JP5029197B2 - Vehicle yaw moment control apparatus and yaw moment control method - Google Patents

Description

  The present invention relates to a yaw moment control device that controls the yaw moment of a vehicle by distributing braking / driving force between left and right wheels.

  For the purpose of improving the running stability of a vehicle, an apparatus that distributes the braking / driving force of the left and right wheels is known to add a yaw moment according to the running state.

For example, Cited Document 1 discloses a device that determines the distribution amount of braking / driving force by feedforward control and corrects the distribution amount by feedback control when an oversteer state of the vehicle is detected.
JP 9-309357 A

  By the way, in order to improve the running stability of the vehicle, the behavior of the vehicle converges when the behavior of the vehicle is oversteered or when the steering is turned back to end the turning of the vehicle. The braking / driving force is distributed so as to add the yaw moment in the direction, that is, the understeer direction.

  In such a case, since the device of Patent Document 1 is configured to simply distribute the braking / driving force to the left and right in order to generate a desired yaw moment, the rear wheel also turns to generate a moment in the understeer direction. The outer wheel (turning outer wheel) generates braking force with respect to the direction, and the inner wheel (turning inner wheel) generates driving force with respect to the turning direction.

  However, in general, an anti-scut angle is set for the suspension of the rear wheel, and when a braking force is applied, a force in a direction of pushing down the vehicle body is generated, and when a driving force is applied, a force in a direction of lifting the vehicle body is generated. Further, during turning, the wheel load of the turning outer wheel increases, and the wheel load of the turning inner wheel decreases. For this reason, when a braking force is applied to the turning outer wheel and a driving force is applied to the turning inner wheel, the wheel load of the turning outer wheel is further increased and the wheel load of the turning inner wheel is further reduced. That is, the amount of movement of the wheel load of the rear wheel is amplified, and the equivalent cornering power that is the source of the cornering force of the rear wheel is reduced.

  In order to generate the cornering force required for the rear wheels in this situation, the vehicle body slip angle must be increased by the amount corresponding to the reduction in equivalent cornering power. As a result, the vehicle body slip angle change becomes large especially at the time of a lane change, and the stability of the vehicle behavior is deteriorated.

  Therefore, an object of the present invention is to perform yaw moment control that can ensure the stability of the behavior of the vehicle body, for example, in a scene where the turning of the vehicle body is terminated.

A vehicle yaw moment control apparatus according to the present invention includes a target yaw moment setting means for setting a target yaw moment, and a yaw moment of a vehicle body including rear wheel braking / driving force distribution means capable of controlling at least braking / braking force distribution of the left and right rear wheels. A control means and a turning stage discriminating means for discriminating a turning stage based on the rudder angle, and at the time of a predetermined turning that is a turning stage after the direction of the target yaw moment is switched from the turning direction to the restoring direction. , before Symbol rear wheel braking and driving force distribution means performs a suppressing so braking-driving force distribution a decrease in equivalent cornering power.

  According to the present invention, since a decrease in equivalent cornering power during a predetermined turn is suppressed, a change in vehicle body slip angle for generating a cornering force necessary to achieve the target yaw moment can be suppressed. Thus, the stability of the vehicle behavior during turning can be ensured.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram illustrating a basic configuration of a yaw moment control device according to the present embodiment, and FIG. 2 is a diagram illustrating a mechanical configuration when mounted on a vehicle.

  In FIG. 1, 1 is a vehicle running state detecting means, 2 is a target yaw moment setting means, 3 is a braking / driving force distribution determining means as a rear wheel braking / driving force distributing means or a front wheel braking / driving force distributing means, 4 is a braking / driving means, It is.

  The vehicle running state detecting means 1 detects the state quantity of the vehicle and the operation amount of the driver. Specifically, it is a sensor that detects a steering angle, an accelerator pedal opening, a brake pedal opening, a yaw rate, a longitudinal acceleration, a lateral acceleration, and a wheel speed of each wheel.

  The target yaw moment setting means 2 calculates the target yaw moment that the vehicle should generate with the braking / driving force of each wheel based on the detection value of the vehicle running state detection means 1.

  As will be described later, the braking / driving force distribution determining means 3 generates a yaw moment in a direction in which the equivalent cornering power increases in the rear wheels, so that the front wheels generate the yaw moment by the difference between the target yaw moment and the braking / driving moment of the rear wheels. The braking / driving force is distributed so as to be generated. The functions as the target yaw moment setting means 2 and the braking / driving force distribution determination means 3 are executed by the control unit 6 described later.

