JPH0518754B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a steering angle control device for a vehicle that controls the wheel steering angle of a vehicle according to preset motion performance. The present invention relates to a steering angle control device for a vehicle that compensates for a response delay of an actuator that steers wheels.

(Prior Art) Conventionally, the driving performance of a vehicle has been controlled by steering the wheels using actuators that are driven and controlled by an electrical control circuit, without using a mechanical link with a steering wheel. Devices have been proposed to enable this (for example,
There is one shown in No. 59-143772.

This conventional device determines the target value of the steering angle of the front and rear wheels corresponding to the steering angle of the steering wheel according to a preset control law, and uses a servo actuator using a hydraulic cylinder to control the steering angle of the front wheels. and the rear wheels are steered to the above-mentioned target steering angle value.

(Problems to be Solved by the Invention) However, since the above-mentioned actuator is generally a first-order delay system that performs integral action, there is a delay in control response, which is a factor that reduces maneuverability during high-speed driving. Become.

Therefore, it is possible to eliminate the above delay by applying differential compensation to the control system of the actuator.

However, when the above-mentioned steering angle target value is determined using a digital circuit such as a microcomputer, the signal to which the above-mentioned differential compensation is applied is a digital signal. Therefore, if this signal is differentiated using a normal differentiating circuit, it will become a discrete differential value signal, making control inaccurate. That is, in a control system using a digital circuit, it is difficult to perform differential compensation using a differential circuit.

(Means for solving the problems) In order to solve the above problems, the present invention provides the first
It is equipped with the means shown in the figure.

The steering angle target value determining means 102 determines at least one of the front wheels and the rear wheels to be controlled, which corresponds to the steering angle θ _S of the steering wheel detected by the steering angle detecting means 100 and the vehicle speed V detected by the vehicle speed detecting means 101. The reference model calculating means 103 uses a differential equation to set a reference model of a wheel steering actuator having ideal dynamic characteristics as an actuator that steers the controlled object wheel, and When the target angle value is given to the reference model, the wheel steering angle δ ^* and the wheel steering angular velocity δ· ^* are determined using the reference model, assuming that the control target wheel is steered.

The steering angle target value modifying means 104 is provided with a numerical model that simulates the dynamic characteristics of the wheel steering actuator 107 that steers the wheels to be controlled, and uses the numerical model to calculate the reference model calculating means 10.
Based on the calculated value δ ^* of the wheel steering angle and the calculated value δ ^* of the wheel steering angular velocity obtained in step 3, a target value δ# of the wheel steering angle including a compensation component for the dynamic delay of the wheel steering actuator 107 is determined. demand.

The actuator control means 106 detects the detected value δ of the actual steering angle of the control target wheel detected by the actual steering angle detection means 105 and the target value δ# of the wheel steering angle determined by the steering angle target value correction means 104. A command value S is given to the wheel steering actuator 107 so that the deviation becomes zero or minimum.

(Operation) The steering angle target value determined by the steering angle target value determining means 102 is the steering angle of the controlled target wheel necessary for realizing the target driving performance in the own vehicle.

Therefore, if the wheels to be controlled are steered so that the steering angle becomes equal to the target steering angle value, the target driving performance can be achieved in the own vehicle.

Here, as described above, since the wheel steering actuator 107 has an operation delay, differential compensation is required for control.

Therefore, the present invention provides the reference model calculation means 103
and determine the wheel steering angle δ ^* and wheel steering angular speed δ・^* of the wheel to be controlled, assuming that the target value of the steering angle is realized using a wheel steering actuator with ideal dynamic characteristics. Angle target value correction means 10
4, the target value of the wheel steering angle is corrected according to the numerical model of the actual wheel steering actuator 107 using the calculated value δ ^* of the wheel steering angle and the calculated value δ· ^* of the wheel steering angular velocity. conduct.

