JPH11240458A - Vehicle movement control unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a stable vehicle behavior control where target yaw rate is adequately set during a steering to modify the vehicle behavior, making a driver to feel no uncomfortableness. SOLUTION: A control unit 50 calculates vehicle speed at a vehicle speed calculation part 51, and vehicle sliding angle at a vehicle sliding angle calculation part 52. A target yaw rate time constant setting part 53 sets a larger time constant as the vehicle sliding angle becomes larger and a spinning tendency becomes stronger, when a spinning tendency is indicated in which codes of the actual yaw rate and the vehicle sliding angle are different from each other and a steering for modification such as a counter steering which quickly changes the vehicle behavior is conducted. A target yaw rate calculation part 55 calculates deviation of the actual yaw rate from the target yaw rate. A braking control unit 56, a longitudinal differential control part 57, and a side differential control part 58 control each of driving units 40, 41, 42 so that the actual yaw rate and the target yaw rate are made identical.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle motion control device for controlling a vehicle to perform a proper vehicle motion in accordance with a steering state of the vehicle.

[0002]

2. Description of the Related Art In recent years, in order to improve the running stability of a vehicle, a target yaw rate of a vehicle having a predetermined response parameter is determined based on a driving condition of the vehicle including a steering angle and vehicle specifications. Various vehicle motion control devices for controlling vehicle motion have been developed and put into practical use.

However, when the target yaw rate is set to one of the steering angles,
When uniformly calculated and set using the response parameters of the second or second order delay system, the driver detects the spin of the vehicle and corrects the attitude of the vehicle. However, there is a problem that the target yaw rate changes too rapidly and the yaw motion control is excessively operated in an attempt to suppress the yaw motion of the vehicle more than necessary.

For this reason, for example, Japanese Patent Application Laid-Open No. 8-33297
Japanese Patent Laid-Open Publication No. 1 (1999) -2005 discloses a technique in which control is performed such that a yaw moment is generated based on a target yaw rate in the first half and an actual yaw rate in the second half during counter steering.

[0005]

Generally, a driver (especially a skilled driver) detects not only the yaw rate of the own vehicle but also the rate of change (yaw angular acceleration), or based on experience, the driver responds to the steering operation. By adding quick correction steering in anticipation of a yaw rate delay, the vehicle's stability is maintained. In other words, such correction steering does not give the driver the desire to proceed in the steering direction, but gives the yaw moment necessary to stabilize the vehicle through the steering angle.

Accordingly, in the control law for setting and controlling the target yaw rate based on such correction steering, the target yaw rate changes rapidly too much due to the steering angle, so that the yaw motion of the vehicle is suppressed more than necessary. Excessive motion control is performed, and the vehicle behavior that the driver intends cannot be obtained. This tendency is further enhanced when the control system has a large delay, that is, when it takes a long time before the control is activated after the correction steering is applied.

[0007] Therefore, as in the prior art described above, the control for distinguishing the first half and the second half of the corrective steering and improving the convergence of the vehicle behavior alone is not enough to appropriately stabilize the vehicle behavior. For the steering that can be regarded as the correction steering without distinction between the first half and the second half of the steering, a control law for reducing the change in the target yaw rate is required.

The present invention has been made in view of the above circumstances, and a vehicle motion control capable of appropriately setting a target yaw rate at the time of corrective steering of vehicle behavior and realizing stable vehicle behavior control without a sense of incongruity for a driver. It is intended to provide a device.

[0009]

According to a first aspect of the present invention, there is provided a vehicle motion control apparatus for controlling a vehicle based on a vehicle operating condition including a steering angle and vehicle specifications. Calculate, in a vehicle motion control device that controls the vehicle behavior by operating the vehicle drive device based on this target yaw rate, according to the steering to correct the behavior of the vehicle,
This is for correcting the target yaw rate.

[0010] The vehicle motion control device according to claim 1 is
The target yaw rate of the vehicle is calculated based on the vehicle operating condition including the steering angle and the vehicle specifications. Here, the target yaw rate is corrected and calculated according to the steering for correcting the behavior of the vehicle. Then, the vehicle driving device is operated based on the target yaw rate to control the vehicle behavior.

According to a second aspect of the present invention, there is provided a vehicle motion control apparatus according to the first aspect, wherein the steering is detected in accordance with an actual yaw rate direction and a body slip angle direction. Specifically, when the vehicle body is traveling with a slip angle in the same direction as the yaw rate with respect to the traveling direction, the steering is determined to correct the behavior of the vehicle.

Further, according to a third aspect of the present invention, in the vehicle motion control apparatus according to the first or second aspect, the correction of the target yaw rate is set at least according to a vehicle body slip angle. And, for example,
The larger the vehicle body slip angle is, the more the correction is made in such a direction that the rapid change of the target yaw rate is suppressed.

According to a fourth aspect of the present invention, there is provided a vehicle motion control apparatus according to the first or third aspect, wherein the correction of the target yaw rate is set at least according to the vehicle speed. For example, as the vehicle speed increases, the correction is made in such a direction that a rapid change in the target yaw rate is suppressed.

According to a fifth aspect of the present invention, there is provided a vehicle motion control apparatus according to the first aspect, wherein the correction of the target yaw rate includes the operation state of the vehicle including the steering angle and the vehicle specifications. This is performed in accordance with the absolute value of the deviation between the target yaw rate calculated based on the target yaw rate and the target yaw rate obtained from the radius of curvature of the road and the vehicle speed, and the absolute value of the steering angular velocity. Despite the small difference between the target yaw rate obtained from the road shape and the target yaw rate obtained from the road shape, the larger the absolute value of the steering angular velocity, that is, the quicker the steering, the sharper the target yaw rate obtained from the vehicle behavior. Is corrected in such a direction as to suppress a significant change.

According to a sixth aspect of the present invention, there is provided a vehicle motion control apparatus which calculates a target yaw rate of a vehicle based on a vehicle operating state including a steering angle and vehicle specifications, and calculates a vehicle yaw rate based on the target yaw rate. In the vehicle motion control device that controls the vehicle behavior by operating the drive device, the input signal of the steering angle used for the calculation of the target yaw rate is obtained by removing the signal component of the correction steering that is set in advance and performing the calculation. It is used.

According to a sixth aspect of the present invention, there is provided a vehicle motion control device comprising:
For example, a signal component for a quick steering is removed from the input signal of the steering angle by cutting a signal at the time of quick steering by a low-pass filter, for example. And
The target yaw rate of the vehicle is calculated based on the driving state of the vehicle including the steering angle and the vehicle specifications, and the vehicle driving device is operated based on the target yaw rate to control the vehicle behavior.

Further, according to a seventh aspect of the present invention, there is provided a vehicle motion control apparatus according to any one of the first, second, third, fourth, fifth and sixth aspects. The device consists of a braking device that independently applies braking force to each selected wheel, a differential limiting device between left and right wheels that limits the differential between left and right wheels, and a differential limiting device between front and rear wheels that limits differential between front and rear wheels. At least one of the devices, based on the target yaw rate, in order to correct the oversteer tendency of the vehicle with the braking device, braking the outer wheel or the outer front wheel with respect to the turning direction, In order to correct the understeer tendency of the vehicle, the inner wheel or the inner rear wheel with respect to the turning direction is braked. Further, in order to correct the behavior of the vehicle oversteering tendency with the above-mentioned differential limiting device between the left and right wheels, differential limiting between the left and right wheels is performed so that the driving force distribution inward in the turning direction is increased, In order to correct the understeer tendency of the vehicle, the difference between the left and right wheels is limited so that the driving force distribution outside the turning direction is increased. Further, in order to correct the behavior of the vehicle oversteering tendency by the above-described front-rear wheel differential limiting device, the front-wheel side driving force distribution is increased by performing the differential limitation between the front and rear wheels, and the vehicle understeering tendency is increased. In order to correct this behavior, the differential between the front and rear wheels is limited so that the driving force distribution on the rear wheel side is increased.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 6 show a first embodiment of the present invention.
FIG. 1 is a functional block diagram of a vehicle motion control device, FIG. 2 is an explanatory diagram showing a schematic configuration of a vehicle equipped with the vehicle motion control device, FIG. 3 is a flowchart of vehicle motion control,
4 is a flowchart of a target yaw rate time constant calculation / setting routine, FIG. 5 is a flowchart of a braking, front / rear, left / right differential limiting control routine, and FIG. 6 is an explanatory diagram of a time constant to be set. The vehicle according to the first embodiment of the present invention will be described by taking a four-wheel drive vehicle having a compound planetary gear type center differential and an automatic transmission as an example.

In FIG. 2, reference numeral 1 denotes an engine arranged at the front of the vehicle.
An automatic transmission (including a torque converter and the like) 2 behind the engine 1 to a transmission output shaft 2a
Is transmitted to the center differential device 3 through
From this center differential device 3, the rear drive shaft 4, propeller shaft 5, and drive pinion 6 are input to the rear wheel final reduction gear 7, while the transfer drive gear 8, transfer driven gear 9, and drive pinion shaft are formed. Front drive shaft 10
Is input to the front-wheel final reduction gear 11 via the. Here, the automatic transmission 2, the center differential device 3, the front wheel final reduction gear 11, etc.
It is provided in the case 12 integrally.

The driving force input to the rear wheel final reduction gear 7 is transmitted to the left rear wheel 14rl via the rear wheel left drive shaft 13rl and to the right rear wheel 14rr via the rear wheel right drive shaft 13rr. The driving force input to the front wheel final reduction gear 11 is
The signal is transmitted to the left front wheel 14fl via the front wheel left drive shaft 13fl and to the right front wheel 14fr via the front wheel right drive shaft 13fr.

The above-mentioned center differential device 3
Has a first sun gear 15 having a large diameter formed on the transmission output shaft 2a on the input side, and the first sun gear 15 meshes with a first pinion 16 having a small diameter to form a first sun gear.
Gear train is formed.

A small-diameter second sun gear 17 is formed on the rear drive shaft 4 for outputting power to the rear wheels. The second sun gear 17 is a large-diameter second pinion 1.
8 and a second gear train is formed.

The first pinion 16 and the second pinion 18 are formed integrally with a pinion member 19,
A plurality (for example, three) of the pinion members 19 are rotatably supported on a fixed shaft provided on the carrier 20.

The transfer drive gear 8 is connected to the front end of the carrier 20 so as to output to the front wheels.

The transmission output shaft 2a is rotatably inserted into the carrier 20 from the front, and the rear drive shaft 4 is rotatably inserted from the rear. The sun gear 15 and the second sun gear 17 are stored. The first pinions 16 of the plurality of pinion members 19 correspond to the first pinions.
The second pinion 18 is meshed with the second sun gear 17.

Thus, the first sun gear 1 on the input side
5 through the first and second pinions 16 and 18 and the second sun gear 17 to one output side and the other through the carrier 20 of the first and second pinions 16 and 18. And a composite planetary gear without a ring gear.

The compound planetary gear type center differential device 3 includes the first and second sun gears 15 and 17 and a plurality of the first and second pinions 1 arranged around the sun gears 15 and 17.
The differential function is provided by appropriately setting the number of teeth 6 and 18.

Further, the first and second pinions 16, 1
By appropriately setting the meshing pitch radii between the gear 8 and the first and second sun gears 15 and 17, the reference torque distribution can be set to a desired distribution (for example, unequal torque distribution with rear wheel biased).
It is possible to be.

Further, in the center differential device 3, the first and second sun gears 15 and 17 and the first and second pinions 16 and 18 are, for example, helical gears, and the first gear train The friction torque generated at both ends of the pinion member 19 by remaining the thrust load without canceling the thrust load by changing the torsion angle of the second gear train and the first and second pinions 16, 18 And the surface of the fixed shaft provided on the carrier 20 is engaged so that the combined force of separation and tangential load acts on the surface to generate a friction torque so that a differential limiting torque proportional to the input torque can be obtained. Thus, the differential limiting function can be obtained by the center differential device 3 itself.

The two output members of the center differential device 3, namely, the carrier 20 and the second output member
A hydraulic multi-plate clutch (front-rear differential limiting clutch) 21 as a variable displacement transmission clutch operated by a front-rear differential limiting clutch operating section 41 is formed between the sun gear 17 and the sun gear 17.

The front / rear differential limiting clutch 21 includes a plurality of driven plates 21 a provided on the side of the rear drive shaft 4 integral with the second sun gear 17 and the carrier 2.
A plurality of drive plates 21b provided on the 0 side are alternately stacked. The front-rear differential limiting clutch 21 is operated by a hydraulic pressure in a hydraulic chamber being variably pressed by a front-rear differential limiting clutch operating unit 41 controlled by a control device 50 by a piston, a pressing plate, or the like (not shown). The front and rear differential limiting clutch operating section 4
Reference numeral 1 denotes a motor, an oil pump, and a hydraulic device having a plurality of valves (a description of a hydraulic-related portion is omitted).

For this reason, the front-rear differential limiting clutch 21
Is released, the torque distribution by the center differential device 3 is output as it is, but when the front and rear differential limiting clutch 21 is completely pressed, the differential of the center differential device 3 is limited and the torque distribution is stopped. Then, it is in a directly connected state.

The pressing force of the front / rear differential limiting clutch 21 (front / rear differential limiting clutch torque) is controlled by the controller 50.
For example, if the reference torque distribution is 35:65 before and after the rear wheel is biased, the front and rear differential limiting clutch torque is added to move the torque distribution largely toward the front wheels from 35:65 before and after the front-rear direct connection state. , The torque distribution control (for example, the front-rear differential limiting control) is performed between 50:50.

In the embodiment of the present invention, the rear wheel final reduction gear 7 is also of a compound planetary gear type similar to the center differential 3 described above.
That is, a crown gear 32 is provided on the outer periphery of the differential case 31 rotatably held, and the driving force of the drive pinion 6 is transmitted to the differential case 31 via the crown gear 32. I have.

In the differential case 31, a carrier 34 whose left portion is formed as a clutch drum 33a in a cylindrical shape is rotatably disposed, and the rear wheel right drive shaft 13rr is inserted into the carrier 34. And is connected to the carrier 34.

Further, the differential case 31
Inside, a large-diameter first sun gear 35 coupled to the differential case 31 is provided, and meshes with a small-diameter first pinion 36 to form a first gear train.

Further, the differential case 3
1, a rear wheel left drive shaft 13rl is inserted therein, and a small-diameter second sun gear 37 is formed at the tip of the rear wheel left drive shaft 13rl, and the second sun gear 37 has a large diameter. The second gear train is formed by meshing with the second pinion 38.

The first pinion 36 and the second pinion 38 are formed integrally with a pinion member 39,
A plurality (for example, three) of the pinion members 39 are rotatably supported on a fixed shaft provided on the carrier 34.

A clutch hub 33b is provided on the rear wheel left drive shaft 13rl at a position facing the clutch drum 33a of the carrier 34. The clutch drum 33a and the clutch hub 33b each include a plurality of drive plates and driven plates. Hydraulic multi-plate clutches (left and right differential limiting clutches) 33 are alternately provided.

The left and right differential limiting clutch 33
Is a left and right differential limiting clutch operating portion 42 controlled by the control device 50 by a piston, a pressing plate, etc. (not shown).
The hydraulic pressure in the hydraulic chamber is variably pressed to operate.
The left and right differential limiting clutch operating section 42 includes a motor,
It is composed of an oil pump and a hydraulic device having a plurality of valves.

That is, the rear wheel final reduction gear 7 transmits the driving force from the drive pinion 6 to the crown gear 3.
2. The power is transmitted to the first sun gear 35 via the differential case 31 and is output from the second sun gear 37 to the rear left drive shaft 13rl, while the carrier 3
4 from the rear wheel right drive shaft 13rr to the rear wheel left drive shaft 13rl, which is one output side, and the carrier 34, which is the other output side. The left and right differential limiting clutch 33 whose frictional force is variably controlled is interposed.

Then, in addition to the differential limiting torque proportional to the input torque generated by the composite planetary differential limiting controller, if necessary, the hydraulic multi-plate clutch applies the differential limiting torque to optimize the differential limiting torque. A dynamic limiting torque is generated.

The composite planetary differential limiting control unit includes the first and second sun gears 35 and 37, and the first and second pinions disposed in plurality around the sun gears 35 and 37. By properly setting the number of teeth of 36 and 38, a differential function is provided.

The first and second sun gears 35, 3
By setting the radius of the meshing pitch circle of the first pinion 36 and the first and second pinions 36 and 38 appropriately, the reference torque distribution has a function of equal torque distribution of 50:50 on the left and right.

Further, the first and second sun gears 35,
37 and the first and second pinions 36 and 38 are, for example, helical gears, and the first gear train and the second gear train have different torsion angles so that the thrust load is not canceled out. The friction torque generated at both ends of the pinion member 39 with the load remaining is reduced by the first and second pinion 3.
The surfaces of the fixed shafts provided on the carrier 34 and the fixed shafts 38 and 38 are separated by meshing, and the combined force of the tangential loads acts to generate a friction torque, so that a differential limiting torque proportional to the input torque can be obtained. By doing so, it is possible to obtain a differential limiting torque proportional to the input torque, so that the differential limiting function can be obtained by the differential limiting device itself.

Therefore, when the left and right differential limiting clutch 33 is released by the left and right differential limiting clutch operating section 42, the reference torque distribution, that is, the left and right 50:50.
The differential between the left and right wheels is limited when the left and right differential limiting clutch 33 is engaged, and, for example, when the oversteer tends to occur during turning, the differential between the left and right wheels is limited. The torque distribution of the wheels is increased, and slipping is prevented, so that the running tends to be stable.

Reference numeral 40 denotes a brake drive unit of the vehicle.
The brake drive unit 40 includes a master cylinder 4 connected to a brake pedal 43 operated by a driver.
4 is connected and the driver operates the brake pedal 4
When the third wheel 3 is operated, the four wheels 14fl, 14fr, 1
4rl, 14rr wheel cylinders (left front wheel cylinder 45fl, right front wheel cylinder 45fr, left rear wheel cylinder 45rl, right rear wheel cylinder 45
A brake pressure is introduced to rr), whereby the four wheels are braked and braked.

The brake drive unit 40 is a hydraulic unit having a pressurizing source, a pressure reducing valve, a pressure increasing valve, and the like. Each of the wheel cylinders 45fl and 45f is operated in accordance with an input signal.
The brake pressure is formed independently for each of r, 45rl, and 45rr.

Each of the wheels 14fl, 14fr, 14rl, 14
rr is such that each wheel speed is detected by a wheel speed sensor 46 (left front wheel speed sensor 46fl, right front wheel speed sensor 46fr, left rear wheel speed sensor 46rl, right rear wheel speed sensor 46rr). The wheel speed signal is
The data is input to the control device 50.

Further, the vehicle 1 has a steering wheel angle sensor 4
7, a yaw rate sensor 48, and a lateral acceleration sensor 49 are provided. Signals of the steering wheel angle θH, the actual yaw rate γ, and the lateral acceleration Gy from these sensors are input to the control device 50.

The control device 30 is a control device formed by a microcomputer and its peripheral circuits. As described above, the wheel speed sensors 46 and the steering wheel angle sensors 4 of the four wheels are used.
7, yaw rate sensor 48 and lateral acceleration sensor 4
9 and outputs drive signals to the brake drive unit 40, the front and rear differential limiting clutch operating unit 41, and the left and right differential limiting clutch operating unit 42 as a driving device as necessary.

As shown in FIG. 1, the control device 50
Vehicle speed calculation unit 51, vehicle body slip angle calculation unit 52, target yaw rate time constant setting unit 53, target yaw rate calculation unit 54, yaw rate deviation calculation unit 55, braking control unit 56, front and rear differential limit control unit 57, and left and right differential limit control It is mainly composed of a part 58.

The vehicle speed calculating section 51 receives the signals of the respective wheel speeds from the wheel speed sensors 46 of the four wheels, and calculates these signals by a preset mathematical expression (for example, the respective wheel speeds). The vehicle speed V is obtained by calculating the average), the vehicle body slip angle calculating section 52, the target yaw rate time constant setting section 53,
It is formed so as to output to the target yaw rate calculation unit 54.

The vehicle body slip angle calculating section 52 calculates the following (1) based on signals (actual yaw rate γ, lateral acceleration Gy, vehicle speed V) from the yaw rate sensor 48, the lateral acceleration sensor 49 and the vehicle speed calculating section 51. The vehicle slip angle β is calculated by the equation.

Here, the integral of the function f (t) with t is expressed as IN
When represented by T {f (t)} dt, β = INT {Gy / V−γ} dt (1) Note that the body slip angle β is not limited to that calculated based on the above equation (1). For example, the detection may be performed using a vehicle slip angle sensor or the like that can directly detect the vehicle slip angle β. The vehicle slip angle β estimated by the vehicle slip angle calculation section 52 is input to the target yaw rate time constant setting section 53.

The target yaw rate time constant setting unit 53
Signals (actual yaw rate γ, vehicle speed V, body slip angle β) from the yaw rate sensor 48, the vehicle speed calculator 51, and the body slip angle calculator 52 are input to approximate and represent the target yaw rate with a first-order delay. The target yaw rate time constant T is calculated as a response parameter of the target yaw rate, and is set in the target yaw rate calculator 54.

That is, the target yaw rate time constant T is calculated as a function of the actual yaw rate γ, the vehicle speed V and the vehicle body slip angle β as follows. The target yaw rate time constant T is as follows: T = K1 · V (2)

The above K1 is set by the following equation (3). K1 = K2 + K3 · β ′ (3) where K2 and K3 are preset constants, and β ′ is a vehicle slip angle set value set under the following conditions. β ′ = − β (γ> 0 and β <0) β ′ = β (γ <0 and β> 0) β ′ = 0 (conditions other than the above) The sign of the left turning direction of the vehicle Is +, and the sign of the right turning direction of the vehicle is-.

Therefore, the target yaw rate time constant T set by the target yaw rate time constant setting section 53 is, as shown in FIG. 6, when the sign of the actual yaw rate γ and the sign of the vehicle body slip angle β are different from each other, K1 in the above equation (2) increases as the vehicle body slip angle β increases and the spin tendency increases, indicating a spin tendency in which corrective steering such as countersteering or the like that quickly changes the behavior of the vehicle is performed. . In the case where the tendency is not the spin tendency, the value becomes a constant value when K1 = K2 in the above equation (2), and becomes the value of the normal target yaw rate time constant T that changes according to the vehicle speed V.

The target yaw rate calculating section 54 receives signals from the steering wheel angle sensor 47, the vehicle speed calculating section 51, and the target yaw rate time constant setting section 53 (the steering wheel angle θH,
The vehicle speed V and the target yaw rate time constant T) are input, and the target yaw rate γ 'is calculated.
Output.

The target yaw rate calculating section 54 obtains a steady-state target yaw rate value as a target yaw rate steady-state value, and performs a first-order lag process on the target yaw rate steady-state value γ'0 by the target yaw rate time constant T. To calculate the target yaw rate γ ′.

That is, assuming that the Laplace operator is s, γ ′ = (1 / (1 + T · s)) · γ′0 (4) γ′0 = (1 / (1 + A · V ² )) · (V / (L · n)) · θH (5) where A is a stability factor, L is a wheel base, and n is a steering gear ratio.

As can be seen from the above equation (4), when the target yaw rate time constant T increases, the change in the target yaw rate γ ′ decreases. That is, the followability of the value of the target yaw rate γ 'to steering is reduced. Accordingly, the target yaw rate time constant setting unit 53 sets the target yaw rate time constant T to a larger value when the vehicle shows a spin tendency, as the spin tendency becomes stronger. The change in γ ′ is set to be small. In the case of a spin tendency in which a corrective steering such as a counter steer for quickly changing the behavior of the vehicle is performed, the target yaw rate γ ′ is determined according to the spin tendency.
Is corrected to be small.

The yaw rate deviation calculating section 55 receives the actual yaw rate γ from the yaw rate sensor 48 and the target yaw rate γ ′ from the target yaw rate calculating section 54, and calculates a deviation Δγ (= γ) between the actual yaw rate γ and the target yaw rate γ ′. .gamma .-. gamma. ') is calculated and output to the braking control unit 56, the front and rear differential restriction control unit 57, and the left and right differential restriction control unit 58.

The braking control unit 56 receives the actual yaw rate γ from the yaw rate sensor 48 and the yaw rate deviation Δγ from the yaw rate deviation calculating unit 55. Δγ is set to 0, that is, whether the actual yaw rate γ and the target yaw rate γ ′ can be matched, and the calculated result is output to the brake drive unit 40 for control. Specifically, control is performed as follows.

When the actual yaw rate γ and the yaw rate deviation Δγ have the same sign: when the vehicle is over-steering, braking the outer wheels or the outer front wheels with respect to the turning direction. The actual yaw rate γ and the yaw rate deviation Δγ have different signs. When the vehicle tends to understeer: Braking the inner wheel or the inner rear wheel with respect to the turning direction The braking force to be applied is based on the motion state of the vehicle and the yaw rate deviation in consideration of the vehicle specifications. It is determined by a calculation formula and a map set in advance.

The front / rear differential limiting control unit 57 receives the actual yaw rate γ from the yaw rate sensor 48 and the yaw rate deviation Δγ from the yaw rate deviation calculating unit 55,
It is calculated whether the yaw rate deviation Δγ can be set to 0, that is, the actual yaw rate γ and the target yaw rate γ ′ can be made equal by controlling the front and rear differential limiting in what direction and by what amount of the vehicle. Is output to the front-rear differential limiting clutch operating section 41 to be controlled. Specifically, control is performed as follows.

When the actual yaw rate γ and the yaw rate deviation Δγ have the same sign: when the vehicle is over-steering, a front-rear differential limiting clutch torque is added so that the driving force distribution on the front wheels is increased. When the deviation Δγ has a different sign: when the vehicle is understeer; when the front-rear differential limiting clutch torque is released so that the driving force distribution on the rear wheel side is increased. Is determined by a calculation formula and a map which are set in advance based on the motion state of the vehicle and the yaw rate deviation.

The left / right differential limiting control unit 58 receives the actual yaw rate γ from the yaw rate sensor 48 and the yaw rate deviation Δγ from the yaw rate deviation calculating unit 55,
It is calculated whether the yaw rate deviation Δγ can be set to 0, that is, the actual yaw rate γ and the target yaw rate γ 'can be made equal by controlling the vehicle in which direction and by what amount of left and right differential limiting control. Is output to the left and right differential limiting clutch operating section 42 for control. Specifically, control is performed as follows.

When the actual yaw rate γ and the yaw rate deviation Δγ have the same sign: when the vehicle is over-steering, a left and right differential limiting clutch torque is added so that the driving force distribution inside the turning direction becomes large. When the yaw rate γ and the yaw rate deviation Δγ have different signs: when the vehicle is understeer, the left and right differential limiting clutch torque is released so that the driving force distribution outside the turning direction is increased. Is determined by a calculation formula and a map which are set in advance based on the vehicle motion state and the yaw rate deviation in consideration of the vehicle specifications.

Next, the operation of the above configuration will be described with reference to the flowcharts of FIGS. FIG. 4 is a flowchart of the vehicle motion control. First, each sensor value is read in step (hereinafter abbreviated as “S”) 101, and the process proceeds to S102.
The vehicle speed calculation unit 51 calculates the vehicle speed V, and the vehicle body slip angle calculation unit 52 calculates the vehicle body slip angle β according to the above equation (1).

Next, the routine proceeds to S103, where the target yaw rate time constant setting section 53 sets the target yaw rate time constant T as a function of the actual yaw rate γ, the vehicle speed V and the vehicle body slip angle β in accordance with a target yaw rate time constant T calculation / setting routine to be described later. Calculate.

Thereafter, the program proceeds to S104, in which the target yaw rate calculating section 54 calculates the target yaw rate γ 'according to the equation (4).
Calculates the yaw rate deviation Δγ (= γ−γ ′) from the actual yaw rate γ and the target yaw rate γ ′.

Then, the program proceeds to S106 in which braking, which will be described later,
The braking control, the front-rear differential restriction control, and the left-right differential restriction control are performed according to the front-rear, left-right differential restriction control routine.

FIG. 4 is a flowchart of the routine for calculating and setting the target yaw rate time constant T in S103.
At 201, it is determined whether or not the actual yaw rate γ has a positive sign (γ> 0) and the vehicle body slip angle β has a negative sign (β <0), and this condition (γ> 0 and β <0) Otherwise, S
Proceeding to 202, the actual yaw rate γ is negative (γ <0)
It is determined whether the vehicle slip angle β is a positive sign (β> 0).

If the condition of S201 (γ> 0 and β <0) is satisfied, the routine proceeds to S203, where the vehicle slip angle set value β ′ is set to β ′ = − β, and the condition of S202 (γ <0)
If 0 and β> 0, the routine proceeds to S204, in which the vehicle body slip angle set value β ′ is set to β ′ = β, and when the condition other than the condition of S202 (γ <0 and β> 0) is satisfied (actual yaw rate). γ
(When the vehicle slip angle β is other than the opposite sign), the routine proceeds to S205, where the vehicle slip angle set value β ′ is set to β ′ = 0.

Thereafter, the flow advances to S206, where S203 and S203 are executed.
The vehicle slip angle set value β ′ set in S204 and S205
, The target yaw rate time constant T is calculated by the equation (2).

Therefore, the target yaw rate time constant T is calculated when the sign of the actual yaw rate γ and the sign of the vehicle body slip angle β are different from each other, ie, when the target yaw rate indicates a spin tendency for performing corrective steering such as counter steer for quickly changing the behavior of the vehicle. The larger the vehicle slip angle β and the stronger the spin tendency, the larger the value is set. In cases other than the spin tendency, the value is calculated and set to the value of the normal target yaw rate time constant T that changes according to the vehicle speed V.

FIG. 5 shows the braking, front / rear,
In the flowchart of the left / right differential limiting control, first, at S301
The calculation formulas in which the braking force, the value of the front and rear differential limiting clutch torque, and the value of the left and right differential limiting clutch torque are set in advance based on the vehicle motion state and the yaw rate deviation in consideration of the vehicle specifications. , And the process proceeds to S302.

In S302, the sign of the actual yaw rate γ is compared with the sign of the yaw rate deviation Δγ. If the signs are the same, the vehicle is in an oversteer tendency, and the process proceeds to S303, where the brake control unit 56 causes the brake driving unit to brake the outer wheel or the outer front wheel in the turning direction. 40, and the front-rear differential limiting control unit 57
Output to the front / rear differential limiting clutch operating section 41 so as to add the front / rear differential limiting clutch torque so that the driving force distribution on the front wheels increases, and the left / right differential limiting control section 58 The right and left differential limiting clutch torque is applied to the left and right differential limiting clutch operating section 42 so as to add the left and right differential limiting clutch torque so as to increase the driving force distribution.

On the other hand, if the signs are different signs from each other, it means that the vehicle has an understeer tendency, and the process proceeds to S304.
The brake control unit 56 controls the brake driving unit 40 to brake the inner wheel or the inner rear wheel in the turning direction.
The front-rear differential limiting control unit 57 outputs to the front-rear differential limiting clutch operating unit 41 so as to release the front-rear differential limiting clutch torque so as to increase the driving force distribution on the rear wheel side. The restriction control unit 58 controls the left and right differential limiting clutch operating unit 42 to release the left and right differential limiting clutch torque so as to increase the distribution of the driving force on the outside in the turning direction.
Output to

As described above, according to the first embodiment of the present invention, when the sign of the actual yaw rate γ and the sign of the vehicle body slip angle β are different from each other, that is, the correction steering such as the countersteer for quickly changing the behavior of the vehicle is performed. When the spin tendency to be performed is shown, the target yaw rate time constant T is set to a larger value and the change in the target yaw rate γ 'is set and corrected to be larger as the body slip angle β is larger and the spin tendency is stronger. The target yaw rate at the time of steering is appropriately set, and stable vehicle behavior control without a sense of incongruity for the driver can be realized.

Next, FIGS. 7 to 16 show a second embodiment of the present invention.
7 is a functional block diagram of the vehicle motion control device, FIG. 8 is an explanatory diagram showing a schematic configuration of a vehicle equipped with the vehicle motion control device, and FIG. 9 is an explanatory diagram of a configuration for obtaining a road shape. 10 is an explanatory diagram of an example of point data obtained from the navigation device, FIG. 11 is an explanatory diagram of how to calculate a radius of curvature of a curve, FIG. 12 is an explanatory diagram of correction of a radius of curvature of the obtained curve, and FIG. Of each case in FIG. 1, FIG.
4 is a flowchart of vehicle motion control, FIG. 15 is an explanatory diagram of a target yaw rate time constant basic value set by a target yaw rate deviation (absolute value), and FIG. 16 is a basic value correction coefficient set by a steering angular velocity (absolute value). FIG. In the second embodiment of the present invention, a basic value of a target yaw rate time constant is set from a deviation between a target yaw rate obtained from a vehicle behavior and a target yaw rate obtained from a road shape. The target yaw rate time constant is set as a response parameter when the target yaw rate is corrected and approximated by a first-order lag and expressed. The same parts as those in the first embodiment of the invention are denoted by the same reference numerals, and description thereof will be omitted.

For this reason, as shown in FIG. 8, the vehicle is equipped with a navigation device 61 and a road shape detection device 62.

As shown in FIG. 9, the navigation device 61 is a general one, for example, a vehicle position detection sensor unit 61a, an auxiliary storage device 61b, and an information display unit 61.
c, an operation unit 61d, and a calculation unit 61e.

The vehicle position detecting sensor section 61a is, specifically, a global positioning satellite system (Global Positioning Satellite System).
ng System (GPS) to receive radio waves from GPS satellites to measure its own position, a geomagnetic sensor to detect the absolute running direction of the vehicle, and to face the outer periphery of the rotor fixed to the wheels A wheel speed sensor that detects a protrusion on the outer periphery of the rotor that rotates as the vehicle travels and outputs a pulse signal is connected, and travel information related to the vehicle position is collected. It has become.

The auxiliary storage device 61b is a CD-ROM
The apparatus is formed in a read-only storage device in which a CD-ROM storing road map information including road information and terrain information is set. In the CD-ROM, road map information is stored at each of a plurality of hierarchical levels having different scales. Further, road type information such as expressways, general national roads, and local roads, and traffic conditions such as intersections, etc., are stored. Information is stored. The road data in the road map information includes, as shown in FIG. 10, point data (nodes) input at predetermined intervals and line data (links) formed by continuously connecting these points.

The information display section 61c is formed of a liquid crystal display for displaying a map, the position of the vehicle (latitude / longitude / altitude), the direction, the position of the vehicle on the map, the optimum route to the destination, and the like. Then, a touch panel as the operation unit 61d is connected integrally with the information display unit 61c (liquid crystal display) to change the scale of the map, display the details of place names,
An operation input for switching the display such as the regional information and the route guidance can be performed.

The arithmetic section 61e combines the traveling information of the vehicle obtained from the vehicle position detecting sensor section 61a with the map information read from the auxiliary storage device 61b while performing arithmetic operations such as map matching and the like. The result is sent to the information display unit 61c based on the operation signal sent from the operation unit 61d, and the current position of the vehicle and a map around the vehicle, the optimal route to the destination, and the like are displayed. In addition, each of the above data (point data of road data,
The road type information, data such as the current position, and the like) are also output to a curve information calculation unit 72 and a second target yaw rate calculation unit 74 of the control device 70, which will be described later, as needed.

In the second embodiment of the present invention, the road shape detecting device 62 is provided so as to particularly detect a road width, and includes a pair of CCD cameras 62a and an image processing unit 62.
b, mainly comprising a road width detector 62c.

The pair of CCD cameras 62a are mounted at a predetermined interval on the left and right in front of the ceiling in the passenger compartment.
An object outside the vehicle is stereo-imaged from a different viewpoint, and a video signal in the traveling direction of the vehicle captured by the pair of CCD cameras 62a is input to the image processing unit 62b.

The image processing section 62b covers the entire image of a set of stereo images of the environment in the traveling direction of the vehicle taken by the CCD camera 62a from the amount of displacement of the corresponding position based on the principle of triangulation. It is configured to perform a process of obtaining distance information, generate a distance image representing a three-dimensional distance distribution, and output the generated distance image to the road width detection unit 62c.

The road width detection unit 62c recognizes a road by performing histogram processing on the distance distribution of the distance image from the image processing unit 62b, calculates the road width, and calculates the road width. The information is output to the curve information calculation unit 72 as needed.

In the road width detecting section 62c, for example, a white line is approximated by a broken line, and a range surrounded by left and right broken lines is determined to be the own lane, and the road width is calculated from the interval between the left and right broken lines of the own lane. . As described above, since the road shape detecting device 62 detects the road shape and obtains the road width from the road shape, the road shape detected by the road shape detecting device 62 and the navigation device 61 are determined.
It is also possible to correct the own vehicle position on the map of the navigation device 61 so as to obtain the own vehicle position more accurately so as to compare and match the road shape data on the map obtained by the above.

The control device 70 is formed by a microcomputer and its peripheral circuits, and includes the four wheel speed sensors 46, the steering wheel angle sensor 47, the yaw rate sensor 48,
Further, signals from the navigation device 61 and the road shape detection device 62 are input, and the brake drive unit 40, the front-rear differential limiting clutch operating unit 41, the left-right differential limiting clutch operating unit as a driving device are input as necessary. A drive signal is output to the control signal.

[0096] As shown in FIG.
Vehicle speed calculating section 71, curve information calculating section 72, first target yaw rate calculating section 73, second target yaw rate calculating section 7
4, target yaw rate deviation (absolute value) calculating section 75, steering angular velocity (absolute value) calculating section 76, target yaw rate time constant setting section 77, final target yaw rate calculating section 78, yaw rate deviation calculating section 79, braking control section 56, front and rear Differential limit control unit 5
7 and a left / right differential limiting control unit 58.

The vehicle speed calculating section 71 receives the signals of the respective wheel speeds from the four wheel speed sensors 46 and calculates these signals by using a preset mathematical expression (for example, the respective wheel speeds). The vehicle speed V is obtained (by calculating an average) and output to the first target yaw rate calculator 73, the second target yaw rate calculator 74, the target yaw rate time constant setting unit 77, and the final target yaw rate calculator 78. Is formed.

The curve information calculation section 72 is provided, for example, in FIG.
As shown in the figure, a three-point detecting section 72a, a Pn-1 Pn distance calculating section 72b, a Pn Pn + 1 distance calculating section 72c, and a length determining section 7
2d, a midpoint calculation unit 72e, a midpoint same distance point calculation unit 72f,
It is mainly composed of a curvature radius calculation unit 72g, a correction unit 72h, and a data reduction unit 72i.

The three-point detecting section 72a outputs the road point data (node) input from the navigation device 61.
, The three points on the road selected by the driver in the traveling direction of the vehicle or the driver are sequentially determined at predetermined intervals (from the side closer to the vehicle) as shown in FIG. Is read as the third point Pn + 1.

From these three read points, the position information of the first point Pn-1 and the second point Pn is obtained from the Pn-1 Pn
The position information of the second point Pn and the third point Pn + 1 is output to the distance calculation unit 72b, and is output to the Pn Pn + 1 distance calculation unit 72c. Pn-1 = (Xn-
1, Yn-1), Pn = (Xn, Yn), Pn + 1 = (Xn +
1, Yn + 1). The representative point of the curve is Pn. Accordingly, the data of the curve of the point P1 is calculated from the points P0, P1, P2, the data of the point P2 is calculated from the points P1, P2, P3,..., And the data of the point Pn is calculated from the points Pn-1, Pn, Pn + 1. Is done.

The Pn-1 Pn distance calculator 72b calculates the first point Pn-1 based on the position information of the first point Pn-1 and the second point Pn input from the three-point detector 72a. Pn-1
And the second point Pn is calculated and output to the length determination unit 72d and the correction unit 72h.

The Pn Pn + 1 distance calculator 72c calculates the second point Pn based on the position information of the second point Pn and the third point Pn + 1 input from the three-point detector 72a. It is configured to calculate a linear distance connecting Pn and the third point Pn + 1 and output the calculated distance to the length determining unit 72d and the correcting unit 72h.

The length determination section 72d calculates the Pn-1 Pn
The linear distance connecting the first point Pn-1 and the second point Pn input from the distance calculator 72b and the second point Pn and the second point Pn input from the Pn Pn + 1 distance calculator 72c. The length of the straight line distance is determined by comparing the straight line distance connecting the third point Pn + 1. Then, each data (position, distance) having the shorter straight-line distance is calculated by the above-mentioned midpoint calculation unit 7.
2e and the correction unit 72g, and outputs the data (position and distance) having the longer linear distance to the midpoint equal distance point calculation unit 72f.

[0104] As a result of the comparison in the length determination section 72d, when both straight distances are determined to be the same length,
Since either of the straight lines may be used, the straight line connecting the first point Pn-1 and the second point Pn is set in advance so as to be treated as a short straight line (the second point Pn and the third point Pn-1). May be treated as a short straight line connecting the point Pn + 1).

The midpoint calculation section 72e calculates half of the shorter straight line distance based on the data (position and distance) of the short straight line input from the length determination section 72d, and calculates the half distance. It is formed so as to determine the position of the midpoint on the shorter straight line. Here, for example, a straight line connecting the first point Pn-1 and the second point Pn is a short straight line, and the middle point is Pn-1, n = (Xn-1, n, Yn-1, n). Then, Pn-1, n = (Xn-1, n, Yn-1, n) = ((Xn-1 + Xn) / 2, (Yn-1 + Yn) / 2)

The data calculated by the midpoint calculation section 72e are output to the midpoint equal distance point calculation section 72f and the curvature radius calculation section 72g.

The midpoint equal distance point calculating section 72f calculates each data (position and distance) of the long straight line inputted from the length determining section 72d and the shorter straight line inputted from the midpoint calculating section 72e. From the data of half the straight line distance, a midpoint equal distance point is determined on the longer straight line at a position half the distance of the shorter straight line distance from the second point. Here, for example, a straight line connecting the second point Pn and the third point Pn + 1 is a long straight line, and
Assuming that n, n + 1 = (Xn, n + 1, Yn, n + 1), Pn, n + 1 = Pn + PnPn, n + 1 = (Xn, Yn) + K2 · (Xn + 1−Xn, Yn + 1−Yn) = (Xn, n + 1, Yn, n + 1) where K2 = ((Xn−Xn−1) ² + (Yn−Yn−1)
) ² ) ^1/2 / (2 · ((Xn + 1 -Xn) ² + (Yn + 1)
−Yn) ² ) ^1/2 )

The position data of the midpoint and equidistant points Pn, n + 1 calculated by the midpoint and equidistant point calculation unit 72f is output to the curvature radius calculation unit 72g.

The curvature radius calculator 72g calculates the position data of the middle point Pn-1, n input from the middle point calculator 72e and the middle point same distance point Pn calculated by the middle point same distance point calculator 72f. , n + 1, as shown in FIG.
A shorter straight line at the midpoint Pn-1, n (here, Pn-1 Pn
) And the straight line perpendicular to the longer straight line (here, Pn Pn + 1) at the midpoint equidistant point Pn, n + 1 is determined as the center position On of the curve of the traveling road. The radius of curvature Rn of the traveling path is calculated based on the lever center position On. This curvature radius calculator 72g
Is output to the correction unit 72h.

That is, On = Pn-1, n + Pn-1, n On = (Xn-1, n, Yn-1, n) + M. (Yn-Yn-1, Xn-1-Xn) (6) ) On = Pn, n + 1 + Pn, n + 1 On = (Xn, n + 1, Yn, n + 1) + N. (Yn + 1-Yn, Xn-Xn + 1) (7)

Therefore, Xn-1, n + M ・ (Yn-Yn-1) = Xn, n + 1 + N ・ (Yn + 1-Yn) (8) Yn-1, n + M ・ (Xn-1- Xn) = Yn, n + 1 + N. (Xn-Xn + 1) (9)

From the above equations (8) and (9), M is deleted and N
, N = ((Xn-1 -Xn). (Xn-1, n-Xn, n + 1) + (Yn-1 -Yn). (Yn-1, n -Yn, n + 1) ) / (Xn-1.Yn + 1-Xn + 1.Yn-1-Xn-1.Yn + Xn.Yn-1-Xn.Yn + 1 + Xn + 1.Yn) ... (10)

Then, the curve center position On is expressed as On = (Xon, Yon) = (Xn, n + 1 + N.Yn + 1-N.Yn, Yn, n + 1 + N.Xn-N.Xn + 1) ... (11)

Accordingly, the radius of curvature Rn is obtained by the following equation. Rn = ((Xn-Xn-1). (Yn + 1-Yn)-(Xn + 1-Xn). (Yn-Yn-1)) / | ((Xn-Xn-1). (Yn + 1) −Yn) − (Xn + 1−Xn) · (Yn−Yn−1)) | · ((Xon−Xn−1, n) ² + (Yon−Yn−1, n) ² ) ^1/2 … ( 12) When the radius of curvature Rn is positive, the vehicle turns left, and when the radius of curvature Rn is negative, the vehicle turns right.

The distance Lon from the curve center position On to the second point Pn which is a representative point of the curve is obtained by the following equation (13). Lon = ((Xon−Xn) ² + (Yon−Yn) ² ) ^1/2 (13) The correction section 72 h calculates the radius of curvature Rn from the radius of curvature calculation section 72 g and the curve center position On to determine the above-mentioned curve. A difference Deln from the distance Lon to the second point Pn is calculated, and when the difference Deln exceeds an error set value described later, the curvature radius Rn is corrected to always keep the difference Deln within the error set value. Things.

The final curve information (the position (Xn, Yn of the representative point Pn of the curve) of each point corrected by the correction section 72h or not corrected because the difference Deln is equal to or less than the error set value. ), Distance Ln between point Pn-1 and point Pn, final radius of curvature Rn, curve center position On
, The curve angle θn of each point obtained from the angle between the straight line Pn-1 Pn and the straight line Pn Pn + 1, the curve start point Lsn (the point perpendicularly lowered from the curve center position On to the straight line Pn-1 Pn) and the point Pn The distance between -1 and the distance Lssn) from the vehicle position to the representative point of each curve are stored in memory and output to the data reduction section 72i.

The error set value is varied according to both the road width D and the shorter straight-line distance of the length determination unit 72d, and is set as (error set value) = αh · D. (Αh is a constant set according to the shorter linear distance: hereinafter, referred to as a point interval correction coefficient).

As the road width D, the value of the road width obtained from the road shape detecting device 62 is usually adopted. However, when data cannot be obtained from the road shape detecting device 62, for example, The road width D is set based on road type information such as an expressway, a general national road, and a local road obtained from the navigation device 61.
Here, as the road width D increases, the error set value increases and the correction is not performed. This indicates that the radius of curvature Rn increases as the road width increases on an actual road. is there.

The fact that the straight line distance is short means that correction is not performed because the point data is set finely and it can be regarded that the road is correctly represented.

Therefore, the point interval correction coefficient αh is
The shorter the straight line distance, the shorter the point interval correction coefficient αh
Becomes larger, the error set value becomes larger, and no correction is performed. For example, the shorter straight line distance is 20m
Αh = 1.2 for shorter distances below, αh = 0.6 for medium distances less than 100 m, αh for larger distances than 100 m
= 0.3.

The detailed correction by the correction section 72h is shown in FIG.
It is shown in FIG. The vector from Pn-1 to Pn is represented by B1ve (subscript
ve indicates a vector), and the vector from P2 to P3 is B2ve (subscript ve indicates a vector)
B1ve = (Xn−Xn−1, Yn−Yn−1) = (X
b1, Yb1), B2ve = (Xn + 1-Xn, Yn + 1-Yn)
= (Xb2, Yb2).

[0122]

The angle θn between B1ve and B2ve is cos θn = (Xb1 · Xb2 + Yb1 · Yb2) / (| B1ve |
・ ｜ B2ve ｜)

The error (ratio) Pdeln between Lon and Rn is: Pdeln = Rn / Lon = cos (θn / 2) = ((cos θn + 1) / 2) ^1/2 (14)

Therefore, the difference Deln between Lon and Rn is as follows. Deln = Lon− | Rn | = Lon · (1-Pdeln) = Lon · (1 − ((cos θn + 1) / 2) ^1/2 ) (15)

Here, the difference Deln is equal to the error set value (αh ·
D), the radius of curvature Rn, Deln =
Correction is performed so as to be αh · D. That is, Lon = Deln / (1 − ((cos θn + 1) / 2) ^1/2 ) = αh · D / (1 − ((cos θn + 1) / 2) ^1/2 ) = αh · D / (1) − ((Xb1 · Xb2 + Yb1 · Yb2 + | B1ve | · | B2ve |) / (2 · | B1ve | · | B2ve |)) ^1/2 ) Rn = Lon · Pdeln = αh · D / (1-((cos θn +1) / 2) ^1/2 ) · ((cos θn +1) / 2) ^1/2 = Αh · D / ((2 / (cos θn + 1)) ^1/2 −1) = αh · D / ((2 · | B1ve | · | B2ve | / (Xb1 · Xb2 + Yb1 · Yb2 + | B1ve | · | B2ve |)) ^1/2 -1) ... (16)

As described above, since the curve information is obtained by the curve information calculation unit 72, point data (nodes) that are not at a constant interval from the navigation device 61 can be used as they are, and data for calculation can be complemented, In particular, the radius of curvature of the traveling road can be quickly and accurately obtained by simple arithmetic processing without performing complicated calculations.

The connection between the respective curve detection points for obtaining the radius of curvature is also natural, and a value accurately representing the actual road shape can be obtained.

Further, a calculation error is also generated to be smaller than the actual radius of curvature of the curve, which is preferable for issuing an appropriate warning in, for example, warning / deceleration control when entering a curve.

Further, by providing the radius of curvature correction section 72h, it is possible to calculate the radius of curvature more accurately, and to vary the error set value used as a reference for correction with the actual road shape and the number of point data. As a result, more accurate calculations can be performed. That is, in order to express that the radius of curvature increases as the road width increases on an actual road, the error setting value increases as the road width increases, and the correction is not performed. In addition, the fact that the straight line distance is short means that the point data (node) is set finely and it can be considered that the road is correctly expressed. Therefore, the shorter the straight line distance is, the larger the error setting value becomes and the correction is performed. No direction.

The data arranging section 72i includes the correcting section 7
The data for each point corrected in 2h is arranged, and unnecessary curve data is arranged to reduce unnecessary calculations.

That is, in the point data (node) from the navigation device 61, one curve may be represented by several points, and even if the curves are separate curves, control is performed on one of the curves. For example, in some cases, control for the other curve can be omitted.

Therefore, in consideration of the above, the data rearranging section 72i applies necessary point data to the case where each point data (node) goes from the point Pn-1 to the point Pn in the following four cases. (Nodes).

Case 1: The curve becomes tight, but the point P
Deceleration distance (= Rn-1 -Rn) from n-1 to point Pn
)) (FIG. 13 (a)) | Rn-1 |> | Rn |, Rn-1 · Rn> 0 and Ln
> | Rn-1 |-| Rn |, the curve information of the points Pn-1 and Pn is required. That is, since there is a margin for deceleration from the point Pn-1 to the point Pn, independent control is required for each of the points Pn-1 and Pn.

Further, since it is considered that the points Pn-1 and Pn represent one curve, the curve angle θn at the point Pn is added to obtain the one curve angle (the entire curve angle θsn). Curve total angle θsn up to point Pn = curve total angle θs (n-1) + 2 · cos ^-1 (Rn / Lon) to case Pn-1 Case 2 ... The curve becomes tight and the point Pn-1 to Pn
When there is no margin in the deceleration distance (= Rn-1 -Rn) before going to (FIG. 13B). | Rn-1 |> | Rn |, Rn-1 · Rn> 0 and Ln
If <| Rn-1 |-| Rn |, the curve information of the point Pn-1 is ignored (reduced). That is, by performing the control on the curve at the point Pn, the control on the curve at the point Pn-1 is absorbed, and the curve information at the point Pn-1 is wasted (reduced) because it becomes useless.

It is also assumed that the points Pn-1 and Pn represent one curve, and the curve angle θn at the point Pn is added in order to obtain this one curve angle (the entire curve angle θsn). Curve total angle θsn up to point Pn = curve total angle θs (n-1) + 2 · cos ⁻¹ (Rn / Lon) to case Pn-1 Case 3 ... The curve becomes loose (FIG. 13 (c)) If | Rn-1 | <| Rn |, Rn-1.Rn> 0, the curve information of the point Pn is ignored (reduced). That is, since the speed is reduced at the point Pn-1, the curve information of the point Pn which is a curve that is gentler than the point Pn-1 becomes unnecessary and is ignored (reduced). If Ln is long and the vehicle accelerates sufficiently (if the points Pn-1 and Pn can be regarded as independent curves), the vehicle speed may increase before reaching the point Pn. Ln
May be stored in accordance with the size of the point Pn.

Further, assuming that the points Pn-1 and Pn represent one curve, the curve angle θn at the point Pn is added to obtain the one curve angle (the entire curve angle θsn). The total angle θsn of the curve up to the point Pn = the total angle θs (n-1) of the curve up to the point Pn−1 + 2 · cos ⁻¹ (Rn / Lon) Note that the points Pn−1 and Pn can be regarded as independent curves. If it is, the curve angle θn at the point Pn is not added, and a new addition is started (determined according to the magnitude of Ln).

Case 4: When the turning direction of the curve is switched (FIG. 13 (d)) Rn-1. If Rn <0, the curve information of the point Pn is necessary. That is, the point Pn-
When going from 1 to the point Pn, since the turning direction is different, the data is not sorted only here.

The total of the curve angles that have continued up to the point Pn-1 is defined as the total curve angle θs (n-1) up to the point Pn-1.

Further, addition is started in order to obtain the total curve angle θsn from the point Pn. The total angle θsn of the curve up to the point Pn = 2 · cos ⁻¹ (Rn / L
on) In addition, in the above cases, when the case where one point is necessary and the case where it is unnecessary overlap, the point is ignored (reduced).

Here, the deceleration distance is defined by the radius of curvature R of the curve.
The reason for calculating the difference between n and Rn-1 is as follows. Assuming that the reference allowable approach speed at the point Pn is Vpn, the deceleration is a, and the allowable lateral acceleration is ayln, the deceleration distance = (Vp (n−1) ² −Vpn ² ) / (2 · a) = (Rn−1 · ayl (n−1) −Rn · ayln) / (2 · a) = (Rn−1−Rn) · ayl / (2 · a) The deceleration a is (１ ／) · 50% of the allowable lateral acceleration ayl. a
yl, deceleration distance = Rn-1-Rn From this result, the deceleration distance can be calculated as the curvature radii Rn and Rn-
It was calculated by the difference of one.

The data organized by the data organizing section 72i is read by the second target yaw rate calculating section 74 as necessary together with the data before organizing.

The first target yaw rate calculation unit 73
Signals (the steering wheel angle θH and the vehicle speed V) from the steering wheel angle sensor 47 and the vehicle speed calculating unit 71 are input, a first target yaw rate γ′1 is calculated, and the first target yaw rate γ′1 is calculated. Target yaw rate deviation (absolute value) calculation unit 75
Output.

That is, the first target yaw rate γ′1
Is the target yaw rate obtained from the vehicle behavior. As in the first embodiment of the present invention, the value of the steady target yaw rate is obtained as the target yaw rate steady value. The target yaw rate γ′1 is calculated by performing a first-order lag processing with the target yaw rate time constant T. Here, the target yaw rate time constant T is, for example, γ′1 = (1 / (1 + Tb · s)) · γ′0 (17) Tb = (m · Lf ·) V) / (2 · L · CPr) (18) m is the vehicle mass, Lf is the distance between the front shaft and the center of gravity, and CPr is the rear equivalent cornering power.

The second target yaw rate calculation unit 74
The navigation device 61, the vehicle speed calculation unit 71,
The signals (vehicle speed V, current position,
The front curvature radius Rn) is read in, a second target yaw rate γ′2 is calculated, and the second target yaw rate γ′2 is output to the target yaw rate deviation (absolute value) calculation unit 75. I have.

That is, the second target yaw rate γ′2
Is a target yaw rate obtained from the road shape, and is calculated by, for example, the following equation (19). γ'2 = V / Rn (19)

The target yaw rate deviation (absolute value) calculating section 75 calculates the first target yaw rate γ′1 from the first target yaw rate calculating section 73 and the second target yaw rate calculating section 74 from the second target yaw rate calculating section 74. γ′2 is input, and the absolute values of these deviations, that is, the target yaw rate deviation (absolute value) | Δγ ′ | (= | γ′1−γ′2 | or | γ′2−
γ′1 |) and calculates the target yaw rate time constant setting unit 7
7 is output.

The steering angular velocity (absolute value) calculation unit 76
The handle angle θH is input from the handle angle sensor 47, the absolute value | δV | of the speed of the handle angle is obtained by performing a differentiation process or the like, and is output to the target yaw rate time constant setting unit 77.

The target yaw rate time constant setting unit 77
The vehicle speed V from the vehicle speed calculator 71, the target yaw rate deviation (absolute value) | Δγ ′ | from the target yaw rate deviation (absolute value) calculator 75, and the steering angular speed (absolute value) from the steering angular speed (absolute value) calculator 76 ΔV | is input, a target yaw rate time constant T is calculated from these input values, and set in the final target yaw rate calculation unit 78.

In the target yaw rate time constant setting unit 77, first, a map in which a reference value (for example, calculated by the equation (18)) is set in advance with the vehicle speed V is determined in advance, and this map is used as a target yaw rate deviation (absolute value). | Δγ '|
A time constant T0 corresponding to the target yaw rate deviation (absolute value) | Δγ '| is set.

The map of the time constant T0 is shown in FIG.
As shown in FIG. 5, as | Δγ ′ |
0 is set to be large, in other words,
The smaller the difference between the target yaw rate (first target yaw rate γ'1) due to the vehicle behavior and the target yaw rate (second target yaw rate γ'2) obtained from the road shape, the smaller the target yaw rate time constant T0 for the predetermined steering. Is set to be large.

Further, a preset map is searched based on the steering angular velocity (absolute value) | δV |, and a time constant T0 corresponding to the target yaw rate deviation (absolute value) | Δγ '|
Is determined, and the time constant T is determined by the product of the correction coefficient K4 and the time constant T0 (T = K4 · T0).

In the map of the correction coefficient K4, for example, as shown in FIG. 16, the larger the steering angular velocity (absolute value) | δV |, the larger the correction coefficient K4 is set, and the faster the steering, the more the target yaw rate time constant T0 is set. Correct to a large value.

That is, the target yaw rate time constant setting unit 77 increases the time constant T as the steering wheel is operated more quickly, despite the small difference between the target yaw rate due to the vehicle behavior and the target yaw rate obtained from the road shape. Correction steering that quickly changes the behavior of the vehicle is detected based on the difference between the target yaw rate due to the vehicle behavior and the target yaw rate obtained from the road shape and the steering angular velocity, and the time constant is determined by that degree. It calculates T.

The final target yaw rate calculating section 78 receives signals (the steering wheel angle θ) from the steering wheel angle sensor 47, the vehicle speed calculating section 71, and the target yaw rate time constant setting section 77.
H, vehicle speed V, target yaw rate time constant T) are input, the final target yaw rate γ's is calculated, and the calculated target yaw rate γ's is output to the yaw rate deviation calculator 79.

In this final target yaw rate calculation section 78,
As in the first embodiment of the present invention, a steady-state target yaw rate value is determined as a target yaw rate steady-state value, and a target yaw rate time constant setting unit 77 determines the target yaw rate steady-state value γ′0. The final target yaw rate γ's is calculated by performing a first-order lag processing with the yaw rate time constant T. That is, γ's = (1 / (1 + T · s)) · γ′0 (20)

Here, as the target yaw rate time constant T increases, the change in the final target yaw rate γ's decreases, and the followability of the value of the final target yaw rate γ's to steering is reduced. Target yaw rate time constant setting unit 7
7, the difference between the target yaw rate due to the vehicle behavior and the target yaw rate obtained from the road shape is small, and the quicker the steering operation, the larger the time constant T is set. Part 78
Thus, the change in the final target yaw rate γ's is set to be small. That is, although the difference between the target yaw rate set from the road shape and the target yaw rate set from the vehicle behavior is small, the steering speedily changes. It is corrected so as to be small, and stable vehicle behavior control without a sense of incongruity for the driver can be realized even during corrective steering.

The yaw rate deviation calculating section 79 receives the actual yaw rate γ from the yaw rate sensor 48 and the final target yaw rate γ's from the final target yaw rate calculating section 78, and calculates the deviation between the actual yaw rate γ and the final target yaw rate γ's. Δγ (= γ−γ ′s) is calculated and output to the braking control unit 56, the front and rear differential restriction control unit 57, and the left and right differential restriction control unit 58. The braking control unit 56, the front / rear differential restriction control unit 57, and the left / right differential restriction control unit 58 are formed as described in the first embodiment of the present invention.

Next, the operation of the above configuration will be described with reference to the flowchart of FIG. FIG. 14 is a flowchart of the vehicle motion control. First, the respective sensor values are read in S401, and the process proceeds to S402. The vehicle speed calculator 71 calculates the vehicle speed V, and the curve information calculator 72 calculates the radius of curvature Rn of the curve of the traveling road. Calculate each curve information.

Next, the process proceeds to S403, where the first target yaw rate calculation unit 73 calculates the target yaw rate based on the vehicle speed V and the steering wheel angle θH.
The first target yaw rate γ′1 is calculated by the above equation (17), and the process proceeds to S404.

In step S404, the second target yaw rate calculation section 74 calculates the above (19) based on the vehicle speed V and the curve information.
The second target yaw rate γ′2 is calculated by the equation.

Then, the flow advances to S405, where the target yaw rate deviation (absolute value) calculating section 75 calculates the absolute value of the deviation between the first target yaw rate γ′1 and the second target yaw rate γ′2.

Thereafter, the flow advances to S 406, where the steering angular velocity (absolute value) calculating section 76 calculates the absolute value | δ of the speed of the steering wheel angle θH.
V | is obtained by performing a differentiation process or the like, and the process proceeds to S407.

In step S407, the target yaw rate time constant setting unit 77 sets the vehicle speed V to a reference value (for example, (18)
Is calculated in advance, and the map is searched for the target yaw rate deviation (absolute value) | Δγ ′ |, and the time constant T0 corresponding to the target yaw rate deviation (absolute value) | Δγ ′ | Setting and steering angular velocity (absolute value)
Search for a preset map based on | δV |
The correction coefficient K4 of the time constant T0 according to the target yaw rate deviation (absolute value) | Δγ '| is determined, and the time constant T is determined by the product of the correction coefficient K4 and the time constant T0 (T = K4 ·
T0).

Here, the target yaw rate time constant setting unit 77 calculates a target yaw rate (first target yaw rate γ′1) based on the vehicle behavior and a target yaw rate obtained from the road shape (second target yaw rate γ′2). Is smaller (the target yaw rate deviation (absolute value) | Δγ ′ |), the faster the steering operation is, the larger the time constant T is set.

Then, the flow advances to S408, where the final target yaw rate calculation unit 78 calculates the steering wheel angle θH, the vehicle speed V, and
Based on the target yaw rate time constant T determined in S407,
The final target yaw rate γ's is calculated by the above equation (20).

Further, the flow proceeds to S 409, where the yaw rate deviation calculator 79 calculates a yaw rate deviation Δγ (= γ−γ ′s) from the actual yaw rate γ and the final target yaw rate γ ′s.

Then, the program proceeds to S410, in which the braking control, the front-rear differential limiting control, and the front-rear differential limiting control routine (FIG. 5) described in the first embodiment of the present invention are performed.
Perform left / right differential limiting control.

As described above, according to the second embodiment of the present invention, the vehicle can be quickly steered despite the small difference between the target yaw rate set from the road shape and the target yaw rate set from the vehicle behavior. Is corrected so that the change in the target yaw rate becomes smaller as the steering speed changes more quickly, and even during the correction steering operation, stable vehicle behavior control that does not give a driver an uncomfortable feeling can be realized.

17 to 19 show a third embodiment of the present invention. FIG. 17 is a functional block diagram of a vehicle motion control device, and FIG. 18 shows a schematic configuration of a vehicle equipped with the vehicle motion control device. FIG. 19 is a flowchart of the vehicle motion control. According to the third embodiment of the present invention, the control for the corrective steering is performed by removing a signal peculiar to corrective steering such as counter steer and inputting the signal from the signal detected by the steering wheel angle sensor. The same reference numerals are given to the same parts as those in the first embodiment of the present invention, and the description will be omitted.

For this reason, in the third embodiment of the present invention,
The control device 80 is formed by a microcomputer and its peripheral circuits, receives signals from the four wheel speed sensors 46, the steering wheel angle sensor 47, and the yaw rate sensor 48, and if necessary, controls the brake as a driving device. A drive signal is output to the drive unit 40, the front and rear differential limiting clutch operating unit 41, and the left and right differential limiting clutch operating unit 42.

As shown in FIG. 17, the control device 80 includes a vehicle speed calculator 81, a filter processor 82, a target yaw rate calculator 83, a yaw rate deviation calculator 84, a brake controller 56, and a front-rear differential limit controller 57. And a left / right differential limiting control unit 58.

The vehicle speed calculating section 81 receives signals of the respective wheel speeds from the four wheel speed sensors 46, and calculates these signals by using a preset mathematical expression (for example, the respective wheel speeds). The vehicle speed V is calculated (by calculating an average) and output to the target yaw rate calculation unit 83.

The filter processing section 82 is configured as a so-called low-pass filter, the cut-off frequency is set to, for example, about 1 to 2 Hz.
From the steering wheel angle θH input from the steering wheel, only a signal of quick steering which is observed at the time of corrective steering such as counter steering is effectively cut. The signal of the steering wheel angle θH filtered by the filter processing unit 82 is defined as θH ′.

The target yaw rate calculating section 83 receives the vehicle speed V from the vehicle speed calculating section 81 and the filtered steering wheel angle θH ′ from the filter processing section 82, calculates the target yaw rate γ ′, and calculates the yaw rate deviation. Arithmetic unit 8
4 is formed.

In the calculation of the target yaw rate γ ′ by the target yaw rate calculation section 83, the value of the steady target yaw rate is obtained as the target yaw rate steady value, as in the first embodiment of the present invention. The target yaw rate γ ′ is calculated by subjecting the value γ′0 to first-order lag processing with the target yaw rate time constant T. Here, the target yaw rate time constant T is, for example, a reference value T set by the vehicle speed according to the equation (18) described in the second embodiment of the invention.
Use b.

That is, the target yaw rate γ ′ is calculated by the following equation (21). γ ′ = (1 / (1 + Tb · s)) · γ′0 (21)

The target yaw rate steady-state value γ′0 is calculated using the filtered steering wheel angle θH ′, and is as follows. γ′0 = (1 / (1 + A · V ² )) · (V / (L · n)) · θH ′ (22)

The yaw rate deviation calculator 84 receives the actual yaw rate γ from the yaw rate sensor 48 and the target yaw rate γ 'calculated from the target yaw rate calculator 83 using the filtered steering wheel angle θH ′.
Deviation Δγ between these actual yaw rate γ and target yaw rate γ '
(= Γ−γ ′) is calculated and output to the braking control unit 56, the front and rear differential restriction control unit 57, and the left and right differential restriction control unit 58. The braking control unit 56, the front / rear differential restriction control unit 57, and the left / right differential restriction control unit 58 are formed as described in the first embodiment of the present invention.

Next, the operation of the above configuration will be described with reference to the flowchart of FIG. FIG. 19 is a flowchart of the vehicle motion control. First, the respective sensor values are read in S501, the process proceeds to S502, the vehicle speed V is calculated by the vehicle speed calculator 81, and the signal of the steering wheel angle θH is filtered by the filter processor 82 ( Handle angle θH ').

Next, the flow proceeds to S503, in which the target yaw rate calculation unit 83 filters the steering wheel angle θH 'with the vehicle speed V.
Based on the above, the target yaw rate γ 'which is not affected by the quick steering signal observed at the time of the correction steering such as the counter steer is calculated by the above equations (21) and (22).

Next, the flow proceeds to S504, where the yaw rate deviation Δγ (= γ−) is calculated from the actual yaw rate γ by the yaw rate deviation calculating section 84 and the target yaw rate γ ′ calculated in S503.
γ ′).

Then, the program proceeds to S505, in which the braking control, the front / rear differential limiting control, the braking / forward / rearward differential limiting control routine (FIG. 5) described in the first embodiment of the present invention are performed.
Perform left / right differential limiting control.

As described above, according to the third embodiment of the present invention, only a quick steering signal observed at the time of correction steering such as countersteering is effectively cut from a steering angle signal and used for control. Therefore, the control does not excessively react to the correction steering, and even during the correction steering, stable vehicle behavior control that does not give a driver a sense of incongruity can be easily realized.

In each of the embodiments of the present invention described above, three types of braking control, front-rear differential limiting control, and left-right differential limiting control are provided, but any one or two of them are provided. It may be provided.

Further, the braking control, the front-rear differential limiting control, and the left-right differential limiting control are other examples (types) as long as the target yaw rate is controlled as one of the parameters for determining the control. Needless to say, the present invention is applicable.

[0187]

As described above, according to the present invention,
The target yaw rate at the time of corrective steering of the vehicle behavior is appropriately set, and stable vehicle behavior control without a sense of incongruity for the driver can be realized.

[Brief description of the drawings]

FIG. 1 is a functional block diagram of a vehicle motion control device according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram illustrating a schematic configuration of a vehicle equipped with the vehicle motion control device according to the first embodiment of the present invention;

FIG. 3 is a flowchart of vehicle motion control according to the first embodiment of the present invention;

FIG. 4 is a flowchart of a target yaw rate time constant calculation / setting routine according to the first embodiment of the present invention;

FIG. 5 is a flowchart of a braking, front-rear, left-right differential limiting control routine according to the first embodiment of the present invention;

FIG. 6 is an explanatory diagram of a time constant set according to the first embodiment of the present invention.

FIG. 7 is a functional block diagram of a vehicle motion control device according to a second embodiment of the present invention.

FIG. 8 is an explanatory diagram showing a schematic configuration of a vehicle equipped with a vehicle motion control device according to a second embodiment of the present invention.

FIG. 9 is an explanatory diagram of a configuration of a part for obtaining a road shape according to the second embodiment of the present invention;

FIG. 10 is an explanatory diagram of an example of point data actually obtained from the navigation device according to the second embodiment of the present invention;

FIG. 11 is a diagram illustrating a method of obtaining a radius of curvature of a curve according to a second embodiment of the present invention.

FIG. 12 is an explanatory diagram of correction of a radius of curvature of a curve obtained according to the second embodiment of the present invention.

FIG. 13 is an explanatory diagram of each case in the data reduction unit according to the second embodiment of the present invention.

FIG. 14 is a flowchart of vehicle motion control according to a second embodiment of the present invention.

FIG. 15 is an explanatory diagram of a target yaw rate time constant basic value set by a target yaw rate deviation (absolute value) according to the second embodiment of the present invention;

FIG. 16 is an explanatory diagram of a basic value correction coefficient set by a steering angular velocity (absolute value) according to the second embodiment of the present invention;

FIG. 17 is a functional block diagram of a vehicle motion control device according to a third embodiment of the present invention.

FIG. 18 is an explanatory diagram showing a schematic configuration of a vehicle equipped with a vehicle motion control device according to a third embodiment of the present invention.

FIG. 19 is a flowchart of vehicle motion control according to a third embodiment of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 3 center differential device 7 rear wheel final deceleration device 21 front and rear differential limiting clutch 33 left and right differential limiting clutch 40 brake driving unit 41 front and rear differential limiting clutch operating unit 42 left and right differential limiting clutch operating unit 46 wheel speed sensor 47 handle angle sensor 48 Yaw rate sensor 49 Lateral acceleration sensor 50 Control device 51 Vehicle speed calculation unit 52 Vehicle slip angle calculation unit 53 Target yaw rate time constant setting unit 54 Target yaw rate calculation unit 55 Yaw rate deviation calculation unit 56 Brake control unit 57 Front-rear differential limit control unit 58 Left and right Differential limit controller

Claims (7)

[Claims] 1. A vehicle motion for controlling a vehicle behavior by calculating a target yaw rate of a vehicle based on a vehicle operating condition including a steering angle and vehicle specifications, and operating a vehicle driving device based on the target yaw rate. A control apparatus for controlling a vehicle motion, wherein the target yaw rate is corrected in accordance with steering for correcting the behavior of the vehicle. 2. The vehicle motion control device according to claim 1, wherein the steering is detected in accordance with an actual yaw rate direction and a vehicle slip angle direction. 3. The vehicle motion control device according to claim 1, wherein the correction of the target yaw rate is set at least according to a vehicle body slip angle. 4. The vehicle motion control device according to claim 1, wherein the correction of the target yaw rate is set at least according to a vehicle speed. 5. The correction of the target yaw rate is performed by calculating an absolute value of a deviation between a target yaw rate calculated from a vehicle operating state including the steering angle and vehicle specifications and a target yaw rate obtained from a curvature radius of a road and a vehicle speed. The vehicle motion control device according to claim 1, wherein the control is performed in accordance with the magnitude and the magnitude of the absolute value of the steering angular velocity. 6. A vehicle motion for calculating a target yaw rate of a vehicle based on a vehicle operating condition including a steering angle and vehicle specifications, and operating a vehicle driving device based on the target yaw rate to control vehicle behavior. In the control device, the input signal of the steering angle used in the calculation of the target yaw rate may be used in the calculation after removing a preset correction steering signal component. 7. A driving device for a vehicle, comprising: a braking device for independently applying a braking force to each selected wheel, a differential limiting device between left and right wheels for limiting differential between left and right wheels, and a differential between front and rear wheels. The vehicle motion control device according to any one of claims 1, 2, 3, 4, 5, and 6, wherein the vehicle motion control device is at least one of a front and rear wheel differential limiting device that restricts the vehicle speed.