JP2861651B2 - Vehicle motion control device - Google Patents

Abstract

PURPOSE:To control the motion of a vehicle by using 4WS and braking force control and perform effective, efficient and optimum control sharing of each system in response to lateral G and/or longitudinal G in use. CONSTITUTION:A device depends on a yaw rate F/B for rear wheel auxiliary steering control and right and left braking force difference control (S110-130). If a lateral G (Yg) is a parameter, the control sharing rate alpha of both controls is determined according to the detected lateral G (S115). The property of the sharing rate is specified to increase each sharing rate in an effective area for both controls. In a low lateral G area, steering angle control which has great effect in such an area is mainly executed, and along with a large non-linear lateral G area the behavior control of the vehicle is mainly changed into right and left braking force difference control which has effect even in such an area. The total effect of behavior control on the vehicle can be improved.

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, and more particularly to a control device for controlling a vehicle behavior by an auxiliary steering control and a braking force control.

[0002]

2. Description of the Related Art Japanese Unexamined Patent Publication (Kokai) No. 2-283555 discloses an apparatus for controlling the movement of a vehicle, which is a combination of a steering angle control (4WS) by auxiliary steering and a brake fluid pressure control (braking force control). .

[0003]

According to the above publication, the steering angle control means and the brake hydraulic pressure control means for controlling the steering angle adjusting means and the brake hydraulic pressure adjusting means in accordance with the deviation between the target yaw rate and the generated yaw rate are used. Regarding the contents, both controls are performed during braking, only steering angle control is performed during non-braking, or only steering angle control is performed when the yaw rate deviation is small, and both controls are performed when the deviation is large. However, the apparatus does not have the function of optimizing the sharing of control between the two adjusting means when viewed from the following points.

FIG. 7 will be referred to later, but this is based on the lateral distribution of the braking force and the longitudinal distribution (b), and the 4WS case (b), based on the vehicle lateral acceleration and longitudinal acceleration. (C) indicates the respective yaw rate control effects (note that each broken line in the figure includes a solid bold line in the case of front-rear distribution (b) and a solid thin line in the case of 4WS (c). ) Indicates the characteristics in the middle part of each yaw rate control effect characteristic surface), the left-right distribution control has a certain effect in all regions, and the front-rear distribution has a large effect in the region where lateral acceleration and longitudinal acceleration are large. , 4W
The effect of S decreases as the lateral acceleration and longitudinal acceleration increase,
There are differences in the characteristics of the effects of each control. Therefore, even if the control by the left and right distribution of the braking force and the steering angle control are used together, depending on the state of the lateral acceleration or the like, the magnitude of the obtained effect varies, and if the control taking this into account is not performed, Overall, efficient and effective vehicle motion control (vehicle behavior control) cannot be expected. According to the publication, when both the steering angle control and the braking force control are being performed, the steering angle control is mainly performed for the purpose of shortening the braking distance. The tendency is likely to be in the non-linear region, and the tendency is more remarkable when the lateral acceleration and the longitudinal acceleration are larger. In such a non-linear region, the effect of the steering angle control is reduced. The use of angular control is not efficient, and tends to reach a certain limit, leading to insufficient control, so that sufficient control cannot be expected. In this respect, it is important how to combine the two efficiently and optimally.However, conventionally, when the vehicle motion is performed using the auxiliary steering control and the braking force control, it is effectively and efficiently performed as a whole. It doesn't even consider how to do that.

According to the present invention, from the standpoint of how to optimally combine the assist steering control and the braking force control, the respective controls are selectively used in an effective area of both controls to improve the overall control effect of the vehicle behavior. It is an object of the present invention to provide a vehicle motion control device capable of efficiently and appropriately controlling the vehicle motion as a whole.

[0006]

According to the present invention, the following vehicle motion control apparatus is provided. In a vehicle in which at least one of a front wheel and a rear wheel can be subjected to auxiliary steering control and a braking force of each wheel can be controlled, auxiliary steering for controlling an auxiliary steering angle of a wheel to be controlled in the auxiliary steering control to a target value. Control means, braking force control means for controlling the braking force of the wheel to be controlled in the braking force control to a target value, traveling state detection means for detecting the traveling state of the vehicle including the steering state of the steering wheel, Vehicle behavior detecting means for detecting vehicle behavior occurring in the vehicle; target vehicle behavior setting means for setting target vehicle behavior based on the output of the traveling state detecting means; and calculating a deviation between the target vehicle behavior and the generated vehicle behavior. Deviation calculating means, acceleration detecting means for detecting at least one of lateral acceleration and longitudinal acceleration generated in the vehicle, lateral acceleration detected by the detecting means, According to at least one of the rear acceleration when the detected acceleration is small, larger control sharing of the auxiliary steering control,
When the detected acceleration is large, a control sharing ratio setting unit that sets a control sharing ratio so as to set a large control sharing of the braking force control, and a control sharing ratio set by the vehicle behavior deviation and the control sharing ratio setting unit. And a calculating means for calculating a target auxiliary steering angle in the auxiliary steering control and a target braking force of a corresponding control target wheel in at least one of the left-right distribution and the front-rear distribution control of the braking force control. A motion control device for a vehicle to be driven.

