JP4984620B2 - Vehicle travel control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce fluctuation of steering reaction accompanied by the control of a steering angle when controlling the steering angle of a steered wheel to cope with a failure of a brake device, and to reduce odd feeling due to the fluctuation of the steering reaction. <P>SOLUTION: When a normal control of braking force for any wheel is impossible (S330), excessive yaw moment Mad caused by a braking force difference of left and right wheels is calculated. Based on the excessive yaw moment Mad and vehicle speed V, correction amount &Delta;&delta;ft of the steering angle of a front wheel is calculated to generate yaw moment required for canceling the excessive yaw moment Mad (S340). A target steering angle &delta;ft of the front wheel is corrected to be the sum of the target steering angle &delta;ft of the front wheel and correction amount &Delta;&delta;ft of the steering angle of the front wheel to attain a target steering gear ratio Rgt (S360). By controlling a turning angle variable device 24 so that the steering angle &delta;f of the front wheel may be the target steering angle &delta;f, a prescribed steering characteristic is attained, and the fluctuation of the steering reaction accompanied by the control of the steering angle is reduced (S370, 380). <P>COPYRIGHT: (C)2008,JPO&amp;INPIT

Description

  The present invention relates to a travel control device for a vehicle, and more particularly to a travel control device for a vehicle including a steering wheel steering angle varying device capable of turning a steered wheel without depending on a driver's steering.

As one of travel control devices for vehicles such as automobiles, for example, as described in Patent Document 1 below, the braking force difference between the left and right wheels is controlled by controlling the steering angle of the front wheels or the rear wheels when the braking device fails. 2. Description of the Related Art Conventionally, a traveling control device that controls the traveling motion of a vehicle so as to reduce the influence of the above is known. According to such a traveling control device, even if the braking device breaks down and an unnecessary braking force difference occurs between the left and right wheels, it is possible to reduce a decrease in the traveling performance of the vehicle, particularly the straight traveling performance due to this.
JP 2004-237927 A

  However, in the conventional travel control device as described above, the lateral force of the front wheel or the rear wheel changes due to the control of the steering angle of the front wheel or the rear wheel, and the steering reaction force fluctuates accordingly. There is a problem that it is inevitable to feel uncomfortable. In particular, when the steering angle of the front wheels is steered by the power steering device as in the travel control device described in Patent Document 1, the steering assist force itself is greatly changed to steer the front wheels. It is inevitable that a person feels an unnatural fluctuation in the steering reaction force.

The present invention solves the above-described problem in the conventional traveling control device configured to reduce the influence of the braking force difference between the left and right wheels by controlling the steering angle of the front wheels or the rear wheels when the braking device fails. The main object of the present invention is to reduce the fluctuation of the steering reaction force accompanying the control of the steering angle when the steering angle of the steering wheel is controlled in order to cope with the failure of the braking device. This reduces the possibility that the driver may feel uncomfortable due to fluctuations in the steering reaction force.
[Means for Solving the Problems and Effects of the Invention]

According to the present invention, the main problem described above is the structure of claim 1, that is, the braking means for applying a braking force to each wheel, and the steering wheel capable of turning the steering wheel without depending on the steering of the driver. A travel control device for a vehicle, comprising: a steering angle varying unit; and a steering assist force generating unit that generates a steering assist force based on at least a target steering assist force corresponding to a steering reaction force. When unnecessary braking force difference between the left and right wheels and the arising Kiniwa estimates the excess yaw moment due to the braking force difference, generating a yaw moment required to combat the excess yaw moment together by the steering wheel steering angle varying means to control the steering angle of the steering wheel, the steering wheel steering angle varying means according to the suppressing variation of the steering reaction force due to the control of the steering angle of the steering wheel so the For extra yaw moment The target steering assist force is corrected Zui, achieved by the traveling control apparatus for a vehicle, characterized in that it comprises a control means for controlling the steering assist force by the steering assist force generating means on the basis of the target steering assist force after correction Is done.

According to the first aspect of the present invention, when an unnecessary braking force difference occurs between the left and right wheels due to an abnormality in the braking means, an extra yaw moment caused by the braking force difference is estimated, and an extra yaw moment is estimated. The steering wheel rudder angle is controlled by the steering wheel rudder angle varying means so as to generate the yaw moment necessary to counteract the steering wheel, and the steering reaction force caused by the steering wheel rudder angle control by the steering wheel rudder angle varying means The target steering assist force is corrected based on the excess yaw moment so as to suppress the fluctuation of the steering force, and the steering assist force by the steering assist force generating means is controlled based on the corrected target steering assist force . Therefore, even when an abnormality occurs in the braking means and an unnecessary yaw moment acts on the vehicle due to an unnecessary difference in braking force between the left and right wheels, the control of the steering angle of the steering wheel counters the excess yaw moment. By generating the yaw moment, the unnecessary yaw moment acting on the vehicle can be surely reduced, and the steering reaction force due to the fluctuation of the lateral force of the steered wheels accompanying the control of the steered angle of the steered wheels Can be reliably reduced.
According to the configuration of the first aspect, the target steering assist force is corrected based on the excess yaw moment, and the steering assist force generated by the steering assist force generating unit is controlled based on the corrected target steering assist force. Compared to the case where the target steering assist force is corrected based on the control amount of the steering angle of the steering wheel, not only can the fluctuation of the steering reaction force accompanying the control of the steering angle of the steering wheel be reliably reduced, The corrected target steering assist force can be easily calculated, and the steering assist force can be controlled efficiently.

According to the invention, to the aspect of the effective, in the configuration of the first aspect, the yaw moment the necessary basis the control means extra yaw moment which is the estimated The control amount of the steering angle of the steered wheel for generating the steering wheel is calculated (configuration of claim 2).

According to this configuration 2, the control amount of the steering angle of the steering wheel for generating a yaw moment required based on the excess yaw moment is estimated is calculated, unnecessary for the left and right wheels Therefore, unnecessary yaw moment acting on the vehicle due to a difference in braking force can be reliably reduced by controlling the steering angle of the steered wheels.

According to the present invention, in order to effectively achieve the main problems described above, in the configuration of claim 1 or 2 , the steering wheel is a front wheel and a rear wheel, and the rear wheel is a It is comprised so that it may steer to the other side (structure of Claim 3 ).

