JP5012314B2 - Vehicle steering system - Google Patents

Description

  The present invention relates to a vehicle steering apparatus.

  In recent years, a steering control system that determines the steering characteristics (steer characteristics) of a vehicle by detecting various state quantities such as vehicle speed and yaw rate, and actively controls the yaw moment of the vehicle based on the determination results has been proposed. Has been.

  For example, in the vehicle steering apparatus described in Patent Document 1, steering is performed by adding a second steering angle (ACT angle) of a steered wheel based on motor drive to a first steered angle of a steered wheel based on a steering operation. And a transmission ratio variable device capable of changing a transmission ratio (gear ratio) between the wheel and the steered wheels. When the steer characteristic is oversteer, a so-called active steer function that stabilizes the vehicle posture by controlling the ACT angle to generate a turning angle opposite to the yaw moment (counter direction) is provided. Have.

Further, in the vehicle steering device described in Patent Document 2, when the steering characteristic is determined to be oversteer, the steering assist direction (counter direction) is returned to the basic assist component calculated based on the steering torque. The reaction force component of) is superimposed. In this way, the driver is prompted to perform counter steering, and the vehicle posture is promptly stabilized.
JP 2005-262926 A JP-A-8-40293

  By the way, in situations where the vehicle posture is likely to be unstable, such as on a frozen road, it may be necessary to execute active steer control a plurality of times before the posture is stabilized. However, since the counter steering by the driver is likely to be delayed in the start timing, in such a case, there is a high possibility that the change of the turning angle by the active steering control and the counter steering of the driver do not coincide. Therefore, the execution of the counter guidance control in such a situation promotes the discrepancy between the steering angle change by the active steer control and the counter steering by the driver, which may hinder the prompt posture stabilization. In this respect, there was still room for improvement.

  The present invention has been made to solve the above-described problems, and the object thereof is to improve the affinity between the active steering control and the counter guidance control, and to stabilize the vehicle posture more quickly. The object is to provide a vehicle steering system.

  In order to solve the above problem, the invention according to claim 1 is provided in the middle of a steering transmission system between a steering wheel and a steered wheel, and a motor is provided at a first rudder angle of the steered wheel based on a steering operation. A transmission ratio variable device that varies the transmission ratio between the steering wheel and the steered wheel by adding a second steering angle of the steered wheel based on driving, and an assist force for assisting the steering system in steering operation A steering force assisting device to be applied, a control unit for controlling the operation of the steering force assisting device, a steer characteristic determining unit for determining the steering characteristic of the vehicle, and a counter steering determining unit for determining whether or not the counter steering is performed, When the steering characteristic is in an oversteer state, the transmission ratio variable device operates to change the second steering angle in a direction opposite to the yaw moment, and the control means In the vehicle steering apparatus for controlling the operation of the steering force assisting device so as to generate a steering reaction force for encouraging unsteer steering, the control means is active steer control using the transmission ratio variable device in the oversteer state. From the start of the counter to the start of the first counter steering, the counter guidance control for generating the steering reaction force that promotes the counter steering is strengthened than after the start of the counter steering. And

  In other words, when continuous active steering control is executed, the change of the steering angle by the active steering control and the counter steering of the driver are likely to be inconsistent. This may promote a discrepancy between the change in the steering angle by the driver and the counter steering by the driver, which may hinder quick posture stabilization. However, such discrepancy between the active steering control and the counter steering is basically due to the delay in the start of the counter steering by the driver, and is relatively smaller than the control amount of the active steering continuously performed thereafter. In the first oversteer control having a large control amount (counter amount), even if there is a slight start delay, the mismatch is unlikely to occur. Therefore, according to the above configuration, early counter steering by the driver can be urged without promoting the discrepancy between the change in the turning angle by the oversteer control and the counter steering. As a result, the affinity between the active steering control and the counter guidance control can be enhanced, and the vehicle posture can be stabilized more promptly.

  According to a second aspect of the present invention, the counter guidance control includes superimposition of a control component in the counter direction on a basic assist component based on a steering torque, and the enhancement of the counter guidance control reduces the basic assist component. It is made into a summary.

  That is, even if the control component in the counter direction is increased in order to enhance the counter guidance control, the control component in the counter direction is canceled out by the basic assist component having the counter counter direction value generated accordingly. However, according to the above configuration, the control component in the counter direction is relatively strengthened by reducing the basic assist component. As a result, it is possible to efficiently generate the steering reaction force in the counter direction while suppressing the interference with the power assist control. As a result, the counter steering by the driver is more effectively guided, and the vehicle posture can be promptly changed. Stabilization can be achieved.

  According to a third aspect of the present invention, the control means assists the steering force so as to generate the assist force that assists the change of the second steering angle when the transmission ratio variable device operates in the oversteer state. The gist is to control the operation of the apparatus.

