JPS62149560A - Steering angle control device for vehicle - Google Patents

Abstract

PURPOSE:To prevent the occurrence of a delay of response to control, by a method wherein, when the wheel steering angle of an automobile according to a set desired motion performance, differential compensation of a wheel steering actuator control system is effected without using a normal differential circuit. CONSTITUTION:A norm model computing means 103 is provided to determine a wheel steering angle delta0 and a wheel steering angle speed delta* of a wheel to be controlled prevailing when it is assumed that a steering angle delta'* is realized by using a wheel steering actuator having ideal dynamic characteristics. By means of an actuator control means 106, a wheel steering actuator 107 is controlled so that an actual steering angle delta and an actual steering angle delta' of the wheel to be controlled are made equal to a computing value delta* of a wheel steering angle and a computing value delta*' of a wheel steering angle speed. This constitution enables differential compensation of the control system of the wheel steering actuator 107 without using a normal differential circuit, and enables prevention of the occurrence of a delay of response to control.

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 own troops according to preset motion performance, and in particular, The present invention relates to a steering angle control device for a vehicle that compensates for a response delay of an actuator that performs steering.

(Conventional technology) Conventionally, it has been possible to control the dynamic performance of a vehicle 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. A device has been proposed (for example, there is one shown in Japanese Patent Laid-Open No. 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 front and rear wheels. The steering angle is steered to the above-mentioned target steering angle value.

(Problem to be Solved by the Invention) However, since the actuator described above 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, if 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, and when this signal is viewed microscopically, , has a step-like shape, so if we differentiate this signal using a normal differentiator circuit, we get
This results in discrete differential value signals, resulting in inaccurate control.

In other words, in a control system using digital circuits,
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 includes means shown in FIG.

The steering angle target value determining means 102 includes the steering angle target value determining means 100.
A target value δ of the steering angle of at least one of the front wheels and the rear wheels to be controlled is determined, which corresponds to the steering angle θS of the steering wheel detected by the vehicle speed detecting means 101 and the vehicle speed V detected by the vehicle speed detecting means 101.

The reference model calculating means 10B sets a reference model of a wheel steering actuator having ideal dynamic characteristics as an actuator for steering the controlled target wheels using a differential phallic equation, and sets the target value 7 of the steering angle to the target value 7. When given to the reference model, the reference model determines the wheel steering angle δ8 and the wheel steering angular velocity - when it is assumed that the control target wheel is steered.

The actuator control means 106 calculates the calculated value of the wheel alignment angle obtained by the reference model calculation means 10B. and the deviation of the detected value δ of the actual steering angle of the controlled wheel detected by the actual steering angle detection means 104, and the calculated value of the wheel steering angular velocity obtained by the reference model calculation means lθ3, and the deviation of the detected value δ of the actual steering angle of the controlled object wheel detected by the actual steering angle detection means 104.
A command value Sk is sent to the wheel steering actuator 107 that turns the wheels to be controlled so that the detected one-to-two deviation of the actual steering angular velocity of the wheels to be controlled detected in step 5 becomes zero or minimum.
give.

(Function) The steering angle target value δ determined by the steering angle target value determining means 102 is the steering angle of the controlled target wheel necessary for realizing the target maneuver performance by the own army. If the wheels to be controlled are steered so that the angle becomes equal to the target angle value δ, the target maneuverability can be achieved by the own army.

Here, as mentioned above, the one-wheel steering actuator □-ta
07 requires differential compensation for control because there is an operation delay.

Therefore, the present invention provides a reference model calculation means 10B,
Assuming that the steering angle target value a is realized using a wheel steering actuator with ideal dynamic characteristics, the wheel steering angle δ8 and the wheel steering angular velocity - of the wheel to be controlled are determined, and further, the actuator control means 106 calculates The wheel steering actuator 107 is controlled so that the actual steering angle δ and the actual steering angular velocity 2 of the wheels to be controlled become equal to the calculated value δ8 of the wheel steering angle and the calculated value a of the wheel steering angular speed, respectively.

As a result, the present invention can perform differential compensation of the wheel steering actuator 1070 control system without using a normal differential circuit.

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

This embodiment controls the steering angle of the rear wheels 48.49 of the vehicle,
It is intended to achieve the target exercise performance.

The front wheels (not shown) are steered by a mechanical link with a steering wheel (not shown), similar to conventional vehicles.

Rear wheel 48.490 steering is performed 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 oil pressure difference between the front pressure chambers 41 and 42 is controlled by the control valve 5θ, and the piston rod 45 is adjusted in response to this oil pressure difference.
is displaced. This displacement of the piston rod 45 is transmitted to the knuckle arm 46.47VC to steer the rear wheels 48.49. Note that 52 is an oil pump and 5B is a reservoir. Further, 43 and 44 are return springs.

