JPH0725317B2 - Actual steering angle control device for vehicle - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle actual steering angle control device that controls the motion characteristics of a vehicle by adjusting the actual steering angle of a wheel.

(Prior Art) A conventional vehicle equipped with a mechanical link type steering device is configured to steer the front wheels in accordance with the steering amount of the steering wheel. It is uniformly determined by the specifications, and the exercise performance is unique to each vehicle type.

On the other hand, the applicant of the present application has previously assumed a target vehicle model (reference model) having a target motion performance in Japanese Patent Application No. 59-188153 (Japanese Patent Laid-Open No. 61-67665),
The target value of the motion state quantity corresponding to the steering wheel steering amount and the vehicle speed, that is, the motion state quantity exhibited by the target vehicle model is obtained based on the vehicle specifications and the motion equation related to the target vehicle model, and this motion state quantity target value is calculated. A device for controlling the steering angles of the wheels (front wheels and rear wheels) of the own vehicle is proposed so that the own vehicle (vehicle equipped with the device) can realize it.

That is, by using this device, the exercise performance can be freely controlled.

(Problems to be Solved by the Invention) By the way, the inventors of the present application have found the following improvements while further researching the above device.

That is, when the rear wheels are controlled by the above device, the front wheels are steered by the steering of the steering wheel, so that when the steering wheel is steered abruptly,
Fluctuations in the vehicle motion state quantity that occur in the initial stage of steering in direct relation to the front wheel steering affect the rear wheel steering angle control for realizing the above-mentioned motion state quantity target value.

For example, when trying to match the response characteristic of the lateral acceleration of the own vehicle with the target response characteristic, in the case of the above device, the target value of the lateral acceleration is obtained from the target vehicle model having the target response characteristic, and The steering angle of the rear wheels will be adjusted so that the target value of acceleration is realized in the own vehicle.

In this case, when the steering angle of the steering wheel changes in a step-like manner, as shown in FIG. 7, due to the fluctuation of the vehicle motion state quantity occurring at the initial stage of steering, which is directly related to the front wheel steering, as shown in FIG. A phenomenon may occur in which the target value of acceleration does not match the lateral acceleration α of the vehicle.

(Means for Solving Problems) In order to solve the above problems, the present invention includes means shown in FIG.

The motion state quantity target value determination means 102 uses the reference model obtained by mathematically modeling the target dynamic characteristics, and the steering angle θs of the steering wheel detected by the steering angle detection means 100 and the vehicle speed V detected by the vehicle speed detection means 101. Then, the target value of at least one of the motion state quantities related to the yawing motion and the lateral motion to be realized by the own vehicle is obtained.

The rear wheel rudder angle command value determining means 103 includes a motion state quantity detecting means 104.
While feeding back the motion state quantity B of the own vehicle of the same type as the at least one motion state quantity detected in step 1, the rear wheel steering angle of the rear wheel for making the motion state quantity of the own vehicle follow the motion state quantity target value. Determine the command value δ.

The rear wheel steering angle command value compensating means 105 is necessary for canceling the fluctuation of the vehicle motion state quantity generated at the initial stage of steering, which is directly related to the front wheel steering, on the basis of the detected steering angle value θs. A rear wheel steering angle compensation value is obtained, and the command value of the rear wheel steering angle is corrected by this compensation value to form a rear wheel steering angle correction command value.

The rear wheel rudder angle adjusting means 106 variably adjusts the actual rudder angle of the rear wheels according to the corrected rear wheel rudder angle correction command value.

(Operation) Basically, the command value of the rear wheel rudder angle, which is determined by the motion state quantity target value determination means 102 and which realizes the motion state quantity target value as the motion state quantity of the vehicle, is obtained and Adjust the actual steering angle of the rear wheels.

By the way, in the present invention, the rear wheel steering angle command value compensating means 105, the rear wheel steering angle command value so as to cancel the fluctuation of the vehicle motion state quantity that occurs at the initial stage of steering directly related to the front wheel steering. By compensating for the above, it is possible to prevent the occurrence of the control error at the initial stage of steering as described above and improve the control response performance at the initial stage of steering.

(Embodiment) FIG. 2 shows the configuration of an embodiment of the present invention.

The arithmetic processing unit 1 is configured by using a microcomputer or other electric circuit, and the steering angle θ _{S of the} steering wheel 8 detected by the steering wheel steering angle sensor 13 is detected.
A vehicle speed V detected by the vehicle speed sensor 3, a lateral acceleration α of the own vehicle detected by the lateral acceleration sensor 13, and a lateral speed Vy of the own vehicle detected by the lateral speed sensor 14,
Yaw rate generated in the vehicle detected by the yaw rate sensor 15 Has been entered.

Then, the arithmetic processing device 1 performs a predetermined arithmetic processing based on the above-mentioned inputs to give a command value of the operation amount of the steering angle of the rear wheels 11 and 12 (hereinafter referred to as "rear wheel steering angle command value"). Output _R.

The rear wheels 11 and 12 are configured to be steered by the hydraulic steering device 7. The hydraulic steering device 7 is controlled by the rear wheel steering device 5.

The rear wheel steering device 5 changes the hydraulic pressure applied to the hydraulic steering device 7 in accordance with the rear wheel steering angle command value _R input from the arithmetic processing device 1 so that the actual steering angles of the rear wheels 11 and 12 are the rear wheels. It operates so as to match the steering angle command value _R (details are described in Japanese Patent Application Laid-Open No. 61-67665 related to Japanese Patent Application No. 59-188153).

The front wheels 9 and 10 are steered by a steering handle 8 by a conventional mechanical link type steering device 6.

FIG. 3 is a block diagram showing the configuration of the arithmetic processing unit 1.

The arithmetic processing unit 1 includes a reference model 21 that mathematically models a preset target dynamic characteristic, and a rear wheel rudder required to realize a lateral acceleration target value determined by the reference model 21 in a vehicle. The steering angle calculation unit 22 determines the operation amount of the angle.

In the reference model 21, the response of the lateral acceleration target value to the steering angle input θ _S is Is configured to be. However, K (V) is a gain determined by the vehicle speed V, τ is a time constant, and S is a Laplace operator.

The values of K (V) and τ are set according to the target dynamic characteristics to be realized as the dynamic characteristics of the own vehicle when the reference model 21 is designed. As K (V), the value at each vehicle speed is stored in the memory in the form of a data table in advance, and when the vehicle speed V is input, the value corresponding to this vehicle speed V is obtained from the data table. To

The steering angle calculation unit 22 performs the function of the front compensator in the model following control, so that the lateral acceleration that actually occurs in the own vehicle follows the lateral acceleration target value that is an input,
The rear wheel steering angle, which is an operation amount, is adjusted.

Then, the steering angle calculation unit 22 determines the optimum control gain K ₁₁ (V), K determined based on the optimum regulator theory.
₁₂ (V), K ₂ (V), and K ₃ (V) are used to perform the feedforward compensation of the output feedback, the state feedback, and the state variables of the reference model. Also, the gain K ₄
Is used to compensate the feed-forward compensation of the steering angle input θ _S for canceling the fluctuation of the motion state amount due to the front wheel steering.

That is, in the model following control according to the present embodiment, the control amount is the lateral acceleration and corresponds to the control of outputting the lateral acceleration target value as the lateral acceleration of the host vehicle.

Therefore, the detected value α of the lateral acceleration of the vehicle detected by the lateral acceleration sensor 13 is input to the steering angle calculation unit 22 to form an output feedback loop. The rudder angle calculation unit 22 obtains the difference between the detected lateral acceleration value α and the lateral acceleration target value, integrates the difference, and then calculates the gain.
By amplifying with K ₂ (V), the operation amount δ of the rear wheel steering angle such that the lateral acceleration target value and the lateral acceleration detection value α match.
Decide on ₂ .

Further, in order to eliminate the influence of disturbance and environmental changes, it is required to feed back the state variables of the own vehicle, which are necessary to know the behavior of the own vehicle. As the yaw rate of the vehicle detected by the yaw rate sensor 15. And the lateral speed Vy of the vehicle detected by the lateral speed sensor 14
Is feedback. In the steering angle calculation unit 22, the detected value of the yaw rate fed back And lateral velocity detection value Vy, gain K
It is amplified by ₁₁ (V) and K ₁₂ (V), and the compensation values δ ₁₁ and δ ₁₂ of the operation amount of the rear wheel steering angle for stabilizing the control are determined.

Further, in this embodiment, the lateral acceleration target value output from the reference model 21 is amplified by the gain K ₃ (V) to compensate the feedforward of the state variable of the reference model, and the steering angle of the rear wheel is manipulated. The quantity compensation value δ ₃ is determined. In this feedforward compensation, the output feedback control controls the dynamic characteristics of the vehicle during steady motion to follow the dynamic characteristics of the reference model. This is to follow the dynamic characteristics.

Each gain K ₁₁ (V), K ₁₂ (V), K ₂ (V), K ₃ (V)
Are the optimum control gains that are determined based on the optimum reguulator theory, and these are dependent on the vehicle speed V. Therefore, in the present embodiment, each gain is stored as a function of the vehicle speed V in advance in the memory in the form of a data table for each vehicle speed, and when the vehicle speed V is input, the data table Each gain is determined by a backup.

The steering angle calculating unit 22, a feedforward compensation of the steering angle input theta _S for canceling the variation of the vehicle motion state quantity associated with the front-wheel steering, amplifying the steering angle input theta _S by a gain K ₄ By doing so, the compensation value δ ₄ of the operation amount of the rear wheel steering angle is determined. The gain K ₄ is represented by the following equation.

Where eK _F is the front wheel equivalent cornering power of the vehicle, K _R is the rear wheel cornering power of the vehicle, and N is the steering gear ratio of the vehicle.

This gain K ₄ is derived as follows.

The dynamic characteristics of the host vehicle are expressed by the following state equation and output equation.

Is. M: vehicle weight I _Z : yaw inertia L _F : distance between front axis and center of gravity L _R : distance between rear axis and center of gravity

The above output equation (4) is a component that appears due to the state feedback (first term), a lateral acceleration direct achievement amount by the steering angle input θ _S (second term), and a lateral acceleration direct achievement amount by the rear wheel steering angle δ _R. (Section 3)

Then, the second and third terms are directly affected by the change in the steering angle of the front and rear wheels. Due to the presence of these lateral acceleration direct achievements, the variation of the motion state quantity of the own vehicle at the initial stage of steering occurs as described above.

Therefore, in order to eliminate the influence of the change in the steering angle of the front wheels by adjusting the rear wheel steering angle, the direct achievement amount b ₂₁ θ _S due to the steering angle input θ _S is changed to the direct achievement amount b ₂₂ due to the rear wheel steering angle. δ _R
You can cancel it with. That is, it suffices if b ₂₁ θ _S + b ₂₂ δ _R = 0 (5) is satisfied.
If we rewrite the relationship between _R and θ _S , And the above gain K ₄ is derived.

Using the gain K ₄ obtained in this way, a compensation value δ ₄ of the operation amount of the rear wheel steering angle is determined from the steering angle input θ _S and added to the operation amount δ ₂ of the rear wheel steering angle.

Therefore, the rear wheel steering angle command value output from the steering angle calculation unit 22
_R becomes _R = δ ₁₁ + δ ₁₂ + δ ₂ + δ ₃ + δ ₄ .

The rear wheel steering angle command value _R determined in this way is given to the rear wheel steering device 5 so that the actual steering angles of the rear wheels 11 and 12 coincide with the rear wheel steering angle command value _R. Steering is performed.

By the above control, the lateral acceleration of the own vehicle matches the lateral acceleration target value, and the own vehicle can realize the dynamic characteristics of the reference model.

Further, in the present embodiment, as described above, the lateral acceleration target value is realized without being affected by the disturbance or the environmental change by performing the feedback compensation of the output feedback, the state feedback, and the state variable of the reference model. it can.

Further, in the present embodiment, the gain K ₄ is used to obtain the compensation value δ ₄ of the operation amount of the rear wheel steering angle that cancels the fluctuation of the motion state amount due to the front wheel steering, and thereby the operation of the rear wheel steering angle is calculated. Amount δ ₂
Thus, as shown in FIG. 4, the lateral acceleration α of the host vehicle changes in accordance with the lateral acceleration target value even at the initial stage of steering, as described above.

FIG. 5 is a flow chart showing processing executed by the arithmetic processing device 1 when the arithmetic processing device 1 is configured by using a microcomputer.

The step 33 corresponds to the reference model 21 in FIG. 3, and is ∫dt (6) Then, the lateral acceleration target value is determined. The gain K (V) is obtained in step 32 from a data table stored in advance in the memory. Also, the time constant τ
Is predetermined at the design stage.

Step 34 corresponds to the steering angle calculation unit 22 in FIG. 3, and e = α− (8) E = ∫edt (9) The rear wheel steering angle command value _R is determined by the following calculation. The gains K ₁₁ (V), K ₁₂ (V), K ₂ (V) and K ₃ (V) are obtained in step 32 from the data table stored in advance in the memory. As the gain K ₄ , the value obtained by the above equation (2) is stored in the memory, and this value is used.

The rear wheel steering angle command value _R obtained in step 34 is output to the rear wheel steering device 5 in step 35.

In the above embodiment, the lateral acceleration of the own vehicle is calculated as the reference model.
Although the device for tracking the lateral acceleration target value obtained from 21 is shown as an example, the present invention is not limited to this, and other motion state quantities can be similarly controlled.

For example, as shown in FIG. 6, with the reference model 41, the target value of the yaw rate is set. Is determined according to the preset target dynamic characteristics, and the steering angle calculation unit 42 outputs the output feedback, the state feedback, the feedback compensation of the state variable of the reference model 21, and the own vehicle by the front wheel steering. The yaw rate target value is set by performing feedback compensation of the steering angle input θ _S for canceling the fluctuation of the motion state quantity. Rear wheel steering angle command value such that the yaw rate of the vehicle follows
A device for determining _R is conceivable.

In this case, the detected value of the vehicle yaw rate used for the output feedback Can also be used as a state variable of the own vehicle used for the state feedback, so that the yaw rate sensor 15 can be shared.

Then, in the case of this example, the yaw rate of the vehicle at the initial steering stage is obtained by the feedback compensation of the steering angle input θ _S. And yaw rate target value The error between and can be reduced.

(Effect of the Invention) According to the present invention, the dynamic characteristics of the own vehicle can be controlled by adjusting the rear wheel steering angle of the own vehicle so that the dynamic characteristics of the own vehicle follow the dynamic characteristics of the reference model. .

Then, the present invention obtains a compensation value of the command value of the rear wheel steering angle operation amount necessary for canceling the fluctuation of the vehicle motion state quantity that occurs directly related to the front wheel steering, and calculates the rear wheel steering angle. By compensating the command value of the operation amount, it is possible to prevent the occurrence of the control error at the initial stage of steering as described above and improve the control response performance at the initial stage of steering.

[Brief description of drawings]

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 showing the configuration of the arithmetic processing unit in FIG. 2, and FIG. FIG. 5 is a characteristic chart showing changes in lateral acceleration and lateral acceleration target value at the initial steering in a vehicle equipped with an example device, FIG. 5 is a flow chart showing processing executed by the arithmetic processing device in FIG. 2, and FIG. FIG. 7 is a block diagram showing the configuration of an arithmetic processing unit in another embodiment of the invention, and FIG. 7 is a characteristic diagram showing changes in lateral acceleration and lateral acceleration target value at the initial steering stage in a vehicle equipped with the device according to the prior application. . 100 ...... Steering angle detection means 101 ...... Vehicle speed detection means 102 ...... Output target value determination means 103 ...... Steering angle operation amount command value determination means 104 ...... Motion state amount detection means 105 ...... Compensation means 106 ...... Actual steering angle adjusting means 1 ... Calculation processing device 2 ... Steering wheel steering angle sensor 3 ... Vehicle speed sensor 5 ... Rear wheel steering device 7 ... Hydraulic steering device 9,10 ... Front wheel, 11, 12 ... Rear wheel 13 …… Lateral acceleration sensor, 14 …… Lateral speed sensor 15 …… Yaw rate sensor 21,41 …… Reference model, 22,42 …… Steering angle calculation unit θ _S …… Steering angle, V …… Vehicle speed α …… Lateral acceleration detection value, Vy …… Lateral velocity detection value …… Lateral acceleration target value _R …… Rear wheel steering angle command value δ ₄ …… Compensation value of rear wheel steering angle operation amount command value K ₄ …… Gain

Claims (2)

[Claims] 1. A steering angle detecting means for detecting a steering angle of a steering wheel for steering front wheels, a vehicle speed detecting means for detecting a vehicle speed, and a reference model in which a target dynamic characteristic is mathematically modeled. A motion state quantity target value determination means for obtaining a target value of at least one of the motion state quantities related to the yawing motion and the lateral motion to be realized by the vehicle by giving the detected value of the vehicle speed, and the at least one motion state quantity. In order to make the motion state amount of the own vehicle follow the motion state amount target value while feeding back the motion state amount of the same vehicle that detects the motion state amount of the same vehicle, and the detected motion state amount of the own vehicle. Rear wheel steering angle command value determination means for determining the command value of the rear wheel steering angle, and based on the detected value of the steering angle, the fluctuation of the vehicle motion state quantity that occurs at the initial stage of steering in direct relation to the front wheel steering. rear A rear wheel rudder angle command value compensating means for obtaining a rear wheel rudder angle compensation value necessary for canceling by steering, and correcting the command value of the rear wheel rudder angle by this compensation value, and the corrected rear wheel rudder angle command An actual steering angle control device for a vehicle, comprising: rear wheel steering angle adjusting means for variably adjusting the actual steering angle of the rear wheels according to a value. 2. The rear wheel steering angle command value compensating means adjusts the steering angle of the steering wheel when the front wheel equivalent cornering power of the vehicle is eK _F , the rear wheel cornering power is K _R , and the steering gear ratio is N. the detected value, for the vehicle according to claims first preceding claims, characterized in that a value obtained by multiplying the K = -eK _F / K _R N becomes the gain K is intended to be the rear-wheel steering angle compensation value Actual steering angle control device.