JP2006327389A - Vehicular steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vehicular steering device capable of easily and rapidly performing the counter steer by a simple configuration. <P>SOLUTION: A PPSECU performs the control to increase the assist force generated by a power steering device when the steer characteristic is over-steer, and the counter-steer is performed by a driver; and to decrease the assist force generated by the power steering device. It is estimated that the counter-steer is performed by the driver if the changing direction of the ACT command angle at the OS control which is the target control component of the ACT angle target when the steer characteristic is over-steer, i.e., the changing direction of the sign of the OS command angular velocity and the steering angle, i.e., the sign of the steering speed ωs is identical (Step 309: YES), and the absolute value of the steering speed ωs is larger than the predetermined value α (Step 310: YES). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a vehicle steering apparatus.

  In recent years, based on a vehicle model (vehicle motion model) that models the relationship between the vehicle state quantity such as vehicle speed and yaw rate and the vehicle motion state, the vehicle steering characteristic (steer characteristic) is determined, and according to the steering characteristic A steering control system for controlling the yaw moment of the vehicle has been proposed.

For example, the vehicle steering apparatus described in Patent Document 1 determines whether the driver is performing counter-steer (counter steer determination) when the determined steer characteristic is oversteer (counter steer determination). If it is, the assist force applied to the steering system is increased, and if the counter steer is not performed, the assist force is decreased. As a result, when the driver is performing the counter steer, the counter steer is more easily performed. When the driver is not performing the counter steer, the counter steer is guided to promptly adjust the vehicle posture. Stabilization can be achieved.
JP 2001-158372 A

  However, in the above-described conventional configuration, the counter steer determination is performed based on the direction of the steering torque applied to the steering. Therefore, in a generally widely used hydraulic power steering apparatus or the like, the steering torque can be detected electrically. It is necessary to add a new sensor. For this reason, there is a problem that the configuration becomes complicated and the manufacturing cost increases, and in this respect, there is still room for improvement.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a vehicle steering apparatus that can perform counter-steer more easily and quickly with a simple configuration. is there.

  In order to solve the above problem, the invention according to claim 1 is directed to assist force applying means for applying an assist force for assisting a steering operation to a steering system, and an assist force generated by the assist force applying means. Control means for controlling, steer characteristic determining means for determining the steer characteristic of the vehicle, and estimation means for estimating the presence or absence of counter steer by the driver, wherein the control means is such that the steer characteristic is oversteer, and For a vehicle that controls to increase the assist force when the counter steer is performed, control the steer characteristic to be oversteer, and decrease the assist force when the counter steer is not performed A steering device, wherein a second rudder angle of the steered wheel based on motor drive is added to a first rudder angle of the steered wheel based on a steering angle of the steering A transmission ratio variable device that varies a transmission ratio between the steering angle of the steering wheel and the steering angle of the steered wheels, and a second control unit that controls the operation of the transmission ratio variable device. When the steering characteristic is oversteer, the control means 2 controls the transmission ratio variable device to change the steered angle of the steered wheels in a direction opposite to the direction of the yaw moment of the vehicle. The means is such that the direction of change of the steering angle of the steering wheel is the same as the direction of change of the control target component of the second steering angle of the steered wheel when oversteering, and the absolute value of the steering speed is a predetermined value. It is assumed that the counter steer is being performed when the value is larger than.

  According to a second aspect of the present invention, there is provided an assist force applying means for applying an assist force for assisting a steering operation to a steering system, a control means for controlling an assist force generated by the assist force applying means, and a vehicle steering system. A steering characteristic determination unit that determines a characteristic; and an estimation unit that estimates the presence or absence of a counter steer by a driver, wherein the control unit has an oversteer and the counter steer is performed. Is a vehicle steering device that controls to increase the assist force, the steer characteristic is oversteer, and to weaken the assist force when the counter steer is not performed. Slip angle detecting means for detecting a slip angle, and the estimating means includes a change direction of the steering angle of the steering and the slip angle. Of direction are the same, and if the absolute value of the steering speed is greater than a predetermined value, it is estimated that the countersteering is being performed, and the gist.

