invention described in claim 2 is that the control means greatly reduces the oversteer control amount as the yaw moment changes in a stable direction.
The gist of the invention described in claim 3 is that the control means greatly reduces the oversteer control amount as the steering operation is performed in the counter direction.

According to each of the above configurations, the oversteer control amount is greatly reduced in situations where overshoot is likely to occur, so that vehicle stabilization can be achieved more quickly.
The gist of the invention described in claim 4 is that the control means gradually reduces the oversteer control amount.

  According to the above configuration, it is possible to prevent the vehicle posture from becoming unstable due to the change in the oversteer control amount, and to suppress the change in the steering reaction force that accompanies this, thereby realizing a good steering feeling.

  According to a fifth aspect of the present invention, the counter steering determination means has the steering operation in a direction opposite to the direction of the yaw moment, the steering speed is higher than a predetermined threshold, and the oversteer control is performed. The gist is to determine that the counter steering has been performed when the amount of change in the steering angle from the steering angle at the start time exceeds a predetermined threshold.

  According to the above configuration, it is possible to reliably determine the presence or absence of counter steering by the driver. Since the steering torque is not used as the state quantity used for the determination, it can be applied to a combination with a hydraulic power steering apparatus that does not normally have a torque sensor without requiring a special additional configuration.

  According to the present invention, it is possible to provide a vehicle steering device that can quickly stabilize the vehicle by suppressing the occurrence of overshoot due to the counter steering return delay by the driver.

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

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

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

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

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

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

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

  In the present embodiment, the IFSECU 8 that controls the gear ratio variable actuator 7 and the EPSECU 18 that controls the EPS actuator 17 are connected via an in-vehicle network (CAN: Controller Area Network) 23. Are connected to a plurality of sensors for detecting the vehicle state quantity. Specifically, a steering angle sensor 24, a torque sensor 25, wheel speed sensors 26a and 26b, a lateral G sensor 28, a vehicle speed sensor 29, a brake sensor 30, and a yaw rate sensor 31 are connected to the in-vehicle network 23. A plurality of vehicle state quantities detected by the sensors, that is, steering angle θs, steering torque τ, wheel speed Vtr, Vtl, turning angle θt, slip angle θsp, vehicle speed V, brake signal Sbk, and yaw rate Ry are as follows: The data is input to the IFSECU 8 and the EPSECU 18 via the in-vehicle network 23.

  In this embodiment, the turning angle θt is obtained by multiplying the steering angle θs by the base gear ratio of the rack and pinion mechanism 4, that is, by adding the ACT angle θta to the steering angle θts, and the slip angle θsp is obtained based on the lateral acceleration detected by the lateral G sensor 28 and the yaw rate Ry. The IFSECU 8 and EPSECU 18 transmit and receive control signals by mutual communication via the in-vehicle network 23. The IFSECU 8 and EPSECU 18 perform the gear ratio variable control and the power assist control in an integrated manner based on the vehicle state quantities and control signals input via the in-vehicle network 23.

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

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

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

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

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

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

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

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

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

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

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

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

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

  More specifically, the vehicle speed V and the steering torque τ are input to the assist control unit 45 and the torque inertia compensation control unit 46, respectively. The assist control unit 45 calculates a basic assist current command Ias * as a base control target component, and the torque inertia compensation control unit 46 is an inertia compensation current command Iti that is a control target component for compensating the inertia of the motor 22. Calculate *.

  The vehicle speed V, the steering torque τ, and the turning angle θt are input to the steering return control unit 47, and the vehicle speed V and the steering speed ωs are input to the damper compensation control unit 48. The steering return control unit 47 calculates a steering return current command Isb *, which is a control target component for improving the return characteristic of the steering 2, and the damper compensation control unit 48 improves the power assist characteristic during high speed running. A damper compensation current command Idp *, which is a control target component for the calculation, is calculated.