  That is, for example, in the configuration in which the basic assist component is increased as the control for generating the assist force for assisting the change of the second steering angle, the control interferes with the reduction of the basic assist component by the counter guidance control. However, by adopting a configuration in which the counter guidance control is strengthened only during the first oversteer control and until the first counter steering by the driver is started, the influence of the interference can be limited.

  ADVANTAGE OF THE INVENTION According to this invention, the steering apparatus for vehicles which enables stabilization of a vehicle attitude | position which can improve the affinity of active steering control and counter guidance control, and can stabilize a vehicle attitude | position more quickly is provided. be able to.

Hereinafter, an embodiment in which the present invention is embodied in a vehicle steering apparatus including a transmission ratio variable device 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, 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 vehicle steering apparatus 1 according to the present embodiment is provided in the middle of a steering transmission system between the steering 2 and the steered wheels 6, and the transmission ratio (gear ratio) of the steered wheels 6 with respect to the steering angle (steering angle) of the steering 2. The gear ratio variable actuator 7 serving as a transmission ratio variable device for varying the gear ratio and the IFSECU 8 for controlling the operation of the gear ratio variable actuator 7 are provided.

  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 device 1 controls an EPS actuator 17 as a steering force assisting device that applies an assist force for assisting a steering operation to the steering system, and the operation of the EPS actuator 17. EPSECU 18 as a control means for performing this.

  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 the present embodiment, the torque sensor 25 employs a so-called twin resolver type torque sensor that detects torque based on the torsion angle of the torsion bar detected by a pair of resolvers. In the middle of the second shaft, that is, between the gear ratio variable actuator 7 and the EPS actuator 17. Further, the turning angle θt is obtained by adding the ACT angle θta to the value obtained by multiplying the steering angle θs by the base gear ratio of the rack and pinion mechanism 4, that is, the steering turning angle θts. The slip angle θsp is obtained based on the lateral acceleration detected by the lateral G sensor 28 and the yaw rate Ry.

  Further, the IFSECU 8 and the 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, FIG. 5 is a flowchart showing the calculation processing procedure on the IFSECU side, and FIG. 6 is a flowchart showing the calculation processing procedure on the EPSECU side. Each control block in FIG. 4 is realized by a computer program executed by an information processing device (microcomputer) provided on each of the IFSECU side and the EPSECU side.

As shown in FIG. 4, 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, a brushless motor is employed as the motor 12 that is a drive source of the gear ratio variable actuator 7. The drive circuit 34 is configured to supply three-phase (U, V, W) drive power to the motor 12 based on a motor control signal input from the microcomputer 33.

  More specifically, the microcomputer 33 of the present embodiment includes an IFS control calculation unit 35, a gear ratio variable control calculation unit 36, and a Lead Steer control calculation unit 37, and each control calculation unit is input with a vehicle state quantity. Based on the above, the control component (and control signal) of the ACT angle θta corresponding to the purpose is calculated. The microcomputer 33 generates a motor control signal for controlling the operation of the motor 12, that is, the gear ratio variable actuator 7, based on the calculated control components.

  A steering angle θs, a turning angle θt, a vehicle speed V, a wheel speed Vtr, Vtl, a brake signal Sbk, a yaw rate Ry, and a slip angle θsp are input to the IFS control calculation unit 35. The IFS control calculation unit 35 calculates the control 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 control. Signal calculation is performed (IFS control calculation).

  Specifically, the IFS control calculation unit 35 determines the steering characteristics (steer characteristics) of the vehicle based on the input state quantities. That is, in the present embodiment, the IFS control calculation unit 35 constitutes a steer characteristic determination unit. Then, the IFS_ACT command angle θifs * and the US control gain Kus are calculated as control components of the ACT angle θta for realizing the active steering function corresponding to the steering characteristic.

  The IFS_ACT command angle θifs * is a control component mainly corresponding to the case where the steering characteristic of the vehicle is oversteer (OS). Based on the IFS_ACT command angle θifs *, the steering angle (in the direction opposite to the yaw moment direction) Oversteer control is performed to change the ACT angle θta so as to give a counter steer). Further, the US control gain Kus is a control gain for reducing the amount of change in the turning angle θt with respect to the cutting operation, that is, reducing the turning angle of the steered wheels 6 when the steering characteristic is understeer (US). The US control gain Kus is output to the gear ratio variable control calculation unit 36. Then, the control component (absolute value) calculated by the gear ratio variable control calculation unit 36 is reduced by the US control gain Kus, thereby executing the understeer control as described above.

  In this embodiment, the OS / US characteristic value Val_st and the US control gain Kus indicating the determination result of the steering characteristic determination are the driver steering state St_ds generated by the IFS control calculation unit 35 and the active steering control being executed. Together with the active control signal S_acv indicating the contents of the control signal, it is output to the EPS ECU 18 as a control signal (see FIG. 1). Here, the driver steering state St_ds is expressed by an analog value that continuously changes in accordance with the operation direction and the operation amount of the steering 2, and the operation direction (“cut” or “switch back”) is a sign (positive / negative). ), The operation amount is shown in the magnitude (absolute value). And based on each of these control signals, EPSECU18 becomes a structure which performs the power assist control cooperated with the above active steering controls.