[0007]

In the above vehicle motion control device, the vehicle motion is controlled by the auxiliary steering control means and the braking force control means.
The target vehicle behavior is set by the system of the traveling state detection means, the target vehicle behavior setting means, and the vehicle behavior detection means, and the deviation between the target vehicle behavior and the generated vehicle behavior is calculated. Although applied to the calculation of the target value in the power control, the control sharing ratio setting means determines the control sharing of the auxiliary steering control when the detected acceleration is small, according to at least one of the detected lateral acceleration and the longitudinal acceleration of the acceleration detecting means. The control sharing ratio is set so that the control sharing of the braking force control is set to be large when the detected acceleration is large, and the target assist in the auxiliary steering control is set based on the vehicle sharing deviation set as described above. Calculating means for calculating a steering angle and a target braking force of a wheel to be controlled in at least one of left-right distribution and front-rear distribution control of braking force control. Calculated, the steering assist means performs control so that the calculated target assist steering angle, performs control so that the braking force control means is calculated target braking force. Accordingly, the vehicle motion is controlled by the auxiliary steering control and the braking force control, and the control sharing ratio of the auxiliary steering control and the braking force control is controlled in accordance with at least one of the generated lateral acceleration and the longitudinal acceleration of the vehicle during the control. It is possible to determine that the effect can be exerted in an effective area, enable efficient use, and improve the effect of comprehensive vehicle behavior control.

[0008]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 2 shows the configuration of an embodiment of the control device of the present invention. The vehicle to be applied is capable of independently controlling the braking force of each wheel with respect to the braking force control system (brake fluid pressure control system). ) Can be controlled. The steering angle control (4WS) system is capable of assisting the steering angle of the front wheels and / or the rear wheels, and shows a case where the present invention is applied to a steering angle control system for steering the rear wheels. 1L, 1 in the figure
R indicates left and right front wheels, and 2L and 2R indicate left and right rear wheels, respectively. Each wheel has a brake disc 3L, 3R, 4L, 4R, respectively.
And wheel cylinders 5L, 5R, 6L, 6R for applying a braking force (braking force) to each wheel by frictionally holding a brake disc by supplying hydraulic pressure (oil pressure). When supplied with hydraulic pressure from the pressure servo unit (pressure control unit) 7, each wheel is individually braked.

The pressure servo unit 7 constitutes a braking force control device together with a controller to be described later including the pressure servo unit 7. The pressure servo unit 7 adjusts the oil pressure from the oil pressure generation source 8 by an input control signal, and controls the wheel cylinders 5L, 5R of each wheel. , 6L, 6R are controlled. The pressure servo unit 7 is configured to include an actuator for each hydraulic pressure supply system (each channel) on the left and right sides of the front and rear wheels. As the actuator, for example, an actuator that can be used for anti-skid control (ABS control) and that can control pressure reduction, pressure holding, and pressure increase can be used. In the pressure servo unit 7, an input hydraulic pressure command signal, specifically, a front wheel left hydraulic pressure command value P _1A (S), a right hydraulic pressure command value P _2A (S), is provided with an actuator for hydraulic control of each supply system. rear left fluid pressure command value P _3A (S), intended to form a regulating pressure for the braking fluid pressure P ₁ ~ P ₄ individually corresponding to the signal of the right liquid pressure command value P _4A (S). In addition, the rear wheel assist steering system includes a steering device 31 for rear wheel steering and a rear wheel steering device 32 for driving the same, thereby enabling the rear wheels 2L and 2R to be steered. The auxiliary steering system may be constituted by a known hydraulic 4WS hydraulic cylinder, pressure servo valve, etc., and the rear wheel steering device 32 constitutes a steering angle control means together with a controller described later and is supplied. the rear wheel steering angle [delta] _r in response to the signal of the rear wheel steering angle command value for controlling driving the steering device 31 so as to match it.

