JPH04293609A - Suspension control device for vehicle - Google Patents

Abstract

PURPOSE:To perform the steering characteristic control so that a vehicle is turned as a driver intends. CONSTITUTION:A turning curvature inference section 11 estimating the turning curvature intended by a driver via inference based on the steering angle detected by a steering angle sensor 6 and the steering angular velocity calculated by a steering angular velocity arithmetic unit 10 and an actual turning curvature inference section 12 estimating the actual turning curvature of a vehicle via inference based on the lateral acceleration detected by the front and rear lateral G sensors 8, 9 are provided, and the damping constants of variable dampers of wheels are determined by an arithmetic section 5 so that the turning curvature estimated by the turning curvature inference section 11 and the actual turning curvature of the vehicle estimated by the actual turning curvature inference section 12 coincide.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a suspension control system for a vehicle such as an automobile, and more particularly to a suspension control system that variably controls the roll stiffness of front and rear wheels for active control of steering characteristics.

0002

2. Description of the Related Art Suspension control devices for vehicles such as automobiles that variably control the roll stiffness of front and rear wheels for active control of steering characteristics have already been proposed.

Conventionally, steering characteristic control using a suspension control device uses a variable damper with a variable damping constant as a damper for each front, rear, left, and right wheel, and uses a G sensor installed at each of the front and rear parts of the vehicle body to control steering characteristics. By controlling the damping constant of the variable damper, the roll stiffness of the rear wheels is adjusted so that, for example, the steering characteristics tend to oversteer at the start of a turn. This makes the roll stiffness of the front wheels higher than that of the rear wheels so that it tends to understeer at the end of a turn, thereby achieving both steering response and stability.

0004

[Problems to be Solved by the Invention] The steering characteristic control by the conventional suspension control device as described above is intended only to control the steering characteristic in transient states such as at the start of a turn and at the end of a turn of the vehicle. This is a significant control for improving steering response at the start of a turn and steering stability at the end of a turn. However, one of the needs for the steering characteristics of a vehicle is to cancel the oversteer and understeer phenomena that occur during a turn so that the vehicle turns rigidly with a turning curvature that matches the turning curvature intended by the driver. However, conventional suspension control devices cannot deal with this problem because they do not take in information about the turning curvature intended by the driver or the actual turning behavior of the vehicle to control steering characteristics. When the steering characteristic is controlled by the device, the turning behavior of the vehicle does not necessarily follow the driver's intention.

The present invention has been made by focusing on the above-mentioned problems in conventional suspension control devices for controlling steering characteristics, and is aimed at ensuring that the turning behavior of the vehicle follows the driver's intention. An object of the present invention is to provide a suspension control device for a vehicle that performs steering characteristic control.

[0006]

[Means for Solving the Problems] According to the present invention, the above object is to provide a suspension control system for a vehicle in which front, rear, left and right wheels are individually suspended by a suspension mechanism including a variable damper having a variable damping constant. A steering angle detection means for detecting a steering angle caused by steering by the driver, a steering angular velocity detection means for detecting a steering angular velocity caused by steering by the driver, and a front portion for detecting lateral acceleration acting on the front portion of the vehicle body. lateral acceleration detection means, rear lateral acceleration detection means for detecting lateral acceleration acting on the rear part of the vehicle body, a steering angle detected by the steering angle detection means, and a steering angular velocity detected by the steering angular velocity detection means. and a turning curvature inference unit that estimates the turning curvature intended by the driver by inference, and a turning curvature inference unit that estimates the turning curvature intended by the driver, and a turning curvature estimation unit that estimates the actual turning curvature of the vehicle based on the lateral acceleration detected by each of the front lateral acceleration detection means and the rear lateral acceleration detection means. an actual turning curvature inference unit that estimates a turning curvature by inference; and a turning curvature intended by the driver estimated by the turning curvature inference unit and an actual turning curvature of the vehicle estimated by the actual turning curvature inference unit. This is achieved by a suspension control device for a vehicle, characterized in that it has a calculation unit that determines the damping constant of the variable damper of each wheel.

[0007]

[Operation] According to the above-described configuration, the turning curvature inferring section estimates the turning curvature intended by the driver, and the actual turning curvature inferring section estimates the actual turning curvature of the vehicle, and these two estimation results match. The damping constant of the variable damper of each wheel is determined based on this, and by controlling the damping constant of the variable damper of each wheel based on this, the vehicle can accurately maintain the turning curvature intended by the driver regardless of the occurrence of oversteer or understeer phenomena. It begins to rotate.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 shows an embodiment of a vehicle suspension control device according to the present invention. Each of the front, rear, left and right wheels of the vehicle is individually suspended from the vehicle body by a suspension mechanism including variable dampers 1, 2, 3 and 4 each having a variable damping constant (not shown).

The variable dampers 1, 2, 3, and 4 are each individually given a damping constant control signal by a damping constant calculating section 5, and the damping constants are individually set variably in accordance with the damping constant control signal. .

A steering angle sensor 6 is provided in the steering section of the vehicle to detect a steering angle θ caused by the driver's steering. The vehicle is also provided with a vehicle speed sensor 7 that detects vehicle speed Cv.

Further, depending on the position of the center of gravity of the vehicle, there is a front lateral acceleration sensor 8 located at the front for detecting lateral acceleration gf acting on the front of the vehicle body, and a front lateral acceleration sensor 8 located at the rear depending on the position of the center of gravity of the vehicle for detecting lateral acceleration gf acting on the rear of the vehicle body. Rear lateral direction G to detect directional acceleration gr
A sensor 9 is provided respectively.

The steering angle θ detected by the steering angle sensor 6 is input to a steering angular velocity calculator 10, and the steering angular velocity calculator 10 calculates a steering angular velocity dθ/dt from the steering angle θ.

The steering angle θ detected by the steering angle sensor 6, the steering angular velocity dθ/dt calculated by the steering angular velocity calculator 10, and the vehicle speed Cv detected by the vehicle speed sensor 7 are input to a turning curvature inference section 11.

The turning curvature inference unit 11 includes a fuzzy inference engine, and receives the steering angle θ and steering angular velocity dθ/ which are inference inputs.
dt are converted into input fuzzy variables according to the membership functions shown in FIGS. 2 and 3 respectively, fuzzy inference is performed according to the fuzzy rules shown in FIG. 4, and the turning intended by the driver is determined as the inference result. The curvature is output as an output fuzzy variable according to the membership function as shown in FIG. By calculation according to the formula, a vehicle speed component is added to the turning curvature intended by the driver to calculate a turning curvature φ that is more accurate than the driver's intention, and this is output to the damping constant calculating section 5. . φ=Sφ・Cv・P However, P is the vehicle speed dependence coefficient of turning curvature. Furthermore, the fuzzy variables of the steering angle θ in this fuzzy inference are PL, PS, Z, NS, NL, and PL is the right turning steering is large, PS indicates a slight right turning steering, Z indicates approximately going straight, NS indicates a slight left turning steering, and NL indicates a large left turning steering. In addition, the fuzzy variables of the steering angular velocity dθ/dt are PL, PS, Z, NS, and NL, where PL is a fast right turn steering, PS is a slow right turn steering, Z is approximately zero, and NS is a slow left turn. Turn steering and NL indicate fast left turn steering, respectively. The fuzzy variables of the turning curvature Sφ are also PL, PS, Z, NS, and NL, where PL is the yaw angular velocity is large in the right turning direction, PS is the yaw angular velocity is small in the right turning direction, Z is approximately zero, and NS is NL indicates that the yaw angular velocity is small in the left turning direction, and NL indicates that the yaw angular velocity is large in the left turning direction.

The lateral acceleration gf detected by the front lateral G sensor 8 and the lateral acceleration gr detected by the rear lateral G sensor 9 are input to an actual turning curvature inference section 12.

The actual turning curvature inference unit 12 includes a fuzzy inference engine, which converts the inference inputs, lateral acceleration gf and gr, into input fuzzy variables according to membership functions as shown in FIGS. 6 and 7, respectively. Fuzzy inference is performed according to the fuzzy rules as shown in Fig. 8, and as an inference result, the actual turning curvature of the vehicle, that is, the actual turning curvature, is expressed as an output fuzzy variable according to the membership function shown in Fig. 9. The fixed value ζ is obtained by the defuzzifier, and this is output to the damping constant calculating section 5.

[0018] Furthermore, the acceleration gf in this fuzzy inference
The fuzzy variables of and gr are PL, PS, Z, NS, NL, where PL has a large rightward lateral acceleration, PS has a little rightward lateral acceleration, Z is approximately straight forward movement, NS has a little leftward lateral acceleration, NL indicates that the leftward lateral acceleration is large. Also, the fuzzy variables of the actual turning curvature ζ are PL, PS
, Z, NS, and NL, where PL indicates that the actual turning curvature is large in the right turning direction, and PS indicates that the actual turning curvature is small in the right turning direction.
Z indicates approximately zero, NS indicates that the actual turning curvature is small in the left turning direction, and NL indicates that the actual turning curvature is large in the left turning direction.

The damping constant calculation section 5 inputs the turning curvature φ intended by the driver from the turning curvature inference section 11 and the actual turning curvature ζ of the vehicle from the actual turning curvature inference section 12, respectively.
Variable dampers 1, 2, and 3 are set so that these two match each other.
, 4, damping constants Dfr, Dfl, D
rr and Drl are calculated. f (φ, ζ) = A (Dfr, Dfl, Drr, Drl)
The damping constant calculation unit 5 calculates damping constants Dfr and Df.
The control signals 1, Drr, and Drl are output to the corresponding variable dampers 1, 2, 3, and 4, respectively. As a result, variable dampers 1, 2,
The damping constants of 3 and 4 are damping constants Dfr and Df
It is variably set according to l, Drr, and Drl, and as a result,
In particular, the front and rear roll rigidities are relatively controlled, allowing the vehicle to accurately turn at the turning curvature intended by the driver, regardless of the occurrence of oversteer or understeer phenomena.

[0020] This front and rear roll rigidity control is performed, for example, when the actual turning curvature is about to become larger than the turning curvature intended by the driver, the roll rigidity of the front wheels is made higher than that of the rear wheels. When attempting to make the turning curvature smaller than the one intended by the operator, the roll stiffness of the rear wheels should be made higher than that of the front wheels.

[0021] Also, the damping constants Dfr, Dfl, Dr
r and Drl may be determined by fuzzy inference using the turning curvature φ intended by the driver and the actual turning curvature ζ of the vehicle as inference inputs.

[0022]

As can be understood from the above description, according to the vehicle suspension control device according to the present invention, the turning curvature inferred by the turning curvature inference section is estimated by the turning curvature intended by the driver.
The actual turning curvature of the vehicle is estimated by the actual turning curvature inference unit, and the damping constant of the variable damper of each wheel is determined so that both estimation results match, and the damping constant of the variable damper of each wheel is controlled accordingly. Therefore, even if an oversteer phenomenon or an understeer phenomenon occurs during a sharp turn, the vehicle can accurately turn at the turning curvature intended by the driver without requiring special driving techniques.

Furthermore, in the vehicle suspension control device according to the present invention, since the turning curvature intended by the driver and the actual turning curvature of the vehicle are determined by inference using fuzzy inference or the like, the acquisition of these data is Compared to cases where logic calculations based on theory, searches using data tables, etc. are used alone, the process can be performed quickly and accurately using a small amount of information.
Further, it is performed without the need for parameter identification, and as a result, steering characteristic control by suspension control becomes compatible with the high control responsiveness required for vehicle driving control.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of a vehicle suspension control device according to the present invention.

FIG. 2 is a graph showing an example of a steering angle membership function used for fuzzy inference of turning curvature intended by a driver.

FIG. 3 is a graph showing an example of a membership function of steering angular velocity used for fuzzy inference of turning curvature intended by the driver.

FIG. 4 is a rule table diagram showing an example of fuzzy rules used for fuzzy inference of turning curvature intended by a driver.

FIG. 5 is a graph showing an example of a membership function of yaw angular velocity used for fuzzy inference of turning curvature intended by a driver.

FIG. 6 is a graph showing an example of a membership function of front lateral acceleration used for fuzzy inference of actual turning curvature.

FIG. 7 is a graph showing an example of a membership function of rear lateral acceleration used for fuzzy inference of actual turning curvature.

FIG. 8 is a rule table diagram showing an example of fuzzy rules used for fuzzy inference of actual turning curvature.

FIG. 9 is a graph showing an example of a membership function of actual turning curvature used for fuzzy inference of actual turning curvature.

[Explanation of symbols]

1~4 Variable damper 5 Damping constant calculation section 6 Steering angle sensor 7 Vehicle speed sensor 8 Front lateral G sensor 9 Rear lateral G sensor 10 Steering angular velocity calculator 11 Turning curvature inference part 12 Actual turning curvature inference part

Claims (1)

[Claims] 1. A suspension control device for a vehicle in which front, rear, left and right wheels are individually suspended by a suspension mechanism including variable dampers each having a variable damping constant.
A steering angle detection means for detecting a steering angle caused by steering by the driver, a steering angular velocity detection means for detecting a steering angular velocity caused by steering by the driver, and a front lateral acceleration for detecting lateral acceleration acting on the front of the vehicle body. A detection means, a rear lateral acceleration detection means for detecting lateral acceleration acting on the rear part of the vehicle body, a steering angle detected by the steering angle detection means, and a steering angular velocity detected by the steering angular velocity detection means. a turning curvature inference unit that estimates a turning curvature intended by a person by inference; and a turning curvature inference unit that estimates the actual turning curvature of the vehicle from the lateral acceleration detected by each of the front lateral acceleration detection means and the rear lateral acceleration detection means. The actual turning curvature inferring unit estimates by inference, and the turning curvature intended by the driver estimated by the turning curvature inferring unit matches the actual turning curvature of the vehicle estimated by the actual turning curvature inferring unit. A suspension control device for a vehicle, comprising: a calculation unit that determines a damping constant of a variable damper for each wheel.