  On the other hand, the steering angle θs, the turning angle θt, and the vehicle speed V are input to the gear ratio variable control calculation unit 36. The gear ratio variable control calculation unit 36 calculates a gear ratio variable ACT command angle θgr * as a control component for varying the gear ratio according to the vehicle speed V based on these vehicle state quantities (and control signals). (Gear ratio variable control calculation).

  In addition, 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 component for improving the responsiveness of the vehicle according to the steering speed 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 control components calculated by the above calculations, that is, IFS_ACT command angle θifs *, gear ratio variable ACT command angle θgr *, and LS_ACT. The 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 to obtain an ACT command angle θta * that is a control target of the ACT angle θta. 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. In the present embodiment, the ACT command angle θta * is output to the EPS ECU 18 as a control signal, and is used for executing the cooperative power assist control. 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 adder 38 b calculates a current command by superimposing the control amount εff and the control amount εfb, and the current command is output to the motor control signal output unit 42. 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 of the ACT angle θta.

  Next, 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 based on the current command, the motor 33 A control signal is output (step 107). The other various control signals, that is, the OS / US characteristic value Val_st, the US control gain Kus, the driver steering state St_ds, the active control signal S_acv, and the ACT command angle θta * are output to the EPS ECU 18 via the in-vehicle network 23. (Step 108).

  On the other hand, the EPSECU 18 also includes a microcomputer 43 and a drive circuit 44 as in the case of the IFSECU 8. In the present embodiment, a brushless motor is also used as the motor 22 that is a drive source of the EPS actuator 17. The drive circuit 44 is configured to supply three-phase (U, V, W) drive power to the motor 22 based on a motor control signal input from the microcomputer 43.

  More specifically, 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 is based on an input vehicle state quantity. Then, the control component of the assist torque generated by the motor 22 is calculated.

  More specifically, the steering torque τ and the vehicle speed V are input to the assist control unit 45, and the assist control unit 45 performs a basic assist force based on the steering torque τ and the vehicle speed V. As a basic control component, that is, a basic assist component, a basic assist current command Ias * is calculated. Specifically, as shown in FIG. 7, a larger basic assist current command Ias * is calculated as the steering torque τ (the absolute value thereof) is larger and the vehicle speed V is slower.

  The torque inertia compensation control unit 46 receives a steering torque differential value dτ and a vehicle speed V, which are differential values of the steering torque τ. Then, the torque inertia compensation control unit 46 calculates the inertia compensation current command Iti * as a control component for compensating for the influence of the inertia of the EPS.

  Here, the “torque inertia compensation control” is a control that suppresses “twist” that occurs in the steering system due to inertia by strengthening the assist force. In the steering operation that occurs due to inertia of the motor, actuator, etc., "A feeling of catching (following delay)" at the time of "", and an "flow feeling (overshoot)" at the time of "cutting end". Further, this torque inertia compensation control acts in a direction to cancel the change of the turning angle not accompanied by the change of the steering torque inputted to the steering. Therefore, there is an effect of suppressing the vibration generated in the steering system due to the application of the reverse input to the steered wheels 6.

  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. Then, the steering return control unit 47 calculates a steering return current command Isb * that is a control 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 traveling. A damper compensation current command Idp *, which is a control component for calculating, is calculated.

  The microcomputer 43 includes, in addition to the above-described control units, an IFS torque compensation control unit 49 that calculates an IFS torque compensation gain Kifs for executing power assist control in cooperation with the above-described active steering control, and an IFS torque compensation current command. A second IFS torque compensation controller 50 for calculating Iifs * is provided.

  In the present embodiment, the IFS torque compensation controller 49, together with the steering speed ωs, various control signals output from the IFSECU 8 side via the in-vehicle network 23, that is, the OS / US characteristic value Val_st, the US control gain Kus, The driver steering state St_ds, the active control signal S_acv, and the ACT command angle θta * are input. Further, the ACT command angle θta * is input to the second IFS torque compensation control unit 50. Then, the IFS torque compensation control unit 49 and the second IFS torque compensation control unit 50 respectively input the respective state quantities and the control signal based on the control signal, the IFS torque compensation gain Kifs, and the IFS torque compensation current command Iifs. Calculate *.

  In the present embodiment, the IFS torque compensation gain Kifs calculated in the IFS torque compensation control unit 49 is input to the multiplier 51 together with the basic assist current command Ias * calculated in the assist control unit 45. The corrected basic assist current command Ias ** corrected by being multiplied by the IFS torque compensation gain Kifs in the multiplier 51 includes other various compensation components, that is, an inertia compensation current command Iti *, a steering return current command Isb *, And the damper compensation current command Idp * are input to the adder 52. The IFS torque compensation current command Iifs * calculated by the second IFS torque compensation controller 50 is input to the adder 52. In the adder 52, these control components are superimposed on the basic assist current command Ias **, whereby 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 52 is input to the motor control signal output unit 53. The motor control signal output unit 53 receives an actual current detected by the current sensor 54 and a rotation angle detected by the rotation sensor 55. The motor control signal output unit 53 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.