The above signals to the pressure servo unit 7,
Signals to the rear wheel steering device 32 are supplied from a controller (control unit) 9, which receives signals from a steering angle sensor 11 that detects a steering angle δ (handle angle) of a steering wheel (handle) 10. signal, the actual yaw rate acting signal, the vehicle from depression sensor 13 for detecting a depression force F _P of the brake pedal 12 (d / dt)
Signal from yaw rate sensor 14 as yaw rate detecting means for detecting φ, wheel speed (rotation speed) for each wheel
Wheel speed sensors 15, 1 that detect V _w1 , V _w2 , V _w3 , V _w4
6, 17, 18 signals from, respectively the input signals and the like from the lateral acceleration (lateral G) sensor 19 serving as a lateral acceleration detecting means for detecting a lateral acceleration Y _g acting on the vehicle. The signal from the steering angle sensor itself is used as a parameter representing the vehicle running state or as a part thereof. The signal from the yaw rate sensor is a yaw rate feedback (F /
It is used as a control parameter in the hydraulic pressure difference control by the B) method and the rear wheel steering angle control. Further, the signal from the wheel speed sensor can be used as information for estimating the vehicle body speed when the vehicle speed is used as a control parameter, and when the controller 9 performs anti-skid control, the wheel speed V _wj (J = 1 to 4) is used for the anti-skid control by obtaining its differential coefficient (d / dt) V _{wj and the} like. In the present embodiment, the detection of the traveling state of the vehicle is performed based on the steering angle and the vehicle speed. Therefore, the traveling state detecting means includes a part of the steering angle sensor 11 and a part of the controller 9 (a vehicle speed estimation calculation described later). Processing part).

A controller 9 corresponding to the braking force control means and the auxiliary steering control means includes a microcomputer or the like, and executes vehicle behavior control by braking force control and rear wheel steering angle control. When the vehicle motion is controlled by the yaw rate F / B method so that the vehicle behavior becomes the target characteristic, basically, a target yaw rate, a yaw rate difference value, and the like are calculated in accordance with a control program described later in the arithmetic processing circuit. Calculating a target wheel cylinder fluid pressure value (command value) as a braking force (braking force) control value for each wheel using the calculated values, and a target auxiliary steering amount (command value) as a rear wheel steering angle control value And the signals corresponding to them are sent to the pressure servo unit 7 and the rear wheel steering device 32
Output to This causes the pressure servo unit 7 to adjust the hydraulic pressure from the hydraulic pressure source 8 so that the actual wheel cylinder hydraulic pressure of each wheel matches the above target hydraulic pressure. 5L, 5R,
The rear wheel steering device 32 drives the steering device 31 so that the steering angles of the rear wheels 2L and 2R match the target values. In this embodiment, a part of the controller 9 also corresponds to the target yaw rate setting means and the deviation calculating means for calculating the deviation of the yaw rate.

In this case, the controller 9 performs the above-mentioned braking force control in the present embodiment by means of a left-right distribution of the braking force, that is, a yaw rate F / B braking force control for generating a braking force difference between the left and right wheels. The angle control is also performed by the yaw rate F / B control, but in a region in which both controls are used in combination to control the vehicle motion, the respective controls may be executed in a combination of appropriate sharing ratios according to the state of the vehicle. Both controls can be executed independently in the respective areas.For example, when no braking is performed, the braking force control is not performed, and the rear wheel steering angle control is performed. However, as in the case of turning braking, the braking force control and the steering angle control are performed. In the region where the vehicle motion can be controlled by using the above, the change control of the control sharing according to the state of the vehicle is also performed. In the present embodiment, the control share ratio of the braking force control and the steering angle control is determined in accordance with the lateral acceleration, and both controls are operated in a more efficient region. By increasing the sharing ratio, the effect of controlling the overall vehicle behavior is improved, and control balanced with the braking distance is achieved. For this reason, in order to properly use each control, the arithmetic processing circuit also calculates the control sharing ratio, and when calculating the target value of each control, the target left and right differential pressure of the braking force control is calculated in accordance with the control sharing ratio. A target auxiliary steering angle in the rear wheel steering control is calculated and a target value is set. Therefore, in the present embodiment, a part of the controller 9 also corresponds to the control sharing ratio setting means for setting the control sharing ratio and the calculation means for calculating the target auxiliary steering angle and the target braking force. In this case, the storage circuit of the controller 9 stores the characteristic data using the lateral acceleration for the above-mentioned control sharing as a parameter.

FIG. 3 shows an example of a control program executed by the controller 9 for the vehicle behavior control including the right and left distribution of the braking force according to the lateral acceleration and the control for changing the share ratio of the rear wheel steering control. This processing is performed by a periodic interrupt at a fixed time interval by an operating system (not shown).
In the figure, first, at step S110, a steering angle sensor,
Based on the output of the pedaling force sensor, wheel speed sensor, yaw rate sensor, and lateral acceleration sensor, the steering angle δ, each wheel 1L, 1R,
The 2L and 2R wheel speeds V _w1 to V _w4 , brake depression force F _P , yaw rate (d / dt) φ, and lateral acceleration Y _g are read, respectively.
In the following step S111, the speed of the vehicle body is estimated based on the wheel speed V _wj (j = 1 to 4). In the present embodiment, the wheel speeds (wheel rotation speeds) of the two non-driven wheels are used, for example,
For an FR car, V = (V _w1) from the front two wheel speeds V _w1 and V _w2.
The vehicle speed (vehicle speed) is obtained by calculation from (+ _Vw2 ) / 2, and this is set as the vehicle speed value V.