  In the present embodiment, the braking / driving means 4 is a braking / driving motor and a motor power supply inverter described later.

  This embodiment is based on the premise that the rear wheel suspension arm 8 described later has an anti-scut angle.

  2, 5 is a steering mechanism, 6 is a control unit as a yaw moment control means, 7a is a braking / driving motor, 7b is a motor power supply inverter, 8 is a rear wheel suspension arm, 9 is a front wheel (9a is a left front wheel, 9b is a right front wheel), 10 is a rear wheel (10a is a left rear wheel, 10b is a right rear wheel), and 11 is a drive shaft. In addition, each sensor as the vehicle running state detecting means 1 is omitted.

  As shown in FIG. 2, the four wheels are driven via a drive shaft 11 by independent braking / driving motors 7a. A motor power supply inverter 7b is also provided for each braking / driving motor 7a.

  The control unit 6 functions as the target yaw moment setting means 2 and the braking / driving force distribution determination means 3, and is based on detection values of respective sensors (not shown) as the vehicle running state detection means 1. And determination of braking / driving force distribution for generating the target yaw moment, and sends a command value corresponding to the braking / driving force distribution to the motor power supply inverter 7b.

  The rear wheel suspension arm 8 will be described with reference to FIG. FIG. 4 is a view of the rear wheel 10 and the rear wheel suspension arm 8 as viewed from the side of the vehicle body, and the left side of the drawing is the traveling direction.

  As shown in FIG. 4, the rear wheel suspension arm 8 has one end on the front side of the vehicle body supported on the vehicle body side and the rear wheel 10 supported on the other end on the rear side of the vehicle body. And, like a general vehicle, one end on the front side of the vehicle body is supported at a position higher than the other end on the rear side of the vehicle body, so-called anti-scut angle (the axial direction and the horizontal direction of the rear wheel suspension arm 8 are The formed angle θ) is attached.

  Note that the rear wheel suspension arm of the present embodiment has a simple form in which one end on the front side of the vehicle body is supported on the vehicle body side and the rear wheel is supported on the other end on the rear side of the vehicle body. Even in the case of a type of suspension arm, the anti-scut angle can be set according to the same principle.

  In the case where the rear wheel suspension arm 8 has an anti-scut angle, when a driving force is applied, a component force having a magnitude of driving force × tan θ, that is, a force for lifting the vehicle body is generated. On the other hand, when the braking force is applied, a component force of the magnitude of braking force × tan θ, that is, a force for pushing down the vehicle body is generated downward.

  Next, a control routine for determining the braking / driving force of each wheel by the target yaw moment setting means 2 and the braking / driving force distribution determining means 3 will be described with reference to the control flowchart of FIG. This control routine is repeatedly executed at regular intervals, for example, every 10 ms.

  In the present embodiment, the stage of turning is not discriminated, and the braking / driving force moment by the wheels 9 and 10 is simply determined according to only the direction of the target yaw moment.

  In step S100, a target yaw moment Mz is calculated. The target yaw moment Mz here is a yaw moment added to the vehicle by the distribution of the braking / driving force of the four wheels 9, 10, and does not include the yaw moment due to the subtraction of the lateral force acting on the four wheels 9, 10.

  For determining the specific value of the target yaw moment Mz, various generally known methods can be applied. Any target value in the turning direction (oversteer direction) or the restoring direction (understeer direction) can be used. It is a precondition to be applied to the present embodiment that the method can also be set.

  In step S110, the direction of the target yaw moment Mz is determined. Here, first, based on the direction of the yaw rate detected by the yaw rate sensor as the vehicle running state detecting means 1, it is determined whether the vehicle is turning, that is, turning right or turning left. Further, when the sign of the yaw rate and the sign of the target yaw moment Mz match, for example, when a braking / driving force moment that turns to the right during a right turn is generated, the moment in the turning direction (oversteer direction) is taken as the yaw rate If the sign of the target yaw moment Mz does not match, for example, when a braking / driving moment that turns to the left during a right turn is to be generated, the moment is defined as a moment in the restoring direction (understeer direction). To do.

  If the direction of the target yaw moment Mz is the restoration direction, the process proceeds to step S120, and if the direction is the turning direction, the process proceeds to step S140.