  According to each of the above configurations, it is possible to estimate the presence or absence of counter-steer by a driver with a simple configuration without using a torque sensor or the like that can electrically detect steering torque. Even in the case of adopting the power steering device, it is possible to control the assisting force according to the presence or absence of the counter steer by the driver. As a result, when the driver is performing the counter steer, the counter steer is more easily performed. When the driver is not performing the counter steer, the counter steer is guided to quickly stabilize the vehicle posture. Can be planned.

The gist of the invention described in claim 3 is that the control means performs the control to increase the assist force until a predetermined time elapses after the oversteer is eliminated.
According to the above configuration, even after the oversteer is resolved, even if the steering characteristic continuously changes from oversteer to oversteer, the steering torque fluctuation is suppressed and good steering feeling is achieved. Can be secured. By keeping the assist force strengthened, it becomes possible to easily stabilize the vehicle posture by making the correction rudder by the driver easy.

  ADVANTAGE OF THE INVENTION According to this invention, the steering apparatus for vehicles which can perform counter steer more easily and rapidly with a simple structure can be provided.

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 a power steering device 14 as an assisting force applying unit that applies an assisting force for assisting a steering operation to the steering system, and an assist generated by the power steering device 14. And a PPSECU 15 as control means for controlling the force. In the present embodiment, the IFSECU constitutes a second control unit.

  More specifically, the power steering device 14 of the present embodiment is a hydraulic power steering device with a solenoid valve for controlling the flow rate, and the fluid pumped from the hydraulic pump 16 is applied to a torsion bar ( It flows into a power cylinder (not shown) provided in the rack 5 via a rotary valve 17 provided integrally with the rack 5. And the solenoid valve 18 (refer FIG. 4) which is a flow control valve is provided in the hydraulic path between the rotary valve 17 and a power cylinder. In other words, the power steering device 14 applies assist force to the steering system by pressing the rack 5 in the direction corresponding to the steering operation by the hydraulic pressure of the fluid flowing into the power cylinder. The PPSECU 15 controls the assist force generated by the power steering device 14 by controlling the opening degree, that is, the flow rate of the fluid flowing into the power cylinder, through the current supply to the solenoid valve 18. Power assist control).

  In the present embodiment, the IFSECU 8 that controls the gear ratio variable actuator 7 and the PPSECU 15 that controls the power steering device 14 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 vehicle speed sensor 25, and a yaw rate sensor 26 are connected to the in-vehicle network 23, and a plurality of vehicle state quantities detected by the sensors, that is, a steering angle θs, a turning angle. θt, vehicle speed V, and yaw rate Ry are input to IFSECU 8 and PPSECU 15 via in-vehicle network 23. In this embodiment, 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. Moreover, IFSECU8 and PPSECU15 transmit / receive a control signal by mutual communication via the in-vehicle network 23. Then, the IFSECU 8 and the PPSECU 15 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 motor 12 that is the drive source of the gear ratio variable actuator 7 is a brushless motor, and the drive circuit 34 applies three-phase (U, V, W) to the motor 12 based on the input motor control signal. ) Is supplied. 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.

  Specifically, the steering angle θs, the turning angle θt, the vehicle speed V, and the yaw rate Ry 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.

  Specifically, as shown in the flowchart of FIG. 5, the IFS control calculation unit 35 first calculates a vehicle model based on the turning angle θt and the vehicle speed V, and calculates the vehicle state quantity related to the yaw moment of the vehicle. A target yaw rate Ry0 as a target value is calculated (step 101). For the method of calculating the target yaw rate Ry0 from the turning angle θt and the vehicle speed V based on this vehicle model, refer to, for example, Japanese Patent Application Laid-Open No. 2002-254964.

  Subsequently, the IFS control calculation unit 35 determines the vehicle steer characteristic, that is, the vehicle is oversteered based on the target yaw rate Ry0 calculated in step 101, the detected yaw rate Ry, the steering angle θs, and the vehicle speed V. It is calculated (determined) whether the state is understeer or neutral steer (steer characteristic calculation, step 102). Then, the OS / US characteristic value Val_st is output as an analog signal indicating the determination result. In this embodiment, the OS / US characteristic value Val_st is obtained by the following equation: Val_st = (L × Ry / V−θt) × Ry, L: wheel base.