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

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

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

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

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

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

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

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

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

  In addition to the yaw rate F / B calculation unit 71 and the slip angle F / B calculation unit 72, the OS control calculation unit 65 of this embodiment calculates a control component for ensuring stability during so-called μ split braking. A yaw angle F / B calculation unit 73 is provided. Then, the yaw angle F / B calculation unit 73 executes the yaw angle F / B calculation based on the target yaw angle θy0 and the yaw angle θy using the determination result in the crossing road determination unit 62 as a trigger, and the yaw angle is calculated based on the deviation Δθy. By multiplying the gain Kyaw, the yaw angle F / B command angle θy * is calculated.

  The yaw rate F / B command angle θRyp * and yaw rate differential F / B command angle θRyd * calculated by the yaw rate F / B calculation unit 71, and the slip angle F / B command calculated by the slip angle F / B calculation unit 72. The angle θsp * and the yaw angle F / B command angle θy * calculated by the yaw angle F / B calculation unit 73 are input to the adder 76. Then, the OS control calculation unit 65 calculates an ACT command angle θos * during OS control by superimposing these control target components in the adder 76 (OS control calculation).

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

  The vehicle speed V, the steering angle θs, the yaw rate Ry, and the OS / US characteristic value Val_st are input to the control ON / OFF determination unit 67. Then, the control ON / OFF determination unit 67 performs oversteer control (OS control) based on the OS control ACT command angle θos * calculated by the OS control calculation unit 65 or the US calculated by the US control calculation unit 66. It is determined whether to perform understeer control (US control) based on the ACT command angle θus * during control, and the determination result is output as a control ON / OFF signal Sc (control ON / OFF determination).

  The IFS_ACT command angle calculator 68 includes an OS control ACT command angle θos * calculated by the OS control calculator 65, a US control ACT command angle θus * calculated by the US control calculator 66, and control ON / OFF. A control ON / OFF signal Sc output from the determination unit 67 is input. When the input control ON / OFF signal Sc indicates “OS control ON”, the IFS_ACT command angle calculator 68 determines the OS control time ACT command angle θos * as the control ON / OFF signal Sc. When “US control ON” indicates “US control ON”, the ACT command angle θus * during US control is output as the IFS_ACT command angle θifs * (IFS_ACT command angle calculation). In the present embodiment, when the control ON / OFF signal Sc is “NS”, that is, indicates that the steering is neutral, the IFS_ACT command angle calculator 68 sets the IFS_ACT command angle θifs * to “0”. And

(Counter correction control)
Next, counter correction control in the vehicle steering apparatus of the present embodiment will be described.
As shown in FIG. 6, in the present embodiment, the IFS control calculation unit 35 serves as a counter steering determination unit that determines the presence or absence of counter steering by the driver during the OS control and a detection unit that detects a change in the yaw moment of the vehicle. Counter steering determination unit 77 is provided. When the counter steering determination unit 77 determines that the counter steering is under OS control and the yaw moment of the vehicle has changed in a stable direction, the IFS control calculation unit 35 performs the OS control calculation unit. The OS control ACT command angle θos * calculated by 65 is corrected (counter correction control).

  More specifically, in the present embodiment, the counter steering determination unit 77 receives the yaw rate Ry, the steering angle θs, and the steering speed ωs. The counter steering determination unit 77 is supplied with a control ON / OFF signal Sc output from the control ON / OFF determination unit 67 together with the vehicle state quantities. Holds the steering angle θs_st at the start of the OS control until the end of the control. Then, the counter steering determination unit 77 determines that there is counter steering by the driver under OS control when all of the following three requirements are satisfied.

-Steering operation in the opposite direction of the yaw moment occurred.
The steering speed ωs (absolute value thereof) is faster than a predetermined threshold value ωs0;
-The steering angle change amount from the steering angle θs_st at the start of the OS control exceeds a predetermined threshold θs0.

  The counter steering determination unit 77 detects a change in the yaw moment of the vehicle based on the change in the yaw rate Ry (the differential value dRy of the yaw rate Ry). Then, after determining that there is counter steering during the OS control, if it is determined that the yaw moment has changed in a stable direction, a counter correction signal S_cs indicating that the counter correction control should be performed is output.