  That is, as shown in the flowchart of FIG. 6, when the microcomputer 43 fetches sensor values from the above sensors as vehicle state quantities (step 201), it first performs an assist control calculation (step 202). Next, torque inertia compensation control calculation (step 203), steering wheel return control calculation (step 204), and damper compensation control calculation are performed (step 205), and then IFS torque compensation control calculation (step 206) is performed.

  Next, the microcomputer 43 corrects the basic assist current command Ias * by multiplying the basic assist current command Ias * calculated by the assist control calculation in step 202 by the IFS torque compensation gain Kifs calculated in step 206. . Further, the inertia compensation current command Iti *, the steering return current command Isb *, and the damper compensation current command Idp * calculated by the respective arithmetic processing in the above step 203 to step 205 are added to the corrected basic assist current command Ias **. By superimposing, a current command as a control target is calculated, and a motor control signal is output based on the current command (step 207).

(IFS torque compensation calculation)
Next, an aspect of the IFS torque compensation calculation in the vehicle steering apparatus of the present embodiment will be described.

  As shown in FIG. 8, the IFS torque compensation control unit 49 of the present embodiment includes an OS control time compensation gain calculation unit 61 for executing cooperative control with oversteer control (OS control), and understeer control (US control). ) And a US control compensation gain calculation unit 62 for executing cooperative control.

  More specifically, the active control signal S_acv, the ACT command angle θta *, the driver steering state St_ds, the yaw rate Ry, and the steering speed ωs are input to the OS control compensation gain calculation unit 61. Then, the OS control compensation gain calculator 61 calculates an OS control compensation gain Kifs_os for executing cooperative control with oversteer control based on these state quantities (control signals). More specifically, the OS control compensation gain Kifs_os for assisting the counter steering by the driver and suppressing the fluctuation of the steering reaction force accompanying the operation of the variable gear ratio actuator 7 to improve the steering feeling is calculated.

  On the other hand, the OS control compensation gain calculator 62 is supplied with the OS / US characteristic value Val_st and the US control gain Kus. Then, the US control compensation gain calculator 62 calculates the US control compensation gain Kifs_us for executing cooperative control with the US control based on these control signals. Specifically, a US control compensation gain Kifs_us for performing assist force application that suppresses the generation of the steering angle θs greater than the current steering angle is calculated.

  In this embodiment, the OS control compensation gain Kifs_os calculated by the OS control compensation gain calculator 61 and the US control compensation gain Kifs_us calculated by the US control compensation gain calculator 62 are supplied to the switching controller 63. Entered. Further, the OS / US characteristic value Val_st is input to the switching control unit 63, and the switching control unit 63 has a value indicating the oversteer (OS) in the OS / US characteristic value Val_st. In some cases, the compensation gain Kifs_os at the time of OS control is output, and when it is a value indicating understeer (US), the compensation gain at the time of US control Kifs_us is output. Note that the switching control unit 63 of the present embodiment is configured to output “1” when the OS / US characteristic value Val_st is a value indicating neutral steer (NS).

  Then, the IFS torque compensation control unit 49 of the present embodiment outputs the OS control compensation gain Kifs_os or the US control compensation gain Kifs_us (or “1”) output by the switching control unit 63 as the IFS torque compensation gain Kifs. It is the composition to do.

  More specifically, as shown in FIG. 9, the OS control time compensation gain calculation unit 61 of the present embodiment suppresses fluctuations in the steering reaction force accompanying the operation of the gear ratio variable actuator 7 during oversteer control. An OS compensation gain calculation unit 64 for calculating the OS compensation gain K_os is provided.

  In the present embodiment, an ACT command angle θta * that is a control target of the ACT angle θta and an ACT command angular velocity ωta * that is a differential value of the ACT command angle θta * are input to the OS compensation gain calculation unit 64. The OS compensation gain calculator 64 determines “the magnitude of change in the ACT angle θta” based on the ACT command angle θta * and the ACT command angular velocity ωta *. Then, the OS compensation gain calculator 64 calculates an OS compensation gain K_os that increases the basic assist current command Ias * more greatly as it is determined that the change in the ACT angle θta is larger.

  The OS compensation gain calculator 64 of this embodiment is configured to calculate the OS compensation gain K_os by map computation based on the ACT command angle θta * and the ACT command angular velocity ωta *, and the OS compensation gain K_os in the map The base value of “1” is set to “1”, that is, the value is set to “1” or more.

  That is, during oversteer control, the gear ratio variable actuator 7 operates to generate the ACT angle θta in the counter direction (the direction opposite to the yaw moment of the vehicle), so that the counter direction (cutting direction) is opposite to the counter direction. A motor reaction force that rotates the steering 2 is generated. That is, the greater the motor torque generated by the motor 12 that is the drive source of the variable gear ratio actuator 7, the greater the reaction force acting on the steering. Therefore, the influence of such a motor reaction force becomes larger as the change in the ACT angle θta due to the execution of the oversteer control is larger and the gear ratio variable actuator 7 is operated more rapidly.

  Here, when the gear ratio variable actuator 7 is operated, in the steering system, the space between the gear ratio variable actuator 7 and the steered wheels 6 is in a so-called “twisted” state. The essence of power assist control by EPS is that such a twist in the steering system is detected by a torque sensor, and an assist force is applied to the steering system in order to change the turning angle θt in a direction to eliminate the twist. is there.

  That is, when the gear ratio variable actuator 7 is actuated, an assist force is applied to the steering system so as to assist in changing the turning angle θt in the counter direction. Therefore, by strengthening the power assist, the operation of the gear ratio variable actuator 7 is assisted, that is, the ACT angle θta can be changed with a small motor torque, thereby suppressing the motor reaction force acting on the steering 2. Can do. In the present embodiment, as described above, the OS compensation gain calculation unit 64 calculates the OS compensation gain K_os that increases the basic assist current command Ias *. It is configured to improve steering feeling by suppressing force fluctuations.

  Further, as shown in FIG. 9, the OS control time compensation gain calculation unit 61 of the present embodiment is used when the driver performs counter steering during oversteer control using the gear ratio variable actuator 7 as described above. An IFS counter correction gain calculator 65 for calculating a counter correction gain K_cs for improving the steering feeling is provided.

  In the present embodiment, an ACT command angle θta *, an ACT command angular velocity ωta *, and a driver steering state St_ds are input to the IFS counter correction gain calculation unit 65, and the IFS counter correction gain calculation unit 65 determines whether the movement of the ACT angle θta by the OS control matches the counter steering of the driver based on each of these state quantities. When the movement of the ACT angle θta and the counter steering coincide with each other, a value that reduces the basic assist current command Ias * to suppress the occurrence of an excessive counter, and when the movement does not coincide, As described above, the counter correction gain K_cs having a value for increasing the basic assist current command Ias * is calculated to assist the movement of the ACT angle θta.

  Note that the IFS counter correction gain calculator 65 of the present embodiment includes maps 65a and 65b corresponding to the match / mismatch between the movement of the ACT angle θta and the counter steering. In the map 65a corresponding to “match”, the counter correction gain K_cs is set to a value that reduces the basic assist current command Ias * as the counter steering amount by the driver increases. Further, in the map 65b corresponding to the “non-coincidence”, the counter correction gain K_cs is set to a value that increases the basic assist current command Ias * as the counter steering amount by the driver increases. The IFS counter correction gain calculation unit 65 is configured to calculate the counter correction gain K_cs by map calculation using these two maps 65a and 65b according to the determination.

  In the present embodiment, the counter correction gain K_cs calculated by the IFS counter correction gain calculation unit 65 is input to the multiplier 67 via the switching control unit 66 described later. The multiplier 67 is supplied with the OS compensation gain K_os calculated by the OS compensation gain calculator 64. Then, the OS control compensation gain calculation unit 61 uses the value obtained by multiplying the OS compensation gain K_os and the counter correction gain K_cs as the OS control compensation gain Kifs_os, and the switching control unit provided in the IFS torque compensation control unit 49. 63 (see FIG. 8).

  Further, the second IFS torque compensation control unit 50 (see FIG. 4) of the present embodiment assists the change of the turning angle θt in the counter direction by the active steer control as the IFS torque compensation current command Iifs * that is output. A control component for applying a strong assist force is calculated. Then, like the OS compensation gain K_os calculated by the OS compensation gain calculation unit 64 described above, the operation of the gear ratio variable actuator 7 during the oversteer control is smoothed, and the steering reaction force caused by the motor reaction force generated by the operation. By suppressing this variation, the steering feeling during the OS control is improved.

  Note that the second IFS torque compensation control unit 50 of the present embodiment calculates the IFS torque compensation current command Iifs * by executing the map calculation similar to the OS compensation gain calculation unit 64. Therefore, for the characteristics of the output IFS torque compensation current command Iifs *, refer to the conceptual diagram regarding the map calculation in the OS compensation gain calculation unit 64 shown in FIG.

  Here, the steering 2 rotates in the counter direction in accordance with the change in the turning angle θt by executing the assist force application that assists the change in the turning angle θt in the counter direction. Then, the driver is prompted to execute the counter steering due to an increase in the steering reaction force received from the steering rotating in the counter direction.

  That is, in the present embodiment, the IFS torque compensation current command Iifs * output from the second IFS torque compensation controller 50 has a side surface as a control component that induces counter steering by the driver. Thus, in addition to the active steering function, the vehicle posture is more quickly stabilized.