The target value δ# of the wheel steering angle corrected by the steering angle target value correction means 104 is a value including a compensation component for the dynamic delay of the wheel steering actuator 107, and is controlled by the actuator control means 106 to Actual steering angle δ of the wheel to be controlled and target value δ of the wheel steering angle
The wheel steering actuator 10 is adjusted so that # matches.
7 control is performed.

Thereby, the present invention can perform differential compensation of the control system of the wheel steering actuator 107 without using a normal differential circuit.

(Example) The configuration of one embodiment of the present invention is shown in FIG.

In this embodiment, the steering angles of the rear wheels 48 and 49 are controlled to achieve the target motion performance. The front wheels (not shown) are steered by a mechanical link with a steering wheel (not shown), similar to conventional vehicles.

The rear wheels 48 and 49 are steered by a hydraulic cylinder 40. This hydraulic cylinder 40 includes two left and right hydraulic chambers 41 and 42, and working pressure is supplied to these hydraulic chambers 41 and 42 via oil passages 54 and 55.

The hydraulic pressure difference between the two hydraulic chambers 41 and 42 is determined by the control valve 5.
0, and the piston rod 45 is displaced in response to this oil pressure difference. This displacement of the piston rod 45 is transmitted to the knuckle arms 46, 47 to steer the rear wheels 48, 49. Note that 52 is an oil pump and 53 is a reservoir. Also, 4
3 and 44 are return springs.

The hydraulic cylinder 40 is controlled by controlling the control valve 50 with the control circuit 30.

The control circuit 30 is a digital control circuit composed of a microcomputer or other digital circuit. In the figure, the configuration of the control circuit 30 is shown in a block diagram for easy understanding.

The data input to this control circuit 30 are the vehicle speed V detected by the vehicle speed sensor 22, the steering angle θ _S of the steering wheel detected by the steering wheel angle sensor 21, and the rear wheel actual value detected by the Strooss sensor 23. The steering angle is _δR .

Further, the control circuit 30 outputs a current target value to the current controller 38.

The stroke sensor 23 actually detects the amount of displacement of the piston rod 45;
Since there is a correlation with the actual steering angle of 8 and 49, the detection signal of this stroke sensor 23 can be regarded as a detection signal of the rear wheel actual steering angle.

The control circuit 30 includes a steering angle target value determination unit 3 that determines a rear wheel steering angle target value _R corresponding to the steering angle θ _S and the vehicle speed V in accordance with a preset target motion performance.
1 and the rear wheel steering angle target value _R determined by this steering angle target value determination unit, according to a reference model of a wheel steering actuator having ideal dynamic characteristics,
Rear wheel steering angle command value δ ^* and rear wheel steering angle speed command value δ・^*
Normative actuator model calculation unit 32 for calculating
According to the numerical model of the servo system of the hydraulic cylinder 40 (hereinafter referred to as "self-actuator model"), from the rear wheel steering angle command value δ ^* and the rear wheel steering angular speed command value δ ^* , A steering angle target value correction unit 33 is provided that forms a rear wheel steering angle target value (hereinafter referred to as "corrected rear wheel steering angle target value") including a differential compensation component of the servo system of the hydraulic cylinder 40.

The steering angle target value determining unit 31 includes a numerical model for simulating a vehicle having preset target wheel motion characteristics (hereinafter referred to as a "target vehicle model"), and a numerical model for simulating the motion of the own vehicle. numerical model (hereinafter referred to as "own vehicle model")
It is equipped with The own vehicle model is constructed using the vehicle specifications of the own vehicle.

The steering angle target value determination unit 31 uses the target vehicle model to determine the yaw rate and yaw angular acceleration exhibited by the vehicle model when the steering angle θ _S and vehicle speed V are given, and converts these into the yaw rate target value and the yaw angular acceleration. , yaw angular acceleration target value..., then give these to the own vehicle model and calculate the rear wheel steering angle (rear wheel The steering angle target value _R ) is determined.

Specifically, the yaw rate target value and the yaw angular acceleration target value are determined by the following calculations.