  That is, as shown in the flowchart of FIG. 7, the counter steering determination unit 77 acquires the yaw rate Ry, the steering angle θs and the steering speed ωs, and the control ON / OFF signal Sc as state quantities (and control signals) (step 201). Then, it is determined whether or not the input control ON / OFF signal Sc indicates “OS control ON” (step 202). If “OS control ON” is indicated (step 202: YES), it is determined whether or not the steering angle θs_st at the time of starting OS control is held (step 203). In (Step 203: NO), the steering angle θs at that time is held (stored) as the steering angle θs_st at the start of OS control (Step 204).

  If it is determined in step 203 that the steering angle θs_st at the start of the OS control is already held (step 203: YES), the counter steering determination unit 77 does not execute the process of step 204. If the input control ON / OFF signal Sc does not indicate “OS control ON” in step 202 (step 202: NO), the above steps 203 and 204, and the following steps 205 to 205 are performed. The process 211 is not executed.

  Next, the counter steering determination unit 77 determines whether or not a counter steering flag indicating that the counter steering is being performed by the driver is set (step 205). If the counter steering flag is not set (step 205: NO), the above-described counter steering determination is executed (step 206 to step 208).

  That is, the counter steering determination unit 77 first determines whether or not a steering operation in the direction opposite to the direction of the yaw moment has occurred depending on whether or not the signs of the yaw rate Ry and the steering speed ωs are inconsistent (step 206). Next, it is determined whether or not the steering speed ωs (absolute value thereof) is faster than a predetermined threshold value ωs0 (step 207). Subsequently, the amount of change in the steering angle from the steering angle θs_st at the start of OS control is the predetermined threshold value. It is determined whether or not θs0 is exceeded (step 208). When all the requirements of Step 206 to Step 208 are satisfied, that is, the signs of the yaw rate Ry and the steering speed ωs do not match (Step 206: YES), and the steering speed ωs (absolute value) is from a predetermined threshold ωs0. Is faster (| ωs |> ωs0, step 207: YES), and the steering angle change from the steering angle θs_st at the start of OS control exceeds a predetermined threshold θs0 (| θs_st−θs |> θs0, step 208: If YES, the counter steering flag is set (step 209), assuming that counter steering by the driver is being performed.

  When it is determined in step 205 that the counter steering flag has already been set (step 205: YES), the counter steering determination unit 77 does not execute the processing in steps 206 to 209. If any of the determination conditions of Step 206 to Step 208 is not satisfied (Step 206: NO, Step 207: NO, or Step 208: NO), the processing of Steps 210 and 211 shown below is executed. do not do.

  Next, the counter steering determination unit 77 determines whether or not the yaw moment of the vehicle has changed in the stable direction, that is, the neutral steering direction, based on the differential value dRy of the yaw rate Ry (step 210). If it is determined that the yaw moment has changed in the stable direction (step 210: YES), a counter correction signal S_cs indicating that the above-described counter correction control should be performed is output (step 211). When it is determined in step 210 that the yaw moment change is not in the stable direction (step 210: NO), the counter steering determination unit 77 does not execute the process of step 211 and does not output the counter correction signal S_cs. .

  As shown in FIG. 6, in this embodiment, the counter correction signal S_cs output from the counter steering determination unit 77 is input to the counter correction gain calculation unit 78. Then, the counter correction gain calculator 78 generates a counter correction gain K_cs for reducing the OS control ACT command angle θos * based on the input of the counter correction signal S_cs.

  More specifically, the counter correction gain calculator 78 receives the steering speed ωs and the yaw rate Ry. The counter correction gain calculation unit 78 greatly reduces the ACT command angle θos * during OS control as the yaw moment changes greatly in the stable direction and as the steering operation is performed in the counter direction. That is, a counter correction gain K_cs having a small value is generated (K_cs = 1 to 0).

  Specifically, in the present embodiment, the counter correction gain calculation unit 78 includes a first gain map in which the change in the yaw moment of the vehicle (the differential value dRy of the yaw rate Ry) and the yaw gain Ky as shown in FIG. FIG. 9 includes two gain maps, a steering operation direction (steering speed ωs) and a second gain map in which the direction gain Kd is associated. In the first gain map, the yaw gain Ky becomes smaller as the differential value dRy of the yaw rate Ry indicates that the yaw moment changes in the stable direction. In the second gain map, The steering speed ωs is set such that the directional gain Kd decreases as the steering operation is performed in the counter direction (Ky, Kd = 1 to 0). Then, the counter correction gain calculator 78 determines the yaw gain Ky and the direction gain Kd by comparing the input steering speed ωs and the yaw rate Ry with the corresponding gain maps, and multiplies these two gains. A counter correction gain K_cs is generated (K_cs = Ky × Kd). When the counter correction signal S_cs is not input, the counter correction gain calculation unit 78 sets the counter correction gain K_cs to “1”.

  As shown in FIG. 6, the counter correction gain K_cs generated in the counter correction gain calculation unit 78 is input to the multiplier 79 together with the OS control ACT command angle θos *. The multiplier 79 multiplies the OS control ACT command angle θos * by the counter correction gain K_cs to reduce the OS control ACT command angle θos *, and the corrected OS control ACT command angle θos. ** is input to the IFS_ACT command angle calculation unit 68.

Next, the processing procedure of each control calculation in the IFS control calculation unit will be described.
As shown in the flowchart of FIG. 10, the IFS control calculation unit 35 first executes vehicle model calculation (step 301), and then executes crossover determination (step 302). Then, a steer characteristic calculation is executed (step 303).

  Next, the IFS control calculation unit 35 executes the yaw rate F / B calculation and the slip angle F / B calculation based on the target yaw rate Ry0 and the target slip angle θsp0 calculated in the vehicle model calculation in step 301 above. An ACT command angle θos * is calculated during OS control (OS control calculation, step 304). If it is determined in step 302 that the μ split braking state is in effect, the yaw angle F / B calculation is executed using the determination result as a trigger. Then, the US control calculation ACT command angle θus * is calculated by executing the US control calculation (step 305).

  Next, the IFS control calculation unit 35 executes control ON / OFF determination (step 306), and subsequently executes counter correction calculation (step 307). The OS control ACT command angle θos * (θos **) or the US control ACT command angle θus * (or “0”) is used as a control target component for realizing the active steering function, that is, IFS_ACT command angle θifs *. Output (IFS_ACT command angle calculation, step 308).

As described above, according to the present embodiment, the following operations and effects can be obtained.
(1) The IFS control calculation unit 35 includes a counter steering determination unit 77 as counter steering determination means for determining whether or not the counter steering is performed by the driver under OS control. When the counter steering determination unit 77 determines that there is counter steering during OS control and the yaw moment of the vehicle has changed in a stable direction, the OS control calculated by the OS control calculation unit 65 is performed. The correction is executed to reduce the hour ACT command angle θos * (counter correction control).

  That is, when the yaw moment of the vehicle changes in a stable direction due to the counter steer, it is desirable to quickly reduce the counter amount and return to the normal steering state. Therefore, when the driver still performs counter steering even though the yaw moment has changed in a stable direction, this means that a “return delay” has occurred. However, according to the above configuration, even in a situation in which the counter steering by the driver is delayed, the oversteer control amount, that is, the counter amount based on the oversteer control is reduced, thereby reducing the counter amount as a whole. It can be kept small. As a result, it is possible to quickly stabilize the vehicle while suppressing the occurrence of overshoot.

  (2) The counter correction signal S_cs output from the counter steering determination unit 77 is input to the counter correction gain calculation unit 78. The counter correction gain calculation unit 78 greatly reduces the ACT command angle θos * during OS control as the yaw moment changes greatly in the stable direction and as the steering operation is performed in the counter direction. That is, a counter correction gain K_cs having a small value is generated (K_cs = 1 to 0).

  According to the above configuration, the oversteer control amount can be greatly reduced as the situation in which overshoot is likely to occur. As a result, the vehicle can be stabilized more quickly.

  (3) The counter steering determination unit 77 generates a steering operation in a direction opposite to the direction of the yaw moment, the steering speed ωs (absolute value thereof) is higher than a predetermined threshold ωs0, and the steering angle at the time of starting OS control. When the steering angle change amount from θs_st exceeds the predetermined threshold θs0, it is determined that there is counter steering by the driver under OS control.