  As described above, when the continuous active steering control is performed, the change of the turning angle by the active steering control and the counter steering of the driver tend to be inconsistent. For this reason, the execution of the counter guidance control under such a situation promotes a discrepancy between the steering angle change by the active steering control and the counter steering by the driver, which may hinder the prompt posture stabilization. is there.

  In consideration of this point, the EPS ECU 18 (microcomputer 43) of the present embodiment has started from oversteer control as active steer control using the gear ratio variable actuator 7 until the first counter steering by the driver is started. In the meantime, power assist control for generating a steering reaction force that encourages the counter steering, that is, counter guidance control is strengthened.

  That is, as shown in the flowchart of FIG. 10, the microcomputer 43 determines whether or not the oversteer control is before the start of the first counter steering by the driver (step 301). If it is determined that it is before the start of the first counter steering (step 301: YES), the counter guidance control is strengthened (enhanced counter guidance control, step 302), and it is determined that it is after the first counter steering is started. If it is (step 301: NO), normal counter guidance control is executed (normal counter guidance control, step 303).

  That is, the discrepancy between the change of the steering angle θt by the active steering control and the counter steering of the driver is basically due to the start delay of the counter steering. In this respect, the control amount (counter amount) in the first oversteer control is usually larger than the control amount of active steer continuously performed thereafter, and even if there is a slight start delay, the counter steering and It is difficult for the change of the turning angle θt by the oversteer control to be inconsistent. Therefore, by adopting a configuration in which the counter guidance control is strengthened only at the time of the first oversteer control, early change by the driver can be achieved without promoting the discrepancy between the change of the turning angle θt by the oversteer control and the counter steering. Counter steering can be encouraged.

  In this case, “strengthening” is strengthening after counter steering by the driver, that is, in comparison with normal counter guidance control. Accordingly, the case where the counter guidance control is not substantially performed normally, that is, the case where the addition of the steering reaction force by the normal counter guidance control is substantially “0” is also included.

  In particular, in the configuration in which the basic assist current command Ias * is increased in order to suppress the fluctuation of the steering reaction force accompanying the execution of the active control as in the present embodiment, the enhancement of the counter guidance control is performed at the time of the active control. There may be interference with the steering reaction force fluctuation suppression control. The “in case of interference” is a case where counter guidance control is strengthened by reducing the basic assist component, as will be described later. However, by adopting a configuration in which the counter guidance control is strengthened only during the first oversteer control and until the first counter steering by the driver is started, the influence of the interference can be limited. In the present embodiment, this improves the affinity between the active steer control and the counter guidance control, thereby stabilizing the vehicle posture more quickly.

  More specifically, in the present embodiment, the strengthening of the counter guidance control from the start of the oversteer control to the start of the first counter steering by the driver is the basic assist component based on the steering torque τ, that is, the basic assist. This is done by reducing the current command Ias *.

  As described above, the counter guidance control according to the present embodiment uses the IFS torque compensation current command Iifs *, which is a control component in the counter direction, and the basic assist current, which is a basic assist component based on the steering torque τ detected by the torque sensor 25. This is done by superimposing on the command Ias *. However, in such a configuration, even if an attempt is made to strengthen the counter induction control only by increasing the IFS torque compensation current command Iifs * that is a component superimposed on the basic assist component, the degree of enhancement is limited.

  That is, by increasing the control component in the counter direction, the driving force generated by the EPS actuator 17 due to execution of the counter guidance control eventually becomes the driving force generated by the gear ratio variable actuator 7 due to execution of the oversteer control. It will exceed. As a result, a steering reaction force that positively rotates the steering 2 in the counter direction is generated in the steering 2.

  However, at this time, the steering system is twisted in the opposite direction, that is, the steered wheel 6 side is twisted in the counter direction. Therefore, the basic assist current command Ias *, which is a basic component of the power assist control, is a value that generates an assist force in the direction to cancel the twist, that is, the counter-counter direction, and the increment of the IFS torque compensation current command Iifs * is Therefore, it is canceled by the inverted basic assist current command Ias *. Since the basic assist current command Ias * is calculated based on the steering torque τ detected by the torque sensor 25, the absolute value of the basic assist current command Ias * increases as the basic steering torque τ, that is, the twist of the steering system increases. Becomes big. Therefore, even if the IFS torque compensation current command Iifs * is further increased, it is offset by the accompanying increase in the basic assist current command Ias * (see FIG. 7, for example, movement from the point P1 to the point P2). A large steering reaction force cannot be generated so as to positively rotate the steering 2 in the counter direction.

  However, by reducing the basic assist current command Ias * that is the basic assist component, the IFS torque compensation current command Iifs * as a control component for inducing counter steering can be relatively strengthened. In this embodiment, the counter guidance control is thereby strengthened.