  In step S120, the braking / driving force moment Mzr of the rear wheel 10 when the target yaw moment Mz is in the restoring direction is determined.

  Here, in order to suppress the load movement between the left rear wheel 10a and the right rear wheel 10b and to increase the equivalent cornering power of the rear wheel 10, it is dared when the target yaw moment Mz of the entire vehicle is in the restoring direction. The rear wheel 10 generates a braking / driving force moment in the turning direction.

  When a moment in the turning direction is applied to the rear wheel 10, an effect of suppressing load movement can be obtained. This is because when the load moves so that the load on the turning outer ring increases and the load on the turning inner ring decreases during turning, the driving force is applied to the turning outer wheel so that the turning torque becomes a moment, and the braking force is applied to the turning inner ring. This is because, as described above, a force that lifts the vehicle body acts on the turning outer wheel, and a force that pushes down the vehicle body acts on the turning inner wheel.

  Although the above-described suppression of load movement can be obtained in any case, it is most effective to apply a larger braking / driving force moment in the turning direction when the load movement is large (when the lateral acceleration is large). is there.

  Therefore, the value of the rear wheel braking / driving force moment Mzr is determined as the following expression (1) in a form proportional to the lateral acceleration ay.

Mzr = Kpr × ay (1)
Kpr: Proportional gain At this time, it is preferable to select the proportional gain Kpr within the range where the turning inner wheel does not exceed the friction circle when the dry road turning limit is reached, that is, when the load movement reaches a maximum value that can be assumed.

  In step S130, the braking / driving force moment Mzf of the front wheel 9 when the target yaw moment Mz is in the restoring direction is determined by the following equation (2).

Mzf = Mz−Mzr (<0) (2)
On the other hand, if it is determined in step S110 that the target yaw moment Mz is in the turning direction, the front wheel braking / driving force moment Mzf and the rear wheel braking / driving force moment Mzr are distributed to a predetermined ratio in step S140. Specifically, as in the conventional general yaw moment control, a moment in the turning direction is applied to both the front wheel 9 and the rear wheel 10.

  By changing the front / rear distribution of the braking / driving force moment, it is possible to change the steering characteristics in a region with a large lateral acceleration to any of understeer, oversteer, and neutral steer. The allocation shall be determined.

  When the distribution of the braking / driving force moments of the front wheels 9 and the rear wheels 10 is determined in step S130 or step S140, the target total braking / driving force Fd is calculated in step S150.

  First, a desired longitudinal acceleration αx is calculated from the accelerator opening, the brake opening, the vehicle body speed, and the like. Then, from this longitudinal acceleration αx, vehicle characteristics (mass, rotational inertia of each part, etc.) and running resistance Fross (rolling resistance, air resistance, gradient resistance), the target total control which is the total value of braking / driving force to be generated in the four wheels. The driving force Fd is obtained by the following equation (3).

Fd = Wjαx + Fross (3)
Wj: Body mass corrected in consideration of rotational inertia In step S160, the front / rear distribution of the total braking / driving force Fd is determined. Here, the front wheel braking / driving force Fdf and the rear wheel braking / driving force Fdr are determined using a method similar to that of conventional general yaw moment control. Further, similarly to step S140, the steering characteristics can be changed by changing the front-rear distribution, so the front-rear distribution may be determined according to the vehicle state.

  In step S170, the braking / driving force command value for each wheel is determined by the following equations (4) to (7) using the values Mzf, Mzr, Fdf, and Fdr obtained in steps S130 to S160.

F _Fout = (Mzf / Trf) + (Fdf / 2) (4)
F _Fin = − (Mzf / Trf) + (Fdf / 2) (5)
F _Rout = (Mzr / Trr) + (Fdr / 2) (6)
F _Rin = − (Mzr / Trr) + (Fdr / 2) (7)

F _Fout : Front turning outer wheel braking / driving force command value, F _Fin : Front turning inner wheel braking / driving force command value, F _Rout : Rear turning outer wheel braking / driving force command value, F _Rin : Rear turning inner wheel braking / driving force command value, Trf: Front wheel tread [m], Trr: Rear wheel tread [m]
The rear wheel equivalent cornering power in the situation where the turning is converged when the above control routine is executed will be described with reference to FIG.

