JPH0319824B2 - - Google Patents

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a steering angle control device for a vehicle that can freely control the dynamic performance of a vehicle during steering, and in particular, to a steering angle control device for a vehicle that can freely control the dynamic performance of a vehicle during steering, and in particular, to The present invention relates to a steering angle control device for a vehicle that appropriately controls yawing motion and lateral motion.

(Prior art) Vehicles equipped with conventional mechanical link steering devices are configured to steer the front wheels in response to the amount of steering from the steering wheel, and the dynamic performance associated with steering depends on the vehicle's vehicle performance. The driving performance is uniformly determined based on specifications, and is unique to each vehicle model.

On the other hand, the applicant of this application previously filed a patent application filed in
In No. 188153, a target vehicle model with target dynamic performance is assumed, and target values of motion variables corresponding to the steering wheel steering amount and vehicle speed are determined based on the vehicle specifications and equation of motion regarding the target vehicle model, that is, the target vehicle speed. The value of the motion variable that represents the motion performance exhibited by the vehicle model is determined, and the steering angle of the wheels (front wheels and rear wheels) of the own vehicle is determined so that the target value of the motion variable is achieved in the own vehicle (vehicle equipped with the device). We are proposing a control device.

In other words, if you use this device, for example, even if your vehicle is a sedan type vehicle, if you set the target vehicle model to a sports car type vehicle, it will be possible to create a sports car even though the body structure etc. are of the sedan type. It is possible to freely control exercise performance, such as maintaining exercise performance.

(Problems to be Solved by the Invention) By the way, the inventors of the present application discovered the following improvements while conducting further research on the above-mentioned device.

That is, the evaluation of the steering stability of a vehicle is generally performed with emphasis on the quality of steering responsiveness of each of yaw rate and lateral acceleration, and also on the correlation between these yaw rates and lateral acceleration.

In both the transient motion state and the steady motion state during steering, a small sideslip angle is a condition for improving steering stability.
Ideally, the best condition would be for the sideslip angle to always be zero, regardless of the above-mentioned transient motion state or steady motion state, and regardless of changes in vehicle speed.

However, it is impossible for conventional vehicles to always maintain a sideslip angle of zero.

This is because, as mentioned above, when we derive the solution of the equation of motion to always make the sideslip angle zero from the linear two-degree-of-freedom (yaw, lateral) approximation formula, we get 〓=Kθ _S ……(1) α=KVθ _S ...(2) (Here, 〓 is the yaw rate, α is the lateral acceleration, θ _S is the steering angle, and V is the vehicle speed).

What the above equations (1) and (2) mean is that if the steering angle θ _S changes from 0 to a certain angle in a certain time Δt seconds, a yaw rate of 〓=Kθ _S has already occurred after Δt seconds. This means that In order to achieve this in a normal vehicle, it is necessary to have a steering mechanism with no response delay at all, or to have a vehicle body structure with zero yaw moment of inertia, which is a virtually impossible condition.

(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 yawing movement target value calculation means 102 calculates the steering angle θ _S of the steering wheel detected by the steering wheel angle detection means 100 and the vehicle speed detection by calculation regarding a first target vehicle model having a preset desired movement performance. A target value of the yawing motion corresponding to the vehicle speed V detected by means 101 is determined.

The lateral movement target value calculating means 103 calculates a lateral movement target value Y such that the sideslip angle at the center of gravity of the vehicle is always zero, based on the yawing movement target value obtained by the yawing movement target value calculating means 102. demand.

The steering angle target value calculating means 104 calculates the target values of the steering angles of the front wheels and the rear wheels from the yawing movement target value, the lateral movement target value, and the vehicle specifications of the host vehicle.

Then, the wheel steering means 105 steers each of the front wheels and the rear wheels corresponding to the wheel steering angle target value.

(Function) A yawing motion target value and a lateral motion target value are determined by the yawing motion target value calculation means 102 and the lateral motion target value calculation means 103,
In order to achieve these motion variable target values in the own vehicle, a target steering angle value of the wheels is determined, and the wheels are steered to this target steering angle value.

Here, the above-mentioned lateral motion target value is obtained under the condition that the sideslip angle at the center of gravity of the vehicle is always zero, so the sideslip angle at the center of gravity of the vehicle equipped with the device of the present invention is always zero. It will be controlled so that

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

The microcomputer 1 inputs the vehicle speed V detected by the vehicle speed sensor 3 and the steering angle θ _S of the steering wheel 8 detected by the steering wheel angle sensor 2, and calculates the motion variable target value and the front wheel steering angle target value. Calculates _F and rear wheel steering angle target value _R.

The front wheel steering device 4 is a device that performs steering control of the front wheels 9 and 10 based on the data of the front wheel steering angle target value _F given from the microcomputer 1.
Similarly, the rear wheel steering device 5 is a device that performs steering control of the rear wheels 11 and 12 based on data of the rear wheel steering angle target value _R given from the microcomputer 1.

The hydraulic steering devices 6 and 7 actually steer the front wheels 9, 10 and the rear wheels 11, 12.
It is.

The front wheel steering device 4, the rear wheel steering device 5, and the hydraulic steering devices 6, 7 are configured as shown in FIG. 3, for example.

The hydraulic steering devices 6 and 7 are equipped with two pistons 32 and 33, and drive a shaft 31 whose both ends are connected to tie rods (not shown) by providing a difference in the working oil pressure between left and right hydraulic chambers 34 and 35. The wheels are steered by moving them in the axial direction.

In addition, in the center chamber 37, repulsion plates 38 and 39 biased in left and right opposite directions by a spring 36 are loosely fitted to the shaft 31, and this is caused by the hydraulic pressure of the left and right hydraulic chambers 34 and 35. This is for returning the shaft 31 to its original neutral position when the shaft 31 is pulled out.

The front and rear wheel steering devices 4 and 5 are composed of a solenoid driver 21, a control valve 22, an oil pump 26, and an oil tank 27.

The control valve 22 includes oil passages 28 and 29 that communicate with the left and right hydraulic chambers 34 and 35 of the hydraulic steering devices 6 and 7.
Spool valve 2 that adjusts the amount of hydraulic oil flowing into the
It is equipped with 5. This spool valve 25 is
The left and right ends are loosely fitted into the electromagnetic solenoids 23 and 24, and move in the axial direction depending on the magnitude of the magnetic force of the electromagnetic solenoids 23 and 24, and the left and right hydraulic chambers 34 and 3
Adjust the amount of hydraulic oil given to 5.

The solenoid driver 21 receives front and rear wheel steering angle target values _F , which are given from the microcomputer 1.
A current signal proportional to δ _R is supplied to either the left or right electromagnetic solenoids 23, 24. In this case, control is performed by switching the electromagnetic solenoid that applies current between the left and right sides depending on the steering direction of the wheels.

FIG. 4 is a flowchart showing the processing executed by the microcomputer 1. The operation of this embodiment will be explained below along with the explanation of this flowchart.

The process shown in Fig. 4 is repeatedly executed every predetermined time Δt, and when the ignition switch is
Initialization is performed when it is turned on and power is supplied.

In the process of step 41, both data of the steering wheel steering angle θ _S and the vehicle speed V input from the steering wheel steering angle sensor 2 and the vehicle speed sensor 3 to the microcomputer 1 are read.

Next, in the process of step 42, vehicle specifications related to the target vehicle model stored in the memory in advance are read out. This target vehicle model (hereinafter abbreviated as "target vehicle") is a vehicle (either a real vehicle or a virtual vehicle) that has target characteristics regarding yawing motion and lateral motion.
The vehicle specifications of this assumed vehicle are assumed to be the target vehicle specifications.

In this embodiment, the following vehicle specifications are used as the target vehicle specifications.

I _Z1 : Yaw inertia of the target vehicle M ₁ : Body mass of the target vehicle L _F1 : Distance between the front axle and center of gravity of the target vehicle L _R1 : Distance between the rear axle and center of gravity of the target vehicle N ₁ : Steering gear of the target vehicle Ratio K _F1 : Cornering power of the front wheels of the target vehicle K _R1 : Cornering power of the rear wheels of the target vehicle Then, in the process of the next step 43, the target value of the yawing motion (in this example Now, calculations are performed to obtain the target values of yaw rate and yaw angular acceleration. This operation is
This is done according to the following formula.

M ₁ (V〓 _y1 +〓 ₁ V) = 2C _F1 +2C _R1 ……(3) I _Z1 ¨ ₁ = 2L _F1 C _F1 −2L _R1 C _R1 ……(4) C _F1 =K _F1 {θ _S /N ₁ − (V _y1 +L _F1 〓 ₁ )/V}……(5
) C _R1 = −K _R1 (V _y1 −L _R1 〓 ₁ )/V ……(6) ¨= ₁ ……(7) 〓=〓 ₁ ……(8) Here, 〓 ₁ : Target vehicle's Yaw rate _¨1 : Yaw angular acceleration of the target vehicle V _y1 : Speed of the target vehicle in the y-axis direction V〓 _y1 : Side slip acceleration of the target vehicle in the y-axis direction C _F1 : Cornering force of the front wheels of the target vehicle C _R1 : Cornering force of the target vehicle's rear wheels This is the cornering force.