  More specifically, as shown in FIG. 9, the OS control compensation gain calculation unit 61 of the present embodiment calculates an assist reduction gain calculation unit 68 that calculates an assist reduction gain K_dc for reducing the basic assist current command Ias *. And a counter steering determination unit 69 that determines the presence or absence of counter steering by the driver.

  The assist reduction gain calculation unit 68 of the present embodiment is configured to output a predetermined value as the assist reduction gain K_dc, and the counter steering determination unit 69 operates based on the steering speed ωs and the yaw rate Ry. The presence or absence of counter steering by the person is determined.

  Specifically, as shown in the flowchart of FIG. 11, the counter steering determination unit 69 of the present embodiment determines whether the sign of the steering speed ωs and the sign of the yaw rate Ry are opposite (whether they are different). Is determined (step 401). If the sign is opposite (step 401: YES), it is determined that there is counter steering (step 402). If the sign is the same (step 401: NO), it is determined that there is no counter steering (step 401). Step 403).

  In this embodiment, the assist reduction gain K_dc output from the assist reduction gain calculation unit 68 and the determination signal Scs indicating the determination result by the counter steering determination unit 69 are the counter correction gain K_cs output from the IFS counter correction gain calculation unit 65. At the same time, it is input to the switching control unit 66. In addition, an active control signal S_acv indicating the content of the active steer control being executed is input to the switching control unit 66, and the switching control unit 66 receives the active control signal S_acv and the determination signal Scs. Based on this, it is determined whether or not it is before the start of the first counter steering from the start of the oversteer control. If it is before the start of the first counter steering, the assist reduction gain K_dc input from the assist reduction gain calculation unit 68 is output to the multiplier 67, and after the start of the first counter steering, the IFS counter correction gain is obtained. The counter correction gain K_cs input from the calculation unit 65 is output to the multiplier 67.

  Thus, in this embodiment, before the start of the first counter steering, the assist reduction gain K_dc having a value for reducing the basic assist current command Ias * is calculated as the OS control compensation gain Kifs_os. Output from the unit 61. The OS control compensation gain Kifs_os is output from the IFS torque compensation controller 49 as the IFS torque compensation gain Kifs (see FIG. 8), and is multiplied by the basic assist current command Ias * in the multiplier 51 (see FIG. 4). The basic assist current command Ias * is reduced to enhance counter guidance control.

As described above, according to the present embodiment, the following operations and effects can be obtained.
(1) The EPS ECU 18 (the microcomputer 43) performs the counter steering from the start of the oversteer control as the active steer control using the gear ratio variable actuator 7 to the start of the first counter steering by the driver. The power assist control for generating the steering reaction force that promotes the control, that is, the counter guidance control is strengthened.

  In other words, when continuous active steering control is executed, the change of the steering angle by the active steering control and the counter steering of the driver are likely to be inconsistent. This may promote a discrepancy between the change in the steering angle by the driver and the counter steering by the driver, which may hinder quick posture stabilization. However, such discrepancy between the active steering control and the counter steering is basically due to the delay in the start of the counter steering by the driver, and is relatively smaller than the control amount of the active steering continuously performed thereafter. In the first oversteer control having a large control amount (counter amount), even if there is a slight start delay, the mismatch is unlikely to occur. Therefore, according to the above configuration, early counter steering by the driver can be urged without encouraging the discrepancy between the change in the turning angle θt by the oversteer control and the counter steering. As a result, the affinity between the active steering control and the counter guidance control can be enhanced, and the vehicle posture can be stabilized more promptly.

  (2) In the counter guidance control, the IFS torque compensation current command Iifs *, which is a control component in the counter direction, is superimposed on the basic assist current command Ias *, which is a basic assist component based on the steering torque τ detected by the torque sensor 25. Is done. The counter guidance control is strengthened by reducing the basic assist current command Ias *, which is a basic assist component based on the steering torque τ.

  That is, even if the IFS torque compensation current command Iifs * is increased to strengthen the counter guidance control, the increment of the IFS torque compensation current command Iifs * is caused by the counter-counter basic assist current command Ias * that is generated along with it. Will be offset. However, as in the above configuration, the IFS torque compensation current command Iifs * is relatively strengthened by reducing the basic assist current command Ias *, thereby efficiently suppressing the interference with the power assist control as described above. A steering reaction force in the counter direction can be generated. As a result, the counter steering by the driver can be guided more effectively, and the vehicle posture can be stabilized more quickly. In addition, in the configuration in which the basic assist current command Ias * is increased in order to suppress the fluctuation of the steering reaction force due to the execution of the active control as in the present embodiment, the reduction of the basic assist current command Ias * as described above is concerned. It interferes with fluctuation suppression control of steering reaction force during active control. However, by adopting a configuration in which the counter guidance control is strengthened only during the first oversteer control and until the first counter steering by the driver is started, the influence of the interference can be limited.

