JPH0632242A - Vehicle motion control device - Google Patents

Abstract

(57) [Summary] [Objective] The vehicle motion is controlled by 4WS and braking force control, and the respective systems are used effectively and efficiently according to optimal control sharing according to lateral G and / or longitudinal G. [Constitution] For example, the rear wheel assist steering control and the left / right braking force difference control are both performed at yaw rate F / B (S110-130).
If the lateral G (Y _g ) is a parameter, the control share rate α of both controls is determined according to the detected lateral G (S115). The sharing rate characteristics are set so that the respective sharing rates increase in the effective regions of both controls. In the low lateral G region, the steering angle control that is highly effective is mainly executed in the region, and as the lateral G becomes large in the nonlinear region, the vehicle behavior control is mainly the left and right braking difference control that is also effective in this region. The effect of comprehensive vehicle behavior control 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 vehicle behavior by auxiliary steering control and braking force control.

[0002]

2. Description of the Related Art As a vehicle motion control device, a combination of steering angle control (4WS) by auxiliary steering and brake fluid pressure control (braking force control) is disclosed in Japanese Patent Application Laid-Open No. 2-283555. .

[0003]

According to the above publication, the steering angle control and the brake fluid pressure control for controlling the steering angle adjusting means and the brake fluid pressure adjusting means according to the deviation between the target yaw rate and the generated yaw rate are used together. 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. The device does not have the function of optimizing the sharing of control of both adjusting means when the following points are taken into consideration.

As will be referred to later in FIG. 7, this is due to the lateral distribution of the braking force considered in the area division of the vehicle lateral acceleration and longitudinal acceleration (a), the case of longitudinal distribution (b) and the case of 4WS ( And (c) show the respective yaw rate control effects (each broken line in the figure includes a solid thick line in the case of front-back distribution (b) and a solid thin line in the case of 4WS (c). ) Represents the characteristics in the middle part of the yaw rate control effect characteristic surface), and the left / right distribution control has a certain effect in the entire region, and the front / rear distribution has a large effect in the regions of large lateral acceleration and longitudinal acceleration. 4W
The effect of S decreases with the increase of lateral acceleration and longitudinal acceleration,
There are differences in the characteristics of the effect of each control. Therefore, even if the control by the lateral distribution of the braking force and the steering angle control are used together, the magnitude of the obtained effect varies depending on the state such as the lateral acceleration, and if the control considering this is not performed, Realization of 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 performed, the steering angle control is the main purpose for the purpose of shortening the braking distance. Since the tendency tends to be in a non-linear region, the tendency is more remarkable when the lateral acceleration or the longitudinal acceleration is large. In such a non-linear region, the effect of the steering angle control decreases. If the angle control is used, it is not efficient, and a certain limit is easily reached, resulting in insufficient control, and sufficient control cannot be expected. In this respect as well, how efficiently and optimally combining the two is important, but in the past, when vehicle movement was performed using auxiliary steering control and braking force control, it was performed effectively and efficiently as a whole. There is no consideration of how to do it.

According to the present invention, from the standpoint of how best to combine the auxiliary steering control and the braking force control, the respective controls are selectively used in the effective areas of both controls to improve the overall control of vehicle behavior. Therefore, 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 device is provided. In a vehicle in which the front wheels and / or the rear wheels can be subjected to auxiliary steering control, and the braking force of each wheel can be controlled, the auxiliary steering control is performed so that the auxiliary steering angle of the control target wheel in the auxiliary steering control reaches a target value. Means, a braking force control means for controlling the braking force of the wheel to be controlled in the braking force control to a target value, a running state detecting means for detecting the running state of the vehicle including the steering state of the steering wheel, and the vehicle The yaw rate detection means for detecting the yaw rate occurring in the vehicle, the target yaw rate setting means for setting the target yaw rate based on the output of the running state detection means, the deviation calculation means for calculating the deviation between the target yaw rate and the generated yaw rate, and the vehicle Rear acceleration and / or longitudinal acceleration detection means for detecting the generated lateral acceleration and / or longitudinal acceleration, and detection by the detection means In the auxiliary steering control, based on the yaw rate deviation and the control allotment ratio, a control allotment ratio setting means for setting a control allotment ratio of the auxiliary steering control and the braking force control according to at least one of lateral acceleration and longitudinal acceleration. The vehicle motion control device includes a target auxiliary steering angle and a calculation unit that calculates a target braking force of a control target wheel in the left-right distribution and / or the front-rear distribution control of the braking force control.