The hydraulic cylinder 40 is controlled by controlling the control valve 50 with the control circuit 80.

The control circuit 80 is a digital control circuit composed of a microcomputer or other digital circuit.

In the main part 1, the configuration of the control circuit 80 is shown using block lines to make it easier to understand.

The data input to this control circuit 30 is the vehicle speed sensor z
The vehicle speed V detected at O, the steering angle θS of the steering wheel detected by the steering wheel angle sensor 21, the rear wheel actual steering angle axis detected by the stroke sensor 28, and the rear wheel steering angle detected by the displacement speed sensor 24. The actual wheel steering angle axis is 1raH. Further, from the control circuit 30, a current controller 8
8, current target value 1 is output.

The stroke sensor 28 actually detects the amount of displacement of the piston rod 45, but since the amount of displacement of the piston rod 45 has a correlation with the actual steering angle of the rear wheels 48 and 49, this stroke The detection signal of the sensor 28 can be regarded as a detection signal of the actual steering angle of the rear wheels. 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 81 that determines a rear wheel steering angle target value δR corresponding to the steering angle θS and the vehicle speed VK according to a preset target and the driving performance; A standard for determining a rear wheel steering angle command value δ9 and a rear wheel steering angular speed command value - based on the rear wheel steering angle target value δ determined in the section, according to a reference model of a wheel steering actuator having ideal dynamic characteristics. Actuator model calculation section 8
It is equipped with 2.

The steering angle target value determination unit 31 uses a mathematical model (hereinafter referred to as "target vehicle model") for simulating a vehicle having preset target vehicle motion characteristics, and simulates the motion of own troops. It is equipped with a mathematical model (hereinafter referred to as the "self-military model") for this purpose. The 1st model was constructed using vehicle specifications of the own military.

The steering angle target value determination unit 81 uses the one vehicle model to determine the yaw rate and yaw τ angular acceleration exhibited by the vehicle model when the steering angle θS and vehicle speed V are given, and converts these into the yaw rate target value. ψ, −TT
.

After setting the yaw angular acceleration target value °J, give these ψ and ψ to the own army model, and calculate the rear wheel steering angle (rear wheel rudder) necessary to make the own army's yaw rate and yaw angle / acceleration equal to ↓, ¥. The angle target value 7R- is determined.

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

M□(ty□+i□V) = 2 GB, □+2OR□
--- (IJ Engineering zl”9'l ”” LFICF
l ” “RICRl ”” (21/
R1= (vyl-LH1?1)/V”・
(4)CFl ""Fl・βF・
... (5) CR engineering=KR1・βR0... (6)9
=ψ1 °−(71ψ=ψ□
... (8) Here, I2□: Yaw inertia of the target vehicle model Mo: Body mass of the target vehicle model LB1□: Eye (distance L between front axis and center of gravity of the vehicle model)
R□: Distance between the rear axle and center of gravity of the target vehicle model KFl” Cornering power of the front wheels of the target vehicle model KR□: Cornering power of the rear wheels of the target vehicle model, yaw rate of the two-target vehicle model V□Two-target vehicle model Yaw angular acceleration ■ y □ Two lateral speeds of the target vehicle model * A □: Lateral acceleration of the target vehicle model β1・1: Side slip angle of the front wheels of the target vehicle model βR1: Side slip angle of the rear wheels of the target vehicle model CF y: Cornering force of the front wheels of the target vehicle model CR □: Cornering force of the rear wheels of the target vehicle model.The rear wheel steering angle target value δR is obtained by the following calculation.

IK2°δ'F2 = N2KS2 (θ8−N2δF2)
'to 2''''ay□-2ξ2CF2...(9)M2
(Vy 2 +F V ) =2 (ljy 2 +2
CRz ・” ' (lO)/F2-
'Fll (Vy2" LF2?) / V
=・(u)CF2=KF2βF2
... (12)17
...(13) CR2= ("F2CF2: ψ■Z
2) / LR2βR2=CR2/KR2... (1
4)'R=βR2+(Vy2-LR2,j)/V
...-(15) where, Engineering z2: Yaw inertia of own army model M2: Vehicle weight of own army model L2: Wheelbase of own vehicle model LF2: Distance between front axis and center of gravity of own army model LR2: Own army model Distance between the rear axle and the center of gravity IK2: Inertia around the kingpin of the own model Ks2: Steering rigidity of the own model DK2: Steering system viscosity coefficient ξ2 of the own model: Trail N2 of the own vehicle model: Steering gear ratio δF2 of the own vehicle model Front wheel steering angle of own army model V: Lateral speed V of own army model, : Lateral acceleration βF2 of own army model ``Side slip angle of front wheels of own army model βR2'' Side slip angle of rear wheels of own army model CF2 ``Side slip angle of rear wheels of own army model Cornering force of the front wheels CR2' Cornering force of the rear wheels of the own model KF2: Cornering power of the front wheels of the own model KH2: [This is the cornering power of the rear wheels of the 1 model.

As described above, the reference actuator model calculation unit 82 is configured to use a reference model of a wheel steering actuator having ideal dynamic characteristics (that is, in this embodiment, the hydraulic cylinder 40
The standard actuator model is a model with ideal dynamic characteristics for the servo system of Find the rear wheel steering angle and rear wheel steering angular velocity assuming that For the sake of distinction, the calculated value of the rear wheel steering angle and the calculated value of the rear wheel steering angular velocity obtained here will be referred to as a rear wheel steering angle command value δr and a rear wheel steering angular velocity command value ``aR*, respectively.

Specifically, the reference actuator model calculation section 82 performs the following calculation to obtain the rear wheel steering angle command value δ? and the rear wheel steering angular velocity command value FR*.

Here, 7M is a time constant of the standard actuator model, and this time constant τ8 is set sufficiently smaller than the time constant of the actual actuator (that is, the servo system of the hydraulic cylinder 40).

Then, in the control circuit 80, a subtraction unit 88 calculates the deviation In between the rear wheel steering angle command value δR* and the detected value δR of the rear wheel actual steering angle,
Further, a subtraction unit 84 calculates the deviation between the rear wheel steering angular speed command value A and the detected value JR of the rear wheel actual steering angular speed.

Furthermore, in the control circuit 80, the current target value 1 is formed by adding the above deviation, the gain to the differential 8, and the like.

The current controller 88 generates an exciting current 1 to be applied to the solenoid 51 of the control pulp 50 in accordance with the current target value i given from the control circuit 80 .

Then, the deviation of δ8 and δ, and the RR of 'a* and JR
A R The rear wheels 48.49 are steered until the deviation 8 becomes zero.

Through such control, the actual steering angle δR of the rear wheels 48 actually steered by the hydraulic cylinder 40 and the actual steering angular velocity "a"
B changes according to the ideal dynamic characteristics possessed by the standard actuator model, and achieves the steering angle target value 7R. Furthermore, by introducing the rear wheel steering angular velocity command value 'aR* into the servo system, differential compensation of this servo system is performed. This point will be specifically explained.

First, assuming that differential compensation is not performed, the transfer function of the rear wheel actual steering angle axis to the rear wheel steering angle command value δR (when considering the servo and po system of the hydraulic cylinder 40) ) is (where a is a constant and S is a Laplace operator), which is a first-order lag form as described above. The servo system at this time is shown in a block diagram as shown in FIG.

On the other hand, an equivalent block diagram of the servo system of this embodiment is shown in FIG.

The transfer function of the rear wheel actual steering angle δR to the rear wheel steering angle command value δR of this servo system is as follows, and when compared with equation (18) above, it can be seen that the coordination has been improved. In other words, the characteristics are the same as those obtained when the differential compensation of the servo system expressed by equation (18) is performed.

In addition, if Kpa > 1 can be taken, °δHr
sl + δR15), and the responsiveness of the actual servo system can be made close to the responsiveness of the above-mentioned standard actuator model with extremely high accuracy.

If the response of the reference actuator model is set as high as possible (the time constant τM of the reference actuator model is set sufficiently short), the response of the actual servo system will also be improved, and the rear wheel steering The target angle value δR is determined by the rear wheel 48. .

This can be realized as an actual steering angle of 49.

Note that the reference actuator model calculation section 82 may be configured as a part of a digital calculation circuit such as a microcomputer, or may be configured as one analog calculation circuit (with a D/A converter interposed at the front stage). FIG. 5 shows a block diagram of the analog calculation circuit, and FIG. 6 shows a specific circuit.

82A in FIG. 6 is a differential amplifier, and 82B 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 given the same reference numerals, and their explanation will be omitted.

In this embodiment, instead of detecting the rear wheel actual steering angular velocity "aR" fed back to the control circuit 80 using the displacement speed sensor z4 as in the previous embodiment, the rear wheel actual steering angular velocity "aR" detected by the Nutrok sensor 28 is used. By differentiating the angle δR using a differentiating circuit 60, it is indirectly detected.

Since the output signal of the storage sensor 28 is an analog signal, a differential output can be obtained using the differential circuit 60.

By using the one-differential circuit 60 in this way, the displacement speed sensor 24 becomes unnecessary, the structure can be simplified, and costs can be reduced.

The differentiating circuit 60 includes, in addition to a true differentiating circuit 61 with a transfer characteristic G-S as shown in FIG. It is also possible to use a second-order bandpass filter 68 with a constant value.

, the above-mentioned differentiation circuit 61. The frequency characteristics of the bypass filter 62 and bandpass filter 68 are shown in FIG. In the figure, (Al is the characteristic of the differentiating circuit 61, (B) is the characteristic of the bypass filter 62, and (C1 is the characteristic of the bandpass filter 68.

Normally, the frequency range of the actual steering angular velocity of the wheels is A in Fig. 9.
, therefore, if the cutoff frequencies of the bypass filter 62 and bandpass filter 68 are set higher than the frequency range A, a differential circuit that is resistant to high frequency noise can be provided. In the example, 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 for controlling the front wheel steering angle, By controlling the rudder angles of both, it is also possible to achieve the desired maneuverability with your own troops. However, when controlling the steering angles of both the front wheels and the rear wheels, the control circuit 80
In addition to finding the target steering angle values for the front and rear wheels,
Standard model of front wheel steering actuator and rear wheel steering,
It is necessary to differentially compensate the front and rear wheel servo systems separately using the standard model of the actuator.

(Effects of the Invention) As described above in detail, the present invention can realize a preset target movement performance as the movement performance of the own army 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.

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 arithmetic circuit, appropriate differential compensation can be performed.

In addition, the calculated value of the wheel steering angular velocity required for the above differential compensation is
By determining the calculated value using the mathematical model having the ideal dynamic characteristics, for example, in order to determine the calculated value of the wheel steering angular velocity, the steering angular velocity of the steering wheel is detected using a dedicated sensor, and this steering angular velocity is There is no need to use steering information, and the number of sensors that detect steering information can be reduced.

[Brief explanation of drawings]

Fig. 1 is a block diagram of the present invention, W2B is a block diagram of an embodiment of the present invention, Fig. 8 is block control of a servo system that does not perform differential compensation, and Fig. 4 is an embodiment shown in Fig. 2. Figure 5 is a block diagram of the standard actuator model calculation unit in Figure 2, Figure 6 is a circuit diagram of the standard actuator model calculation unit configured with an analog circuit, Figure 7 is a block diagram of another embodiment of the present invention, Figures 8 (A) to (0) are circuit diagrams showing specific examples of the differential circuit in Figure 7, and Figure 9 is the same as that shown in Figure 8. It is a frequency characteristic diagram of each circuit. ioo... Steering angle detection means 101... Vehicle speed detection means 102... Steering angle target value determination means 10B... Normative model calculation unit 104... Actual steering angle detection means 105... Actual steering angle speed detection Means 106...Actuator control means 107...Wheel steering actuator 21...Handle steering angle sensor z2...Vehicle speed sensor 28...Stroke sensor '2
4... Displacement speed sensor 80... Control circuit 81.
... Rudder angle value determination section 82 ... Normative actuator model calculation section 40 ...
Hydraulic cylinder 45...piston rod 48,
49... Rear wheel 50... Control valve 60
... Differential circuit θ8 ... Steering angle V ... Vehicle speed 1 ... Current target (ict δR ... Rear wheel steering angle target value δ
1ge... Rear wheel horizontal angle command value I... Rear wheel steering angular speed command value δ,... Rear wheel actual steering angle λR... Rear wheel actual steering angular speed Patent applicant Nissan Motor Co., Ltd. Figure 1 Figure 2 Figure 23 Stroke sensor 49 No. 3
Figure 5 Figure 7 n Figure 8 Figure 9

Claims (1)

[Scope of Claims] 1. Steering angle detection means for detecting a steering angle of a steering wheel; vehicle speed detection means for detecting vehicle speed; A steering angle target value determining means that determines a target value of the steering angle of at least one of the front wheels or the rear wheels to be controlled corresponding to the vehicle speed; and a wheel steering actuator that steers the wheel to be controlled according to a given command value. A reference model of the wheel steering actuator having ideal dynamic characteristics is set using a differential equation, and when a target value of the steering angle is given to the reference model, the reference model determines that the wheel to be controlled is a reference model calculating means for calculating a wheel steering angle and a wheel steering angular speed when assuming that the wheel is steered; an actual steering angle detecting means for detecting an actual steering angle of the wheel to be controlled; and an actual steering angular speed of the wheel to be controlled. actual steering angular velocity detection means for detecting the deviation between the calculated value of the wheel steering angle obtained by the reference model calculation means and the detected value of the actual steering angle, and the deviation of the wheel steering angular velocity obtained by the reference model calculation means. so that the deviation between the calculated value and the detected value of the actual steering angular velocity is zero or minimum,
A steering angle control device for a vehicle, comprising actuator control means for giving a command value to the wheel steering actuator.