In addition, you may change this embodiment as follows.
In the present embodiment, as a control component for guiding the counter steering by the driver, the IFS torque compensation current command Iifs *, which is also a control component in the counter direction, that is, the steering reaction force originally associated with the execution of the active steering control In order to suppress the fluctuation, a control component for applying an assist force that assists in changing the steering angle θt in the counter direction is used. However, the present invention is not limited to this, and a control component in the counter direction may be separately calculated as a control component for prompting the driver to perform counter steering, and this may be superimposed on the basic assist current command Ias * that is the basic assist component. .

  In this embodiment, in addition to the IFS torque compensation current command Iifs * calculated in the second IFS torque compensation control unit 50, the OS compensation gain calculation is performed in order to suppress the fluctuation of the steering reaction force accompanying the execution of the active steering control. The unit 64 calculates an OS compensation gain K_os that increases the basic assist current command Ias *. However, the present invention is not limited to this, and it is configured to execute the steering reaction force fluctuation suppression control accompanying the operation of the gear ratio variable actuator 7 by either superimposing the control component on the basic assist component or increasing the basic assist component. Also good.

  In this embodiment, the IFS torque compensation current command Iifs * (and the OS compensation gain K_os as the control component for inducing counter steering by the driver and the control component for suppressing the fluctuation of the steering reaction force accompanying the execution of the active steering control. ) Is calculated based on the ACT command angle θta * and the ACT command angular velocity ωta *. However, the present invention is not limited to this, and the calculation may be performed based on either one. Moreover, it is good also as a structure which uses the further differential value (angular acceleration), Furthermore, for example, the actual ACT angle (theta) ta, an electric current command value, an actual electric current value, or these differential values (further differential value), etc. It is good also as a structure calculated using another state quantity.

  In the present embodiment, the steering determination is made based on the steering speed ωs and the yaw rate Ry. However, the present invention is not limited to this, and other state quantities such as ACT command angular velocity ωta *, ACT angular velocity, or steering torque may be used.

  In the present embodiment, the assist reduction gain K_dc for executing the counter guidance control is set to a predetermined value, but may be obtained by calculation as needed.

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 flowchart which shows the process sequence of the arithmetic processing in EPSECU. Explanatory drawing which shows the aspect of assist control calculation. The control block diagram which shows schematic structure of an IFS torque compensation control part. The control block diagram which shows schematic structure of a compensation gain calculating part at the time of OS control. The flowchart which shows the process sequence of reinforcement | strengthening counter guidance control start determination. The flowchart which shows the process sequence of counter steering determination.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Vehicle steering device, 2 ... Steering, 6 ... Steered wheel, 7 ... Gear ratio variable actuator, 8 ... IFSECU, 17 ... EPS actuator, 18 ... EPSECU, 43 ... Microcomputer, 45 ... Assist control part, 49 ... IFS torque Compensation control unit 50 ... second IFS torque compensation control unit 51, 67 ... multiplier 52 ... adder 61 ... OS control time compensation gain calculation unit 64 ... OS compensation gain calculation unit 66 ... switch control unit 68 Assist reduction gain calculation unit 69 Counter counter determination unit θs Steering angle ωs Steering speed θt Steering angle θts Steering steering angle θta ACT angle θta * ACT command angle ωta * ... ACT command angular velocity, Ias *, Ias ** ... basic assist current command, τ ... steering torque, Ry ... yaw rate, Iifs * ... IFS torque compensation current command, Kifs ... IFS torque compensation gain, Kif s_os: OS control compensation gain, K_os: OS compensation gain, K_dc: assist reduction gain, S_acv: active control signal, Scs: determination signal.

Claims (3)

Steering is performed by adding a second rudder angle of the steered wheel based on motor drive to a first rudder angle of the steered wheel that is provided in the middle of a steering transmission system between the steering wheel and 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 steering force assist device that applies an assist force for assisting a steering operation to a steering system, and an operation of the steering force assist device is controlled. A control means, a steer characteristic judging means for judging the steering characteristic of the vehicle, and a counter steering judging means for judging the presence or absence of counter steering, and when the steer characteristic is in an oversteer state, the transmission ratio variable device Operates to change the second rudder angle in the direction opposite to the yaw moment, and the control means generates the steering reaction force to promote the counter steering. The vehicular steering device for controlling the operation of the steering force assist device,
The control means is configured so that the period from the start of the active steer control using the transmission ratio variable device in the oversteer state to the start of the first counter steering is greater than that after the start of the counter steering. A vehicle steering apparatus characterized by strengthening counter guidance control for generating a steering reaction force that promotes steering. The vehicle steering apparatus according to claim 1,
The counter guidance control includes superimposition of a control component in a counter direction on a basic assist component based on a steering torque, and the enhancement of the counter guidance control includes reduction of the basic assist component. Vehicle steering system. The vehicle steering apparatus according to claim 2,
The control means controls the operation of the steering force assisting device to generate the assist force that assists the change of the second steering angle when the transmission ratio variable device operates in the oversteer state. A vehicle steering apparatus.

Images