  Next, the IFS control calculation unit 35 performs feedback calculation so that the actual yaw rate Ry follows the target yaw rate Ry0 calculated in step 101. Based on the feedback calculation, the control target component for the ACT angle θta when the steer characteristic is oversteer, that is, the control target component for generating the steering angle (counter steer) in the direction opposite to the yaw moment, The control time ACT command angle θos * is calculated (OS control calculation, step 103). In addition, the IFS control calculation unit 35, when the steering characteristic is understeer based on the steering angle θs and the steering speed ωs and the OS / US characteristic value Val_st calculated in step 102, that is, the turning angle of the steered wheels 6 ACT command angle θus * during US control is calculated as a control target component of ACT angle θta for reducing the ACT angle (US control calculation, step 104).

  When the OS / US characteristic value Val_st indicates oversteer, the IFS control calculation unit 35 indicates the ACT command angle θos * during OS control, and when the OS / US characteristic value Val_st indicates understeer, The control time ACT command angle θus * is output as IFS_ACT command angle θifs * (IFS_ACT command angle calculation, step 105).

  In this embodiment, when the OS / US characteristic value Val_st indicates neutral steering, the IFS control calculation unit 35 sets the output IFS_ACT command angle θifs * to “0”. Then, the OS / US characteristic value Val_st is transmitted to the PPSECU 15 via the in-vehicle network 23. In the present embodiment, the OS control ACT command angle θos * calculated in the OS control calculation (see FIG. 5, step 103) is also transmitted to the PPSECU 15 in the same manner. The OS / US characteristic value Val_st and the OS control time ACT command angle θos * are used for power assist control by the PPSECU 15 (see FIG. 4).

  Further, as shown in FIG. 4, the steering angle θs and the 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 38. The adder 38 superimposes the IFS_ACT command angle θifs *, the gear ratio variable ACT command angle θgr *, and the LS_ACT command angle θls * to thereby 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 is input to the position control calculation unit 40 together with the ACT angle θta detected by the rotation angle sensor 39 provided in the motor 12, and the position control calculation unit 40 The current command ε is calculated by feedback calculation based on the input ACT command angle θta * and ACT angle θta, and the current command ε is input to the motor control signal output unit 42. Then, the motor control signal output unit 42 generates a motor control signal based on the current command ε, and the driving circuit 34 supplies driving power based on the input motor control signal to the motor 12 of the gear ratio variable actuator 7. Thus, the operation of the variable gear ratio actuator 7 is controlled.

  On the other hand, the PPSECU 15 includes a microcomputer 43 that outputs a current command for driving the solenoid valve 18 and a drive circuit 44 that supplies drive power to the solenoid valve 18 based on the current command.

  In the present embodiment, the microcomputer 43, in addition to the basic assist force calculation unit 45 that calculates the basic assist current command Ias * as a control target component serving as a base for the assist force generated by the power steering device 14, is used for vehicle steer characteristics and driving. An assist force correction calculation unit 46 is provided that calculates a correction current command Icom * for correcting the basic assist current command Ias * according to the presence or absence of counter steer by a person.

  More specifically, in the present embodiment, the vehicle speed V is input to the basic assist force calculation unit 45, and the basic assist force calculation unit 45 decreases the basic assist current command Ias as the vehicle speed V increases. * Is output (basic assist force calculation).

  On the other hand, the assist force correction calculation unit 46 includes an OS correction calculation unit 47 that calculates a correction component when the steer characteristic is oversteer, and a US correction calculation unit 48 that calculates a correction component when the steer characteristic is understeer. It has.

  The OS correction calculation unit 47 includes an OS counter correction calculation unit 49 that calculates an OS counter correction current command Ios_c * as a correction component when the driver is performing the counter steer, and a correction component when the driver is not performing the counter steer. And an OS non-counter correction calculating unit 50 for calculating an OS non-counter correction current command Ios_nc *. In the present embodiment, a turning angular velocity ωt (a differential value of the turning angle θt) is input to the OS counter correction calculation unit 49, and the OS counter correction calculation unit 49 increases the basic assist as the turning angular velocity ωt increases. An OS time counter correction current command Ios * _c that increases the current command Ias *, that is, increases the assist force generated by the power steering device 14 is calculated (OS counter correction calculation). The OS non-counter correction calculation unit 50 receives the OS / US characteristic value Val_st output from the IFSECU 8 (microcomputer 33). The OS non-counter correction calculation unit 50 receives the value indicated by the OS / US characteristic value Val_st. The non-counter correction current command Ios * _nc during OS is calculated so that the basic assist current command Ias * is reduced as the strong oversteer tendency is shown, that is, the assist force generated by the power steering device 14 is weakened (OS non-counter correction). Calculation). The OS / US characteristic value Val_st is input to the US correction calculation unit 48, and the US correction calculation unit 48 increases the basic assist current command Ias as the value indicated by the OS / US characteristic value Val_st shows a stronger understeer tendency. The US correction current command Ius * is calculated to reduce *, that is, weaken the assist force generated by the power steering device 14 (US correction calculation).