In the next step S112, the brake pedal force F
Calculating a reference value P ₀ of the brake pressure from _P. In this embodiment, we obtain the reference value P ₀ by _{P 0} = k · F P. here,
k is a proportional constant determined by vehicle specifications. In addition, the reference value P ₀ is not simply proportional to the brake pedal force F _P , but is adjusted so as to match the human feeling.
_It may be a certain function of the _P value. That is, it may be obtained as P ₀ = f (F _P ). In the present embodiment, the brake is completely brake-by-wire. Of course, in consideration of fail-safe and the like, in the event of a failure, the brake is configured to be directly connected to the brake pedal 3 and the brake caliper. You may.

Next, for the yaw rate feedback braking force control and the rear wheel steering angle control, step S
At 113, the target yaw rate (d
/ Dt) Calculate φ _ref . In the present embodiment, the target yaw rate is calculated according to the following equation.

(D / dt) φ _ref = δ × V (1 + KV ² ) (1) where A is a constant determined by the wheelbase and the steering gear ratio of the vehicle, and K is the steering of the vehicle. It is a constant representing the characteristic. In the next step S114, the actual yaw rate and the target yaw rate (d / dt) φ _ref obtained in step S113 (d / dt) φ yaw rate difference value which is the difference between the (actual yaw rate) Δ (d / dt) φ Is

Calculated by Δ (d / dt) φ = (d / dt) φ _ref − (d / dt) φ --- (2)

Next, in step S115, the lateral acceleration
In accordance with Y _g , the control sharing ratio α of both the braking force control and the steering angle control (4WS) is set. Here, in this example, the value α is set as a value within the range of 0 ≦ α ≦ 1, and as shown in Expression 3 (the target left-right differential pressure calculation expression in step S116) and the like, the value α In the example of the program, specifically, it functions as the distribution ratio to the braking force control (therefore, in this case, the distribution ratio to the other steering angle control is 1-α). In order to make effective use of the control effect of the control, for example, the control sharing ratio α is set to a characteristic as shown in FIG.

[0017] In the figure showing an example of change characteristics due to the lateral acceleration Y _g of the control distribution ratio alpha, control sharing rate, lateral acceleration
In the small region of Y _g , the steering angle control is mainly performed (therefore, the ratio of the braking force control is reduced).
α takes a small value (accordingly, 1−α is a large value), and as the lateral acceleration Y _g increases, the braking force control becomes the center (so that the distribution to the steering angle control side decreases). The characteristic is set as shown in the drawing according to the lateral acceleration Y _g so that α takes a large value (accordingly, 1-α is a small value).

Next, in step S116, a target differential pressure to be generated between the left and right wheels is calculated. In the present embodiment, step S
From the yaw rate difference value Δ (d / dt) φ obtained in step 114 and the sharing rate α value obtained by searching according to the lateral acceleration Y _g at that time based on the above characteristics, the left and right wheel cylinders of the controlled wheel are obtained. Is calculated according to the following equation.

ΔP = H × Δ (d / dt) φ × α (3) where H is a constant (F / B gain in yaw rate control) determined by vehicle specifications. In the case of the above three equations, a so-called proportional control method is used as a feedback control method for the yaw rate difference value Δ (d / dt) φ, but the present invention is not limited to this. A control method that adds one or both may be used. With this configuration, when the braking force control is performed in the main region, the response and stability of the actual yaw rate of the vehicle with respect to the target yaw rate can be further improved.

In this example of the program, if the target left-right differential pressure ΔP has been calculated as described above, then in step S117, the target wheel cylinder hydraulic pressure P _{j of} each wheel is calculated.
Calculate (S). The wheel cylinder hydraulic pressure target value P _j (S)
Is the value of ΔP and the value of step S1
By calculating the reference pressure P ₀ value at 12, it is calculated according to the following equation.