  The vertical axis in FIG. 5 is the rear wheel equivalent cornering power, the horizontal axis is the wheel load, the black star in the figure is the control in FIG. 3, the white star is the conventional yaw moment control (the direction in which the rear wheels also converge (restore) Direction)), and black circles indicate equivalent cornering power in each case of no yaw moment control.

  In any case, the wheel load of the turning inner wheel is smaller than that of the turning outer wheel due to the load movement by turning.

Like the conventional yaw moment control, when the braking force is applied to the turning outer wheel and the driving force is applied to the turning inner wheel in order to generate a moment in the restoring direction also at the rear wheel, the anti-scut angle is attached as described above. by, wheel load of the turning outer wheel is large, the wheel load of the inner wheel becomes smaller. Therefore, as shown in FIG. 5, the equivalent cornering power is smaller than the case where the yaw moment control is not performed for both the turning inner wheel and the turning outer wheel, and the vehicle body slip angle is increased in order to generate the necessary cornering force. This results in a loss of vehicle behavior stability.

On the other hand, when the control of the present embodiment is performed, the driving force is applied to the turning outer wheel and the braking force is applied to the turning inner wheel, so that the wheel load of the turning outer wheel is small and the wheel load of the turning inner wheel is large . As a result, the equivalent cornering power becomes larger than when the yaw moment control is not performed. Therefore, the target yaw moment can be generated with the vehicle body slip angle being reduced, and the stability of the vehicle behavior can be improved.

  Next, the case where the above control is applied to actual turning will be described with reference to the time chart of FIG.

  FIG. 6 is a time chart of a scene where the steering is first increased for the lane change and then switched back.

  The target yaw moment Mz is set in the turning direction in the first half (0 to t1) in which the steering is increased, and is set in the restoring direction in the second half (t1 to t2) in which the steering is returned.

  In the latter half of the scene, the rear wheel 10 is controlled to generate a braking / driving force moment in the turning direction, contrary to the conventional yaw moment control. The front wheel 9 generates a braking / driving force moment in a restoring direction larger than that of the conventional yaw moment control.

  As a result, the rear wheel 10 can achieve the target yaw moment when the load movement amount is reduced and the equivalent cornering power is increased. Therefore, the vehicle body slip angle can be reduced as compared with the conventional yaw moment control. it can.

  In step S120 in FIG. 3, the braking / driving force moment of the rear wheel 10 may be zero. Even in this case, it is possible to suppress the reduction of the equivalent cornering power of the rear wheel 10 and improve the stability of the vehicle.

  As described above, in the present embodiment, the following effects can be obtained.

  A target yaw moment setting means 2 for setting a target yaw moment, and a control unit 6 including a braking / driving force distribution determining means 3 capable of controlling the braking / driving force distribution of at least the rear wheels 10 and 10b. During turning, the target yaw moment is generated and the braking / driving force distribution that suppresses the decrease in equivalent cornering power is performed, so the change in vehicle body slip angle to generate the cornering force necessary to achieve the target yaw moment Thus, the stability of the vehicle behavior during turning can be ensured.

  During a predetermined turn, for example, a turn in which the target yaw moment is in the restoring direction, the braking / driving force distribution determining means 3 generates a braking / driving force moment in the direction opposite to the direction of the target yaw moment on the left and right of the rear wheel. Since the braking / driving force is distributed to the left and right of the rear wheel, it is possible to suppress a reduction in the equivalent cornering power of the rear wheel 10 even when the rear wheel suspension arm 8 has an anti-scud angle.

  The braking / driving force distribution of the left and right front wheels 9a, 9b can be controlled, and the target generated at the left and right rear wheels 10a, 10b by the braking / driving force moment generated by the braking / driving force distribution of the left / right front wheels 9a, 9b during the predetermined turning Since the target yaw moment is generated by compensating the braking / driving force moment in the direction opposite to the yaw moment, even if the braking / driving force moment in the direction opposite to the target yaw moment is generated in the left and right rear wheels 10a, 10b, A target yaw moment can be added.

  A second embodiment will be described.

  In this embodiment, the basic configuration is the same as that of the first embodiment, and the control routine for determining the braking / driving force command value is different.

  FIG. 7 is a flowchart showing a control routine for determining the braking / driving force of this embodiment. This control routine is executed at regular intervals as in FIG.

  In this control, the turning stage is discriminated based on the steering amount, and control is performed to add a suitable braking / driving force moment of the rear wheel 10 according to the turning stage and the transition of the turning stage.