[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 yaw rate is set by the system of the running state detecting means, the target yaw rate setting means, and the yaw rate detecting means, and the deviation between the yaw rate and the generated yaw rate is calculated.The yaw rate deviation is the target value in the auxiliary steering control and the target value in the braking force control, respectively. Is applied to the calculation of the lateral acceleration and / or the longitudinal acceleration detecting means, and the control sharing rate setting means sets the control sharing rate of the auxiliary steering control and the braking force control according to at least one of the detected lateral acceleration and longitudinal acceleration. Then, based on the yaw rate deviation and the control share ratio thus set, the target auxiliary steering angle in the auxiliary steering control and the target braking force of the corresponding control target wheel in the lateral distribution of the braking force control and / or the front / rear distribution control are calculated. Is calculated, the auxiliary steering means controls the calculated target auxiliary steering angle, and the braking force control means calculates the calculated target control angle. Performs control so that the force. Therefore,
The vehicle motion is controlled by the auxiliary steering control and the braking force control, and the effective control of the auxiliary steering control and the braking force control is controlled according to the generated lateral acceleration and / or the longitudinal acceleration of the vehicle. It is possible to decide to exert an effect in the area, enable efficient use, and improve the effect of comprehensive vehicle behavior control.

[0008]

Embodiments of the present invention will now be described 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 which the braking force control system (brake hydraulic pressure control system) is applicable can control the braking force of each wheel independently. In this embodiment, the front and rear wheels have left and right braking forces (braking hydraulic pressure). ) Shall be controlled. Further, regarding the steering angle control (4WS) system, the steering angles of the front wheels and / or the rear wheels can be supplementarily steered, and here, the case where it is applied to the steering angle control system for steering the rear wheels is shown. 1L, 1 in the figure
R indicates the left and right front wheels, and 2L and 2R indicate the left and right rear wheels, respectively. Each wheel has a brake disc 3L, 3R, 4L, 4R, respectively.
And wheel cylinders 5L, 5R, 6L, 6R that apply a braking force (braking force) to each wheel by frictionally sandwiching the brake disc by the supply of hydraulic pressure (hydraulic pressure). When hydraulic pressure is supplied from the pressure servo unit (pressure control unit) 7, each wheel is braked individually.

The pressure servo unit 7 constitutes a braking force control device together with a controller, which will be described later, including this. The pressure servo unit 7 adjusts the hydraulic pressure from the hydraulic pressure generation source 8 by an input control signal, and the wheel cylinders 5L, 5R of each wheel. , 6L, 6R to control the brake fluid pressure (brake fluid pressure). The pressure servo unit 7 is configured to include an actuator for each hydraulic pressure supply system (each channel) on the front and rear wheels. As the actuator, for example, an actuator that can be used for anti-skid control (ABS control) and can control pressure reduction, pressure holding, and pressure increase can be used. In the pressure servo unit 7, the input hydraulic pressure command signal, specifically the front wheel left hydraulic pressure command value P _1A (S), the same right hydraulic pressure command value P _2A (S), is provided with actuators for controlling the hydraulic pressure of each supply system. The braking hydraulic pressures P ₁ to P ₄ are individually adjusted according to the signals of the rear wheel left hydraulic pressure command value P _3A (S) and the right hydraulic pressure command value P _4A (S). Further, the rear wheel auxiliary steering system includes a steering device 31 for steering the rear wheels and a rear wheel steering device 32 for driving the steering device 31, which enables the rear wheels 2L and 2R to be steered. The auxiliary steering system may be configured by a known hydraulic 4WS hydraulic cylinder, pressure servo valve, etc., and the rear wheel steering device 32 constitutes steering angle control means together with a controller described later, and is supplied. The steering device 31 is drive-controlled so as to match the rear wheel steering angle Δ _r with the signal of the rear wheel steering angle command value.

Each of 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 to the controller 9 from a steering angle sensor 11 that detects a steering angle δ (steering wheel angle) of a steering wheel (steering wheel) 10. Signal, the signal from the pedal force sensor 13 that detects the pedaling force F _P of the brake pedal 12, the actual yaw rate (d / dt) that acts on the vehicle
A signal from the yaw rate sensor 14 as a yaw rate detecting means for detecting φ, the wheel speed (rotational speed) of each wheel
Wheel speed sensor 15, 1 for detecting V _w1 , V _w2 , V _w3 , V _w4
The signals from 6, 17, 18 and the signal from a lateral acceleration (lateral G) sensor 19 as a lateral acceleration detecting means for detecting the lateral acceleration Y _g acting on the vehicle are input. The signal from the steering angle sensor is used by itself as a parameter indicating the vehicle traveling state or as a part thereof. The signal from the yaw rate sensor is the yaw rate feedback (F /
It is used as a control parameter in the hydraulic pressure difference control by the method B) and the rear wheel steering angle control. Further, the signal from the wheel speed sensor can be used as information for estimating the vehicle speed when the vehicle speed is used as a control parameter, and when the controller 9 performs the anti-skid control, the wheel speed V _wj (J = 1 to 4) is also used for the anti-skid control by obtaining its differential coefficient (d / dt) V _wj . In the present embodiment, the traveling state of the vehicle is detected based on the steering angle and the vehicle speed. Therefore, the traveling state detecting means includes the steering angle sensor 11 and a part of the controller 9 (vehicle speed estimation calculation described later). Processing part) is equivalent.

The controller 9 corresponding to the braking force control means and the auxiliary steering control means includes a microcomputer and the like, and executes the vehicle behavior control by the braking force control and the rear wheel steering angle control. When controlling the vehicle motion by the yaw rate F / B method so that the vehicle behavior becomes a target characteristic, basically, the target yaw rate, the yaw rate difference value, etc. are calculated in accordance with a control program described later in the arithmetic processing circuit. , Calculating a target wheel cylinder hydraulic pressure value (command value) as a braking force (brake force) control value for each wheel using these calculated values, and a target auxiliary steering amount (command value) as a rear wheel steering angle control value Is calculated and signals corresponding to them are sent to the pressure servo unit 7 and the rear wheel steering device 32
Output to. As a result, the pressure servo unit 7 is used to adjust the hydraulic pressure from the hydraulic pressure generation source 8 so that the actual wheel cylinder hydraulic pressure for each wheel matches the above-mentioned 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 coincide with the target value. In this embodiment, the target yaw rate setting means and the deviation calculation means for calculating the deviation of the yaw rate correspond to a part of the controller 9.

In this case, the controller 9 performs the braking force control by distributing the braking force to the left and right, that is, by controlling the yaw rate F / B braking force to generate a braking force difference between the left and right wheels. The angular control is also performed by the yaw rate F / B control, but in the area where both controls are used together to control the vehicle motion, each control is executed in combination with an appropriate share ratio according to the state of the vehicle. Both controls can be executed independently in their respective areas. For example, the braking force control is not performed during non-braking, the rear wheel steering angle control is performed, but the braking force control and the steering angle control like turning braking are performed. In the area where the vehicle motion can be controlled using and, the control sharing change control according to the vehicle state is also performed. In the present embodiment, the control share of the braking force control and the steering angle control is determined according to the lateral acceleration, and both controls are operated in a more efficient region. By increasing the sharing rate, the effect of the overall control of the vehicle behavior is improved, and at the same time, the control balanced with the braking distance is achieved. Therefore, in order to properly use each control, the arithmetic processing circuit also calculates the control share 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 share ratio. The target auxiliary steering angle in the rear wheel steering control is calculated and the target value is set. Therefore, in the present embodiment, a part of the controller 9 corresponds to each of the control share ratio setting means for setting such a control share ratio and the calculating 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 having the lateral acceleration as a parameter for the above-mentioned control sharing.

FIG. 3 shows an example of a control program executed by the controller 9 for vehicle behavior control including distribution of the braking force to the left and right according to the lateral acceleration and control of changing the share of the rear wheel rudder control. This processing is executed by a regular interrupt at regular time intervals by an operating system (not shown).
In the figure, first, in step S110, a steering angle sensor,
Based on the outputs of the pedaling force sensor, the wheel speed sensor, the yaw rate sensor, and the lateral acceleration sensor, the steering angle δ, each wheel 1L, 1R,
2L, 2R wheel speeds V _w1 to V _w4 , brake pedal force F _P , yaw rate (d / dt) φ, 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 speed (wheel rotation speed) of two non-driving wheels is used, and for example,
In the case of FR cars, V = (V _w1 from the front two wheel speeds V _w1 and V _w2
The vehicle speed (vehicle speed) is calculated from + V _w2 ) / 2, and this is set as the vehicle speed value V.

In the next step S112, the brake pedal force F
_The brake pressure reference value P ₀ is calculated from P. In this embodiment, the reference value P ₀ is calculated by P ₀ = k · F _P. here,
k is a proportional constant determined by vehicle specifications. Further, the reference value P ₀ is not simply proportional to the brake pedal force F _P , but F
_It may be a function of the _P value. That is, it may be obtained as P ₀ = f (F _P ). In this embodiment, the brake is a complete brake-by-wire, but of course, in consideration of fail-safe and the like, the brake pedal 3 and the brake caliper are directly connected to each other at the time of a failure so as to have a hard structure. May be.

Next, for the yaw rate feedback type braking force control and the rear wheel steering angle control, here, step S is used.
At 113, based on the vehicle speed V and the steering angle δ, the target yaw rate (d
/ Dt) Calculate φ _ref . In this embodiment, the target yaw rate is calculated according to the following equation.

## EQU1 ## (d / dt) φ _ref = δ × V (1 + KV ² )-(1) where A is a constant determined by the vehicle wheel base and steering gear ratio, and K is the steering of the vehicle. It is a constant that represents the characteristic. In the next step S114, the yaw rate difference value Δ (d / dt) φ which is the difference between the target yaw rate (d / dt) φ _ref obtained in step S113 and the actual yaw rate (d / dt) φ (actual yaw rate). Is

[Equation 2] Δ (d / dt) φ = (d / dt) φ _ref − (d / dt) φ --- (2)

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

In the figure, which shows an example of the change characteristics of the control share rate α with the lateral acceleration Y _g , the control share rate is the lateral acceleration.
In a small Y _g range, the steering angle control should be the main control (and therefore the braking force control ratio should be small).
α takes a small value (thus, 1-α has a large value), so that the braking force control becomes the center as the lateral acceleration Y _g increases (so that the distribution to the steering angle control side decreases). The characteristic is set as shown in the figure according to the lateral acceleration Y _g so that α takes a large value (therefore, 1-α has a small value).

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

## EQU3 ## 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 feedback control method is not limited to this, and either a differential operation or an integral operation is performed. A control method in which one or both are added may be used. With this configuration, when the braking force control is executed in the main region, the actual yaw rate response and stability of the vehicle with respect to the target yaw rate can be further improved.

However, in this program example, if the target left-right differential pressure ΔP is calculated as described above, then in step S117, the target wheel cylinder hydraulic pressure P _{j of} each wheel is calculated.
Calculate (S). This wheel cylinder hydraulic pressure target value P _j (S)
In the present embodiment, is the ΔP value and the step S1
It is calculated according to the following formula by the calculated reference pressure P ₀ value in 12.

[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)

In this way, in step S117, the target wheel cylinder hydraulic pressure P _{j of} each wheel is related to the braking force control.
(S) is due to the left-right braking force difference distribution, and the value ΔP, which is the control amount, is set by the control share rate α corresponding to the lateral acceleration Y _g at that time, as shown in the above equation 3. The target value of the wheel cylinder hydraulic pressure of the corresponding wheel is set by the sharing ratio according to the acceleration. Here, for the sake of simplicity, the left-right difference is generated only on the front wheel side (in this case, the hydraulic pressure command value is set as shown in the second term on each right side of the equations 4 and 5). ,
(It means that a braking force difference is generated by depressurizing one of the left and right sides and increasing the pressure of the other side), and a left-right difference may be generated by only the rear wheels or both the front and rear wheels.
In such a case, the left / right distribution control may be performed by the one-side pressure reduction control.

After the target wheel cylinder hydraulic pressure P _j (S) value is obtained in step S117, the next step S118,
In S119, it may happen that the value P _j (S) becomes a negative value. In that case, the target wheel cylinder hydraulic pressure P _j (S) is set to a value of 0 to prevent it from becoming a negative value. 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 share rate α.
The target auxiliary steering amount δr (S) for L and 2R is calculated. In this embodiment, the Δr (S) value is calculated according to the following equation.

## EQU8 ## δr (S) = G × Δ (d / dt) φ × (1-α) --- (8) where G is the yaw rate control F / B gain. It is needless to say that the control method including the differential operation and the integral operation may be used here, as in the case of calculating the control amount ΔP of the braking force control. Thus, in step S120, in the steering angle control, the ratio of the rear wheel target auxiliary steering amount δr (S), which is the control amount, is (1-α) depending on the lateral acceleration Y _g at that time as shown in the above equation (8). Will be set by the control share rate.

However, as described above, the target of each wheel
Determine wheel cylinder hydraulic pressure and target rear wheel steering assist amount
Then, in step S130, the control is executed every time this step is executed.
In the power control system, the wheel cylinder hydraulic pressure (block
Brake fluid pressure so that the rake fluid pressure) becomes the target fluid pressure.
Control, and the auxiliary steering in the rear wheel steering angle control system.
The steering angle is controlled so that the rear wheel steering angle matches with the target amount.
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)) is determined individually and pressure servo
It consists of processing to be output to the unit 7,
By supplying the knit to the wheel cylinder hydraulic pressure P of each wheel
₁~ P_FourIs the target hydraulic pressure P_j(S) to control the actual hoi
Cylinder hydraulic pressure P_j(Hydraulic pressure) is adjusted so that
To be given to the wheel cylinders 5L, 6L, 6R
Therefore, specifically, the vehicle behavior is changed by making a difference between the left and right braking forces.
Controlled. In the latter system, the target auxiliary steering amount δr
The process consists of determining and outputting the control signal corresponding to (S).
This signal is input to the rear wheel steering system 32, which
The tearing device 31 is driven and the rear wheel 2L is moved by the above δr (S).
2R will be steered, and the vehicle behavior will be controlled by rear wheel steering.
Controlled. Also, when 0 <α <1, both are activated at the same time.
In the case of control of α value and (1-α) value,
Momo yaw rate F / B control braking force control and rear wheel steering angle control
The vehicle behavior control according to the yaw rate deviation by the combined use of
Is performed, which controls vehicle movement.

By executing the control as described above, in the present embodiment, the vehicle motion can be efficiently controlled by properly using the rear wheel steering angle control and the left / right braking difference control according to the lateral acceleration Y _g. . As can be seen from the characteristics of Equations 3, 4 to 7, Equation 8 and FIG. 4 described above, the region in which the lateral acceleration Y _g is small when the α value is small (according to the control share ratio α, (1
-Α) value is large, and the yaw rate F / B control contribution by the rear wheel steering is large), the steering control is the main vehicle motion control (only 4WS control when α = 0). When the acceleration Y _g is large (that is, the α value is large, and thus the (1-α) value approaches 0), the contribution of 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 can be shifted to the control (finally, 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, and in the high lateral G region, the vehicle behavior is similarly controlled by the yaw rate F / B system braking force control. It is possible to control the vehicle behavior by generating a difference in braking force between the left and right wheels according to the yaw rate deviation and controlling the yawing moment using the braking force difference.
Moreover, the control sharing ratio α of the two controls for controlling the yaw of the vehicle is set to the lateral acceleration Y
It can be changed appropriately according to _g , and both controls can be operated in a more effective area in accordance with the vehicle condition. 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 yaw rate F / B of the vehicle motion, each system can be operated in the most effective area. You can
According to this control, as shown in FIG.
(Rear wheel steering control) and braking force left / right distribution (right / left braking force difference control) can be increased in their respective share ratios, and the yaw rate control effect as shown by the one-dot chain line in the figure can be seen in the lateral acceleration Y _g region. Can be secured.

As shown in FIG. 5 and as shown in FIG. 7, focusing on the lateral acceleration, the yaw rate control effect by the lateral distribution of the braking force (a in FIG. 7) is irrespective of the magnitude of the lateral acceleration. While almost constant effect can be exhibited, the yaw rate F / B4WS has a significant difference depending on the magnitude of the lateral acceleration, and the effect is very large when the lateral acceleration is small, and becomes large as the lateral acceleration increases. The control effect tends to decrease (C in FIG. 7). 4WS
Is essentially effective in the linear range (small rudder angle), the effect decreases when braking is applied, and the effect gradually decreases as the lateral acceleration increases. 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 in the case where the longitudinal acceleration is large), the tendency becomes even larger. In such a non-linear region, 4WS (steering angle The effect of control) is diminished.
On the other hand, the control force left / right distribution control can obtain substantially the same effect in each region of lateral acceleration, and is also effective in a non-linear region of large lateral acceleration. Therefore, as in the present embodiment, by controlling so as to change the control share factor α in accordance with the magnitude of the lateral acceleration Y _g , the rear wheel steering control is a non-linear region in which the lateral acceleration Y _g exhibits a higher effect. In order to be able to fully utilize the effect by making it possible to use it mainly in the area where it is difficult to become, on the other hand, in the area where the lateral acceleration Y _g is large, which is a non-linear area, that effect is Even if the rear wheel steering control is large, the sharing ratio α of the braking force left / right distribution control can be increased so that the effect can be fully utilized and exerted. By changing the control sharing, both controls can be combined. It can be used effectively and the effect of comprehensive control of vehicle behavior can be improved.

From the standpoint of how best to divide the steering angle control and the braking force control, the present control, which can be optimized as described above, is effective for both of these controls. As a result of increasing the sharing in each region and using each control properly, the control efficiency may be good, and even in the case of yaw rate F / B control, deterioration of the control effect such as deterioration of the convergence of the yaw rate. It is also possible to improve the effectiveness of comprehensive vehicle motion control while avoiding deterioration.

Compared with the system in which the magnitude of the yaw rate deviation is viewed and the braking force control is also added when the deviation is large (the braking force control is also introduced), the result is that in the steering angle control, Since the control is no longer effective in a region where it is ineffective (for example, a region where the lateral acceleration is large in the case of FIG. 7), the deviation becomes large as a result, so the braking force control is performed at that time. However, if the steering angle control is insufficient, the braking force control is simply added, and the efficiency is poor and the responsiveness is low. According to the present embodiment, the sharing ratio α is determined according to the lateral acceleration Y _g . Therefore, in the region where the lateral acceleration Y _g is large, the braking force control, which has a large effect from the beginning of the control during braking, is effective. (H × α acts as an apparent gain with respect to the predetermined deviation Δ (d / dt) φ as shown in Expression 3), and the controllability is not deteriorated and the efficiency is high. .

In the above embodiment, the control of the rear wheel steering system is explained 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 the yaw rate deviation is generated, further steering may be performed in addition to the steering state. Further, it goes without saying that the steering angle control is not limited to the rear wheel assist steering, including the case of the above-described modified example, and can also be implemented by assist steering of at least one of the front wheel and the rear wheel.

Further, in the above embodiment, the sharing rate of both controls is set by the lateral acceleration Y _g detected by the lateral acceleration sensor, but the present invention is not limited to this. For example, the longitudinal acceleration can be targeted as a parameter for setting the control share rate α, and the longitudinal acceleration X _g is also detected, and the share rate α is set from the longitudinal and lateral accelerations according to the characteristics shown in FIG. 6, for example. You may do it.

The characteristic shown in FIG. 3 is a cross-sectional view of three portions of the α-value curved surface by a three-dimensional graph.
As can be seen in the characteristic trends of the α value curves A to C at the points, α
The value curved surface is higher on the front side of the figure. Specifically, even if the same Y _g value is applied, the greater the longitudinal acceleration X _g is (the brake is depressed so that a large X _g is generated),
As indicated by α (large), (medium), and (small) in the figure as a representative, the value α has a large value (therefore, the (1-α) value has a small value). Is set to (note that 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. 4 even with this α curved surface characteristic). 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 like the characteristic A,
When the lateral acceleration Y _{g is} also large (that is, both the lateral G and the front-rear G are large), the state is in the non-linear region more and more,
In such a case, it is preferable that the steering angle control (4WS) is not performed and the braking force control is emphasized as much as possible. Therefore, the α value is set to be relatively high even in a region where the lateral acceleration is not relatively large.

On the other hand, even if the lateral acceleration Y _g becomes slightly large, if the longitudinal acceleration X _g is small (the closer to the characteristic B and the characteristic C), the brake is not so depressed in that state, and the degree of nonlinearity is still present. However, it is less than in the above case, and is less likely to be in the linear range. So in such areas,
Since the effect of the steering angle control can also be expected, as shown in the characteristic B, or as seen in the characteristic C, the α value characteristic curved surface is gently raised to take advantage of 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),
The characteristics are as follows. In the non-linear region, the effect of the steering angle control is weakened (the yaw rate control effect in that case decreases as the lateral acceleration increases and the longitudinal acceleration increases). Not only that, the longitudinal acceleration may be added to the parameters. Therefore, when the characteristics of FIG. 6 are applied, the α value is small in the region where the lateral acceleration Y _g and the longitudinal acceleration X _g are small and the non-linear region is unlikely to occur, and therefore the value (1-α) is large and large in the region. The higher the ratio of effective steering angle control, the larger the lateral acceleration Y _g and the longitudinal acceleration X _g , the lower the ratio of effective steering angle control in the non-linear region, while the α value is large. The control shifts the specific gravity to the braking force left / right distribution control (the degree of distribution is increased). Therefore, each control can be effectively used according to X _g and Y _g , and the lateral acceleration Y _g In addition to this, if the longitudinal acceleration X _g is added as a parameter, more detailed control can be performed in this manner. Also in this case, similarly, it is possible to increase the share of each in the effective region of each corresponding control, improve the effect of the control of the overall vehicle behavior, improve the control efficiency, and increase the control energy level. From the viewpoint, the vehicle motion control can be appropriately performed by the yaw rate F / B control. In the case of performing in the above mode, a map search with parameters Y _g and X _g is performed, or, for example, the α value searched in the basic α-Y _g table is corrected by a correction coefficient corresponding to the longitudinal acceleration X _g. You may also call.

As a parameter, the longitudinal acceleration X
_g may be alone. The steering angle control is less effective during braking (during braking, the lateral force of the tire is reduced by the braking force, and the effect of the steering angle control (4WS) is reduced by that amount). It is advantageous to increase the division of labor. In addition, a large longitudinal acceleration means that the brake is stepped on that much, so that the control range in the braking force control can be widened accordingly, and it can be said that this point is also effective.

In the above description, the braking force control side uses the left / right distribution control (left / right braking force difference control). However, the invention is not limited to this, and the braking force front / rear distribution control exhibiting a great effect in a region where lateral acceleration and longitudinal acceleration are large. You may use. The yaw rate control based on the front / rear distribution of the braking force is 4 WS of the yaw rate F / B control.
This is the opposite of the control effect characteristic in the case of, and although the effect is small in the region of small lateral acceleration and longitudinal acceleration, lateral acceleration,
It is effective in a non-linear region where the longitudinal acceleration is large (Fig. 7, B). Therefore, when the braking force control is mainly used in the non-linear region, the control efficiency is improved by using the front / rear distribution control having such characteristics. Braking force control can be carried out in any of left-right distribution, front-rear distribution, left-right and front-rear distribution,
Further, in the combination of left and right and front and rear, the control sharing of themselves may be changed and controlled so as to be effective in light of the characteristics of FIG. 7. The front / rear distribution control may be performed by changing the split point.

Further, when the steering angle control is mainly controlled according to the set share ratio α, when the rear wheel steering angle is controlled to the maximum, not only the share ratio α but also the braking force control is performed. It is also possible to adopt a method of performing. That is, the area where the steering angle control is main is 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 is more effective. I can't. Therefore, even in that case, if the control is executed while maintaining the set share ratio, the control of the vehicle motion is performed mainly by the steering angle control that has reached the limit. Instead, the braking force control may be performed. Further, when the driver releases the brake pedal during braking force control and rear wheel steering control at a certain share rate α during braking, the share rate α is gradually increased to α =
The control effect may be secured by changing it to 0 (a state in which only the rear wheel steering control is performed).

Furthermore, according to the set share rate α,
For example, when the target differential pressure cannot be generated sufficiently while controlling mainly the braking force control by the left and right distribution, the shortage is added by the rear wheel steering angle control regardless of the control share ratio α. It is also possible to adopt a method of performing such control. That is, although the braking force control is the main area, for example, when the reference value P ₀ is so small that the target left-right differential pressure required for the one-side pressure reduction cannot be sufficiently generated (the brake is not stepped too much). In such a case, since the left and right distribution control is the limit and no further effect can be achieved, even in such a case, if the braking force distribution is uniformly maintained at the set control share rate α, the control effect is improved. Has its limits. In such a case, the left and right distribution control at that time may be assisted by the steering angle control which is the other combination control regardless of the set share ratio.

Further, when the above equations 3 and 8 are applied, the feedback gains H and G of both controls are constants. However, considering that the effect changes depending on the region,
G may also be a function of lateral acceleration, for example. Further, for example, the lateral acceleration may be applied to the search parameter by using 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 control is determined according to the lateral acceleration and / or the longitudinal acceleration generated in the vehicle during the control. It is possible to efficiently control the vehicle behavior in accordance with the effective region of each control with the sharing ratio, and it is possible to improve the effectiveness of the overall control of the vehicle motion.

[Brief description of drawings]

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

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

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

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

FIG. 5 is a diagram showing an example of an effect of comprehensive vehicle behavior control accompanying a change in the share rate when the characteristics are the same.

FIG. 6 is a diagram showing an example of a control share ratio characteristic when including longitudinal acceleration.

FIG. 7 is a diagram illustrating the principle of main sharing control, and is a diagram for explaining 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 cylinder 7 Pressure servo unit 8 Hydraulic pressure source 9 Controller 10 Steering wheel 11 Steering angle sensor 12 Brake pedal 13 Tread force sensor 14 Yaw rate sensor 15 to 18 Wheel speed sensor 19 Lateral acceleration sensor 31 Steering device 32 Rear wheel steering device

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location B62D 105: 00 109: 00 111: 00 113: 00 137: 00 (72) Inventor Naoki Maruko Kanagawa 2 Takaracho, Kanagawa-ku, Yokohama City, Japan Nissan Motor Co., Ltd.

Claims (1)

[Claims] 1. In a vehicle in which the front wheel and / or the rear wheel can be controlled by auxiliary steering and the braking force of each wheel can be controlled, the auxiliary steering angle of a control target wheel in the auxiliary steering control is set to a target value. Auxiliary steering control means for controlling, braking force control means for controlling the braking force of the wheel to be controlled in braking force control so as to reach a target value, and running state for detecting the running state of the vehicle including the steering state of the steering wheel Detection means, yaw rate detection means for detecting the yaw rate generated in the vehicle, target yaw rate setting means for setting the target yaw rate based on the output of the running state detection means, and deviation calculation for calculating the deviation between the target yaw rate and the generated yaw rate. Means, and lateral acceleration and / or longitudinal acceleration detection means for detecting lateral acceleration and / or longitudinal acceleration generated in the vehicle, Based on at least one of the lateral acceleration and the longitudinal acceleration detected by the detection means, the control share ratio setting means for setting the control share ratio of the auxiliary steering control and the braking force control, based on the yaw rate deviation and the control share ratio, A vehicle motion control including a target auxiliary steering angle in the auxiliary steering control and a calculation means for calculating a target braking force of a corresponding control target wheel in the left / right distribution and / or the front / rear distribution control of the braking force control. apparatus.