JP2006315481A - Vehicular steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vehicular steering device capable of ensuring higher vehicle stability even in a low μ road. <P>SOLUTION: The vehicular steering device (a steering device) is provided with a target state amount correction operation part 73 correcting target state amount (a target yaw rate Ry0 and a target slip angle θsp0) computed by a vehicular model operation part 61 so as to make the value (an absolute value) small. An OS control operation part 65 computes an OS control time ACT command angle θos* which is a control target component of an ACT angle for over-steering control, from feed-back computing on the basis of a deviation between a value of the target state amount (a target yaw rate Ry0' and a target slip angle θsp) after correction corrected by the target state amount correction operation part 73 and an actual value (a yaw rate Ry and a slip angle θsp). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a vehicle steering apparatus.

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

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, on a low μ road such as a frozen road, the response of the vehicle behavior to the change of the turning angle is dull and the stable region in which the vehicle posture can be kept stable, that is, the change speed at which the yaw rate can be stably controlled. The range of (yaw angular acceleration) is extremely narrow. Therefore, such a change in the turning angle on the frozen road should be performed in such a manner that the change rate of the yaw rate is kept as low as possible, that is, the change amount is quickly minimized so as not to cause a sudden change in the vehicle posture. desirable.

  However, in the conventional configuration described above, in an environment where the actual value does not quickly follow the target state value, the time required for the oversteer control becomes longer, and the counter amount (counter direction) The rudder angle change amount) tends to be large. For this reason, there is a possibility that the change rate of the yaw rate exceeds the stable region, and the vehicle posture may not be stabilized quickly due to the occurrence of overshoot due to the excessive change rate of the yaw rate. .

  The present invention has been made to solve the above problems, and an object of the present invention is to provide a vehicle steering apparatus capable of ensuring higher vehicle stability even on a low μ road.

  In order to solve the above problems, the invention according to claim 1 is directed to a vehicle based on a drive unit capable of changing the turning angle of the steered wheels, a control unit for controlling the operation of the drive unit, and a vehicle model. Vehicle model calculation means for calculating the target value of the vehicle state quantity related to the yaw moment of the vehicle, and steer characteristic determination means for determining the steer characteristic of the vehicle by comparing the calculated target value with its actual value. The control means is a vehicle steering apparatus that executes oversteer control for operating the drive means to generate the turning angle in a direction opposite to the yaw moment when the vehicle is in an oversteer state. And a target state quantity correction unit that corrects the calculated target value so that the absolute value thereof is reduced, and the control unit is configured to provide a deviation between the corrected target value and the actual value. The feedback calculation based, computing the control target components in the oversteer control, and the gist.

The gist of the invention described in claim 2 is that the vehicle state quantity related to the yaw moment of the vehicle is at least one of a yaw rate and a slip angle.
According to each of the above configurations, the corrected target state quantity has a smaller value (absolute value) than the original target state quantity. Therefore, the deviation used for the feedback calculation is the case where the original target state quantity is used. The value (absolute value) is larger than the deviation. Accordingly, a control target component having a large value (absolute value) is calculated at the start of oversteer control, thereby speeding up the turning angle change in the counter direction, shortening the time required for the control, and finally This counter amount can be reduced. As a result, it is possible to quickly change the yaw rate while suppressing the yaw rate changing speed, thereby suppressing the overshoot caused by the excessive yaw rate changing speed and quickly stabilizing the vehicle posture. .

  In addition, when the driver performs the steering operation in the counter direction during the oversteer control, the value of the target state quantity has already shifted to the counter direction side at the end of the control, that is, at the time of the neutral steer. In such a case, the overshoot as described above may occur and the oversteer in the opposite direction may occur. However, when the value of the target state quantity shifts to the one indicating the opposite side from the beginning of control, the elapsed time until becoming neutral steer in feedback calculation is more than the elapsed time until becoming neutral steer in the steer characteristic determination Will also be shorter. Therefore, the control for eliminating the oversteer in the initial direction converges quickly, thereby suppressing the yaw rate change rate in the counter direction and suppressing the occurrence of oversteer in the opposite direction due to overshoot. . Further, since the steer characteristic determination is performed using the target state quantity before correction, the oversteer in the opposite direction is performed from the time when the neutral steer for feedback calculation is reached until the neutral steer for the steer characteristic determination. The driving means is controlled so as to change the turning angle in a direction to eliminate the problem. Therefore, the excessive yaw rate change speed caused by the control for eliminating the oversteer in the initial direction is quickly canceled, the overshoot caused by it is suppressed, and the occurrence of oversteer in the opposite direction is effectively suppressed. Can do.

  The invention according to claim 3 includes a road surface frictional resistance estimating unit that estimates a frictional resistance of a road surface, and a gain variable calculating unit that calculates a correction gain that changes in accordance with the estimated frictional resistance. The gist of the amount correction means is to correct the target value by multiplying the target value by the correction gain.

The gist of the invention described in claim 4 is that the variable gain calculation means calculates the smaller correction gain as the estimated frictional resistance is lower.
According to each of the above configurations, the target state quantity can be accurately corrected in accordance with the road surface condition, and as a result, the vehicle's stable performance can be improved while suppressing the excessive response of the oversteer control and maintaining a good steering feeling. Further improvement can be achieved. In particular, by adopting the configuration of claim 4, the rate of change is suppressed in a situation where the frictional resistance of the road surface is low, the response of the vehicle behavior to the change of the turning angle is dull, and the stable region is in a narrower environment. Thus, the yaw rate can be changed quickly, thereby suppressing overshoot caused by an excessive yaw rate change speed, and the vehicle posture can be quickly stabilized.

  According to the present invention, it is possible to provide a vehicle steering apparatus that can ensure higher vehicle stability even on a low μ road.

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

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

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

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

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

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

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

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

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

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

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

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

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

  In the present embodiment, the IFS control calculation unit 35 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 of calculating the target yaw rate Ry0 and the target slip angle θsp0 from the turning angle θt and the vehicle speed V based on the vehicle model is described in, for example, Patent Document 1 described above Please refer to.

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

  The steering characteristic calculator 63 receives the steering angle θs, the vehicle speed V, the yaw rate Ry, and the target yaw rate Ry0 calculated by the vehicle model calculator 61. Based on these vehicle state quantities, the steer characteristic calculation unit 63 calculates the steer characteristic of the vehicle, that is, whether the vehicle is in oversteer, understeer, or neutral steer, and indicates the characteristic. An OS / US characteristic value Val_st is calculated (steer characteristic calculation). In 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).

  Further, the IFS control calculation unit 35 includes a target state quantity correction calculation unit 73 that corrects each target state quantity calculated by the vehicle model calculation unit 61 so that the value (absolute value) thereof becomes small. In the present embodiment, the target state quantity correction calculation unit 73 includes a target yaw rate correction calculation unit 74 that corrects the target yaw rate Ry0 calculated by the vehicle model calculation unit 61, and a target slip angle correction calculation unit that corrects the target slip angle θsp0. 75. In this embodiment, the target yaw rate correction calculation unit 74 and the target slip angle correction calculation unit 75 multiply the target yaw rate Ry0 and the target slip angle θsp0 input from the vehicle model calculation unit 61 by respective predetermined gains. The value (absolute value) is corrected so as to be small. The OS control calculation unit 65 calculates the OS control ACT command angle θos * based on the corrected target yaw rate Ry0 ′ and target slip angle θsp0 ′ corrected by the target state quantity correction calculation unit 73.

  More specifically, the yaw rate F / B calculating unit 71 receives the yaw rate Ry and the corrected target yaw rate Ry0 ′ corrected by the target yaw rate correction calculating unit 74, and the yaw rate F / B calculating unit 71 A feedback calculation is performed 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 differentiates it into the differential amount of the deviation ΔRy ′. The yaw rate differential F / B command angle θRyd * is calculated by multiplying / B gain KD (yaw rate F / B calculation). Similarly, the slip angle F / B calculation unit 72 receives the slip angle θsp and the corrected target slip angle θsp0 ′ calculated by the target slip angle correction calculation unit 75, and the slip angle F / B calculation unit 72. Calculates the slip angle F / B command angle θsp * by multiplying the deviation Δθsp ′ by the slip angle F / B gain Kslip (slip angle F / B calculation).

  The yaw rate proportional F / B command angle θRyp * and yaw rate differential F / B command angle θRyd * calculated by the yaw rate F / B calculation unit 71 and the slip angle F / B calculated by the slip angle F / B calculation unit 72 are calculated. The command angle θsp * is input to the adder 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 OS control calculation unit 65 of the present embodiment includes a yaw angle F / B calculation unit 77 in addition to the yaw rate F / B calculation unit 71 and the slip angle F / B calculation unit 72. The B calculation unit 77 executes a yaw angle F / B calculation based on the target yaw angle θy0 and the yaw angle θy using the determination result in the crossing road determination unit 62 as a trigger. Then, the OS control calculation unit 65 calculates the yaw angle F / B command angle θy * calculated by the yaw angle F / B calculation unit 77 to ensure the stability during the so-called μ split braking. Is output as an ACT command angle θos * during OS control.

  The US control calculation unit 66 receives the steering angle θs, the steering speed ωs, and the OS / US characteristic value Val_st calculated by the steering characteristic calculation unit 63. Then, the US control calculation unit 66 calculates the ACT command angle θus * during US control 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

Next, the processing procedure of each control calculation in the IFS control calculation unit will be described.
As shown in the flowchart of FIG. 7, the IFS control calculation unit 35 first executes vehicle model calculation (step 201), and then executes crossover determination (step 202). Then, a steer characteristic calculation is executed (step 203).

  Next, the IFS control calculation unit 35 corrects each target state quantity calculated in the vehicle model calculation in step 201, that is, the target yaw rate Ry0 and the target slip angle θsp0 (target state quantity correction calculation, step 204). Based on the corrected target yaw rate Ry0 ′ and target slip angle θsp0 ′, the yaw rate F / B calculation and the slip angle F / B calculation are executed to calculate the OS control ACT command angle θos * ( OS control calculation, step 205). If it is determined in step 202 that the μ split braking state is in effect, the yaw angle F / B calculation is executed using the determination result as a trigger.

  Next, the IFS control calculation unit 35 calculates the US control ACT command angle θus * by executing the US control calculation (step 206), and then executes the control ON / OFF determination (step 207). Based on the determination result of step 207, the ACT command angle θos * during OS control or the ACT command angle θus * (or 0) during US control is a control target component for realizing the active steering function, that is, IFS_ACT command angle θifs. * Is output (IFS_ACT command angle calculation, step 208).

(Action / Effect)
Next, the operation and effect of the steering apparatus of the present embodiment configured as described above will be described.

  FIG. 8 shows the target when the driver performs the steering operation in the counter direction (the direction opposite to the direction (+) of the yaw rate Ry (−)) during the oversteer control on the low μ road. It is a wave form diagram which shows transition of yaw rate Ry0 and yaw rate Ry. In the figure, the waveform M shows the transition of the yaw rate Ry, the waveform M0 shows the transition of the target yaw rate Ry0, and the waveform M0 ′ shows the transition of the corrected target yaw rate Ry0 ′. Hereinafter, for convenience of explanation, only the yaw rate Ry (target yaw rate Ry0, Ry0 ′) will be described, but it goes without saying that the tendency is the same for the slip angle θsp (target slip angle θsp, θsp ′). .

  As described above, on the low μ road, the response of the vehicle behavior to the change in the turning angle θt is dull, and the change speed that can stably control the yaw rate Ry, that is, the stable region in which the vehicle posture can be kept stable. The range of (yaw angular acceleration) is extremely narrow. Therefore, even if the counter-direction ACT angle θta is given by the oversteer control, the actual value (actual value, yaw rate Ry, slip angle θsp) with respect to the value of the target state quantity (target yaw rate Ry0, slip angle θsp0). However, as a result, the time required for the control is long and the counter amount (the amount of change in the steering angle in the counter direction) tends to be large. For this reason, there is a possibility that the change rate of the yaw rate Ry exceeds the stable region, and the vehicle posture may not be stabilized quickly due to the occurrence of overshoot due to the excessive yaw rate change rate. is there.

  In consideration of this point, the steering device 1 according to the present embodiment corrects the target state quantities (target yaw rate Ry0 and target slip angle θsp0) calculated by the vehicle model calculation unit 61 so that the values (absolute values) become small. The target state quantity correction calculation unit 73 is provided. Then, the OS control calculator 65 corrects the target state quantity (target yaw rate Ry0 ′ and target slip angle θsp0 ′) corrected by the target state quantity correction calculator 73 and the actual value (yaw rate Ry and slip angle θsp). ), An OS control ACT command angle θos *, which is a control target component of the ACT angle θta for oversteer control, is calculated (see FIG. 6).

  That is, as shown in FIG. 8, the corrected target yaw rate Ry0 ′ has a smaller value (absolute value) than the original target yaw rate Ry0, and therefore its deviation ΔRy ′ (yaw rate) used in yaw rate F / B calculation. (Deviation from Ry) is a value (absolute value) larger than the deviation ΔRy when the original target yaw rate Ry0 is used. Accordingly, when the oversteer control is started, the OS control ACT command angle θos * having a large value (absolute value) is output, and thereby, the rising of the ACT angle θta in the counter direction is accelerated and the control is performed. The time required can be shortened and the final counter amount can be reduced. As a result, it is possible to quickly change the yaw rate Ry while suppressing the change speed, thereby suppressing overshoot caused by an excessive yaw rate change speed and quickly stabilizing the vehicle posture. Become.

  In addition, as shown in the figure, when the driver performs a steering operation in the counter direction during the oversteer control, the value of the target yaw rate Ry0 and the actual yaw rate Ry are equalized when the control ends. In some cases, the target yaw rate Ry0 has already moved to the counter direction side when the neutral steer is reached (neutral point Pn, elapsed time tn in the figure). In such a case, the amount of change in the yaw rate Ry is large, and the time required for the control is also long, so the yaw rate change rate is likely to increase, and the excessive yaw rate change rate causes oversteer in the opposite direction. There is a risk.

  However, the corrected target yaw rate Ry0 'is corrected so that its absolute value becomes smaller. Therefore, when the direction of the target yaw rate Ry0 shifts to the opposite side, the neutral point becomes a neutral steer in yaw rate F / B calculation. Pn ′, that is, the elapsed time tn ′ until the corrected target yaw rate Ry0 ′ and the actual yaw rate Ry coincide with each other is a neutral point on the steering characteristic determination (steer characteristic calculation and control ON / OFF determination). The elapsed time tn is shorter until Pn is reached. Accordingly, the control for eliminating the oversteer in the initial direction (the (+) direction in the figure) quickly converges, thereby suppressing the yaw rate change speed in the counter direction (the (−) direction in the figure). Thus, it is possible to suppress the occurrence of oversteer in the opposite direction (the (−) direction in the figure) due to the overshoot.

  Further, since the steer characteristic determination is performed using the target yaw rate Ry0 before correction, from the neutral point Pn ′ in the yaw rate F / B calculation to the neutral point Pn in the steer characteristic determination, that is, the elapsed time from the elapsed time tn ′. Until tn, the ACT command angle θos * during OS control for generating the ACT angle θta in the direction to eliminate the oversteer in the opposite direction (the (+) direction in the figure) is output. As a result, the excessive yaw rate change speed caused by the control to eliminate the oversteer in the initial direction ((+) direction in the figure) is quickly canceled, the overshoot caused by it is suppressed, and the overshoot in the opposite direction is suppressed. The occurrence of steer can be effectively suppressed.

In addition, you may change this embodiment as follows.
In the present embodiment, the present invention is embodied in the steering device 1 that realizes the active steering function by changing the ACT angle θta of the gear ratio variable actuator 7, but the present invention is not limited thereto, and the steered wheels and the steering are It may be embodied in a so-called steer-by-wire vehicle steering device that is mechanically separated.

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

  In the present embodiment, the vehicle model calculation unit 61 and the target state quantity correction calculation unit 73 are provided in the IFS control calculation unit 35 on the IFSECU 8 side that controls the operation of the gear ratio variable actuator 7. However, both or any one of these may be provided outside the IFSECU 8, such as an EPSECU.

  In the present embodiment, the vehicle model calculation unit 61 calculates the target yaw rate Ry0 and the target slip angle θsp0 as target state quantities. Then, the OS control calculation unit 65 calculates the yaw rate F / B based on the corrected target yaw rate Ry0 ′ corrected by the target state quantity correction calculation unit 73, and the slip angle F based on the corrected target slip angle θsp0 ′. The ACT command angle θos * during OS control is calculated by performing / B calculation. However, the present invention is not limited to this, and the OS control ACT command angle θos * may be performed by either the corrected target yaw rate Ry0 ′ or the corrected target slip angle θsp0 ′. The OS control calculation unit 65 calculates the ACT command angle θos * during OS control by feedback calculation based on the vehicle state amount related to the yaw moment of the vehicle other than the yaw rate and the slip angle, and the target state amount correction calculation unit The target state quantity may be corrected.

  In the present embodiment, the target state quantity correction calculation unit 73 (target yaw rate correction calculation unit 74 and target slip angle correction calculation unit 75) receives the target state quantity (target yaw rate Ry0 and target slip) input from the vehicle model calculation unit 61. By multiplying the angle θsp0) by a predetermined gain, the value (absolute value) is corrected to be small. However, the present invention is not limited to this, and as shown in FIG. 9, the IFS control calculation unit 80 changes according to the road surface frictional resistance estimation calculation unit 81 that estimates the road surface frictional resistance μ and the estimated frictional resistance μ. A variable gain calculation unit 82 for calculating the correction gain Kv is provided. The target state quantity calculation unit 83 may be configured to correct the target state quantity by multiplying the target state quantity (target yaw rate Ry0 and target slip angle θsp0) by the correction gain Kv. As a result, the target state quantity can be accurately corrected in accordance with the road surface condition, and as a result, the excessive response of the ACT angle θta in the oversteer control is suppressed, and a good steering feeling is maintained and the vehicle stability performance is improved. Further improvement can be achieved. The road surface frictional resistance μ may be estimated from, for example, the wheel speed difference between the driving wheel and the driven wheel.

  Further, in this case, as shown in FIG. 10, the correction gain Kv may be made smaller as the road frictional resistance μ is lower. With such a configuration, the frictional resistance μ becomes lower, the response of the vehicle behavior to the change in the turning angle becomes duller, and the more the stable region is narrower, the more quickly the yaw rate Ry is changed while suppressing the change speed. As a result, overshoot caused by an excessive yaw rate change speed can be suppressed, and the vehicle posture can be quickly stabilized.

The schematic block diagram of a steering device. Explanatory drawing of gear ratio variable control. Explanatory drawing of gear ratio variable control. The control block diagram of a steering device. The flowchart which shows the aspect of the arithmetic processing in IFSECU. The control block diagram of an IFS control calculating part. The flowchart which shows the aspect of the IFS control calculation process in an IFS control calculation part. The wave form diagram which shows transition of the target yaw rate at the time of oversteer control in a low micro road, and an actual yaw rate. The schematic block diagram of the IFS control calculating part of another example. Explanatory drawing which shows the aspect of variable correction | amendment gain.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Steering device, 2 ... Steering, 6 ... Steering wheel, 7 ... Gear ratio variable actuator, 8 ... IFSECU, 35, 80 ... IFS control calculating part, 61 ... Vehicle model calculating part, 63 ... Steer characteristic calculating part, 65 ... Low speed correction gain calculation section, 67 ... Control ON / OFF determination section, 73,83 ... Target state quantity correction calculation section, 81 ... Road friction resistance estimation calculation section, 82 ... Gain variable calculation section, Ry ... Yaw rate, Ry0, Ry0 '... target yaw rate, θsp ... slip angle, θsp0, θsp0' ... target slip angle, θt ... steering angle, θts ... steer steering angle, θta ... ACT angle, θifs * ... IFS_ACT command angle, θos * ... when OS is controlled ACT command angle, Val_st: OS / US characteristic value, Sc: Control ON / OFF signal, Kv: Correction gain, μ: Friction resistance.

Claims (4)

Driving means capable of changing the turning angle of the steered wheels, control means for controlling the operation of the driving means, and vehicle model calculation for calculating a target value of the vehicle state quantity related to the yaw moment of the vehicle based on the vehicle model Means and a steer characteristic determining means for determining a steer characteristic of the vehicle by comparing the calculated target value with its actual value, and the control means, when the vehicle is in an oversteer state, A vehicle steering apparatus that performs oversteer control for operating the drive means to change the steering angle in a direction opposite to the yaw moment,
A target state quantity correcting means for correcting the calculated target value so that the absolute value thereof becomes small;
The control means calculates a control target component in the oversteer control by a feedback calculation based on a deviation between the corrected target value after correction and an actual value;
A vehicle steering apparatus characterized by the above. The vehicle steering apparatus according to claim 1,
The vehicle steering apparatus according to claim 1, wherein the vehicle state quantity related to the yaw moment of the vehicle is at least one of a yaw rate and a slip angle. In the vehicle steering device according to claim 1 or 2,
Road surface frictional resistance estimating means for estimating road surface frictional resistance;
Gain variable calculation means for calculating a correction gain that changes according to the estimated frictional resistance,
The vehicle steering apparatus, wherein the target state quantity correction means corrects the target value by multiplying the target value by the correction gain. The vehicle steering apparatus according to claim 3,
The vehicular steering apparatus, wherein the variable gain calculation means calculates the smaller correction gain as the estimated frictional resistance is lower.

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