  This is because, for example, the target yaw moment is switched in a driving situation where the target yaw moment is switched from control in the turning direction (oversteer direction) to control in the convergence direction (understeer direction), such as lane change or slalom. This is because if the braking / driving force can be gradually changed before the vehicle starts, the vehicle body slip angle changes continuously, and the running stability of the vehicle can be further improved.

  In step S200, the target yaw moment Mz is calculated as in step S100 of FIG.

  In step S210, the sign of the rudder angle value, rudder angular velocity value, rudder angle acceleration value, and the change of this sign, whether the turn is started or the end of the turn, the load movement amount The turning stage is determined as to whether or not it is at a maximum, and the sign is discriminated before the target yaw moment is switched (turning stage discriminating means).

  Specifically, when the signs of the rudder angle value, the rudder angular speed, and the rudder angular acceleration all match or after the sign of the rudder angle value and the rudder angular acceleration has changed, the process proceeds to step S220. The value of the braking / driving force moment in the turning direction of the rear wheel 10 is increased.

  When only the sign of the steering angular velocity is changed, the process proceeds to step S230, and the value of the braking / driving force moment in the turning direction of the rear wheel 10 is decreased.

  If only the steering angular acceleration has changed, the process proceeds to step S240, and the value of the braking / driving force moment of the rear wheel 10 at the previous stage is maintained.

  If the braking / driving force moment of the rear wheel 10 is determined in step S220, S230, or S240, the process proceeds to step S250.

  Steps S250 to S280 are the same as steps S130 and S150 to S170 in FIG.

  A case where the above control is executed will be described with reference to FIG. FIG. 8 is a diagram showing examples of the steering angle value, the steering angular speed value, the sign change of the steering angular acceleration value, and the preferable rear wheel braking / driving force moment from the start to the end of the single lane change. Each time the sign changes, the stage is separated.

  The first stage is a state immediately after the start of turning, and all of the steering angle value, the steering angular velocity value, and the steering angular acceleration value are positive values. In this case, since the target yaw moment of the vehicle is the turning direction, the value of the braking / driving force moment in the turning direction of the rear wheel 10 is increased from zero as in the conventional control.

  The second stage is the same as the first stage in the steering angle value and the steering angular velocity value, but only the steering angle acceleration value is changed to a negative sign. This is a state in which the amount of load movement is increasing, and since it is predicted that the time at which the steering is turned back will be close, it is predicted that the same control as in the first embodiment will be performed in the next stage. it can. Therefore, in order to ensure continuity with the first stage and the next third stage, the value of the braking / driving force moment in the turning direction of the rear wheel 10 in the first stage is maintained.

  The third stage is after the sign of only the steering angular velocity value has changed. As the sign of the steering angular speed changes, the amount of load movement becomes maximum at the beginning of this stage. Therefore, it is desirable to apply a braking / driving force moment in the turning direction to the rear wheel 10. However, since the rudder angle value is approaching zero, the sign of the rudder angle value is reversed and the turning direction is changed in the next fourth stage, and there is almost no load movement at the end of the current stage. It is predicted. Therefore, the value of the braking / driving force moment in the turning direction of the rear wheel 10 is decreased toward zero.

  The fourth stage is after the signs of the steering angle value and the steering angle acceleration value have changed. For this reason, the load movement is rapidly increased, and the next stage is predicted to be the same control as in the first embodiment as in the second stage. Therefore, the braking / driving force moment in the turning direction of the rear wheel 10 is increased from zero in the opposite direction to the first stage.

  The fifth stage is after only the rudder angular velocity value has changed. Therefore, at this stage, the load movement is first maximized, so it is desirable to apply a braking / driving force moment in the turning direction to the rear wheel 10. However, since the rudder angle is getting smaller, it is predicted that the amount of load movement will decrease at the end of the fifth stage, so the value of the braking / driving force moment in the turning direction of the rear wheel 10 decreases toward zero. I will let you.

  The sixth stage is after the sign of only the steering angular acceleration value has changed. Since the load movement is small here, the braking / driving force moment in the turning direction of the rear wheel 10 is maintained at zero in consideration of continuity with the fifth stage.

  The case where the above control is performed is compared with the control of the first embodiment. 9 is similar to FIG. 6, when the control of the present embodiment is executed in a scene where the steering is first increased for the lane change and then switched back, that is, from the first stage to the third stage in FIG. It is a time chart. Note that t1 in FIG. 6 corresponds to the end of the second stage in FIG.

  When both are compared, a difference appears from the second stage of FIG. In the first embodiment, during the period corresponding to the second stage, the braking / driving force moment in the turning direction of the rear wheel 10 is reduced, whereas in the present embodiment, the rear wheel 10 is in the first stage of turning direction. The moment is maintained.

  At t1, in the first embodiment, the braking / driving force moments of the front wheel 9 and the rear wheel 10 change stepwise, and accordingly, the load movement amount of the rear wheel 10, the equivalent cornering power of the rear wheel 10, the vehicle body The slip angle also changes stepwise. On the other hand, in the present embodiment, the braking / driving force moment continuously changes in both the front wheel 9 and the rear wheel 10 at t1, and accordingly, the load movement amount of the rear wheel 10 and the equivalent cornering power of the rear wheel 10 are changed. The vehicle body slip angle also changes continuously and smoothly. For this reason, the running stability of the vehicle is further improved.

  As described above, in the present embodiment, in addition to the same effects as in the first embodiment, the following effects can be obtained.

  The vehicle running state detection means 1 discriminates the turning stage based on the sign of the rudder angle value, rudder angular speed value, and rudder angle acceleration value and the change in sign, and the braking / driving force distribution determination means 3 provides the rudder angle value, rudder angular speed. In the case where all the positive and negative signs of the value and the rudder angular acceleration value coincide with each other and after the transition in which only the rudder angle value and the rudder angular acceleration value change, the braking / driving in the turning direction generated by the left and right rear wheels 10a and 10b After the transition in which the value of the force moment is increased and only the rudder angular velocity value changes in sign, the value of the braking / driving force moment generated by the left and right rear wheels 10a and 10b is decreased, and after the transition in which only the rudder angular acceleration value changes in sign Distributes the braking / driving force to the left and right rear wheels 10a, 10b so as to maintain the value of the braking / driving force moment in the turning stage one stage before. For example, in a scene such as a lane change or a slalom, Moment in the scene switching to restore direction from turning round direction, it is possible to smooth the longitudinal force changes in each wheel 9,10. For this reason, when the braking / driving force distribution control for suppressing the reduction in the equivalent cornering power is performed, the change in the vehicle body slip angle becomes continuous, and the stability of the vehicle behavior can be further improved.

  A third embodiment will be described.

  This embodiment is the same as the second embodiment in the basic configuration and the like, and the control routine for determining the braking / driving force command value is different.

  FIG. 10 is a flowchart showing a control routine for determining the braking / driving force of this embodiment. This control routine is executed at regular intervals as in FIG.

  In the present embodiment, from the viewpoint of the friction circle, by effectively utilizing the turning outer wheel having a sufficient upper limit of the braking / driving force that can be added, the rear wheel 10 is more effective than the conventional yaw moment control without changing the target moment. Control to earn the equivalent cornering power. Hereinafter, description will be given according to the steps of the flowchart. Steps S300 to S380 are the same as steps S200 to S280 in FIG. 7 and thus will not be described. Steps S390 and subsequent steps will be described.

In step S390, the longitudinal force F _{xij of} each wheel (the calculated braking / driving force at the previous calculation), each wheel lateral force estimated value F _yij , each wheel load estimated value F _zij , and the road surface friction coefficient estimated value μ The frictional circle margin ΔF _xij in the front-rear direction of each wheel is estimated from the equation (8).

In consideration of a case where the estimated road surface friction coefficient value μ is not known, a tire slip ratio may be used instead of the estimated frictional circle margin value. The tire slip ratio of each wheel is obtained from the wheel speed V _wij of each wheel and the vehicle body speed V _{ij at} the installation point of each wheel.

  In step S400, it is determined whether the braking / driving force of the turning inner wheel exceeds the friction circle limit (friction circle limit determination means). If the estimated friction circle margin is negative, that is, if the actual braking / driving force is greater than the size of the friction circle, or if the slip ratio is greater than or equal to a preset first threshold, the friction circle limit is exceeded. It is determined that

  If the estimated frictional circle margin exceeds the frictional circle limit, the process proceeds to step S410. If not, the process ends.

  In step S410, it is determined whether the amount by which the braking / driving force of the turning inner wheel exceeds the friction circle limit is less than a preset second threshold value. This is because different control is performed depending on the degree of exceeding the friction circle limit. Therefore, the second threshold value is provided outside the friction circle limit.

