JPH01202580A - Steering angle control device - Google Patents

Abstract

PURPOSE:To obtain an optimum steering angle, when either one steering angle control quantity of front or rear wheel reaches a predetermined value, by changing the other steering angle control characteristic in a manner wherein a change of the yaw rate characteristic of a vehicle is suppressed to a minimum limit. CONSTITUTION:A steering angle control device is provided with hydraulic actuators 11, 12, steering angle control quantity sensors 13, 14, hydraulic valves 15, 16 and a controller 20 which calculates an optimum steering angle control quantity by a car speed signal and a steering angle signal or the like outputting a control signal to the hydraulic valves 15, 16. The controller 20 has a control circuit separately performing respectively a front and rear wheel steering angle control with a car speed V, steering angle theta and a steering angle control quantity delta serving as the input information. This circuit includes a content in which when either one target steering angle control quantity of front or rear wheel reaches a limit value, the other steering angle control characteristic is changed in a direction of suppressing a change of the yaw rate characteristic of a vehicle to a minimum limit.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a steering angle control device that controls the steering angle to an optimum steering angle by auxiliary steering of front and rear wheels depending on the driving condition.

(Prior art) Conventionally, as a steering angle control device, for example,
The one described in Japanese Patent No. 61265 is known.

(Problem to be Solved by the Invention) However, in such a conventional steering angle control device, there are control limits due to mechanical factors of the steering angle (for example, limits on the allowable displacement of the rubber bushing that mounts the gear housing). Even if either the front or rear wheels reach the limit, the steering angle control characteristics of the other wheel will not be changed. There was a problem in that the yaw rate characteristics of the vehicle would be significantly deteriorated.

(Means for Solving the Problems) The present invention has been made for the purpose of solving the above-mentioned problems, and in order to achieve this purpose, the present invention includes the following:
In a steering angle control device including a steering angle control means for controlling the steering angle of each of a front wheel and a rear wheel according to driving conditions, the steering angle control means controls a steering angle control amount of either the front wheels or the rear wheels. When the steering angle reaches a predetermined value, the other steering angle control characteristic is changed in a direction in which a change in the yaw rate characteristic of the vehicle is minimized.

(Function) When the steering angle control amount of either the front wheels or the rear wheels exceeds a predetermined value, the steering angle control means minimizes the steering angle control characteristics of the other wheel to minimize changes in the vehicle's yaw rate characteristics. Control is performed to change the direction in which the

Therefore, even when one steering angle control amount suppresses the mechanical limit, such as when steering from a large steering angle or when operating the steering wheel quickly, the control characteristics of the side that has not yet reached its limit will be changed. This makes it possible to minimize changes in the yaw rate characteristics of the vehicle.

(Example) Embodiments of the present invention will be described below based on the drawings.

In this embodiment, a steering angle control device that controls the steering angles of front and rear wheels using external hydraulic pressure is taken as an example.

First, the configuration will be explained.

As shown in FIG. 1, the vehicle to which the steering angle control device of the embodiment is applied includes a steering wheel 1, a steering link shaft 2, and a power steering gear unit 3 as a front wheel steering device.
, steering rack 4, knuckles 5, 6, front wheel 7.8
It is equipped with

The steering angle control device includes an electronic control system and a hydraulic control system, and includes a hydraulic actuator 11.12 that controls the steering angles of the front wheels 7.8 and the rear wheels 9.10, and each of the hydraulic actuators 11.12. The steering angle control amount δ1. a steering angle control amount sensor 13.14 that detects δ, a hydraulic valve 15.16 that controls the operating amount of the hydraulic actuator 11.12, and an oil pump 17 that supplies hydraulic pressure to the hydraulic valve 15.16. A vehicle speed sensor 18 that detects the vehicle speed V, and a steering angle sensor 19 that detects the steering wheel steering angle θ.
Then, the optimum steering angle control amount is calculated based on the vehicle speed signal, steering angle signal, etc., and the front wheel control signal S1. Rear wheel control signal S.

The controller 20 (rudder angle control means) outputs the following.

The front wheel side hydraulic actuator 11 has its rod 11
a is connected to the steering rack 4, and is arranged so as to drive an increase/decrease in the amount of steering of the front wheels 7.8 relative to the steering wheel steering angle θ when the steering wheel is operated.

The rear wheel side hydraulic actuator 12 has its rod 12
It extends left and right, and is arranged so that the rear wheels 9 and 10 are steered by knuckles 21 and 22 at both ends.

The controller 20 controls vehicle speed V, steering angle θ, and steering angle control amount δ1. This is a control circuit that independently controls the front and rear wheel steering angles using input information such as δ, etc., and the control processing includes:
Target steering angle control amount for either the front wheels 7.8 or the rear wheels 9.10. *(orr*) is the limit value 611111
111 (or 17..), the other steering angle control characteristic is changed in a direction that minimizes the change in vehicle characteristics (yaw rate change).

Next, the effect will be explained.

First, the flow of the steering angle control processing operation performed by the controller 20 will be explained with reference to the flowchart shown in FIG.

In step a, vehicle speed V, steering angle θ, steering angle control value δ1.
δ1. and other necessary control information parameters are read.

In step b, target steering angle control amounts δ,* are determined based on vehicle speed V, steering angle θ, and other necessary control information.

δ and * are obtained by calculation.

In step C, it is determined whether the front wheel side target steering angle control amount R, * exceeds the limit value δTmax.
≦6. . If it is not exceeded by 8, proceed to step f,
δ, *〉δ,. If it exceeds 8, proceed to step d and step e.

In step d, the limit value δfma++ is set to the limit value δfma++ in step b
The target steering angle control amount δ, * is set in place of the value obtained in .

In step e, the target steering angle control amount for the rear wheels obtained in step b is corrected and calculated.

In step f, the rear wheel side target steering angle control amount * is the limit value 6. It is determined whether the value exceeds -8, and 6. *≦
6, □. If it does not exceed δ, proceed to step i, and δ
,*>reactor,. If it exceeds 8, the process advances to step 9 and step h.

In step 9, the limit value 6° is set as the target steering angle control amount * in place of the value obtained in step b.

In step e, the target steering angle control amount for the front wheels obtained in step b is corrected and calculated.

In step i, if both the front and rear wheels do not exceed the limit value, step b; if the front wheel exceeds the limit value, step d, e.
When the rear wheel side exceeds the limit value, the target steering angle control amount δ,* determined in steps g and h.

Actual steering angle control amount 6. Each control signal S, , S, is output from the controller 20 to each hydraulic valve 15, 16 such that , δ, match.

Next, an explanation will be given of the effect when the steering wheel 1 is operated in a step manner when the target steering angle control amounts of the front and rear wheels are controlled by the control transfer function shown in the following equation.

δ, * = (k, +Tf-s)θ - (1)
* = (k, −■, −s)
θ ・ (2) However, θ:
+, T+, kr, T − for the steering wheel steering angle: Constant S nira plus operator based on vehicle specifications and vehicle speed V First, the steering wheel steering angle θ and the steering angle control amount δ1 when the steering wheel 1 is turned stepwise and returned. ．． The characteristics of RO are as shown in FIG.

As shown in the left part of Fig. 4, when the steering wheel 1 is turned, the target steering angle control amount δ,* for the front wheels based on the above equation (1) exceeds the limit value δ1,8. In such a case, the target steering angle control amount δ,* on the front wheel side is set to the limit value δ by the process in step d. , 8 (upper right hatched part).

On the other hand, the steering angle control amount δ on the front wheel side is at the limit value δ1. When reaching a8, the yaw rate generation on the front wheel side decreases, so for the rear wheel side, which has not reached its limit, the yaw rate generation is increased by the process in step e above, and the total yaw rate of the front and rear wheels is changed. The target steering angle control amount δ, *
is corrected (lower right hatched area).

Therefore, even if the front wheels reach their mechanical limit when the steering wheel 1 is turned, the reduction in yaw rate at the front wheels compensates for this at the rear wheels so that there is no change in the total yaw rate, resulting in changes in vehicle characteristics. is kept to a minimum.

Next, as shown on the right side of FIG. 4, when the steering wheel 1 is returned, the target steering angle control amount δ for the rear wheels is
If * exceeds the limit value δ, 7.8,
Through the process in step 9, the rear wheel side steering angle control amount δ,
is suppressed to the limit value δ71.8 (upper right hatched area).

On the other hand, since the steering angle control amount R on the rear wheel side reaches the limit value δ, 118, and the occurrence of yaw rate on the rear wheel side decreases, the process in step h is performed on the front wheel side, which has not reached its limit. By increasing the yaw rate, the target steering angle is controlled so that there is no change in the total yaw rate between the front and rear wheels. is corrected (lower right hatched area).

Therefore, when the handlebar 1 is returned to its original position, the reduction in yaw rate on the rear wheel side is compensated for on the front wheel side so that there is no change in the total yaw rate, and changes in vehicle characteristics are suppressed to a minimum.

Here, we will discuss how to obtain the steering angle correction amount on the side where the limit has not been reached.

First, the total yaw rate φ is expressed by the following equation.

φ=a-C1・β, -b-c,・β, ...(3) However, β: tire slip angle C; cornering power a: distance between center of gravity and distance between center of gravity and rear wheels, subscript f ; Front wheel side subscript r: Rear wheel side Here, for example, in the case of β, →β, −Δβ, in order to maintain the total yaw rate ψ, β, →β, −Δβ1
It is necessary to do this, and this 8β becomes the correction value.

Therefore, β, = β, −Δβ1. β, = β, −△β.

By substituting and into equation (3), the following equation is obtained.

φ=a−Cf・(β,−△β,)−b−C,・(β,−
△β, )... (4) Since the total yaw rate ψ is the same in equations (3) and (4), Δβ1 is calculated as follows: a-C1 △β, = □・Δβ, ・−・(5 )b-c.

becomes.

Although the embodiment has been described above based on the drawings, the specific configuration is not limited to this embodiment.

For example, in the embodiment, the operation in the case of a step-like operation of the steering wheel 1 was described, but the same control is applied when the limit is reached steadily, that is, when the limit is reached when the rear wheels are in the same phase as the front wheels. By doing so, the total yaw rate decreases when the front wheels reach their limit, and the total yaw rate increases when the rear wheels reach their limit, by correcting the steering angle control characteristics on the side that has not reached its limit. can be kept to a minimum.

(Effects of the Invention) As explained above, in the steering angle control device of the present invention, the steering angle control means for controlling the respective steering angles of the front wheels and the rear wheels according to the driving conditions is configured to control the steering angles of the front wheels or the rear wheels. When the steering angle control amount of one of the wheels reaches a predetermined value, the steering angle control characteristics of the other wheel are changed in a direction that minimizes changes in the vehicle's yaw rate characteristics, so large steering wheel operations are required. Even when one side of the steering angle control amount reaches its limit, such as during firefly steering or fast steering operation, the vehicle's yaw rate characteristics can be adjusted by changing the control characteristics of the side that has not yet reached its limit. This has the effect of minimizing changes.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a steering system of a vehicle to which a steering angle control device according to an embodiment of the present invention is applied, FIG. 2 is a flowchart showing the flow of the steering angle control processing operation in the controller, and FIG. Fig. 4 is a time chart of the steering angle control amount and the steering angle control amount during step steering, and Fig. 4 is a time chart of the steering angle control amount showing the control state when the steering angle control amount exceeds the limit value during step steering. be. 11.12...Hydraulic actuator 13.14...Steering angle control amount sensor 15.16...Hydraulic valve 18...Vehicle speed sensor 19-...Handle steering angle sensor 20...Controller patent applicant Nissan Jidosha Co., Ltd.Figure 2Figure 3Figure 4

Claims (1)

[Scope of Claims] 1) A steering angle control device including a steering angle control means for controlling the respective steering angles of a front wheel and a rear wheel according to driving conditions, wherein the steering angle control means controls a steering angle of a front wheel or a rear wheel. A steering angle characterized by being means for changing the steering angle control characteristic of the other one in a direction in which a change in the yaw rate characteristic of the vehicle is minimized when the steering angle control amount of either one reaches a predetermined value. Control device.