Equations (3) and (4) above are equations of motion for the target vehicle. To solve these equations, two integral operations are required for each Δt. This integral operation is, for example, A(t+Δt )=A(t)+Δt・A〓(t) An appropriate integration method is used depending on the required integration precision, such as the rectangular integration method or the Rungekutta method.

During the above calculation, the equation of motion related to the lateral motion is also calculated, but the lateral movement variables (V _y1 and V〓 _y1 ) determined by this calculation include a sideslip component, so they will be explained later. Target steering angle value
It is not used in the calculation of _F. The target value of this lateral motion variable is determined by the process of the next step 44.

That is, from the yaw rate target value 〓 obtained in step 43 and the vehicle speed V read in step 41, the lateral acceleration target value is calculated by the following calculation: =〓V (9).

Also, when equation (9) holds true, V〓 _y1 (=
Since α−〓 ₁ V)=0 holds, its integral value V _y1 is also “=
Therefore, the y-axis direction acceleration target value _y is set to "=0".

Next, in steps 45, 46, and 47, the target values 〓, 〇 of the motion variables obtained by separate calculations as described above are applied to the front and rear of the own vehicle (vehicle equipped with this embodiment). By controlling the wheel steering angle, control is achieved as a dynamic characteristic of the own vehicle.

That is, in the process of step 45, the vehicle specifications of the own vehicle stored in the memory in advance are read, and in the process of step 46, the previous vehicle specifications are calculated from the own vehicle specifications and the above motion variable target values 〓, ¨, , the rear wheel steering angle target values _F , _R are determined and outputted to the front wheel steering device 4 and the rear wheel steering device 5 in step 47.

The vehicle specifications read in step 45 above are as follows:
These are shown below.

I _Z2 : Yaw inertia of own vehicle M ₂ : Vehicle mass of own vehicle L _F2 : Distance between own vehicle's front axle and center of gravity L _R2 : Distance between own vehicle's rear axle and center of gravity L ₂ : Own vehicle's wheelbase K _F2 : Cornering force of the front wheels of the automatic vehicle K _R2 : Cornering force of the rear wheels of the automatic vehicle The calculations executed in step 46 are as follows.

C _F2 = 1/2L ₂ (M ₂ L _R2 + I _Z2 ¨) ……(10) C _R2 = 1/2L ₂ (M ₂ L _F2 −I _Z2 ¨) ……(11) β _F2 = C _F2 /K _F2 …(12) β _R2 = C _R2 /K _R2 …(13) _F = β _F2 + ( _y −L _F2 〓) / V … (14) _R = β _R2 + ( _y −L _R2 〓) /V...(15) Where, C _F2 : Front wheel cornering power of the own vehicle C _R2 : Rear wheel cornering power of the own vehicle β _F2 : Side slip angle of the front wheels of the automatic vehicle β _R2 : Side slip angle of the rear wheels of the automatic vehicle .

Then, the front wheel steering angle target value _F and the rear wheel steering angle target value _R obtained by the above equations (14) and (15) are
47, and the front wheel steering device 4 and rear wheel steering device 5 perform the operations necessary to steer the front wheels 9, 10 or the rear wheels 11, 12 to the given steering angle target value _F or _R. Hydraulic pressure is supplied to the hydraulic steering devices 6, 7, and thereby the front wheels 9,
10 and rear wheels 11 and 12 are steered.

Through the above control operations, the yawing motion of the host vehicle becomes equal to the yawing motion characteristic of the target vehicle, and the lateral motion of the host vehicle is controlled so that the sideslip angle β at the center of gravity becomes zero.

This means that the lateral acceleration target value satisfies the above equation (9), and the y-axis direction speed target value _y =
This effect is obtained because the calculation is performed with the value set to 0. In other words, if =〓V, then the sideslip angular velocity β〓 at the center of gravity is expressed as β〓=α/V−ψ〓(=V _y /V), so substitute α for α (or V〓 _y
By substituting the differential value (=0) of _y (=0) into
Since β=0, the center-of-gravity side slip angle β, which is this integral value, also becomes “=0”.

Therefore, for example, when a sudden steering is performed as shown in FIG. 5, the change in yaw rate is similar to the yaw rate change characteristic ( The response is better than that shown by characteristic b in the figure.

Here, in a vehicle equipped with a device that performs steering angle control without always controlling the center-of-gravity sideslip angle to zero, such as the device in the prior application, the yaw rate change will be the same as in the vehicle equipped with the device of this embodiment. A good response as shown in characteristic a can be obtained, but when looking at the lateral acceleration, as shown in Fig. 7, the change characteristic of the lateral acceleration in the vehicle equipped with the device of the prior application is the characteristic d in the figure. As shown in Figure 2, although it is non-vibratory compared to the characteristics of the conventional vehicle (indicated by characteristic e in the figure), compared to the characteristics of the vehicle equipped with the device of this embodiment (indicated by characteristic c in the figure), The onset is somewhat slow.

On the other hand, in the vehicle equipped with the device of the present invention, the sideslip angle at the center of gravity is always zero, as shown by the characteristic f in FIG. (h indicates the case of a conventional vehicle), the responsiveness of the lateral acceleration is also increased as shown in the characteristic c shown in FIG.

In addition, in the above embodiment, an example was shown in which the present invention is applied to a four-wheel steering vehicle having a structure in which both front wheels 9, 10 and rear wheels 11, 12 are steered using hydraulic steering devices 6, 7. However, in addition to this, it is also possible to apply the present invention to a vehicle in which the front wheels 9 and 10 are steered using a conventional mechanical link type steering device.

In this case, as shown in FIG.
2, similarly to the above embodiment, the hydraulic steering device 7 is used to perform steering, and the front wheels 9, 1
0 is a front wheel steering angle target value for which steering is performed by the mechanical link type steering device 14 in conjunction with the steering of the steering wheel 8, and the auxiliary steering device 13 is provided to perform dynamic characteristic control.
It is conceivable to adopt a structure in which the front wheel steering angle is corrected so that it matches _F.

The correction amount Δδ _F of the front wheel steering angle at this time is obtained by substituting equations (12) and (14) among the calculations executed at step 46 in FIG. 4 in the above embodiment as follows. Just change it to equations (16) and (17).

β _F2 = C _F2 /eK _F ……(16) Δδ _F = β _F2 + ( _y2 −L _F3 〓)/V−θ _S /N ₂ ……(1
7) Here, eK _F2 : Front equivalent cornering power of own vehicle N ₂ : Steering gear ratio of own vehicle, eK _F2 is, when steering stiffness is K _S and trail is ξ, eK _F2 = K _S / It is expressed as 1+2ζ/N ² / ₂ K _S K _F.

If this is done, it will be equivalent to performing the same operation as in the above embodiment, and the same effect will be obtained.

(Effects of the Invention) As described above in detail, the present invention obtains a target value of yawing motion from calculations related to the target vehicle, and uses this target value of yawing motion to ensure that the sideslip angle at the center of gravity is always zero. By determining the target values for lateral motion and controlling the wheel steering angle to achieve these target values, it is possible to freely control the vehicle's dynamic performance, and it is much faster than conventional vehicles. Therefore, it is possible to provide a vehicle that has ideal maneuverability in which the sideslip angle at the center of gravity is always zero, which is impossible to achieve with other vehicles.

[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, and Fig. 3 is a block diagram of the front wheel steering device, rear wheel steering device, and hydraulic steering device in Fig. 2. , FIG. 4 is a flowchart showing the processing executed by the microcomputer in FIG. 2, and FIGS. FIG. 9 is a characteristic diagram showing a comparison with a vehicle equipped with the device of the present invention, and is a configuration diagram of another embodiment of the present invention. 100...Steering wheel steering angle detection means, 101...
...Vehicle speed detection means, 102... Yawing movement target value calculation means, 103... Lateral movement target value calculation means, 104... Steering angle target value calculation means, 105...
Wheel steering means, 1...Microcomputer, 2
...Handle steering angle sensor, 3...Vehicle speed sensor,
4...Front wheel steering device, 5...Rear wheel steering device, 6,
7... Hydraulic steering device, 8... Steering handle, 9, 10... Front wheels, 11, 12...
...Rear wheel, 〓...Yaw rate target value, ψ¨...Yaw angular acceleration target value, ...Lateral acceleration target value, _F ...
Front wheel steering angle target value, _R ...Rear wheel steering angle target value.

Claims (1)

[Scope of Claims] 1. Steering wheel angle detection means for detecting a steering angle of a steering wheel; vehicle speed detection means for detecting vehicle speed; Yawing movement target value calculation means for calculating a target value of yawing movement corresponding to the steering angle of the steering wheel and the vehicle speed, and a sideslip angle at the center of gravity of the vehicle based on the yawing movement target value calculated by the yawing movement target value calculation means. a lateral motion target value calculating means for calculating a target value of the lateral motion such that the yaw motion is always zero; A steering angle target value calculating means for calculating each target value of the rear wheel steering angle, and a wheel steering means for steering each of the front wheels and the rear wheels corresponding to each of the determined wheel steering angle target values. A vehicle steering angle control device characterized by: 2. The yawing movement target value calculation means calculates at least a target value of the yaw rate, and
The lateral motion target value calculation means calculates the target value of lateral acceleration from the yaw rate target value 〓 and the vehicle speed V detected by the vehicle speed detection means by calculating =〓V. The vehicle steering angle control device according to item 1.