[Equation 4] P ₁ (S) = P ₀ − (1/2) · ΔP --- (4)

[Equation 5] P ₂ (S) = P ₀ + (1/2) · ΔP --- (5)

[Equation 6] P ₃ (S) = P ₀ --- (6)

[Equation 7] P ₄ (S) = P ₀ --- (7)

As described above, in step S117, regarding the braking force control, the target wheel cylinder hydraulic pressure P _{j of} each wheel is set.
(S) is based on the distribution of the difference between the left and right braking forces, and the value ΔP, which is the control amount, is set by the control sharing ratio α corresponding to the lateral acceleration Y _g at that time as in the above equation (3). The target value of the wheel cylinder hydraulic pressure of the corresponding wheel is set at the sharing ratio according to the acceleration. Here, for the sake of simplicity, a left-right difference is generated only on the front wheel side. (In this case, the hydraulic pressure command value is as shown in the second term of each right-hand side of Equations 4 and 5. ,
It means that a braking force difference is generated by one of the left and right pressure reduction and the other pressure increase), the rear wheel alone, or the front and rear wheels may generate a left and right difference,
Including the case, the left-right distribution control may be performed by one-side pressure reduction control.

After the target wheel cylinder hydraulic pressure P _j (S) value is determined in step S117, the process proceeds to step S118.
In step S119, the value P _j (S) may be a negative value. In this case, the target wheel cylinder hydraulic pressure P _j (S) is set to a value of 0 to prevent the value from becoming negative. Execute the process.

Next, in step S120, the rear wheel 2 is determined based on the yaw rate difference value Δ (d / dt) φ and the control allotment rate α.
The target auxiliary steering amount δr (S) of L and 2R is calculated. In this embodiment, the Δr (S) value is calculated according to the following equation.

Δr (S) = G × Δ (d / dt) φ × (1-α) (8) where G is the yaw rate control F / B gain. Here, it is needless to say that the control method may include a differential operation and an integral operation as in the case where the control amount ΔP of the braking force control is calculated. In this manner, in step S120, the ratio of (1-α) in which the rear wheel target auxiliary steering amount δr (S), which is the control amount, corresponds to the lateral acceleration Y _g at that time as shown in the above equation (8). Will be set at the control sharing ratio.

Thus, as described above, the target of each wheel
Determine wheel cylinder hydraulic pressure and rear wheel target auxiliary steering amount
After that, in step S130, every time this step is executed,
In the power control system, the wheel cylinder hydraulic pressure (
Rake fluid pressure) to achieve the target fluid pressure.
Control, and the rear steering angle control system
The steering angle is controlled so that the rear wheel steering angle matches the
Control and terminate this program. The processing content is
In the former system, the target wheel cylinder hydraulic pressure P_j(S)
The corresponding control signal (P_jA(S)) individually and pressure servo
It consists of processing to output to the unit 7, and
By supplying to the knit, the wheel cylinder hydraulic pressure P of each wheel
₁~ P_FourIs the target hydraulic pressure P_j(S)
Cylinder pressure P_j(Hydraulic pressure) is adjusted for each wheel
Given to wheel cylinders 5L, 6L, 6R
And, specifically, the vehicle behavior
Controlled. In the latter system, the target auxiliary steering amount δr
The process consists of determining and outputting the control signal corresponding to (S).
The signal is input to the rear wheel steering device 32, which
The tearing device 31 is driven and the rear wheels 2L, δr (S) are
2R is steered, and vehicle behavior is controlled by rear wheel steering.
Is controlled. Also, when 0 <α <1, both are activated at the same time.
In this case, the distribution of the control of the α value and the (1-α) value
Braking force control and yaw rate F / B control and rear wheel steering angle control
Vehicle behavior control according to yaw rate deviation
A vehicle movement is controlled.

[0024] By executing the control as described above, in this embodiment, it is possible to perform efficient control of the vehicle motion distinguish between wheel steering angle control after in accordance with the lateral acceleration Y _g and the left and right brake difference control . As can be seen from the above-described equations (3), (4) to (7), and (8), and the characteristics of FIG. 4, the region where the lateral acceleration Y _g is small when the α value is small (accordingly, (1
-Α) value is large and the contribution of yaw rate F / B control by rear wheel steering is large), the vehicle motion control is mainly steering angle control (when α = 0, only 4WS control), When the acceleration Y _g is large (that is, the α value is large and thus the (1−α) value approaches the value 0), the contribution by the left-right differential pressure ΔP is increased, and the control of the vehicle motion is controlled by the left-right braking force difference. The main control can be shifted to the control (eventually, that is, when α = 1, only the braking force control is performed).