  In the present embodiment, the OS correction counter command Ios_c * and the OS non-counter correction current command Ios * _nc calculated by the OS correction calculation unit 47, and the US correction current command Ius calculated by the US correction calculation unit 48 are used. * Is input to the assist correction calculation unit 51 together with the OS / US characteristic value Val_st and the changing speed of the ACT command angle θos * during OS control, that is, the OS command angular speed ωos *. In this embodiment, the OS command angular velocity ωos * is calculated by differentiating the OS control ACT command angle θos *. Then, the assist correction calculation unit 51 performs each correction calculation according to the vehicle steer characteristic estimated based on the input OS / US characteristic value Val_st and the OS command angular velocity ωos * and the presence or absence of the counter steer by the driver. The OS counter correction current command Ios_c *, the OS non-counter correction current command Ios * _nc, or the US correction current command Ius * (or 0) is output as the correction current command Icom *. (Assist correction calculation).

  The basic assist current command Ias * output from the basic assist force calculation unit 45 and the correction current command Icom * output from the assist force correction calculation unit 46 are input to the adder 52. Then, the microcomputer 43 outputs a value obtained by superimposing the correction current command Icom * on the basic assist current command Ias * in the adder 52 to the drive circuit 44 as a current command.

  That is, as shown in the flowchart of FIG. 6, the microcomputer 43 first calculates the basic assist current command Ias * by executing the basic assist calculation (step 201), and then the OS counter correction calculation (step 202). Non-counter correction calculation (step 203) and US correction calculation (step 204) are executed. Next, the microcomputer 43 executes the assist correction calculation, so that the OS / US among the correction current commands (Ios_c *, Ios_nc *, Ius *) calculated in the correction calculations in Step 201 to Step 203 is performed. A correction current command Icom * is determined (calculated) according to the vehicle steer characteristic estimated based on the characteristic value Val_st and the OS command angular velocity ωos * and the presence or absence of counter steer by the driver (step 205). The microcomputer 43 outputs a value obtained by superimposing the correction current command Icom * calculated in step 205 on the basic assist current command Ias * calculated in step 201 to the drive circuit 44 as a current command (step 206).

Next, an aspect of power assist control in the steering device of the present embodiment and a method for estimating the presence or absence of counter steer will be described.
In the present embodiment, the PPSECU 15 increases the assist force generated by the power steering device 14 and performs counter-steering when the driver is performing counter-steering when the steering characteristic is oversteer. If not, control is performed so that the assist force generated by the power steering device 14 is weakened. The change direction of the ACT command angle θos * during OS control, which is the control target component of the ACT angle θta when the steer characteristic is oversteer, that is, the sign (+/−) of the OS command angular velocity ωos * and the steering angle θs When the sign of the change direction, that is, the steering speed ωs is the same, and the absolute value of the steering speed ωs is larger than the predetermined value α, it is estimated that the counter steer is being performed by the driver.

  More specifically, as shown in the flowchart of FIG. 7, the assist correction calculation unit 51 first determines whether or not the OS / US characteristic value Val_st indicates oversteer (OS) (step 301). If it is not steered (step 301: NO), it is subsequently determined whether or not it is determined that oversteering is performed in step 301 at the time of sampling one cycle before (previous OS ?, step 302). If it is determined that the OS is the previous OS (step 302: YES), the timer for measuring the elapsed time t from the oversteer cancellation is cleared (t = 0, step 303), and it is determined that the OS is not the previous OS. If so (step 302: NO), the timer is incremented (t = t + 1, step 304).

  After clearing the timer in step 303 or incrementing the timer in step 304, the assist correction calculation unit 51 next determines whether or not the OS / US characteristic value Val_st indicates understeer (US). (Step 305). When understeer (step 305: YES), the US correction current command Ius * is output as the correction current command Icom * to weaken the assist force generated by the power steering device 14 (US correction: Icom * = Ius *, step 306), if it is neutral steer (step 305: NO), the correction current command Icom * is set to “0” (no correction: Icom * = 0, step 307).

  On the other hand, if it is determined in step 301 that the oversteer is present (step 301: YES), the assist correction calculation unit 51 next determines whether the elapsed time t from the oversteer elimination has passed the predetermined time t0. It is determined whether or not (step 308). If the predetermined time t0 has elapsed (t ≧ t0, step 308: YES), it is estimated whether or not the counter steer is being performed by the driver (steps 309 and 310).

  Specifically, first, the sign (+/-) of the OS command angular velocity ωos * and the sign of the steering speed ωs are the same, that is, the change direction of the ACT command angle θos * during OS control is the same as the change direction of the steering angle θs. (Step 309), if they are the same (step 309: YES), it is subsequently determined whether or not the absolute value of the steering speed ωs is larger than a predetermined value α (step 310). If the absolute value of the steering speed ωs is larger than the predetermined value α (| ωs |> α, step 310: YES), it is estimated that the counter-steer is being performed by the driver, and the power steering device 14 In order to increase the generated assist force, the OS counter correction current command Ios_c * is output as the correction current command Icom * (OS counter correction: Icom * = Ios_c *, step 311). When it is determined in step 309 that the sign (+/−) of the OS command angular speed ωos * and the sign of the steering speed ωs are not the same (step 309: NO), or in step 310, the absolute value of the steering speed ωs. Is determined to be equal to or less than the predetermined value α (| ωs | ≦ α, step 310: NO), it is estimated that the counter-steer is not performed by the driver, and the assist force generated by the power steering device 14 is In order to weaken, the OS non-counter correction current command Ios_nc * is output as the correction current command Icom * (OS non-counter correction: Icom * = Ios_nc *, step 312).

  In the present embodiment, when it is determined in step 308 that the elapsed time t from the oversteer cancellation has not passed the predetermined time t0 (t <t0, step 308: NO), the assist correction calculation unit 51 does not execute the processing of steps 309 and 310 described above. Then, step 311 is executed without estimating the presence or absence of counter steer by the driver, and the OS time counter correction current command Ios_c * is output as the correction current command Icom *.

  As described above, the assist correction calculation unit 51 (microcomputer 43) performs the assist correction calculation by executing the processes in steps 301 to 312 for each scheduled interruption. This makes it possible to estimate the presence or absence of counter-steering by a driver with a simple configuration without using a torque sensor or the like that can electrically detect steering torque. Even in the case of the adoption, the assist force can be controlled according to the presence or absence of the counter steer by the driver. As a result, when the driver is performing the counter steer, the counter steer is more easily performed. When the driver is not performing the counter steer, the counter steer is guided to quickly stabilize the vehicle posture. Can be planned.

  Further, until the elapsed time t from the oversteer elimination exceeds the predetermined time t0, the oversteer can be eliminated by controlling the assist force generated by the power steering device 14 regardless of the change in the steering characteristic. Thereafter, even when the steering characteristic continuously changes from oversteer to oversteer again, it is possible to suppress the fluctuation of the steering torque and ensure a good steering feeling. Then, by keeping the assist force strengthened, the driver can easily make a correction rudder.

In addition, you may change this embodiment as follows.
In the present embodiment, the present invention includes the gear ratio variable actuator 7 as a transmission ratio variable device, and changes the ACT angle θta to control the turning angle θt to control the yaw moment of the vehicle. The present invention is embodied in a steering device 1 having a so-called active steering function. However, the present invention is not limited to this, and any power steering apparatus that does not have such an active steering function may be used as long as it has a function as a steering characteristic determination unit capable of determining a steering characteristic. In that case, for the estimation of the presence or absence of counter-steer by the driver (see FIG. 7, step 309), the change speed of the vehicle slip angle is used instead of the OS command angular speed ωos *, that is, the sign of the slip angular speed and the steering speed. It may be performed by determining whether or not the sign of ωs (change direction of the steering angle θs) is the same. The slip angle detecting means may be configured to detect the slip angle based on the yaw rate Ry and lateral acceleration detected by using the yaw rate sensor 26 and the lateral G sensor.

  In the present embodiment, the OS counter correction calculation unit 49 constituting the estimating means calculates the OS counter correction current command Ios * _c based on the turning angular velocity ωt (differential value of the turning angle θt). did. However, the present invention is not limited to this, and the calculation may be performed based on the differential value of the IFS_ACT command angle θifs * (IFS_ACT command angular velocity) or the target turning angular velocity (IFS_ACT command angular velocity + steering speed ωs).

  In addition, in the calculation of the OS non-counter correction current command Ios * _nc and the US correction current command Ius *, the OS control ACT command angle θos * or the OS command angular velocity ωos * is used instead of the OS / US characteristic value Val_st. May be used.

  Although not specifically mentioned in the present embodiment, the assist force correction profiles (see FIG. 4) in the US correction calculation and the OS non-counter correction calculation may be the same or different.

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 IFS control calculation process in an IFS control calculation part. The flowchart which shows the process sequence of the arithmetic processing in the microcomputer by the side of PPSECU. The flowchart which shows the process sequence of the assist correction calculation in an assist correction calculating part.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Steering device, 2 ... Steering, 6 ... Steering wheel, 7 ... Gear ratio variable actuator, 8 ... IFSECU, 12 ... Motor, 14 ... Power steering device, 15 ... PPSECU, 33, 43 ... Microcomputer, 35 ... IFS control calculation 45, basic assist force calculation unit, 46 ... assist force correction calculation unit, 47 ... OS correction calculation unit, 48 ... US correction calculation unit, 49 ... OS counter correction calculation unit, 50 ... OS non-counter correction calculation unit, 51 ... Assist correction calculation unit, θs ... steering angle, ωs ... steering speed, α ... predetermined value, θt ... steering angle, ωt ... steering angular velocity, θts ... steer turning angle, θta ... ACT angle, θta * ... ACT command Angle, θos *: ACT command angle during OS control, ωos *: OS command angular velocity, Ias *: Basic current command, Ios_c *: Counter correction current command during OS, Ios_nc *: Non-counter correction current command during OS, Ius * ... S during the correction current command, Icom * ... correction current command, Val_st ... OS / US characteristic value, t ... elapsed time, t0 ... a predetermined period of time.

Claims (3)

An assist force applying means for applying an assist force for assisting a steering operation to the steering system; a control means for controlling an assist force generated by the assist force applying means; and a steer characteristic determining means for determining a steer characteristic of the vehicle; An estimation means for estimating the presence or absence of counter steer by the driver, and the control means strengthens the assist force when the steer characteristic is over steer and the counter steer is performed, When the steering characteristic is oversteer and the countersteer is not performed, the vehicle steering device controls the assist force to be weakened,
A transmission ratio between the steering angle of the steered wheel and the steered angle of the steered wheel by adding the second steered angle of the steered wheel based on the motor drive to the first steered angle of the steered wheel based on the steered angle of the steering And a second control means for controlling the operation of the transmission ratio variable apparatus, wherein the second control means is configured to control the vehicle when the steering characteristic is oversteer. Controlling the transmission ratio variable device to change the steering angle of the steered wheels in a direction opposite to the direction of the yaw moment of
The estimating means has the same direction of change of the steering angle of the steering wheel and the direction of change of the control target component of the second steering angle of the steered wheel in the case of the oversteer, and the absolute value of the steering speed is A vehicle steering apparatus characterized by estimating that the counter-steer is being performed when larger than a predetermined value. An assist force applying means for applying an assist force for assisting a steering operation to the steering system; a control means for controlling an assist force generated by the assist force applying means; and a steer characteristic determining means for determining a steer characteristic of the vehicle; An estimation means for estimating the presence or absence of counter steer by the driver, and the control means strengthens the assist force when the steer characteristic is over steer and the counter steer is performed, When the steering characteristic is oversteer and the countersteer is not performed, the vehicle steering device controls the assist force to be weakened,
Comprising slip angle detecting means for detecting the slip angle of the vehicle,
The estimating means performs the counter steer when the steering angle change direction of the steering and the slip angle change direction are the same and the absolute value of the steering speed is larger than a predetermined value. A vehicle steering apparatus characterized by estimating. In the vehicle steering device according to claim 1 or 2,
The vehicle steering apparatus according to claim 1, wherein the control means performs the control to increase the assist force until a predetermined time elapses after the oversteer is eliminated.

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