According to the configuration of the third aspect , since the steered wheels are the front wheels and the rear wheels, and the rear wheels are steered to the left and right sides opposite to the front wheels, the control of the steering angle of the steered wheels is described in detail later. As a result, the amount of control of the steering angle of the front wheels can be reduced as compared with the case where the steering angle of the rear wheels is not controlled. The possibility of the neutral position offset of the front wheels due to the operation of the variable means can be reduced.
[Preferred embodiment of problem solving means]

According to one preferable aspect of the present invention, in the configuration according to any one of the first to third aspects, the control means provides a yaw moment necessary for canceling an excess yaw moment caused by a difference in braking force between the left and right wheels. The steering wheel rudder angle is controlled by the steered wheel rudder angle varying means so as to generate a moment (preferred aspect 1).

According to another preferred aspect of the present invention, in the configuration of claim 2 or 3 or preferred aspect 1 , the control means sets the necessary yaw moment based on the estimated extra yaw moment and vehicle speed. It is comprised so that the control amount of the steering angle of the steering wheel for generating may be calculated (Preferred aspect 2).

According to the aspect of the present invention, the claim 2 or 3 or the preferred In configuration of embodiments 1 or 2, the control means estimates the excess yaw moment on the basis of the braking force of each wheel (Preferred aspect 3).

According to the aspect of the present invention, in the any one of the preceding claims 1 to 3 or the preferred embodiments 1 to 3, the control means calculates a target yaw moment of the vehicle, each wheel The yaw moment resulting from the braking force difference between the left and right wheels is calculated based on the braking force, and the excess yaw moment is estimated as the deviation between the target yaw moment and the yaw moment resulting from the braking force difference between the left and right wheels (Preferred embodiment 4).

According to another preferred aspect of the present invention, in the configuration according to claim 3 or preferred aspects 1 to 4, the magnitude of the rear wheel turning amount is larger than the front wheel turning amount. It is comprised so that it may be smaller than this (Preferable aspect 5).

  The present invention will now be described in detail with reference to a few preferred embodiments with reference to the accompanying drawings.

  FIG. 1 is a schematic configuration diagram showing a first embodiment of a vehicle travel control device according to the present invention applied to a vehicle capable of controlling the steering angle of a front wheel.

  In FIG. 1, 10FL and 10FR respectively indicate left and right front wheels as steering wheels of the vehicle 12, and 10RL and 10RR respectively indicate left and right rear wheels. The left and right front wheels 10FL and 10FR, which are the steering wheels, are driven via a rack bar 18 and tie rods 20L and 20R by a rack-and-pinion type electric power steering device 16 driven in response to an operation of the steering wheel 14 by a driver. Steered.

  The steering wheel 14 is drivingly connected to the pinion shaft 30 of the power steering device 16 through an upper steering shaft 22, a turning angle varying device 24, a lower steering shaft 26, and a universal joint 28. In the illustrated embodiment, the turning angle varying device 24 is connected to the lower end of the upper steering shaft 22 on the housing 24A side, and is connected to the upper end of the lower steering shaft 26 on the rotor 24B side. An electric motor 32 for turning driving is included.

  Thus, the turning angle varying device 24 rotationally drives the lower steering shaft 26 relative to the upper steering shaft 22, thereby steering the left and right front wheels 10FL and 10FR to the steering wheel for the purpose of steering gear ratio control and vehicle travel control. 14 functions as an automatic steering device that drives the auxiliary steering relatively, and is controlled by the steering angle control unit of the electronic control device 34.

  If an abnormality in which the lower steering shaft 26 cannot be driven to rotate relative to the upper steering shaft 22 occurs in the turning angle varying device 24, a lock device not shown in FIG. The relative rotation of the housing 24A and the rotor 24B is mechanically prevented so that the relative rotation angle of the lower steering shaft 26 with respect to 22 does not change.

  In the illustrated embodiment 1, the electric power steering device 16 is a rack coaxial type electric power steering device, and converts the electric motor 36 and the rotational torque of the electric motor 36 into a force in the reciprocating direction of the rack bar 18. For example, a ball screw type conversion mechanism 38 is provided. The electric power steering device 16 is controlled by an electric power steering device (EPS) control unit of the electronic control device 34, and generates an auxiliary steering force that drives the rack bar 18 relative to the housing 42, thereby enabling the driver. It functions as an auxiliary steering assist force generator that reduces the steering burden. The auxiliary steering assist force generator may have any configuration known in the art.

  The braking force of each wheel is controlled by controlling the pressure Pi (i = fl, fr, rl, rr) in the wheel cylinders 46FL, 46FR, 46RL, 46RR, that is, the braking pressure, by the hydraulic circuit 44 of the braking device 42. It has become so. Although not shown in the drawing, the hydraulic circuit 44 includes an oil reservoir, an oil pump, various valve devices, and the like, and the braking pressure of each wheel is normally driven in response to the depression operation of the brake pedal 48 by the driver. Based on the pressure Pm of the master cylinder 50, the braking force control unit of the electronic control unit 34 controls the pressure increase / decrease control valve and the like. When an abnormality occurs in a member common to all wheels such as an oil pump, the wheel cylinders 46FL to 46RR are connected to the master cylinder 50, whereby the braking pressure of each wheel is directly controlled by the master cylinder 50.

  In the illustrated embodiment, the upper steering shaft 22 is provided with a steering angle sensor 60 for detecting the rotation angle of the upper steering shaft as the steering angle θ and a steering torque sensor 62 for detecting the steering torque Ts. Signals indicating the steering angle θ and the steering torque Ts are input to the electronic control unit 34. The electronic control unit 34 detects a relative rotation angle θre of the turning angle varying device 24 detected by the rotation angle sensor 64, that is, a signal indicating a relative rotation angle of the lower steering shaft 26 with respect to the upper steering shaft 22, and is detected by the vehicle speed sensor 66. A signal indicating the vehicle speed V, a signal indicating the master cylinder pressure Pm detected by the pressure sensor 68, and a signal indicating the braking pressure Pi of each wheel detected by the pressure sensors 70FL to 70RR are input.

  Each control unit of the electronic control unit 34 may include a microcomputer having a CPU, a ROM, a RAM, and an input / output port device, which are connected to each other by a bidirectional common bus. Further, the steering angle sensor 60, the steering torque sensor 62, and the rotation angle sensor 64 detect the steering angle θ, the steering torque Ts, and the relative rotation angle θre, respectively, when the vehicle is steered or steered in the left turn direction.

  As will be described later, the electronic control unit 34 calculates the target braking pressure Pti of each wheel to a value equal to or higher than the master cylinder pressure Pm based on the master cylinder pressure Pm indicating the amount of braking operation of the driver in the normal state, and controls each wheel. The braking pressure Pi of each wheel is controlled so that the power becomes a braking force corresponding to the target braking pressure Pti.