  If it is less than the second threshold, the process proceeds to step S420, and if it exceeds, the process proceeds to step S430.

  In step S420, as indicated by the black arrows in FIG. 11A, the braking / driving forces of the front and rear wheels 9, 10 outside the turn are increased. Thereby, wheel load movement can be further suppressed while satisfying the target yaw moment. As the wheel load movement amount decreases, the friction circle of the turning inner wheel increases, and the upper limit of the inner wheel braking / driving force increases. As described above, in the control of the first and second embodiments, even when the braking / driving force of the turning inner wheel exceeds the friction circle, the braking / driving force of the turning inner wheel is obtained while obtaining the equivalent cornering power of the rear wheel 10. Can be kept in the friction circle.

  From these facts, it can be seen that the second threshold value is determined by the size of the friction circle increased by the decrease in the wheel load movement amount.

  In step S430, as indicated by the black arrows in FIG. 11 (b), the braking / driving force of the front and rear wheels 9, 10 inside the turning is decreased, and the braking / driving force of the turning inner wheel exceeds the friction circle limit. The process is repeated until the amount becomes less than the preset second threshold value (until the determination in step S410 becomes yes). As a result, the equivalent cornering power of the rear wheel 10 can be obtained as compared with the conventional yaw moment control while satisfying the target yaw moment.

  FIG. 11 is a view of the vehicle body from above. The white arrow represents the braking / driving force of each wheel determined in step S380, and the black arrow represents the braking / driving force corresponding to the increase / decrease in step S420 or S430.

  As described above, in the present embodiment, in addition to the same effects as those in the first and second embodiments, the following effects can be further obtained.

  It is determined whether or not the friction circle limit has been exceeded and the excess amount. If the braking / driving force of the turning inner wheel exceeds the friction circle limit, the second value is determined if the excess amount is equal to or greater than a preset second threshold value. The braking / driving force of the inner turning wheel is reduced until it becomes less than the threshold, and then the braking / driving force is corrected so as to increase the braking / driving force of the outer turning wheel. Since the driving force is increased, it is possible to reduce the burden on the turning inner wheel where the wheel load is lost and the friction circle is reduced, and to make more work on the turning outer wheel. As a result, the friction circle can be used effectively. Become. Furthermore, since the equivalent cornering power of the rear wheel 10 higher than that of the conventional yaw moment control can be maintained while achieving the target yaw moment, the conventional yaw moment control can be performed even in a scene where the turning inner wheel exceeds the friction circle. Compared with, the stability of vehicle behavior can be improved.

  In each of the above-described embodiments, the vehicle in which the four wheels are driven by the braking / driving motor 7a via the drive shaft 11 has been described. However, the vehicle in which the four wheels are driven by the in-wheel motor, and the braking / driving force of the four wheels. Naturally, the present invention can also be applied to a vehicle including another braking / driving device capable of distributing the above-described braking / driving device.

  Further, only the rear wheel 10 can distribute braking / driving force, and the front wheel 9 has braking / driving force control such as a steering angle control device that corrects the steering amount of the driver according to the vehicle state. The present invention can also be applied to a vehicle including a device that can generate a yaw moment by a method other than the above.

  The present invention is not limited to the above-described embodiments, and it goes without saying that various modifications can be made within the scope of the technical idea described in the claims.

It is a figure showing the basic composition of a 1st embodiment. It is the schematic of the structure of the vehicle body to which 1st Embodiment is applied. It is a flowchart showing the control routine of 1st Embodiment. It is the schematic of a rear-wheel suspension arm. It is a figure showing the relationship between an equivalent cornering power and a wheel load. It is a time chart at the time of applying 1st Embodiment in the case of a lane change. It is a flowchart showing the control routine of 2nd Embodiment. It is a figure for demonstrating the discriminating method of a turning stage. It is a time chart at the time of applying 2nd Embodiment in the case of a lane change. It is a flowchart showing the control routine of 3rd Embodiment. (a) is a figure showing the braking / driving force distribution when the excess amount from the friction circle is larger than the second threshold, and (b) is similarly small.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Vehicle running state detection means 2 Target yaw moment setting means 3 Braking / driving force distribution deciding means 4 Braking / driving means 5 Steering mechanism 6 Control unit 7a Braking / driving motor 7b Motor power supply inverter 8 Rear wheel suspension arm 9 Front wheel 10 Rear wheel 11 Drive shaft

Claims (8)

Target yaw moment setting means for setting the target yaw moment;
And car body yaw moment control means including a wheel longitudinal force distribution means after capable of controlling the braking-driving force distribution of at least rear wheels left and right,
A turning stage discriminating means for discriminating the turning stage based on the rudder angle;
With
The target yaw moment at the time of direction given a turning step after the transition to the switched restore direction from turning round direction turning of suppressing braking-driving force distribution a decrease in the equivalent cornering power before Symbol rear wheel braking and driving force distribution means A yaw moment control device for a vehicle, characterized in that During the predetermined turn, the rear wheel braking / driving force distributing means generates braking / driving force on the left and right of the rear wheel so as to generate a rear wheel braking / driving force moment in a direction opposite to the direction of the target yaw moment on the left and right of the rear wheel. The yaw moment control device for a vehicle according to claim 1, wherein: 2. The rear wheel braking / driving force distributing means controls the braking / driving force distribution so that the rear wheel braking / driving force moment generated on the left and right of the rear wheel becomes zero during the predetermined turning. A yaw moment control device for a vehicle according to claim 1. The braking / driving force distribution by the rear wheel braking / driving force distributing means at the predetermined turning time gives a driving force to the turning outer wheel of the rear wheel when turning in the turning direction, and turns in the turning direction. 4. The vehicle yaw moment control device according to claim 2, wherein a braking force is applied to the turning inner wheel of the rear wheel. The turning stage discriminating means discriminates the turning stage based on the sign of the rudder angle value, rudder angular velocity value and rudder angular acceleration value and the change in sign,
The rear wheel braking / driving force distribution means includes:
In the case where all the positive and negative signs of the rudder angle value, the rudder angular speed value, and the rudder angular acceleration value coincide with each other, and after the transition in which only the rudder angle value and the rudder angular acceleration value are changed, the rear wheel The braking / driving force is distributed to the left and right rear wheels so as to increase the value of the rear wheel braking / driving force moment in the turning direction generated by the left and right,
After the transition in which only the rudder angular velocity value changes in sign, the braking / driving force is distributed to the left and right rear wheels so as to reduce the value of the rear wheel braking / driving force moment generated by the left and right rear wheels,
Wherein the rear transition steering angle acceleration value only has sign change claims characterized by distributing the braking-driving force to the rear wheel left to maintain the value of the rear wheel longitudinal force moment in the turning phase of one step before Item 2. The vehicle yaw moment control device according to Item 1 . Front wheel braking / driving force control distribution means capable of controlling braking / driving force distribution on the left and right front wheels,
During the predetermined turning, the front wheel braking / driving force distribution means compensates for the braking / driving force moment in the opposite direction or zero magnitude from the target yaw moment generated by the rear wheel braking / driving force distribution means to achieve the target yaw moment. 6. The vehicle yaw moment control device according to claim 2, wherein a braking / driving force moment having a magnitude as defined above is generated. Friction circle limit judging means for judging whether or not the friction circle limit has been exceeded and the excess amount is provided,
When the braking / driving force of the inner turning wheel exceeds the friction circle limit, if the excess amount is greater than or equal to a preset threshold, the braking / driving force of the inner turning wheel is reduced until it falls below the threshold, and then the turning outer wheel Modify the braking / driving force to increase the braking / driving force,
7. If the excess amount is less than the threshold value, the braking / driving force of the outer turning wheel is increased within a range of an applicable braking / driving force determined from the viewpoint of a friction circle. A yaw moment control device for a vehicle according to claim 1. Target yaw moment setting means for setting the target yaw moment;
And car body yaw moment control means including a wheel longitudinal force distribution means after capable of controlling the braking-driving force distribution of at least rear wheels left and right,
A turning stage discriminating means for discriminating the turning stage based on the rudder angle;
In a vehicle yaw moment control method comprising:
Setting a target yaw moment for the vehicle;
Determining that the direction of the target yaw moment is a predetermined turning time which is a turning stage after switching from the turning direction and transitioning to the restoring direction ;
A step wherein the predetermined in the case of the cornering previous SL rear wheel braking and driving allocation means controls the suppressing so braking-driving force distribution a decrease in equivalent cornering power,
A yaw moment control method for a vehicle characterized by comprising: