JP2523118B2 - Vehicle steering angle control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention, in order to improve the steering stability of a vehicle, when the front wheels are steered according to the steering amount, the front wheels or the rear wheels are assisted by steering. The present invention relates to a corner control device.

(Prior Art) As this type of steering angle control technology, there is one such as that disclosed in Japanese Patent Application Laid-Open No. 60-161266 filed by the present applicant.

This technology, in particular regarding the front wheels, determines the front wheel steering angle by the sum of a steady component proportional to the steering amount and a transient component according to the differential value of the steering amount. By adding a component to the front wheel steering angle and increasing the number of front wheels, it is possible to perform transient control that improves the turning performance of the vehicle at the beginning of turning.

This rudder angle control theory can be applied to the case where the rear wheels are auxiliary steered, and the case where the rear wheels are steered in-phase with the front wheels at high vehicle speed and opposite phase at low vehicle speed will be explained as an example. δ _r is expressed by the following equation.

δ _r = (k−T · S) θ In this equation, k and T are control constants according to the vehicle speed, k is negative at low vehicle speed, positive at high vehicle speed, and T is always positive. Further, S indicates a Laplace operator, and θ indicates a steering angle (steering wheel steering angle). According to the above formula, the rear wheel (steering angle δ _r ) is steered to the opposite phase at low vehicle speed and to the same phase at high vehicle speed by the steady component proportional to steering angle θ (constant K), and added to this. Then, due to the transient component according to the steering angular velocity, the steering wheel is steered in a phase opposite to that of the front wheels, and the transient component can improve the rise of the yaw direction motion during the rotating operation of the steering wheel.

(Problems to be solved by the invention) However, in any case, conventionally, when the arithmetic control amount exceeds the hardware limit value, the limiter is set as the maximum control amount and the further control is not performed. Therefore, the following problems occurred.

That is, for example, in order to avoid an obstacle, as shown in FIG. 8, the steering wheel steering angle θ is set to θ ₁ and then the steering operation is performed to return it to 0, and as a result, the rear wheel steering control amount calculated by the above equation is obtained. Assuming that δ _r is as shown by the one-dot chain line and the control directions of the transient component and the steady component are opposite, even if the calculated value of δ _r is like the one-dot chain line, the actual control amount is As indicated by the solid line, the limit is reached at the hardware limit α. Therefore, during the returning operation of the steering wheel, the control of the transient component corresponding to the hatched portion in FIG. 8 cannot be performed,
The transient characteristic of the steering wheel during the returning operation deteriorates, and the turning delay of the vehicle, which should be eliminated by the transient component, remains unresolved, which gives the driver a feeling of strangeness. This problem occurs not only in the above-described returning operation of the steering wheel, but also during turning.

(Means for Solving Problems) The present invention provides the above-mentioned problem when the steering directions of the stationary component and the transient component are opposite to each other, and in this case, the maximum value of the stationary component is set to the hardware limit or less. If this is done, from the viewpoint that it becomes possible to control by the transient component while changing the steering angle, the maximum control amount of the steady component when the steered direction of the steady component and the transient component is opposite is made smaller than the hardware limit value. It was done.

(Operation) In controlling the steering angle of the wheel by the control amount defined by the steady component and the transient component according to the running condition, the device of the present invention is provided in the case where the steering directions of the steady component and the transient component are opposite. The maximum control amount of the stationary component is made smaller than the hardware limit value.

By the way, when the steered direction of the steady component and the transient component are the same,
The control amount by both these components can be considered as one, and it is sufficient to steer to the hardware limit in order to increase the steering amount and secure the low speed small turning property. The maximum control amount of the component can be regarded as the hardware limit.

Therefore, the maximum control amount of the steady component when the turning direction of the steady component and the transient component are opposite is suppressed below the hardware limit, and there is a margin for controlling the steering angle of the transient component between them. However, the control in the reverse direction can be performed by the component, and the transient turning delay of the vehicle can be eliminated as intended. Therefore, the driver does not feel any discomfort due to this delay in turning, and the driver is safe.

(Example) Hereinafter, the Example of this invention is described in detail based on drawing.

FIG. 1 shows an embodiment of the present invention, in which 1L and 1R represent left and right front wheels, and 2L and 2R represent left and right rear wheels, respectively. A vehicle having these wheels can be steered by steering the left and right front wheels 1L, 1R basically through the steering gear 4 by the steering wheel 3, but the steering angle control device of the present invention described below It is assumed that the front wheels 1L and 1R and the rear wheels 2L and 2R are both auxiliary steered.

That is, for the front wheels, the steering gear 4 is attached to the vehicle body via the front wheel steering angle control actuator 5, and the left and right front wheels 1L and 1R can be assisted by the displacement of the steering gear 4 by the stroke of the actuator. Also, for the rear wheels, these are attached to the vehicle body so that they can be steered,
The rear wheel steering angle control actuators 6 are linked to each other by linking, and the left and right rear wheels 2
Auxiliary steering can be applied to L and 2R.

Hydraulic switching valves 7 and 8 are provided to individually control the strokes of the actuators 5 and 6, and these valves are pump 9
It is assumed that a common hydraulic pressure source constituted by the reservoir 10 and the reservoir 10 is appropriately supplied to the selection chambers of the actuators 5 and 6 to make the actuators 5 and 6 stroke. The changeover valves 7 and 8 are electronically controlled by a controller 11, and this controller receives signals from a steering angle sensor 12 that detects a steering angle θ of the steering wheel 3 and a vehicle speed sensor 13 that detects a vehicle speed V. Signal from the control steering angle sensor 14 that detects the auxiliary steering angle (control steering angle) θ _F of the front wheels from the stroke of the actuator 5, and the auxiliary steering angle (control steering angle) δ _R of the rear wheels to the actuator 6 The signal from the control rudder angle sensor 15 detected from the stroke is input.

The controller 11 calculates the steering angle control amounts of the front and rear wheels from the steering angle θ and the vehicle speed V, and controls the valves 7 and 8 based on the deviation between these and the control steering angles δ _F and δ _R to control the steering angle δ _F. , δ _R are made to match the calculated values.

The operation of the above embodiment will be described below with respect to the rear wheel steering angle control.

In this rear wheel steering angle control, it is known that it is preferable to determine the rear wheel turning amount δ _r as δ _r = (k−T · S) θ (1) as described above. ing. This calculation is executed by the controller 11 according to the procedure shown in FIG. That is, first, the vehicle speed V is read, and then the control constants k and T are calculated by the following equations on the assumption that the steady side slip angle of the vehicle center of gravity is zero and the yaw rate frequency characteristic is flat.

∵A = C ₂ (IC ₁ l-C ₁ mabl-b ² m ² V ² ) These control constants k and T change with respect to the vehicle speed V as shown in FIGS. 3 and 4, respectively, and k and T have the same sign in the high vehicle speed region where the vehicle speed V is 80 km / h or more, and the above ( Steady-state component kθ in Eq. 1) (a component that produces rear wheel lateral acceleration by steering the rear wheels in-phase in the high vehicle speed range) and transient component −TSθ (rear wheels transiently steer in the opposite direction) Then, the steering direction is opposite to that of the component for eliminating the turning delay of the vehicle).

Thereafter, as shown in FIG. 2, the steering wheel steering angle θ is read, and then the steady component kθ is calculated from the control constant k and the steering angle θ obtained as described above. Then, k and T have the same sign, that is, the stationary component kθ and the transient component −
When the steering direction is opposite to TSθ, the rear wheel control amount δ _r1 based on the steady component kθ is calculated as a function f (kθ) of kθ. Also, k and T have different signs, that is, the stationary component kθ and the transient component −TS.
When the steering direction is the same as θ, the value of kθ is used as it is as the rear wheel control amount δ _r1 based on the steady component kθ. Next, the rear wheel control amount δ _r2 due to the transient component is calculated by δ _r2 = T · S · θ. After that, the final rear wheel steering amount δ _r is _calculated as (δ _r1 −
calculated as a function g (δ _r1 -δ _r2) of [delta] _r2).

The controller 11 calculates the calculated turning amount δ _r and the actual turning angle δ _R
On the basis of the deviation from the above, the hydraulic switching valve 8 is electronically controlled so that the actual turning angle δ _R matches the calculated turning amount δ _r .

By the way, in the present invention, in the above calculation, as shown in FIGS. 5 and 6, the maximum control amount | δ _r1 | _max of the steady component is made smaller than the maximum value of the calculated turning amount | δ _r |
The maximum control amount of the steady component when the steered directions of the steady component and the transient component are opposite is made smaller than the maximum control amount of the steady component when the steered directions of the steady component and the transient component are the same.

On the other hand, when the steering directions of the steady component and the transient component are the same, the control amounts by these components can be considered as one group, and it is sufficient to steer up to the hardware limit α. The control amount can be regarded as the hardware limit α. Therefore, the maximum control amount of the steady component when the steered directions of the steady component and the transient component are opposite to each other is suppressed below the hardware limit α.

Therefore, in the same steering mode as in FIG. 8, the rear wheel steering control amount δ _r is as shown in FIG. 7, the steady component maximum value | δ _r1 | _max.
Is smaller than the hardware limit α, and there is a margin margin Δδ between the two, which enables the steering angle control of the transient component. Therefore, the control corresponding to the hatching portion by the transient component can be performed, and the transient turning delay of the vehicle can be eliminated as intended.

When the control constants k and T have different signs due to traveling conditions such as vehicle speed, that is, when the steered directions of the stationary component and the transient component are always the same, the stationary component maximum value = hardware limit value may be controlled.

(Effect of the Invention) As described above, the steering angle control device of the present invention is configured to set the maximum control amount of the steady component when the steered directions of the steady component and the transient component are opposite to each other below the hardware limit. Even when the control amount of the component is the maximum, the control by the transient component is possible, the transitional turning delay elimination effect by the control can be achieved as intended, and the discomfort due to the turning delay can be eliminated.

[Brief description of drawings]

FIG. 1 is an overall system diagram showing an embodiment of the steering angle control device of the present invention, FIG. 2 is a flow chart showing a rear wheel steering angle calculation procedure of a controller in the device of the same example, and FIGS. 3 and 4 are rear wheels. Diagrams exemplifying the steering angle control constants, FIGS. 5 and 6 show the rear wheel steering amount by the steady component,
FIG. 7 is a time chart showing a rear wheel steering mode by the device of the present invention, and FIG. 8 is a time chart showing a conventional rear wheel steering mode. 1L, 1R …… Front wheel, 2L, 2R …… Rear wheel 3 …… Steering wheel 4 …… Steering gear 5 …… Front wheel steering angle control actuator 6 …… Rear wheel steering angle control actuator 7,8 …… Hydraulic switching valve 11 ...... Controller, 12 …… Steering angle sensor 13 …… Vehicle speed sensor 14,15 …… Control rudder angle sensor

Claims (1)

(57) [Claims] 1. In a device for controlling a steering angle of a wheel by a control amount defined by a steady component and a transient component according to a running condition, the maximum of the steady component when the steered direction of the steady component and the transient component is opposite. A steering angle control device for a vehicle, wherein a control amount is smaller than a hardware limit value capable of being steered by the steering angle control device.