Therefore, in the low lateral G region, the yaw rate F /
By the B-type rear wheel steering angle control, the vehicle behavior can be controlled according to the deviation between the yaw rate and the target yaw rate. In the high-lateral G region, the vehicle behavior is similarly controlled by the yaw rate F / B type braking force control. A difference in braking force is generated between the left and right wheels according to the yaw rate deviation, and the yawing moment is controlled using the difference in braking force to control vehicle behavior.
In addition, the control ratio α of the two controls for controlling the yawing of the vehicle is determined by the lateral acceleration Y generated in the vehicle.
It can be changed appropriately according to _g , and both controls can be operated in a more effective range according to the state of the vehicle. In a vehicle equipped with a steering angle control system (device) and a braking force control system (device) as shown in FIG. 2, in controlling the vehicle motion in yaw rate F / B, it is necessary to operate each system in the most effective area. Can,
According to this control, as shown in FIG.
(Rear wheel steering control) and raised the share of an effective area of each of the braking force right and left distribution (braking force difference control), the such yaw rate control effect shown by the one-dot chain line shown as viewed in the lateral acceleration Y _g region Can be secured.

As shown in FIG. 5 and FIG. 7, when paying attention to the lateral acceleration, the yaw rate control effect (a in FIG. 7) by the left and right distribution of the braking force is independent of the magnitude of the lateral acceleration. While a substantially constant effect can be exerted, the yaw rate F / B4WS has a remarkable difference depending on the magnitude of the lateral acceleration. The effect is extremely large when the lateral acceleration is small, and increases as the lateral acceleration increases. The control effect tends to decrease (c in FIG. 7). 4WS
Is originally effective in the linear region (small steering angle), the effect is reduced when braking is applied, and the effect gradually decreases in the region where the lateral acceleration is large. During braking, the force generated by the tire tends to be in a non-linear region, and when the lateral acceleration is large (and also when the longitudinal acceleration is large), the tendency is further increased. In such a non-linear region, 4WS (steering angle) Control) effect is reduced.
On the other hand, the control force left / right distribution control can obtain substantially the same effect in each region of the lateral acceleration, and is effective even in a nonlinear region where the lateral acceleration is large. Therefore, by performing control to change the control sharing ratio α in accordance with the magnitude of the lateral acceleration Y _g as in the present embodiment, the rear wheel steering control is performed in a non-linear region where the lateral acceleration Y _g is small, which shows a higher effect. In the region where the lateral acceleration Y _g is large, which is a non-linear region, the effect can be sufficiently exerted by making it mainly used on the side of the region where it is difficult to achieve the effect. By increasing the sharing ratio α of the braking force left-right distribution control, which is larger than the rear wheel steering control, the effect can be fully utilized and exerted. Effective use can be performed, and the effect of comprehensive vehicle behavior control can be improved.

From the standpoint of optimally performing the sharing between the steering angle control and the braking force control, the present control, which can optimize the control as described above, is effective for both controls. As a result, the control can be used properly by increasing the allotment in an appropriate area. As a result, control efficiency may be improved, and even in the case of yaw rate F / B control, control effects such as deterioration of convergence of the yaw rate may be obtained. It can also improve the effectiveness of comprehensive vehicle motion control while avoiding deterioration.

When comparing the yaw rate deviation with the system in which the braking force control is also added when the deviation is large (braking force control is also introduced), the result is that in the steering angle control, In a region in which the control is not effective (for example, a region where the lateral acceleration is large in the case of FIG. 7), the control is no longer effective, and as a result, the deviation becomes large. However, since the deviation becomes large and the steering angle control is insufficient, it is merely an addition of the braking force control, and the efficiency is low and the response is low. According to this embodiment, and than share ratio in accordance with the lateral acceleration Y _g alpha is determined, thus the lateral acceleration Y _g large area, a large effect from the beginning of control during braking, the braking force control is effective (H × α acts as an apparent gain on the predetermined deviation Δ (d / dt) φ as in Equation 3), and the efficiency is good without lowering the controllability. .

In the above embodiment, the control of the rear wheel steering system has been described by the yaw rate feedback control. However, not only the control but also the steering is usually performed according to the steering angle.
Only when a yaw rate deviation occurs, the steering may be further performed in addition to the steering state. In addition, the steering angle control is not limited to the rear wheel assist steering including the case of the above-mentioned modified example, and may be carried out for the assist steering of at least one of the front wheel and the rear wheel.

Further, the above embodiment is to set the share of both controlled by the lateral acceleration Y _g detected by the lateral acceleration sensor, but is not limited thereto. For example, the longitudinal acceleration can be targeted as a parameter for setting the control sharing ratio α, the longitudinal acceleration X _g is also detected, and the sharing ratio α is set based on the longitudinal and lateral accelerations, for example, according to the characteristics shown in FIG. You may do so.

