JPH0580389B2 - - 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,
59-148772).

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 or 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. Determine the target value of the rudder angle.

The reference model calculation means 103 sets a reference model of a wheel steering actuator having ideal dynamic characteristics as an actuator that steers the controlled object wheel using a differential equation, and sets the target value of the steering angle to the reference model. Then, the reference model is used to determine the wheel steering angle δ ^* and the wheel steering angular velocity δ· ^* when it is assumed that the control target wheel is steered.

The actuator control means 106 calculates the deviation between the calculated value δ ^* of the wheel steering angle obtained by the reference model calculation means 108 and the detected value δ of the actual steering angle of the controlled wheel detected by the actual steering angle detection means 104, and The deviation between the calculated value δ* of the wheel steering angular velocity obtained by the reference model calculation means 103 and the detected value δ ^* of the actual steering angular velocity of the controlled wheel detected by the actual steering angular velocity detection means 105 is zero or minimum. A command value S is given to the wheel steering actuator 107 that steers the wheels to be controlled.

(Function) The steering angle target value determined by the steering angle target value determining means 102 is the steering angle of the wheel to be controlled that is 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
Assuming that the target steering angle value is realized using a wheel steering actuator with ideal dynamic characteristics, determine the wheel steering angle δ ^* and the wheel steering angular velocity δ ^* of the wheel to be controlled. The control means 106 causes the wheels to be rotated so that the actual steering angle δ and the actual steering angular velocity δ· of the wheels to be controlled become equal to the calculated value δ ^* of the wheel steering angle and the calculated value δ· ^* of the wheel steering angular velocity, respectively. A rudder actuator 107 is controlled.

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 of the vehicle are controlled to achieve the target driving performance, and therefore the rear wheels 48 and 49 are the wheels to be controlled. 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, 49 are steered by a hydraulic cylinder 40, which is a wheel steering actuator.
This hydraulic cylinder 40 has two hydraulic chambers 4 on the left and right.
1, 42, and these hydraulic chambers 41, 4
2 is supplied with hydraulic pressure through 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 58 is a reservoir. Also, 4
8 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 steering angle θ _S of the steering wheel detected by the steering wheel angle sensor (steering angle detecting means) 21 and the vehicle speed V detected by the vehicle speed sensor (vehicle speed detecting means) 22.
and a stroke sensor 2 as an actual steering angle detection means.
3, and the rear wheel actual steering angle speed δ _{· R} detected by the displacement speed sensor 24 as an actual steering angular speed detection means. In addition, the control circuit 3
From 0, the current target value is output to the current controller 38 as a steering angle command value for the rear wheels (wheels to be controlled).

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 the stroke sensor 23 can be regarded as a detection signal of the rear wheel actual steering angle. Similarly, the detection signal of the displacement speed sensor 24 can be regarded as a detection signal of the rear wheel actual steering angular velocity.

The control circuit 30 includes a steering angle target value determination unit (a steering angle target value determination unit) 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. Means) 31 and the rear wheel steering angle target value _R determined by this steering angle target value determination unit, a rear wheel steering angle command value is determined according to a reference model of a wheel steering actuator having ideal dynamic characteristics. Standard actuator model calculation unit (standard model calculation means) 32 for calculating δ ^* and rear wheel steering angular velocity command value δ^・*
It is equipped with

The steering angle target value determining unit 31 includes a mathematical model (hereinafter referred to as "target vehicle model") for simulating a vehicle having preset target vehicle motion characteristics, and a mathematical model for simulating the motion of the own vehicle. mathematical 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 vehicle model to calculate the rear wheel steering angle (rear wheel steering angle) required to make the vehicle's yaw rate and yaw angular acceleration equal to... 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 ‥ ₁ =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) ・＝・ …(8) Where, I _z1 : Yaw inertia of the target vehicle model M ₁ : Body mass of the target vehicle model L _F1 : Front axis and center of gravity of the target vehicle model Distance between L _R1 : Distance between the rear axle and center of gravity of the target vehicle model K _F1 : Coating power of the front wheels of the target vehicle model K _R1 : Cornering power of the rear wheels of the target vehicle model ・,: Yaw rate of the target vehicle model ‥ ₁ : Yaw angular acceleration of the target vehicle model V _y1 : Lateral velocity of the target vehicle model V・_y1 : Lateral acceleration of the target vehicle model β _F1 : Side slip angle of the front wheels of the target vehicle model β _R1 : Rear wheels of the target vehicle model Side slip angle 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 The rear wheel steering angle target value _R is obtained by the calculation shown below.

I _K2 δ‥ _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 _R2・)/V (15) Here, I _Z2 : Yaw inertia M ₂ of own vehicle model : Vehicle weight of own vehicle model L ₂ : Wheelbase of own vehicle model L _F2 : Distance between front axle and center of gravity of own vehicle model L _R2 : Distance between rear axle and center of gravity of own vehicle model I _K2 : Own vehicle model Inertia around the kingpin K _S2 = Steering rigidity of the own vehicle model D _K2 : Steering system viscosity coefficient of the own vehicle model ξ ₂ : Trail N of the own vehicle model ₂ : Steering gear ratio of the own vehicle model δ _F2 : Front wheel of the own vehicle model Rudder angle V _y2 : Lateral speed of own vehicle model V・_y2 : Lateral acceleration of own vehicle model β _F2 : Side slip angle of front wheels of own vehicle model β _R2 : Side slip angle of rear wheels of own vehicle model C _F2 : Side slip angle of own vehicle model Cornering force of the front wheels of the car model C _R2 : Cornering force of the rear wheels of the car model K _F2 : Cornering power of the front wheels of the car model K _R2 : Cornering power of the rear wheels of the car model.

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 standard actuator model is a standard actuator _model .
The steering angle of the rear wheels and the steering angular velocity of the rear wheels are determined assuming that the steering wheel 49 is turned. For the sake of distinction below, the calculated value of the rear wheel steering angle and the calculated value of the rear wheel steering angular speed obtained here will be referred to as the rear wheel steering angle command value δ _R ^* and the rear wheel steering angular speed command value δ・_R ^* , respectively. .

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, T _M is the time constant of the standard actuator model. This time constant τ _M is set to be sufficiently smaller than the time constant of the actual actuator (that is, the servo system of the hydraulic cylinder 40).

In the control circuit 30, the subtraction unit 33 calculates the difference I _A between the rear wheel steering angle command value δ _R ^* and the detected value δ _R of the rear wheel actual steering angle.
In addition, the subtraction unit 34 calculates the deviation I _B between the rear wheel steering angular speed command value δ· _R ^* and the detected value δ· _R of the rear wheel actual steering angular speed.

Furthermore, in the control circuit 30, the above deviation I _A and the deviation
I _B is given gains K _P and K _D and then added to form the current target value.

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.

Then, the deviation I _A between δ _R ^* and δ _R , and the deviation between δ・_R ^* and δ・_R
The rear wheels 48 and 49 are steered until I _B becomes zero. Therefore, the subtraction units 33 and 34 constitute actuator control means in the present invention.

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.

First, assuming that no differential compensation is performed, the transfer function of the rear wheel actual steering angle δ _R to the rear wheel steering angle command value δ _R ^* (considering the servo system of the hydraulic cylinder 40) is ) is δ _R (s) / δ _R ^* (s) = K _p a / S + K _p a … (18) (However, a is a constant and S is the Laplace operator)
As mentioned above, it is a first-order delayed form. The servo system at this time is shown in a block diagram as shown in FIG.

On the other hand, if the servo system of this embodiment is represented by an equivalent block diagram, it will be as shown in FIG.
The transfer function of the rear wheel actual steering angle δ _R to the rear wheel steering angle command value δ _R ^* of this servo system is δ _R (s)/δ _R ^* (s)=K _D aS+K _P a/(1+K _D a) S
+K _P a (19) When compared with the above equation (18), it can be seen that the rapid response has been improved. In other words, the characteristics are the same as when the differential compensation of the servo system expressed by equation (18) is performed.

If K _D a≫1 can be taken, then δ _R (s) 〓 δ _R ^* (s), which means that the response of the actual servo system can be expressed as the response of the above standard actuator model with extremely high accuracy. You can get closer to sex.

If the response of the reference actuator model is set as high as possible (the time constant τ _M of the reference actuator model is set sufficiently short), the response of the actual servo system will also be improved. , the rear wheel steering angle target value _R of the own vehicle in a responsive manner,
This can be realized as an actual steering angle of 49.

Note that the reference actuator model calculation section 3
In addition to being part of a digital arithmetic circuit such as a microcomputer, 2 can also be configured as an analog arithmetic circuit (with a D/A converter interposed at the front stage). FIG. 5 shows a block diagram of a circuit configured with this analog arithmetic circuit, and FIG. 6 shows a specific circuit. In FIG. 6, 32A is a differential amplifier, and 32B is an integrator.

Next, FIG. 7 shows the configuration of another embodiment of the present invention. In this figure, the same components as those in the embodiment shown in FIG. 2 are designated by the same reference numerals, and their explanation will be omitted.

In this embodiment, instead of detecting the rear wheel actual steering angular velocity δ· _R , which is fed back to the control circuit 30, using the displacement speed sensor 24 as in the previous embodiment, the rear wheel actual steering angular velocity detected by the stroke sensor 23 is used. By differentiating the angle δ _R using a differentiating circuit 60, it is indirectly detected. Therefore, in this example,
The differentiation circuit 60 constitutes actual steering angular velocity detection means.

Since the output signal of the stroke sensor 23 is an analog signal, a differential output can be obtained using the differential circuit 60.

In this way, by using the differential circuit 60, the displacement speed sensor 24 becomes unnecessary, the structure can be simplified, and costs can be reduced.

The differentiating circuit 60 has a transfer characteristic G=S/1+τS (however, τ is a time constant) and a first-order high-pass filter 62, and a transfer characteristic G= as shown in FIG.
It is also possible to use a second-order bandpass filter 63 of bS/S ² +aS+b (where a and b are constants).

FIG. 9 shows the frequency characteristics of the differential circuit 61, high-pass filter 62, and band-pass filter 63. In the figure, A is the characteristic of the differentiating circuit 61, B is the characteristic of the high-pass filter 62, and C is the characteristic of the band-pass filter 63.

Normally, the frequency range of the actual steering angular velocity of the wheels is the 9th
Since this is the region indicated by A _f in the figure, if the cutoff frequencies of the high-pass filter 62 and band-pass filter 63 are set higher than the frequency region A _f , a differentiating circuit that is resistant to high frequency noise can be provided.

In addition, in the above 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 provides an example in which the front wheels are controlled as wheels to be controlled. By controlling the steering angle, or by controlling the steering angles of both the front wheels and the rear wheels, it is also possible to achieve the target driving performance for the own vehicle.
However, when controlling the steering angles of both the front wheels and the rear wheels, the control circuit 30 calculates the target steering angle values of the front wheels and the rear wheels, and also calculates the standard model of the front wheel steering actuator and the rear wheel steering actuator. It is necessary to differentially compensate the front and rear wheel servo systems separately using the reference model.

(Effects of the Invention) As described above in detail, the present invention can realize 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 up as a mathematical model, and this mathematical model is used to apply the force to the actual wheel steering actuator. By determining the calculated values of the steering angle and the wheel steering angular velocity, the actual wheel steering actuator has dynamic characteristics close to the ideal dynamic characteristics described above.

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 in the servo system.

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 calculated value of the wheel steering angular velocity necessary for the differential compensation using the mathematical model having the ideal dynamic characteristics, for example, in order to obtain the calculated 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.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of the present invention, Fig. 2 is a block diagram of an embodiment of the present invention, Fig. 3 is a block diagram of a servo system without differential compensation, and Fig. 4 is shown in Fig. 2. A block diagram of the servo system in the example, FIG. 5 is a block diagram of the standard actuator model calculation section in FIG. 7 is a circuit diagram of another embodiment of the present invention, and FIG. 8 is a circuit diagram of another embodiment of the present invention.
FIGS. A to C are circuit diagrams showing specific examples of the differentiating circuit in FIG. 7, and FIG. 9 is a frequency characteristic diagram of each circuit shown in FIG. 8. 100... Steering angle detection means, 101... Vehicle speed detection means, 102... Steering angle target value determination means, 103... Normative model calculation means, 104... Actual steering angle detection means, 10
5... Actual steering angular velocity detection means, 106... Actuator control means, 107... Wheel steering actuator,
21...Handle steering angle sensor (steering angle detection means),
22... Vehicle speed sensor (vehicle speed detection means), 23... Stroke sensor (actual steering angle detection means), 24... Displacement speed sensor (actual steering angle speed detection means), 30... Control circuit, 31... Steering angle target value determination unit (studder angle detection means) 32... Reference actuator model calculation unit (normative model calculation unit), 33... Subtraction unit (actuator control unit), 34... Subtraction unit (actuator control unit), 40... Hydraulic cylinder (wheel rotation unit). rudder actuator), 45...piston rod, 48,
49... Rear wheel (control target wheel), 50... Control valve,
60... Differential circuit (actual steering angular speed detection means), 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 angular speed command value, _δR ...Rear wheel actual steering angle, δ・_R ...Rear wheel actual steering angular speed.

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; , an actual steering angle detection means for detecting the actual steering angle of the wheel to be controlled; an actual steering angular speed detection means for detecting the actual steering angular velocity of the wheel to be controlled; The deviation between the calculated value and the detected value of the actual steering angle, and the deviation between the calculated value of the wheel steering angular speed obtained by the reference model calculating means and the detected value of the actual steering angular speed are zero or minimum. 1. A steering angle control device for a vehicle, comprising: actuator control means for giving a command value to a wheel steering actuator.