  Further, the electronic control unit 34 calculates a target steering gear ratio Rgt for achieving a predetermined steering characteristic based on the vehicle speed V during normal times, and calculates a target steering angle δft of the front wheels based on the target steering gear ratio Rgt. The turning angle varying device 24 is controlled so that the steering angle δf of the front wheels becomes the target steering angle δf.

  Further, the electronic control unit 34 calculates a target assist torque Ta for generating a steering assist force for reducing the driver's steering burden based on the steering torque Ts and the vehicle speed V in the normal state, and the assist torque becomes the target assist torque Ta. Control of the steering assist force is executed by controlling the electric power steering device 16 so as to be.

  Note that the above-described normal braking force control, steered wheel steering angle control, and steering assist force control itself do not form the subject of the present invention, and these controls are arbitrary known in the art. It may be executed as follows.

  On the other hand, if the pressure sensor 68 is normal, but the abnormality that the control of the normal braking pressure cannot be performed for any of the wheels occurs in the braking device 42, the electronic control unit 34 causes the abnormal braking pressure of the wheels to be controlled. The control is stopped and the wheel cylinder of the wheel is connected to the master cylinder 50, but the control of the braking pressure of the other normal wheels is continued.

  Then, the electronic control unit 34 calculates an extra yaw moment Mad resulting from the difference in braking force between the left and right wheels, and generates a yaw moment necessary to cancel the extra yaw moment Mad based on the extra yaw moment Mad and the vehicle speed V. The front wheel target rudder angle is calculated to be the sum of the front wheel target rudder angle δft and the front wheel rudder angle correction amount Δδft to calculate a predetermined steering characteristic. By correcting δft, the steering angle δf of the front wheels is controlled so as to achieve a predetermined steering characteristic and generate a yaw moment necessary to counter the excess yaw moment Mad.

  Further, the electronic control unit 34 calculates a correction amount ΔTa of the steering assist torque for suppressing the fluctuation of the steering reaction force caused by the control of the steering angle of the front wheels based on the excess yaw moment Mad, thereby reducing the driver's steering burden. The target assist torque Ta is corrected so as to be the sum of the target assist torque Ta that generates the reduced steering assist force and the correction amount ΔTa, and the electric power steering device 16 is controlled based on the corrected target assist torque Ta. This reduces the driver's steering burden and prevents fluctuations in the steering reaction force accompanying the control of the steering angle of the front wheels.

  Next, vehicle travel control in the illustrated embodiment 1 will be described with reference to the flowcharts shown in FIGS. 2 to 4 are flowcharts showing a control routine for braking force, a control routine for the steering angle of the front wheels, and a control routine for steering assist torque, respectively. Each control is performed by closing an ignition switch not shown in the figure. It is started and executed repeatedly every predetermined time.

  In step 210 of the braking force control routine shown in FIG. 2, a signal indicating the master cylinder pressure Pm is read, and in step 220, the positive coefficient Kbi of each wheel and the master cylinder pressure are read. The target braking pressure Pti for each wheel is calculated as the product of Pm.

  In step 230, it is determined whether or not normal braking pressure control is possible for all wheels. If a negative determination is made, the process proceeds to step 250. If an affirmative determination is made, the process proceeds to step 250. After the flag Fb is reset to 0 at 235, the routine proceeds to step 240.

  In step 240, feedback (FB) control is performed so that the braking pressure Pi of each wheel becomes the corresponding target braking pressure Pti, so that the braking force of each wheel becomes the braking force corresponding to the target braking pressure Pti. Then, control returns to step 210.

  In step 250, it is determined whether or not the pressure sensors 70FL to 70RR are normal. If an affirmative determination is made, the process proceeds to step 265. If a negative determination is made, a flag is set in step 255. After Fb is set to 1, the routine proceeds to step 260.

  In step 260, feedback (FB) control is performed so that the braking pressures Pi of the wheels having normal pressure sensors (70FL to 70RR) become the corresponding target braking pressures Pti. Each of the wheels is controlled so as to have a braking force corresponding to the target braking pressure Pti, and feedforward is performed so that the braking pressures of the wheels whose pressure sensors (70FL to 70RR) are abnormal are the same as the braking pressures of the opposite wheels. FF) As a result of the control, the braking force of the wheel is controlled to be the same as the braking force of the opposite left and right wheels, and then the process returns to step 210.

  In step 265, the flag Fb is set to 2. In step 270, the braking pressure of the wheel whose pressure sensor (70FL to 70RR) is abnormal is not controlled, and the wheel cylinder of the wheel is set to the master cylinder 50. Although connected, the feedback (FB) control is performed so that the braking pressure Pi of the wheel whose pressure sensor (70FL to 70RR) is normal becomes the corresponding target braking pressure Pti, so that the braking force of each of the wheels is controlled. Control is performed so that the braking force corresponds to the target braking pressure Pti, and then the process returns to step 210.

In step 310 of the front wheel steering angle control routine shown in FIG. 3, a signal indicating the steering angle .theta. Is read, and in step 320, based on the vehicle speed V, the signal shown in FIG. A target steering gear ratio Rgt is calculated from a map corresponding to the graph, and a target steering angle δft of the front wheels for achieving a predetermined steering characteristic is calculated according to the following formula 1.
δft = θ / Rgt (1)

  Note that the standard steering gear ratio is Rgo (a positive constant), and the target steering angle δft is a steering angle δw (= θ / Rgo) corresponding to the driver's steering operation and control steering to achieve a predetermined steering characteristic. It is the sum with the angle δc. Further, the control of the steering characteristic itself does not form the gist of the present invention, and the target steering gear ratio Rgt may be calculated in an arbitrary manner known in the art. For example, the transient response of the vehicle to the steering can be calculated. In order to improve, it may change also with steering speed (change rate of steering angle (theta)).

  In step 330, it is determined whether or not the flag Fb is 2, that is, whether or not the normal braking pressure cannot be controlled for any of the wheels. If yes, the process proceeds to step 370, and if a positive determination is made, the process proceeds to step 340.

In step 340, W is the tread of the vehicle, Kbwi is the conversion coefficient from the braking pressure of each wheel to the braking force, and the difference in braking force between the left and right wheels according to the following formula 2 based on the braking pressure Pi of each wheel An extra yaw moment Mad is calculated. In this case, the braking pressure Pi of the wheel whose pressure sensor (70FL to 70RR) is abnormal is set to the master cylinder pressure Pm.
Mad = (KbwflPfl + KbwrlPrl−KbwfrPfr−KbwrrPrr) W / 2 (2)

  In step 350, the steering angle of the front wheels for generating the yaw moment necessary to cancel the excess yaw moment Mad from the map corresponding to the graph shown in FIG. 6 based on the excess yaw moment Mad and the vehicle speed V. The correction amount Δδft is calculated.