The characteristic shown in FIG. 3 is a sectional view of three portions of the α-value curved surface in a three-dimensional graph.
As can be seen from the characteristic trends of the α value curves A to C at the locations,
The value surface is higher toward the front of the figure. Specifically, as the same Y _g is large longitudinal acceleration X _g in value (which brake is depressed enough large becomes X _g occurs),
As shown in the figure, α (large), (medium), and (small) are typically added, so that the value α takes a large value (thus, conversely, the (1-α) value takes a small value). Is set to (X _g
The tendency of the characteristics A, B, and C when viewed in a constant state is the same as the tendency of FIG. More specifically, if the control sharing ratio α = 1 or α ≒ 1, it is only the braking force control or the control center,
In the region where the longitudinal acceleration X _g is large as in the characteristic A,
When the lateral acceleration Y _{g is} also large (that is, both the lateral G and the longitudinal G are large), the state is in an increasingly nonlinear region, and
In such a case, it is preferable that the steering angle control (4WS) does not perform the steering angle control as much as possible, and the braking force control is more important. Therefore, the α value is set high even in a region where the lateral acceleration is not relatively large.

On the other hand, even if the lateral acceleration Y _g is somewhat large, if the longitudinal acceleration X _g is small (closer to the characteristic B or the characteristic C), the brake is not applied so much in that state, and the degree of nonlinearity is still small. Is smaller than in the above case, and is less likely to be in the relative linear region. So in such an area,
Since the effect of the steering angle control can also be expected, as shown in the characteristic B or the characteristic C, the α-value characteristic surface is gently increased in order to utilize the effect of the steering angle control. Since it is effective and efficient to reflect the steering angle control in the vehicle motion control by the value of α), FIG.
The characteristics are as follows. In the non-linear region, the steering angle control is less effective (the yaw rate control effect in that case decreases as the lateral acceleration increases and the longitudinal acceleration increases). In addition, the longitudinal acceleration may be added to the parameter. Therefore, when the characteristic of FIG. 6 is applied, in a region where the lateral acceleration Y _g and the longitudinal acceleration X _g are small and the nonlinear region is hard to be in the nonlinear region, the α value is small, and therefore the value (1−α) is large and large in the region. high percentage of the steering angle control is effective, the lateral acceleration Y _g large, vehicle behavior at higher becomes the longitudinal acceleration X _g large areas, whereas the ratio of the steering angle control falling of effect can be reduced in the nonlinear region, alpha value large In the control, the specific gravity shifts to the braking force left / right distribution control (the distribution degree is increased). Therefore, each control can be effectively used in accordance with X _g and Y _g , and the lateral acceleration Y _g If the longitudinal acceleration X _g is added as a parameter in addition to the above, finer control can be performed in such an embodiment. In this case, similarly, the respective share ratios can be increased in the respective effective areas of the control, and the effect of the control of the overall vehicle behavior can be improved. From the viewpoint, the vehicle motion control can be appropriately performed by the yaw rate F / B control. Note that, in the case of performing the above-described manner, the search is performed by a map search in which the parameters are Y _g and X _g , or, for example, a correction coefficient corresponding to the longitudinal acceleration X _g is added to the α value searched in the basic α-Y _g table. May be applied.

As a parameter, the longitudinal acceleration X
_g may be used alone. In the steering angle control, the effect is reduced during braking (when braking, the lateral force of the tire is reduced by the braking force, and the effect of the steering angle control (4WS) is reduced accordingly). It is advantageous to increase the share of the other. In addition, when the longitudinal acceleration is large, since the brake is depressed accordingly, the control width in the braking force control can be made large accordingly, and it can be said that this point is also effective.

In the above description, the braking force control side employs the left-right distribution control (left-right braking force difference control). However, the present invention is not limited to this. May be used. The yaw rate control based on the front-rear distribution of the braking force is based on 4WS of the yaw rate F / B control.
In contrast to the control effect characteristics in the case of, the effect is small in the region where the lateral acceleration and the longitudinal acceleration are small, but the lateral acceleration,
This is effective in the nonlinear region where the longitudinal acceleration is large (b in FIG. 7). Therefore, in the case where the braking force control is mainly used in the non-linear region, the control efficiency is improved by using the front-rear distribution control of such characteristics. The braking force control can be implemented in any of left-right distribution, front-rear distribution, left-right and front-rear distribution,
Further, in the combination of the left and right and the front and rear, change control may be performed so that their own control sharing is also effective in light of the characteristics shown in FIG. Note that the front-rear distribution control may be based on a split point change.

Further, when the steering angle control is mainly performed according to the set sharing ratio α, and when the rear wheel steering angle is controlled to the maximum, the braking force control is performed not only by the sharing ratio α. It is good also as a method to perform. In other words, the area where the steering angle control is the main area is, for example, an area where the lateral acceleration is small, but when the rear wheels are fully steered in such an area, the steering angle control system has a further effect. I can't. Therefore, in this case, if the control is to be executed while maintaining the set sharing ratio, the vehicle motion is controlled mainly by the steering angle control that has reached the limit, and therefore, regardless of the sharing ratio as described above. Instead, braking force control may be performed. Further, during braking, when the braking force control and the rear wheel steering control are performed at a certain sharing rate α, when the driver releases the brake pedal, the sharing rate α is gradually increased to α =
The control effect may be ensured by changing to 0 (a state in which only the rear wheel steering control is performed).

Further, according to the set sharing ratio α,
For example, when the target differential pressure cannot be sufficiently generated when the control is performed mainly on the braking force control by the left and right distribution, the shortage is added by the rear wheel steering angle control, not only by the control sharing ratio α. It is also possible to adopt a method of performing control that can be performed. That is, albeit at region braking force control the main, for example when the target lateral differential pressure as sufficiently small reference value P ₀ to the extent that can not occur is (brake not depressed much needed at one side vacuum In such a case, since the left-right distribution control is at its limit and no further effect can be obtained, even in such a case, if the braking force distribution is uniformly maintained at the set control sharing ratio α, the control effect will be improved. Has limitations. In such a case, the right and left distribution control at that time may be assisted (assisted) by the steering angle control, which is another combination control, regardless of the set sharing ratio.

Further, when the above equations (3) and (8) are applied, the feedback gains H and G of the two controls are constants.
G may be a function of the lateral acceleration, for example. Further, for example, the lateral acceleration may be applied to a search parameter with an estimated value from other information.

[0038]

According to the present invention, the vehicle motion can be controlled by the auxiliary steering control and the braking force control, and the acceleration is controlled according to at least one of the lateral acceleration and the longitudinal acceleration generated in the vehicle during the control. The control sharing ratio of the auxiliary steering control is set to be large when it is small, and the control sharing ratio is set so that the control sharing of the braking force control is set to be large when the acceleration is large. The vehicle behavior can be efficiently controlled in accordance with the effective area, and the effectiveness of comprehensive vehicle motion control can be improved.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of a vehicle motion control device of the present invention.

FIG. 2 is a system diagram showing one embodiment of the present invention.

FIG. 3 is a flowchart illustrating an example of a control program of a controller in the example.

FIG. 4 is a diagram showing an example of a characteristic of a lateral acceleration-control sharing ratio applicable to the program.

FIG. 5 is a diagram showing an example of the effect of comprehensive vehicle behavior control accompanying a change in the sharing ratio when the characteristics are used.

FIG. 6 is a diagram illustrating an example of a control sharing ratio characteristic including a longitudinal acceleration.

FIG. 7 is a diagram for explaining the principle of the allotment control, which is used to explain the yaw rate control effect.

[Explanation of symbols]

 1L, 1R Left and right front wheels 2L, 2R Left and right rear wheels 3L, 3R, 4L, 4R Brake discs 5L, 5R, 6L, 6R Wheel cylinders 7 Pressure servo unit 8 Oil pressure source 9 Controller 10 Steering wheel 11 Steering angle sensor 12 Brake pedal 13 Tread force sensor 14 Yaw rate sensor 15-18 Wheel speed sensor 19 Lateral acceleration sensor 31 Steering device 32 Rear wheel steering device

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI B62D 105: 00 109: 00 111: 00 113: 00 137: 00 (72) Inventor Naoki Maruko 2 Takaracho, Kanagawa-ku, Yokohama-shi, Kanagawa No. Nissan Motor Co., Ltd. (56) References JP-A-3-239673 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) B62D 6/00

Claims (1)

(57) [Claims] With claim 1 is a at least one of the front wheels及beauty rear wheel supplemental steering control, the controllable vehicle braking force of each wheel, the auxiliary steering angle of the controlled wheel in the auxiliary steering control becomes the target value Steering control means for controlling the vehicle, braking force control means for controlling the braking force of the wheel to be controlled in the braking force control to a target value, and detecting the traveling state of the vehicle including the steering state of the steering wheel Traveling state detecting means, vehicle behavior detecting means for detecting vehicle behavior occurring in the vehicle, target vehicle behavior setting means for setting target vehicle behavior based on the output of the traveling state detecting means, target vehicle behavior and generated vehicle behavior a deviation calculating means for deviation calculating a with at least one lateral acceleration及beauty before after acceleration generated in the vehicle
The auxiliary when the acceleration detecting means that detect a person, according to at least one of the detected lateral acceleration and the longitudinal acceleration by the detecting means, detects the acceleration is small
Set the control share of steering control to be large, and detect
Set the control allotment of the braking force control large
Setting a control allocation rate setting means for setting a control allocation rate, by said vehicle behavior deviation said control sharing rate setting means so as
Based on a control distribution ratio to be a target assist steering angle in the steering assist control, a target braking force of the corresponding controlled wheel in at least one of right and left distribution及beauty before <br/> after distribution control of the braking force control And a calculating means for calculating the vehicle motion.