M ₁ (V・_y1 +・₁ V)=2C _F1 +2C _R1 ...(1) I _Z1 ...=2L _F1 C _F1 −2L _R1 C _R1 ...(2) β _F1 =θ _S /N ₁ −(V _y1 +L _F1・₁ )/V …(3) β _R1 =−(V _y1 +L _R1・₁ )/V …(4) C _F1 =K _F1・β _F1 …(5) C _R1 =K _R1・β _R1 ……(6) ‥＝‥ ₁ ……(7) ・＝・₁ ……(8) Here, I _z1 : Yaw inertia of the target vehicle model M ₁ : Body mass of the target vehicle model L _F1 : Distance between the front axle and center of gravity of the target vehicle model L _R1 : Distance between the rear axle and center of gravity of the target vehicle model K _F1 : Cornering power of the front wheels of the target vehicle model K _R1 : Cornering power of the rear wheels of the target vehicle model・₁ : Yaw rate of the target vehicle model... ₁ : Yaw angular acceleration of the target vehicle model V _y1 : Lateral acceleration of the target vehicle model V・_y1 : Lateral acceleration β of the target vehicle model _F1 : Side slip angle of the front wheels of the target vehicle model β _R1 : Side slip angle of the rear wheels of the target vehicle model C _F1 : Cornering force of the front wheels of the target vehicle model C _R1 : Cornering force of the rear wheels of the target vehicle model And the above rear wheel steering angle target value _R is shown below. It can be found by the following calculation.

I _K2 ‥ _F2 = N ₂ K _S2 (θ _S −N ₂ δ _F2 −D _K2 δ・_F2 −2ξ ₂ C _F2 ...(9) M ₂ (V・_y2 +・V)=2C _F2 +2C _R2 ... (10) β _F2 = δ _F2 − (V _y2 +L _F2・)/V …(11) C _F2 = K _F2 β _F2 …(12) C _R2 = (L _F2 C _F2 −1/2‥I _Z2 )/L _R2 ...(13) β _R2 = C _R2 /K _R2 ...(14) _R = β _R2 + (V _y2 −L _Ra・)/V...(15) Here, I _Z2 : Own vehicle Yaw inertia of the model M ₂ : Vehicle weight of the vehicle model L ₂ : Wheelbase of the vehicle model L _F2 : Distance between the front axle and center of gravity of the vehicle model L _R2 : Distance between the rear axle and center of gravity of the vehicle model I _K2 : Steering inertia around the king pin of own vehicle model K _S2 : Steering rigidity of own vehicle model D _K2 : Steering system viscosity coefficient ξ ₂ of own vehicle model : Trail N of own vehicle model ₂ : Steering gear ratio δ of own vehicle model _F2 : Front wheel steering angle of own vehicle model V _y2 : Lateral speed of own vehicle model V・_y2 : Lateral acceleration β of own vehicle model _F2 : Side slip angle of front wheels of own vehicle model β _R2 : Rear wheel of own vehicle model Side slip angle C _F2 : Cornering force of the front wheels of the own vehicle model C _R2 : Cornering force of the rear wheels of the own vehicle model K _F2 : Cornering power of the front wheels of the own vehicle model K _R2 : Cornering force of the rear wheels of the own vehicle model It is power.

As described above, the reference actuator model calculation unit 32 is configured to create a reference model of a wheel steering actuator having ideal dynamic characteristics (that is, in this embodiment, the servo system of the hydraulic cylinder 40 has ideal dynamic characteristics). The reference actuator model is a reference model), and when the above rear wheel steering angle target value _R is given, it is assumed that the rear wheels 48 and 49 are steered by this reference actuator model. Find the rear wheel steering angle and rear wheel steering angle speed. In order to distinguish below, the calculated value of the rear wheel steering angle and the calculated value of the rear wheel steering angle speed obtained here are respectively used as the rear wheel steering angle command value δ _R ^*
and rear wheel steering angular speed command value δ・_R ^* .