  In step 360, the target rudder angle δft of the front wheels is set to be the sum of the target rudder angle δft of the front wheels calculated in step 320 and the correction amount Δδft of the rudder angle of the front wheels calculated in step 350. It is corrected.

  In step 370, based on the target steering angle δft of the front wheels, the target relative rotation angle of the steering angle varying device 24 for changing the steering angle δf of the front wheels to the target steering angle δft in a manner known in the art. θret is calculated, and in step 380, the steered angle varying device 24 is controlled so that the relative rotational angle θre of the steered angle varying device 24 becomes the target relative rotational angle θret. Control is performed to achieve the target rudder angle δft.

  In step 410 of the steering assist torque control routine shown in FIG. 4, a signal indicating the steering torque Ts is read, and in step 420, the signal shown in FIG. 7 is shown based on the steering torque Ts. The basic assist torque Tab is calculated from the map corresponding to the graph. In step 430, the vehicle speed coefficient Kv is calculated from the map corresponding to the graph shown in FIG. 8 based on the vehicle speed V. In step 440, the vehicle speed is calculated. The target assist torque Ta is calculated as the product of the coefficient Kv and the basic assist torque Tab.

  In step 450, it is determined whether or not the flag Fb is 2, that is, whether or not the normal braking pressure cannot be controlled for any of the wheels. If so, the process proceeds to step 490, and if an affirmative determination is made, the process proceeds to step 460.

  In step 460, as in step 340, the excess yaw moment Mad resulting from the difference in braking force between the left and right wheels is calculated according to the above equation 2 based on the braking pressure Pi of each wheel. Note that the value calculated in step 340 may be used as the extra yaw moment Mad.

  In step 470, the fluctuation of the steering reaction force caused by the control of the steering angle of the front wheel based on the correction amount Δδft of the steering angle of the front wheel is calculated based on the excess yaw moment Mad based on the map corresponding to the graph shown in FIG. A steering assist torque correction amount ΔTa for suppression is calculated.

  In step 480, the target assist torque Ta is corrected so as to be the sum of the target assist torque Ta calculated in step 440 and the steering assist torque correction amount ΔTa calculated in step 470. In this case, a control signal corresponding to the target assist torque Ta is output to the motor 36, whereby the assist torque is controlled so that the assist torque becomes the target assist torque Ta.

  Next, control of the braking force, control of the steering angle of the front wheels, and control of the steering assist torque in the first embodiment configured as described above will be described in various cases.

(1) When normal braking pressure control is possible for all wheels First, at step 220, the target braking pressure Pti of each wheel is calculated based on the master cylinder pressure Pm, and an affirmative determination is made at step 230. In step 235, the flag Fb is reset to 0, and in step 240, the braking force of each wheel is controlled to become the braking force corresponding to the target braking pressure Pti.

  In step 320, the target steering gear ratio Rgt is calculated based on the vehicle speed V, and the target steering angle δft of the front wheels for achieving a predetermined steering characteristic is calculated based on the target steering gear ratio Rgt. A negative determination is made at 330, and the steering angle variable device 24 is controlled so that the steering angle δf of the front wheels becomes the target steering angle δft at steps 370 and 380, whereby the steering gear ratio becomes the target steering gear. The ratio Rgt is controlled.

  In steps 420 to 440, the target assist torque Ta is calculated based on the steering torque Ts and the vehicle speed V, a negative determination is made in step 450, and the assist torque becomes the target assist torque Ta in step 490. Thus, the steering assist torque is controlled.

(2) When the pressure sensor is abnormal and normal braking pressure control is impossible The control of the normal braking pressure for the wheel is not possible because the pressure sensors 70FL to 70RR of any of the wheels are abnormal. If possible, a negative determination is made in steps 230 and 250, whereby the flag Fb is set to 1 in step 255 and the pressure sensor (70FL to 70RR) is normal in step 260. The braking force of a wheel is controlled to be a braking force corresponding to the target braking pressure Pti, and the braking force of the wheel whose pressure sensor (70FL to 70RR) is abnormal is the same as the braking force of the opposite wheel. It is controlled so that the braking force becomes.

  Further, in this case, since the difference in braking force between the left and right wheels does not substantially occur, the control of the steering angle δf of the front wheels and the control of the steering assist torque by the turning angle varying device 24 are the same as in the case of the above (1). To be executed.

(3) When the pressure sensor is normal but control of normal braking pressure is impossible The pressure sensors 70FL to 70RR are normal, but an increase / decrease control valve or the like of any wheel is abnormal. If normal braking pressure control is not possible for the wheel, a negative determination is made at step 230, but an affirmative determination is made at step 250, whereby a flag is set at step 265. Fb is set to 2 and the braking force of the wheel whose pressure sensor (70FL to 70RR) is abnormal in step 270 is not controlled, and the wheel cylinder of the wheel is connected to the master cylinder 50, but the pressure sensor ( 70FL to 70RR) are controlled so that the braking force of the wheel having a normal value becomes a braking force corresponding to the target braking pressure Pti.

  In step 330, an affirmative determination is made. In step 340, an excess yaw moment Mad resulting from the difference in braking force between the left and right wheels is calculated. In step 350, the excess yaw moment Mad and the vehicle speed V are calculated. A front wheel rudder angle correction amount Δδft for generating a yaw moment necessary to cancel the excess yaw moment Mad is calculated, and in step 360, the front wheel target rudder angle for achieving the target steering gear ratio Rgt is calculated. The target steering angle δft of the front wheels is corrected so as to be the sum of δft and the correction amount Δδft of the steering angle of the front wheels.

  In Steps 370 and 380, the steered angle varying device 24 is controlled so that the steering angle δf of the front wheels becomes the target steering angle δft, so that the steering gear ratio becomes the target steering gear ratio Rgt and the excess yaw moment. The steering angle δf of the front wheels is controlled so as to generate a yaw moment necessary to cancel out Mad.

  In step 450, an affirmative determination is made. In step 460, an excess yaw moment Mad resulting from the difference in braking force between the left and right wheels is calculated. In step 470, the front wheel rudder is calculated based on the excess yaw moment Mad. A correction amount ΔTa of the steering assist torque for suppressing the fluctuation of the steering reaction force caused by the angle control is calculated.

  In step 480, the target assist torque Ta is corrected so as to be the sum of the target assist torque Ta and the steering assist torque correction amount ΔTa, and in step 490, the assist torque is adjusted so that the assist torque becomes the target assist torque Ta. Control is executed, thereby reducing the driver's steering burden and suppressing fluctuations in the steering reaction force due to the control of the steering angle of the front wheels.

  Therefore, according to the first embodiment shown in the drawing, in a situation where an abnormality occurs in the pressure increasing / decreasing control valve or the like of one of the wheels and the braking pressure of the wheel cannot be normally controlled, the braking force difference between the left and right wheels Because the steering angle of the front wheels is controlled so as to generate the yaw moment necessary to offset the extra yaw moment Mad caused by the vehicle, the vehicle responds to the rotational position of the steering wheel 14 during braking due to the extra yaw moment. The steering assist torque is controlled so as to offset the fluctuations in the steering reaction force caused by the control of the steering angle of the front wheels. It is possible to prevent unnatural fluctuations in the steering reaction force associated with the angle control, and thereby reliably prevent the driver from feeling uncomfortable due to the unnatural fluctuations in the steering reaction force.

  For example, FIG. 10 shows a situation where an abnormality has occurred in which braking force cannot be applied to the right front wheel 10FR. In this case, the braking forces Fbrl and Fbrr of the left and right rear wheels are the same, but the braking force Fbfl of the left front wheel is different from the braking force Fbfr of the right front wheel (for convenience of explanation, it is 0). Excess yaw moment Mad caused by the difference in braking force between the left and right front wheels is applied during braking, and the vehicle 100 tries to turn left even when the steering wheel 14 is in the straight traveling position.

  In the case of the conventional travel control device shown in FIG. 10A, the front wheels (or the rear wheels) are steered in the right turning direction of the vehicle, so that the yaw moment Mct in the right turning direction is changed to the vehicle. This prevents the vehicle 100 from turning leftward. However, when the front wheels are steered in the right turn direction of the vehicle, the left side self-alignment torque Tsa acts on the front wheels, and thus the left turn direction torque acts on the steering wheel 14, and the driver moves straight ahead. The rudder torque must be increased to maintain. This is the same except that the left and right directions are reversed when the front wheels (or rear wheels) are steered in the left turning direction of the vehicle.

  On the other hand, according to the first embodiment shown in the figure, the front wheels are steered in the right turning direction of the vehicle, whereby a yaw moment Mct in the right turning direction is applied to the vehicle, whereby the vehicle 100 is turned in the left turning direction. The steering assist torque is not only maintained in the straight traveling state of the vehicle but also maintained in a straight line, as shown by the arrow Tcsa in FIG. 10B so as to cancel the self-alignment torque Tsa. Because it is controlled, if the driver does not need to increase the steering torque so as to maintain the straight traveling position, the driver feels uncomfortable due to the unnatural fluctuation of the steering reaction force accompanying the steering control of the front wheels. There is nothing.

  In particular, according to the illustrated first embodiment, since only the steering angle of the front wheels is controlled, it is not necessary to control the steering angle of the rear wheels, and therefore, the rear wheel steering device is also unnecessary. Further, the steering angle of the steered wheels can be easily controlled as compared with the case where the steered angle of the rear wheels is also controlled.

  In the illustrated embodiment 1, the front wheel steering angle correction amount Δδft for generating the yaw moment necessary for canceling the excess yaw moment Mad is calculated to achieve a predetermined steering characteristic. The front wheel target rudder angle δft is corrected to be the sum of the front wheel target rudder angle δft and the front wheel rudder angle correction amount Δδft. The control of the angle may be omitted, and the steering angle of the front wheels may be controlled only when it is necessary to generate the yaw moment necessary to cancel the excess yaw moment Mad.

  FIG. 11 is a schematic diagram showing a second embodiment of the vehicle travel control device according to the present invention applied to a vehicle capable of controlling the steering angles of the front wheels and the rear wheels. In FIG. 11, the same members as those shown in FIG. 1 are denoted by the same reference numerals as those shown in FIG.

  In the second embodiment, the left and right rear wheels 10RL and 10RR are separated from the left and right front wheels 10FL and 10FR by the hydraulic or electric power steering device 54 of the rear wheel steering device 52 and the tie rods 56L and 56R. The rear wheel steering device 52 is controlled by the steering angle control unit of the electronic control device 34.

  As in the case of the first embodiment, the electronic control unit 34 calculates the target steering angle δft of the front wheels based on the vehicle speed V so that a predetermined steering characteristic is achieved, and based on the steering angle θ and the vehicle speed V. The rear wheel target rudder angle δrt is calculated in a manner known in the art. The electronic control unit 34 can control the normal braking pressure for all the wheels so that the steering angle of the front wheels and the rear wheels becomes the target steering angle δft of the front wheels and the target steering angle δrt of the rear wheels, respectively. The turning angle varying device 24 and the rear wheel steering device 52 are controlled.

  In the second embodiment, the pressure sensor (70FL to 70RR) is normal, but if an abnormality occurs in the braking device 42 that makes it impossible to control the normal braking pressure for any of the wheels, the electronic control is performed. The device 34 calculates an extra yaw moment Mad resulting from the difference in braking force between the left and right wheels, and generates a yaw moment necessary to cancel the extra yaw moment Mad based on the extra yaw moment Mad and the vehicle speed V. The steering angle correction amount Δδft and the rear wheel steering angle correction amount Δδrt are calculated.

  The electronic control unit 34 corrects the front wheel target rudder angle δft so as to be the sum of the front wheel target rudder angle δft and the front wheel rudder angle correction amount Δδft to achieve a predetermined steering characteristic. The rear wheel target rudder angle δrt is corrected to be the sum of the rear wheel target rudder angle δrt and the rear wheel rudder angle correction amount Δδrt to achieve the steering characteristics. By controlling so that the corrected target steering angle δft of the front wheels and the corrected target steering angle δrt of the rear wheels are achieved, the yaw moment necessary for achieving the predetermined steering characteristics and canceling the excess yaw moment Mad is obtained. generate.

  Further, the electronic control unit 34 calculates the steering assist torque correction amount ΔTa for suppressing the fluctuation of the steering reaction force caused by the control of the steering angle of the front wheels and the rear wheels based on the excess yaw moment Mad, and the above-described implementation. As in the case of Example 1, the target assist torque Ta is corrected so as to be the sum of the target assist torque Ta that generates the steering assist force that reduces the driver's steering burden and the correction amount ΔTa, and the corrected target assist torque Ta is corrected. By controlling the electric power steering device 16 based on this, the steering burden on the driver is reduced and fluctuations in the steering reaction force associated with the control of the steering angles of the front wheels and the rear wheels are prevented.

  In the second embodiment, the braking force of each wheel is controlled according to the control routine shown in FIG. 2 as in the first embodiment. The magnitude of the rear wheel steering angle correction amount Δδrt is smaller than the size of the front wheel steering angle correction amount Δδft. Further, the magnitude of the correction amount Δδft of the front wheel rudder angle in the second embodiment is the same as the correction amount Δδft of the front wheel rudder angle in the first embodiment described above with respect to the excess yaw moment Mad having the same magnitude. Therefore, the magnitude of the steering assist torque correction amount ΔTa in the second embodiment is smaller than the magnitude of the steering assist torque correction amount ΔTa in the first embodiment.

  FIG. 12 is a flowchart showing a control routine for the steering angle of the front and rear wheels in the second embodiment, and FIG. 13 is a flowchart showing a control routine for the steering assist torque in the second embodiment. The control according to the flowcharts shown in FIGS. 12 and 13 is also started by closing an ignition switch (not shown), and is repeatedly executed at predetermined time intervals. Further, in FIG. 12 and FIG. 13, the same step numbers as those shown in FIG. 3 and FIG. 4 are assigned to the same steps as those shown in FIG. 3 and FIG. .

  In the routine for controlling the steering angle of the front wheels and the rear wheels in the second embodiment, the target of the front wheels for achieving a predetermined steering characteristic in the same manner as in the first embodiment in step 320. The steering angle δft is calculated, and the target steering angle δrt of the rear wheels for achieving a predetermined steering characteristic is calculated based on the steering angle θ and the vehicle speed V in a manner known in the art.

  In step 350, the steering angle of the front wheels for generating the yaw moment necessary to counter the excess yaw moment Mad from the map corresponding to the graph shown in FIG. 14 based on the excess yaw moment Mad and the vehicle speed V. In step 355, the correction amount Δδft is calculated and a yaw moment necessary to counter the excess yaw moment Mad is generated based on the excess yaw moment Mad in the map corresponding to the graph shown in FIG. A correction amount Δδrt for the steering angle of the rear wheels is calculated. In this case, the front wheel rudder angle correction amount Δδft and the rear wheel rudder angle correction amount Δδrt are generated by the front wheel rudder angle correction amount Δδft and the rear wheel rudder angle correction amount Δδrt. The sum of the yaw moment is calculated to cancel out the excess yaw moment Mad.

  In step 360, the front wheel target rudder angle δft is calculated to be the sum of the front wheel target rudder angle δft calculated in step 320 and the front wheel rudder angle correction amount Δδft calculated in step 350. Is corrected, and the rear wheel target rudder angle δrt calculated in step 320 and the rear wheel rudder steering angle correction amount Δδrt calculated in step 355 are equal to the sum. The angle δrt is corrected.

  Further, in step 385 executed after step 380, the rear wheel steering device 52 is controlled so that the rear wheel steering angle δr becomes the target steering angle δrt. The other steps of the control routine for the steering angle of the front wheels and the rear wheels are executed in the same manner as in the first embodiment.

  In the steering assist torque control routine of the second embodiment, steps 410 to 460 and steps 480 and 490 are executed in the same manner as in the first embodiment. In step 470, the correction amount ΔTa of the steering assist torque for suppressing the fluctuation of the steering reaction force due to the control of the steering angle is calculated from the map corresponding to the graph shown in FIG. 15 based on the excess yaw moment Mad. Is done.

  Thus, according to the second embodiment shown in the figure, in the case of the above (3), that is, when the pressure sensor (70FL to 70RR) is normal but the normal braking pressure cannot be controlled, the step is performed. In step 340, an extra yaw moment Mad resulting from the difference in braking force between the left and right wheels is calculated. In step 350, the yaw moment necessary to counter the extra yaw moment Mad based on the extra yaw moment Mad and the vehicle speed V is calculated. A steering angle correction amount Δδft for generating the front wheel is calculated, and in step 355, based on the extra yaw moment Mad, the rear wheel for producing the yaw moment necessary to counter the extra yaw moment Mad is calculated. A steering angle correction amount Δδrt is calculated.

  In step 360, the front wheel target rudder angle δft is corrected so as to be the sum of the front wheel target rudder angle δft and the front wheel rudder angle correction amount Δδft to achieve a predetermined steering characteristic. The rear wheel target rudder angle δrt is corrected so as to be the sum of the rear wheel target rudder angle δrt and the rear wheel rudder angle correction amount Δδrt to achieve the steering characteristics.

  In steps 370 and 380, the turning angle varying device 24 is controlled so that the front wheel steering angle δf becomes the target steering angle δft, and in step 385 the rear wheel steering angle δr becomes the target steering angle δrt. By controlling the rear wheel steering device 52, a predetermined steering characteristic is achieved and a steering angle δf of the front wheels and a steering angle δr of the rear wheels are generated so as to generate a yaw moment necessary to cancel the excess yaw moment Mad. Is controlled.

  In step 460, an extra yaw moment Mad resulting from the difference in braking force between the left and right wheels is calculated. In step 470, the steering reaction caused by controlling the steering angle of the front wheels and the rear wheels based on the extra yaw moment Mad. A steering assist torque correction amount ΔTa for suppressing force fluctuation is calculated.

  In step 480, the target assist torque Ta is corrected so as to be the sum of the target assist torque Ta and the steering assist torque correction amount ΔTa, and in step 490, the assist torque is adjusted so that the assist torque becomes the target assist torque Ta. The control is executed, thereby reducing the driver's steering burden and suppressing the variation in the steering reaction force caused by the control of the steering angles of the front wheels and the rear wheels.

  Therefore, according to the second embodiment shown in the drawing, in a situation where an increase or decrease control valve or the like of one of the wheels is abnormal and the braking pressure of the wheel cannot be normally controlled, the difference in braking force between the left and right wheels Since the steering angles of the front wheels and the rear wheels are controlled so as to generate the yaw moment necessary to offset the extra yaw moment Mad caused by the vehicle, the vehicle rotates the steering wheel 14 during braking due to the extra yaw moment. Steering assist torque is controlled so that it is possible to reliably prevent traveling in a direction different from the direction corresponding to the position, and to offset fluctuations in steering reaction force due to control of the steering angles of the front and rear wheels. Therefore, it is possible to prevent unnatural fluctuations in the steering reaction force associated with the control of the steering angles of the front wheels and the rear wheels, and reliably prevent the driver from feeling uncomfortable due to the unnatural fluctuations in the steering reaction force. be able to.

  Further, according to the illustrated second embodiment, the steering angles of the front wheels and the rear wheels are controlled so as to generate the yaw moment necessary for canceling the excess yaw moment Mad caused by the braking force difference between the left and right wheels. Alternatively, it is possible to reliably reduce unnecessary movement in the lateral direction of the vehicle that occurs when only the steering angle of the rear wheels is controlled, and thereby to improve the running performance of the vehicle as compared with the case of the first embodiment. Can be improved.

  For example, as shown in FIG. 17A, an abnormality in which braking force cannot be applied to the right front wheel 10FR occurs, and the steering angles of the front wheels 10FL and 10FR are steered in the right turn direction to cope with this. When controlled, a lateral force acting in the right direction acts on the front wheels 10FL and 10FR, so that the vehicle 100 moves in the right direction while traveling in a straight direction as in the case of receiving a lateral wind from the left. To do. Although not shown in the drawing, when the steering angles of the front wheels 10FL and 10FR are steered to the left, the lateral force acts on the front wheels 10FL and 10FR in the left direction. It moves to the left while traveling in a straight direction as if it had received a crosswind from the right.

  Further, as shown in FIG. 17B, an abnormality in which the braking force cannot be applied to the right front wheel 10FR occurs, and the steering angles of the rear wheels 10RL and 10RR are set in the right turn direction of the vehicle to cope with this. When the vehicle is steered to the left, a lateral force in the left direction acts on the rear wheels 10RL and 10RR, so that the vehicle 100 travels in a straight direction as if it had received a crosswind from the right. Move to the left. Although not shown in the figure, when the steering angle of the rear wheels 10RL and 10RR is steered to the left turning direction of the vehicle, a lateral force in the right direction acts on the rear wheels 10RL and 10RR, Therefore, the vehicle 100 moves in the right direction while traveling in a state where the vehicle 100 is moving in the straight direction as if the crosswind was received from the left.

  On the other hand, according to the illustrated embodiment 2, the front wheels are steered to the right and the rear wheels are steered to the left, so that a yaw moment Mct in the right turn direction is applied to the vehicle. Thus, the vehicle 100 is prevented from turning in the left turn direction, and the lateral forces acting on the front wheels and the rear wheels are opposite to each other, so that the vehicle travels straight while reducing lateral movement of the vehicle. be able to.

  Further, according to the illustrated second embodiment, the magnitude of the correction amount Δδft of the steering angle of the front wheels in the second embodiment when the excess yaw moment Mad having the same size is seen is the same as that in the first embodiment described above. Therefore, the magnitude of the steering assist torque correction amount ΔTa in the second embodiment is smaller than the magnitude of the steering assist torque correction amount ΔTa in the first embodiment. Therefore, the control amount of the steering assist torque necessary for reducing unnatural fluctuations in the steering reaction force accompanying the control of the steering angles of the front wheels and the rear wheels can be reduced.

  In particular, according to the illustrated embodiment 2, the magnitude of the rear wheel rudder angle correction amount Δδrt is smaller than the front wheel rudder angle correction amount Δδft, and hence the rear wheel rudder angle correction amount Δδrt. Can be made smaller in the amount of control of the steering angle of the rear wheels of the rear wheel steering device 52 than in the case where is the same as the magnitude of the correction amount Δδft of the steering angle of the front wheels. 52 can be reduced in size.

  In the illustrated embodiment 2, the front wheel steering angle correction amount Δδft and the rear wheel steering angle correction amount Δδrt for generating the yaw moment necessary to cancel out the excess yaw moment Mad are calculated. The front wheel target rudder angle δft is corrected so as to be the sum of the front wheel target rudder angle δft and the front wheel rudder angle correction amount Δδft to achieve the predetermined steering characteristic, and the predetermined steering characteristic is achieved. Therefore, the rear wheel target rudder angle δrt is corrected so as to be the sum of the rear wheel target rudder angle δrt and the rear wheel rudder angle correction amount Δδrt, but the predetermined steering characteristic is achieved. Even if the control of the steering angle of the front wheels is omitted and the steering angle of the front wheels and the rear wheels is controlled only when it is necessary to generate the yaw moment necessary to cancel out the excess yaw moment Mad, Good.

  Further, according to the above-described first and second embodiments, the turning angle varying device 24 that controls the steering angle of the front wheels is a means different from the electric power steering device 16 that controls the steering assist torque. It is possible to reliably prevent control interference between the control of the angle and the control for reducing the change in the steering reaction force, and necessary to cancel the excess yaw moment Mad caused by the difference in braking force between the left and right wheels. While the yaw moment is reliably generated by controlling the steering angle of the front wheels, unnatural fluctuations in the steering reaction force accompanying the control of the steering angle of the front wheels can be reliably reduced.

  Further, according to the first and second embodiments described above, the extra yaw moment Mad resulting from the difference in braking force between the left and right wheels is calculated, and the steering reaction force resulting from the control of the steering angle of the front wheels is calculated based on the extra yaw moment Mad. Since the steering assist torque correction amount ΔTa for suppressing the fluctuation is calculated, for example, compared to the case where the steering assist torque correction amount ΔTa is calculated based on the steering angle correction amount Δδft of the front wheels and the vehicle speed V, for example. The correction amount ΔTa of the steering assist torque can be easily calculated, and the steering assist force can be efficiently controlled to prevent unnatural fluctuations in the steering reaction force.

  Further, according to the above-described first and second embodiments, the steering angle correction amount Δδft is calculated based on the excess yaw moment Mad and the vehicle speed V. Therefore, the steering angle correction amount can be calculated without considering the vehicle speed V. Compared to the case, the steering angle correction amount can be calculated more accurately, whereby the steering angle of the steered wheels can be accurately controlled according to the excess yaw moment actually acting on the vehicle. Even when the steering angle correction amount is calculated without considering the vehicle speed V, a yaw moment that opposes the excess yaw moment caused by the difference in braking force between the left and right wheels is applied to the vehicle and the vehicle does not act on the vehicle. Since the necessary yaw moment can be reduced, consideration of the vehicle speed V may be omitted.

  Further, according to the first and second embodiments described above, the target rudder angle δft (and δrt) generates the yaw moment necessary for offsetting the target rudder angle and the excess yaw moment Mad for achieving a predetermined steering characteristic. The direction in which the vehicle corresponds to the rotational position of the steering wheel 14 during braking due to unnecessary yaw moment while achieving a predetermined steering characteristic is calculated as the sum of the correction amount for It is possible to reliably prevent traveling in a different direction.

  Further, according to the first and second embodiments described above, the target assist torque Ta is a fluctuation of the steering reaction force caused by controlling the target assist torque and the steering angle of the steered wheels to achieve a predetermined steering assist according to the vehicle speed. Since it is calculated as the sum of the correction amount ΔTa of the steering assist torque for suppressing, the steering reaction force accompanying the control of the steering angle of the steered wheels is unnatural while achieving a predetermined steering assist. Variation can be reliably reduced.

  Furthermore, according to the above-described first and second embodiments, if any of the wheel pressure sensors 70FL to 70RR is abnormal and normal braking pressure cannot be controlled for the wheel, the pressure sensor Control is performed so that the braking force of the normal wheel becomes a braking force corresponding to the target braking pressure Pti, and the braking force of the wheel whose pressure sensor is abnormal is the same as the braking force of the opposite wheel. Therefore, it is necessary to control the steering angle of the steered wheels so as to effectively reduce the possibility of an excess yaw moment acting on the vehicle and to generate a yaw moment against the excess yaw moment. Can be eliminated.

  Although the present invention has been described in detail with reference to specific embodiments, the present invention is not limited to the above-described embodiments, and various other embodiments are possible within the scope of the present invention. It will be apparent to those skilled in the art.

  For example, in each of the above-described embodiments, the steering angle correction amount Δδft (and Δδrt) is calculated as a correction amount for generating the yaw moment Mct necessary for canceling the excess yaw moment Mad, and the necessary yaw amount is calculated. Although the magnitude of the moment Mct is the same as the magnitude of the extra yaw moment Mad, even if the steering angle correction amount is calculated so that the magnitude of the necessary yaw moment Mct is smaller than the magnitude of the extra yaw moment Mad. Good.

Further, in each of the above-described embodiments, the braking pressures of the left and right wheels are normally controlled to be the same pressure, and the excess yaw caused by the difference in braking force between the left and right wheels according to the above equation 2 based on the braking pressure Pi of each wheel. The moment Mad is calculated. For example, the target yaw moment Mt of the vehicle is calculated for the purpose of controlling the traveling motion of the vehicle, and the braking force of each wheel is set so that the yaw moment of the vehicle becomes the target yaw moment. When controlled, the excess yaw moment Mad resulting from the difference in braking force between the left and right wheels may be calculated according to Equation 3 below.
Mad = Mt− (KbwflPfl + KbwrlPrl−KbwfrPfr−KbwrrPrr) W / 2 (3)

  In each of the above-described embodiments, the turning angle varying device 24 rotates the lower steering shaft 26 relative to the upper steering shaft 22 so that the left and right front wheels 10FL do not depend on the driver's steering operation. As long as the steering wheel can be steered independently of the driver's steering operation, for example, a steering angle variable device of a type that expands and contracts the tie rods 20L and 20R. Any configuration known in the art may be used.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic configuration diagram illustrating a first embodiment of a vehicle travel control device according to the present invention applied to a vehicle capable of controlling a steering angle of a front wheel. 3 is a flowchart illustrating a braking force control routine according to the first embodiment. 3 is a flowchart illustrating a control routine for a steering angle of a front wheel in the first embodiment. 3 is a flowchart illustrating a steering assist torque control routine according to the first embodiment. It is a graph which shows the relationship between the vehicle speed V and the target steering gear ratio Rgt. It is a graph which shows the relationship between the excess yaw moment Mad and vehicle speed V, and the correction amount (DELTA) deltaft of the steering angle of the front wheel for generating the yaw moment required to oppose the excess yaw moment Mad. It is a graph which shows the relationship between steering torque Ts and target assist torque Ta. It is a graph which shows the relationship between the vehicle speed V and the vehicle speed coefficient Kv. It is a graph which shows the relationship between the correction amount (DELTA) Ta of the steering assist torque for suppressing the fluctuation | variation of the steering reaction force resulting from control of the excess yaw moment Mad and the steering angle of a front wheel. Regarding the situation where an abnormality in which braking force cannot be applied to the right front wheel occurs, the vehicle state (A) in the case of the conventional travel control device and the vehicle state (B) in the case of the travel control device of the first embodiment It is explanatory drawing shown. It is a schematic block diagram which shows Example 2 of the traveling control apparatus of the vehicle by this invention applied to the vehicle which can control the steering angle of a front wheel and a rear wheel. 7 is a flowchart showing a control routine for steering angles of front wheels and rear wheels in the second embodiment. 7 is a flowchart showing a steering assist torque control routine in the second embodiment. It is a graph which shows the relationship between the excess yaw moment Mad and vehicle speed V, and the correction amount (DELTA) deltaft of the steering angle of the front wheel for generating the yaw moment required to oppose the excess yaw moment Mad. It is a graph which shows the relationship between the correction amount (DELTA) deltart of the steering angle of a rear wheel for generating the yaw moment required to oppose the excess yaw moment Mad and the excess yaw moment Mad. It is a graph which shows the relationship between the correction amount (DELTA) Ta of the steering assist torque for suppressing the fluctuation | variation of the steering reaction force resulting from control of the excess yaw moment Mad and the steering angle of a front wheel. In a situation where an abnormality has occurred in which braking force cannot be applied to the right front wheel, the vehicle state (A) when only the steering angle of the front wheel is controlled and when only the steering angle of the rear wheel is controlled It is explanatory drawing which shows the state (B) of a vehicle.

Explanation of symbols

DESCRIPTION OF SYMBOLS 14 Steering wheel 16 Electric power steering device 24 Steering angle variable device 34 Electronic control device 42 Braking device 60 Steering angle sensor 62 Torque sensor 64 Rotation angle sensor 66 Vehicle speed sensor 68 Pressure sensor 70FL-70RR Pressure sensor

Claims (3)

Based on a braking means for applying a braking force to each wheel, a steering wheel steering angle varying means capable of turning the steering wheel without depending on the driver's steering, and at least a target steering assist force corresponding to the steering reaction force a travel control device for a vehicle having a steering assist force generating means for generating a steering assist force, the unnecessary braking force difference between the left and right wheels caused by abnormal to said braking means arising Kiniwa, An extra yaw moment due to the braking force difference is estimated, and the steering wheel steering angle variable means controls the steering angle of the steered wheels so as to generate a yaw moment necessary to counter the extra yaw moment. The target steering assist force is corrected based on the excess yaw moment so as to suppress the fluctuation of the steering reaction force caused by the control of the steering angle of the steering wheel by the steering wheel steering angle varying means , and the corrected target steering Travel control device for a vehicle, characterized in that it comprises a control means for controlling the steering assist force by the steering assist force generating means on the basis of the cysts force. The control means vehicle steering control apparatus according to claim 1, characterized in that calculates the control amount of the steering angle of the steering wheel for generating the required yaw moment based on the excess yaw moment . The steering wheel is a front wheel and a rear wheel, the rear wheel is a running control apparatus for a vehicle according to claim 1 or 2, characterized in that it is steered to the left and right side opposite to the front wheels

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