  According to the above configuration, it is possible to reliably determine the presence or absence of counter steering by the driver. Since the steering torque τ is not used as a state quantity used for the determination, it can be applied to a combination with a hydraulic power steering apparatus that does not have a torque sensor without requiring a special additional configuration. .

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

-When the counter control amount is reduced, the counter control amount may be gradually reduced.
In addition, the determination condition in the steering steering determination, “when the amount of change in the steering angle from the steering angle θs_st at the start of the OS control exceeds a predetermined threshold θs0” is “the maximum steering angle after the vehicle enters the oversteer state” From ... "

The schematic block diagram of the steering apparatus for vehicles. Explanatory drawing of gear ratio variable control. Explanatory drawing of gear ratio variable control. The control block diagram of the steering device for vehicles. The flowchart which shows the process sequence of the arithmetic processing in IFSECU. The control block diagram of an IFS control calculating part. The flowchart which shows the process sequence of a counter correction calculation. Explanatory drawing of the gain map linked | related with the yaw moment change of a vehicle. Explanatory drawing of the gain map linked | related with the steering operation direction. The flowchart which shows the process sequence of IFS control calculation.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Steering device for vehicles, 2 ... Steering, 6 ... Steered wheel, 7 ... Variable gear ratio actuator, 8 ... IFSECU, 35 ... IFS control calculating part, 61 ... Vehicle model calculating part, 63 ... Steer characteristic calculating part, 65 ... OS control calculation unit, 67 ... control ON / OFF determination unit, 77 ... counter steering determination unit, 78 ... counter correction gain calculation unit, θt ... turning angle, θts ... steer turning angle, θta ... ACT angle, θifs * ... IFS_ACT command angle, θos *, θos ** ... ACT command angle during OS control, Val_st ... OS / US characteristic value, Sc ... control ON / OFF signal, S_sc ... counter correction signal, Ry ... yaw rate, dRy ... differential value, θs , Θs_st: steering angle, θs0: threshold, ωs: steering speed, ωs0: threshold, K_cs: counter correction gain, Ky: yaw gain, Kd: direction gain.

Claims (5)

A transmission ratio variable device that varies a transmission ratio between the steering wheel and the steered wheel by adding a second rudder angle of the steered wheel based on motor drive to the first steered angle of the steered wheel based on the steering operation; And a control means for controlling the operation of the variable transmission ratio device and a steer characteristic determining means for determining the steer characteristic of the vehicle, the control means being based on a control target component for controlling the yaw moment of the vehicle. When the vehicle is in an oversteer state in order to stabilize the posture, and when the vehicle is in an oversteer state, by calculating an oversteer control amount as the control target component, the vehicle A vehicle steering apparatus that performs oversteer control for operating the transmission ratio variable device to change the second steering angle in a direction opposite to a yaw moment of
A counter steering determination means for determining presence or absence of counter steering during the oversteer control;
Said control means, said counter steering is there, and when the yaw moment is changed to a stable direction, to a value after correction in reducing the oversteer control amount and the control target element, and wherein Vehicle steering system. The vehicle steering apparatus according to claim 1,
The vehicle steering apparatus according to claim 1, wherein the control means greatly reduces the oversteer control amount as the yaw moment changes in a stable direction. In the vehicle steering device according to claim 1 or 2,
The vehicle steering apparatus according to claim 1, wherein the control means greatly reduces the oversteer control amount as the steering operation is performed in a counter direction. In the steering device for vehicles according to any one of claims 1 to 3,
The control means gradually reduces the oversteer control amount;
A vehicle steering apparatus characterized by the above. In the vehicle steering device according to any one of claims 1 to 4,
The counter steering determination means has a steering angle from a steering angle at which the steering operation in the direction opposite to the direction of the yaw moment occurs, the steering speed is faster than a predetermined threshold, and the oversteer control is started. A vehicle steering apparatus, wherein when the amount of change exceeds a predetermined threshold, it is determined that the counter steering has been performed.

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