Specifically, the reference actuator model calculating section 32 performs the following calculations to obtain the rear wheel steering angle command value δ _R ^* and the rear wheel steering angular speed command value δ· _R ^* .

δ _R ^* =∫δ・_R ^* dt...(16) δ・_R ^* =1/τ _M ( _R δ _R ^* )...(17) Here, τ _M is the time constant of the standard actuator model The time constant τ _M is set to be sufficiently smaller than the time constant of the actual actuator (ie, the servo system of the hydraulic cylinder 40).

The steering angle target value correction unit 33 calculates a corrected rear wheel steering value from the wheel steering angle command value δ _R ^* and the rear wheel steering angle speed command value δ・_R ^* according to the self-actuator model by the following calculation. Calculate the angle target value δ _R #.

δ _R # = 1/A (δ _R ^* + τδ・_R ^* ) ... (18) Here, τ is the time constant of the own actuator model, that is, the time constant of the servo system of the hydraulic cylinder 40. , A is the gain of the same servo system.

Further, the control circuit 30 sends the deviation |δ _R # −δ _R | between the corrected rear wheel steering angle target value δ _R # including the differential compensation component and the rear wheel actual steering angle δ _R | to the current controller 38 as a current target value. give.

The current controller 38 controls the control valve 5 in accordance with the current target value given from the control circuit 30.
0 generates an excitation current i to be applied to the solenoid 51.

Through such control, the actual steering angle _δR and the actual steering angular velocity δ・_R of the rear wheels 48 actually steered by the hydraulic cylinder 40 can be adjusted to the ideal dynamics possessed by the above reference actuator model. It changes according to the characteristics, and the above-mentioned steering angle target value _R is realized. Furthermore, by introducing the rear wheel steering angular velocity command value δ· _R ^* into the servo system, differential compensation of this servo system is performed. This point will be specifically explained.

That is, assuming that no differential compensation is performed, the transmission characteristic between the rear wheel steering angle command value δ _R ^* and the rear wheel actual steering angle δ _R (considering the servo system of the hydraulic cylinder 40) ( ₁₉ ) is a first ^- order lag system _. Here, S is a Laplace operator.

In contrast, in this embodiment, the hydraulic cylinder 4
The transmission characteristic of the servo system at 0 remains unchanged at A/(τs+1), but since the corrected rear wheel steering angle target value δ _R # including the above-mentioned differential compensation component is used as an input, δ _R = A/τs + 1δ _R # ...(20) Here, by substituting the above equation (18) into equation (20), δ _R = A/τs + 1・1/A (δ _R ^* + τδ・_R ^* ) = A/τs + 1・1 + τs/A・δ _R ^* = δ _R ^* ...(21) Therefore, the response of the servo system of the hydraulic cylinder is
It is equal to the responsiveness of the above reference actuator model.

and the time constant τ _M of the normative actuator model
If is set sufficiently small with respect to the frequency of the rear wheel steering angle target value _R , it can be regarded as _R δ _R ^* , so the relationship δ _R δ _R can be obtained from equation (21). That is, the actual actuator (servo system of the hydraulic cylinder 40) has no delay in operation, has extremely high responsiveness, and can steer the rear wheels 48 and 49 to the rear wheel steering angle target value _R.

In addition, in the above-mentioned embodiment, an example was shown in which the rear wheel steering angle is controlled in order to achieve the target driving performance in the own vehicle, but the present invention also includes controlling the front wheel steering angle, By controlling the steering angles of both the front and rear wheels, the vehicle can achieve the desired driving performance. However, when controlling the steering angles of both the front wheels and the rear wheels, the control circuit 30 calculates the steering angle target values of the front wheels and the rear wheels, and
It is necessary to differentially compensate the front and rear wheel servo systems separately using the reference model and own actuator model of the front wheel steering actuator and the reference model and own actuator model of the rear wheel steering actuator.

(Effects of the Invention) As described above in detail, the present invention can achieve a preset target driving performance as the driving performance of the own vehicle by controlling the steering angle of the wheels.

In addition, as a means of compensating for the delay in the operation of the actuator that steers the wheels, a wheel steering actuator with ideal dynamic characteristics is set as a numerical model, and this numerical model is used to apply the force to the actual wheel steering actuator. Calculated values of the steering angle and wheel steering angular velocity are obtained, and further, using a numerical model of the actual wheel steering actuator, a target value of the wheel steering angle including the differential compensation component of the actual wheel steering actuator is determined from the calculated values. By doing so, the actual wheel steering actuator will have dynamic characteristics equal to the ideal dynamic characteristics.

Furthermore, by intervening the wheel steering angular velocity in the servo system of the actual wheel steering actuator, differential compensation can be performed without using a differential circuit.

As a result, even when it is difficult to perform differential compensation using a differential circuit, as in the case where the wheel steering angle control is performed using a digital calculation circuit, appropriate differential compensation can be performed.

Further, by determining the command value of the wheel steering angular velocity necessary for the differential compensation using the numerical model having the ideal dynamic characteristics, for example, the steering wheel steering wheel can be used to determine the command value of the wheel steering angular velocity. There is no need to detect the steering angular velocity using a dedicated sensor and utilize this steering angular velocity, and the number of sensors that detect steering information can be reduced. Similarly, since the target value of the wheel steering angle including the differential compensation component is used, the actual steering angle detection means of the wheel steering actuator does not need to detect the steering angular velocity, and only a sensor capable of detecting the steering angle is required.

[Brief explanation of drawings]

FIG. 1 is a block diagram of the present invention, and FIG. 2 is a block diagram of an embodiment of the present invention. 100... Steering angle detection means, 101... Vehicle speed detection means, 102... Steering angle target value determination means, 103
...Reference model calculation unit, 104... Steering angle target value correction means, 105... Actual steering angle detection means, 106...
Actuator control means, 107...wheel steering actuator, 21...handle steering angle sensor,
22... Vehicle speed sensor, 23... Stroke sensor, 30... Control circuit, 31... Steering angle target value determination section, 32... Reference actuator model calculation section,
38... Steering angle target value correction unit, 40... Hydraulic cylinder, 45... Piston rod, 48, 49... Rear wheel, 50... Control valve, 60... Differential circuit, θ _S
... Steering angle, V ... Vehicle speed, ... Current target value,
_R ... Rear wheel steering angle target value, δ _R ^* ... Rear wheel steering angle command value,
δ・_R ^* ... Rear wheel steering angle speed command value, δ _R # ... Corrected rear wheel steering angle target value, δ _R ... Rear wheel actual steering angle.

Claims (1)

[Scope of Claims] 1. A steering angle detection means for detecting a steering angle of a steering wheel; a vehicle speed detection means for detecting a vehicle speed; and steering angle target value determining means for determining a target value of the steering angle of at least one of the front wheels or the rear wheels corresponding to the vehicle speed, and a vehicle that steers the controlled wheel according to a given command value. A wheel steering actuator and a reference model of the wheel steering actuator having ideal dynamic characteristics are set using differential equations,
Normative model calculating means for calculating a wheel steering angle and a wheel steering angular speed when the target wheel to be controlled is assumed to be steered by the reference model when the target value of the steering angle is given to the reference model; , comprising a mathematical model that simulates the dynamic characteristics of the wheel steering actuator, and using the mathematical model, based on the calculated value of the wheel steering angle and the calculated value of the wheel steering angular velocity obtained by the reference model calculating means, a steering angle target value correcting means for determining a target value of a wheel steering angle including a compensation component for dynamic delay of a wheel steering actuator; an actual steering angle detecting means for detecting an actual steering angle of the wheel to be controlled; and the actual steering angle. actuator control means for giving a command value to the wheel steering actuator so that a deviation between the detected angle value and the steering angle target value after correction by the steering angle target value correction means becomes zero or minimum; A vehicle steering angle control device comprising: