JPS61238571A - Control device for vehicle steering system - Google Patents

Abstract

PURPOSE:To prevent the steering angle of rear wheels from increasing in a high speed range, by controlling the ratio of a steering gear in accordance with a desired steady-state steering gain value and a vehicle speed, and by controlling the steering angle of rear wheels in accordance with a desired steering gear ratio value, the vehicle speed and a steering wheel steered angle. CONSTITUTION:A desired steady-state steering gain value setting means 101 calculates a desired steady state steering gain value G corresponding to a vehicle speed V in accordance with a previously set steering characteristic. A desired steering gear ratio value computing means 102 computes a desired steering gear ratio value N in accordance with the above-mentioned desired value G and the vehicle speed V by using the specific items of the vehicle so that a desired steady-state side slip value is set at a value around zero value. A steering gear ratio changing means 103 sets the gear ratio at the desired value N. Meanwhile a desired rear wheel steering angle value computing means 105 computes a desired rear wheel steering angle deltaR, in accordance with the desired value N, the vehicle speed V and a steering angle and a steering wheel steered angle. The rear wheels are therefore steered to attain this value alphaR.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a vehicle steering system control device that can freely control the steering characteristics of a vehicle, and in particular, the invention relates to a vehicle steering system control device that can freely control the steering characteristics of a vehicle, and in particular, the steady-state engine slip angle can be controlled independently of changes in vehicle speed. The present invention relates to a vehicle steering system (1) control device in which the sideslip angular acceleration is always near zero even during transient motion.

(Prior Art) Conventional two-wheel steering vehicles (refers to ordinary vehicles in which only the front wheels are steered by steering wheel operation) only the front wheels are steered, so there are two ways to improve its steering stability. .

There was a limit.

Therefore, as a measure to improve steering stability, in a four-wheel steering vehicle that also allows rear wheel steering, the steering angle of the rear wheels can be controlled to achieve more ideal steering stability. The technology has been proposed first. This is "Academic lecture preprint collection 842058" published by the Society of Automotive Engineers of Japan in 1982.
J, pages 307-310.

The content of the above technology is to control the rear wheel steering angle so that the steady-state angle β is β-0 in order to eliminate the phase delay in the side-to-side speed of the vehicle.

(Problem to be Solved by the Invention) However, in the above technique 2, in order to set the steady tank slip angle β=O, by using a configuration in which only the rear wheel steering angle is controlled, it is difficult to solve the problem in the high speed range (for example, If β=0 is attempted to be achieved at a speed of 100 kJn/h or more), the rear wheel steering angle becomes large, and as a result, the yaw rate gain rapidly decreases by ζ.

For this reason, when steering to change lanes, etc., it becomes necessary to perform more steering than necessary, resulting in poor maneuverability.

is not good.

In addition, since the above technology is aimed at control during steady turning motion, proper control is not performed during transient motion from the start of the vehicle turning motion to the steady turning motion, and the O (Means for solving the problem) In order to solve the above problem, the present invention includes means shown in FIG. 1.

The steady steering gain target value setting means 101 sets a steady steering gain target value G corresponding to the vehicle speed V detected by the vehicle speed detecting means 100 according to a preset target steering characteristic.
Ask for e.

Steering gear ratio target value calculation means 02 corresponds to the steady steering gain target value n and vehicle speed V mentioned above,
Target value N' of the steering gear ratio to keep the steady angle β of the center of gravity of the own vehicle always close to zero regardless of changes in vehicle speed.
is calculated using the vehicle specifications of the own vehicle.
,! 1. Steering gear ratio variable means 08 sets the actual steering gear ratio of the host vehicle to the steering gear ratio target value N obtained by the above calculation.

The rear wheel steering angle target value calculation means 105 detects the vehicle speed V and the steering wheel steering angle based on the steering gear ratio target value N and the vehicle specifications of the own vehicle used by the steering gear ratio target value calculation means 102. It corresponds to the steering angle θS of the steering wheel detected by the means 104, and
A target value δR11 of the rear wheel steering angle is determined so that the sideslip angular acceleration λ at the center of gravity of the own vehicle is always near zero.

The rear wheel steering means 106 steers the rear wheels so that the rear wheel steering angle of the own vehicle becomes the rear wheel steering angle target value δR.

(Function) By the steady steering gain target value setting means] 01, the steering gear ratio target value calculation means 102, and the steering gear ratio variable means 103, a preset target steering characteristic and a sideslip angle βζ0 at the center of gravity are realized in the own vehicle. Control your vehicle's steering gear and 1° ratio so that This is mainly involved in controlling the steering characteristics of the own vehicle during 1 t during steady turning motion.

Furthermore, rear wheel steering angle target value calculation means] 05 and rear wheel steering means 1
06, the rear wheel steering angle of the vehicle is controlled so that the target steering characteristic and the sideslip angular acceleration of the center of gravity; Therefore, it is possible to properly control the steering characteristics even during transient motion.

Then, the target steering characteristics and the steady tank angle β#
In order to realize this in one's own vehicle, by performing both control of the rear wheel steering angle and control of the steering gear ratio, high speed The rear wheel steering angle does not become larger than necessary in the range, and therefore,
The low yaw rate gain arithmetic processing device 1 is configured by a microcomputer or other electric circuit and calculates the steering angle θS of the steering wheel 8 detected by the steering angle sensor 2 and the vehicle speed sensor 8. 2
．． .

The vehicle speed of the vehicle equipped with the device of this embodiment (hereinafter referred to as "own vehicle") is input, a predetermined calculation is performed, and a steering gear ratio target value 100 and a rear wheel steering angle target value are output.

The power steering controller 4 variably sets the steering gear ratio N by controlling the working oil pressure of the power steering device 5 which performs full steering of the front wheels by 9 degrees.The power steering controller 4 variably sets the steering gear ratio N. The above-mentioned working oil pressure is changed in magnitude in accordance with the magnitude of the ratio target value m. In other words, even if the steering angle θS of the steering wheel 8 is the same, the larger the steering gear ratio target value N is, the larger the actual steering angle δ1 of the front wheels 9, 10 is controlled to be. An example of a technique for hydraulically controlling a power steering device is a device disclosed in Japanese Utility Model Application No. 59-246651.

The rear wheels 11 and 12 are configured to be steered by a hydraulic steering device 7, and the hydraulic steering device 7 is controlled by the rear wheel steering device 6. This rear wheel steering device #6 changes the hydraulic pressure applied to the hydraulic steering device 7 in accordance with the rear wheel steering angle target value sieve inputted from the arithmetic processing device J, and the actual steering angle δR of the rear wheels 11.12. The hydraulic steering device 7 is controlled so that the rear wheel steering angle becomes the rear wheel steering angle target value δR (details are described in Japanese Patent Application No. 59-188158).

FIG. 8 is a flowchart showing the processing executed by the arithmetic processing device 1 when the arithmetic processing device 1 is configured using a microcomputer, and is repeatedly executed at predetermined time intervals.

In step 21, the vehicle speed ■ detected by the vehicle speed sensor 2 is read, and in the next step 22, a steady steering gain (in this embodiment, a steady yaw rate gain is used) corresponding to the read vehicle speed V is read. The target value n is determined.

This G is determined by the following equation (11).

■ Here, Ao, No, Lo are the target steering time 2
．． .

In the case of assuming a vehicle with stability, this value is added to the stability factor A of the vehicle. and steering gear ratio N. , and wheelbase Lo. These A. , No, and Lo are stored in the memory in advance and read out before performing the above calculation.

The reason why the steady yaw rate gain target value 100 is expressed by equation (1) will be described below.

In general, steady yaw rate association. . nst changes in proportion to the steering angle θ8 of the steering wheel, and has the following relationship: 1..■. Here, A□ is the stability factor,
No. is the steering gear ratio, L□ is the wheel r.

It is the base.

Therefore, the coefficient when 08 on the right side is used as a variable is the steady yaw rate gain, and the above equation (1) can be obtained.

Next, in the process of step 28, the above-mentioned steady yaw, .

A calculation is performed to find the target value N of the steering gear ratio in the own vehicle (the vehicle equipped with this example) in order to realize the rate gain G in the own vehicle (the vehicle equipped with this embodiment).This calculation is obtained by the following equation (8). .

This equation (8) is an equation derived as follows.

The steady-state equation of motion that approximates the motion of a vehicle that can steer the rear wheels using two degrees of freedom, lateral and iodine, is: LFOF = LROR... (5) OR = KR (aRI 4 - LR9' /V)
=・(71 Here, !11 0F: Own vehicle's front wheel cornering force 1OR:
Rear wheel cornering force M of own vehicle: Body mass α of own vehicle: Lateral acceleration β of own vehicle: Side slip angle of own vehicle (at center of gravity) φ: Yaw rate of own vehicle δR: Rear wheel steering angle of own vehicle eKF: Own vehicle's front equivalent cornering power KR;
Rear cornering power of own vehicle L] 8.: Distance between front axle and center of gravity of own vehicle LR: Distance N between rear axle of own vehicle and center of gravity; Steering gear ratio of own vehicle In this example, target steering The characteristics are A above. .

It is determined by No1Lo, and the steady sideslip angle β
The steady sideslip angle target value β-0 is included in the above equation (3) because the target is to always keep β-0 regardless of changes in vehicle speed.

That is, by substituting β(-0) for β in the above equations (61, (71), equations (61, (7)) are rewritten as follows.

0R-KR (δR+LR meeting/V)...
(9) Therefore, by substituting equation (5) into equation (4), where L is the wheel pace of the own vehicle, L = Ly + LR
It is.

Also, by substituting equation (8) into equation (lO), this equation (1
Rearranging 1), the above equation (8) can be obtained.

In this way, the steering gear ratio target value m is the steering gear ratio that allows the vehicle to achieve the steady yaw rate gain target value n, and also the steering gear ratio that allows the vehicle to achieve the steady sideslip angle target value 7. There are also things.

Next, in the process of step 25, a calculation is performed to obtain a target value of the rear wheel steering angle for realizing the target steering characteristic, that is, the steady yaw rate gain target value i in the host vehicle.

This can be done by incorporating the same vehicle specifications as those used in step 23 above into the steering gear ratio target value N' obtained by taking into account the above 1C/steady yaw rate gain target value G. The value corresponding to the vehicle speed V read in step 21 and the steering wheel steering angle θ8 read in step 24 is determined. Furthermore, the rear wheel steering angle target value δ is such that the lateral 1-slip angular acceleration λ of the center of gravity is always zero.
The calculation contents are set so that it is also R.

This calculation of δ□ is performed according to the following formula.
'f' = 2LFOF-2LROR...(13)
,,.

OF = eKFβF...(15) α=V-÷ (β-〇)...(]
6) OR= Mα/2 0F ・
...(]7) βR=OR/KR...(18) Sieve=βR-LRφ/V ...(]9)
Here, ≠° is the yaw angle force daily speed of the own vehicle, and z is the yaw inertia of the own vehicle. Other vehicle specifications of the own vehicle are the same as those used in calculating the steering gear ratio target value N, except for the lateral acceleration α.

The reason why the lateral acceleration α is different is to set the rear wheel steering angle target value δR'' to a value that always makes the lateral slip angular acceleration β at the center of gravity zero.This is due to the setting of the above equation (]6) In other words, the lateral acceleration α is usually expressed as α−■·φ+vy = v (small + β) (20), so in order to always set the lateral slip angle acceleration of the center of gravity to zero, If we set fi=o, :, the above formula (16) is obtained.The lateral acceleration obtained by this formula (16) ]1 is the "lateral acceleration target value") is obtained by the formula (]7 )～(19
), and as a result, δR becomes a value that realizes the lateral acceleration π, that is, a value that realizes Table-0.

In the next step 26, the steering gear ratio target value N obtained in step 23 and the rear wheel steering angle target value outside obtained in step 25 are sent to the C-wheel steering controller 4 or the rear wheel steering device 6. Output processing is performed.

From this ship, the power steering controller 4 is
The working oil pressure of the power steering device 5 corresponds to the above-mentioned steering gear ratio target value N. L T: f9! l l1iI
Ij, the actual steering gear ratio N is controlled to match the steering gear ratio target value 100.

Further, the rear wheel steering device 6 includes a hydraulic steering 1 device 7.
The hydraulic pressure supplied to the rear wheel steering angle is controlled in accordance with the rear wheel steering angle target value sieve so that the actual rear wheel steering angle δR coincides with the rear wheel steering angle target value sieve.

In this way, in this embodiment, by controlling the steering gear ratio and the rear wheel steering angle, it is possible to achieve the preset target steering characteristics and sideslip angle β-〇 at the center of gravity in the own vehicle. Become. In addition, during transient motions in which sufficient torque control cannot be achieved by controlling only the steering gear ratio, the rear wheel steering angle control is used to achieve the desired steering characteristics, and also to control the sideslip angular acceleration at the center of gravity. ? -o1 can also be realized.

Since the sideslip angular acceleration 7j=o, the sideslip angle β is naturally also β=0, and as a result, the angle is always l during steady turning motion and during transient motion.

A center-of-gravity exclusive lateral slip angle β=0 is realized.

Next, in order to specifically explain all the effects of this example, the fourth
Changes in the actual center-of-gravity lateral slip angle β, yaw rate, and lateral acceleration α when the steering wheel is operated as shown in the figure are shown in FIGS. 5, 6, and 7, respectively.

The characteristic indicated by the solid line A in FIG. 5 is the characteristic indicating the change in the center-of-gravity lateral slip angle β of the vehicle equipped with this embodiment, and the broken line B in the figure
The characteristic shown by is a change in the center-of-gravity exclusive lateral slip angle of a vehicle that only controls the steering gear ratio.

As can be seen from the figure, in a vehicle that only controls the steering gear ratio, it is almost impossible to realize β=O.
The vehicle equipped with the device of this embodiment can always realize this β-〇.

Furthermore, changes in the yaw rate and changes in the lateral acceleration α are always stable during transient motion and during steady turning motion, as shown by solid line O in Figure 6 and solid line E in Figure 7. (In other words, this always stable steering characteristic is set as the target steering characteristic, and this target steering characteristic is faithfully realized by the own vehicle). On the other hand, in a vehicle in which only the steering gear ratio is controlled, both the yaw rate and the lateral acceleration α are unstable, as shown by the broken line in FIG. 6 and the broken line F in FIG.

It is.

Note that in the above embodiment, the vehicle specifications used for calculation are fixed (
For example, it is set to the value of each vehicle specification at the time of shipment)
For example, the front equivalent cornering power eKF may be changed as the steering gear ratio changes, or the front and rear wheel cornering powers KF may be changed.

If the KR value is changed in response to changes in road surface conditions and degree of tire wear, the accuracy of achieving the target steering characteristics will be further improved.

In addition to calculating the steering gear ratio target value N from the calculations described above, the steering gear ratio target value N can be obtained by table lookup processing by equipping a data table with data obtained in advance for multiple vehicle speed V values. By calculating 11- by 11-, the calculation speed can be increased by 1°. The same thing can be said about the steady yaw rate gauge target value 100.

(Effects of the Invention) As explained in detail above, the present invention provides a steering wheel 1. .

By controlling both the steering gear ratio and the rear wheel steering angle, the vehicle can faithfully achieve the target steering characteristics during steady turning motion and during transient motion, regardless of changes in vehicle speed. can do. Therefore, by freely setting the target steering characteristics, the steering characteristics of the vehicle can be freely controlled.

In addition, steering gear ratio control and rear wheel steering angle control
It is impossible to keep the center-of-gravity exclusive sideslip angle β always close to zero regardless of changes in vehicle speed.During transient motion, rear wheel steering angle control keeps the center-of-gravity exclusive sideslip angle (acceleration 1...speed) constant regardless of vehicle speed. It can be close to zero. This makes it possible to achieve extremely ideal steering characteristics.

Furthermore, in order to achieve such ideal steering characteristics, not only rear wheel steering angle control but also steering gear ratio control is performed to achieve the desired steering characteristics at high speeds (for example,
In order to realize the characteristic that the steady sideslip angle β = 0),
It is possible to prevent the occurrence of a situation in which the rear wheel steering amount is too large and cause a decrease in the yaw rate, and it is possible to improve steering stability. 1゜

[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. 8 is a flowchart showing processing executed in the arithmetic processing unit in the embodiment; Fig. 4 is a turning FIG. 5 is a diagram showing an example of a change in steering angle of the steering wheel during operation, and FIG. 5 is a characteristic showing a change in the transverse polygon of the center of gravity in a vehicle equipped with the device of the embodiment when the steering angle of the steering wheel is changed as shown in FIG. 4. 1...FIG. 6 is a characteristic diagram similarly showing changes in yaw rate, and FIG. 7 is a characteristic diagram similarly showing changes in lateral acceleration. 100...Vehicle speed detection means 101...Steady steering gain target value setting means 102...
Steering gear ratio target value calculation means 108...Steering gear ratio variable means 104...Handle steering angle detection means 105...Rear wheel steering angle target value calculation means 106...Rear wheel steering means]...Calculation Processing device 2... Handle steering angle sensor 3... Vehicle speed sensor 4... Power steering controller (steering gear ratio variable means) 5... Power steering device 6... Rear wheel steering device, 7... Hydraulic type Steering device 8...Steering handle 9, ]0...Front wheel 11, 12...Rear wheel θ
S...Handle steering angle ■...Vehicle speed N...Steering gear ratio target value δ,...Rear wheel steering angle target value G...Steady yaw rate gain target value (steady steering gain i. ) β...center-of-gravity exclusive lateral slip υ angle β...center-of-gravity exclusive lateral slip angle acceleration Fig. 1 Fig. 2

Claims (1)

[Scope of Claims] 1. Steering wheel steering angle detection means for detecting the steering angle of the steering wheel; vehicle speed detection means for detecting vehicle speed; Steady steering gain target value setting means for setting a target value of a steering gain; and a means for setting a steady steering gain target value corresponding to the steady steering gain target value and vehicle speed, and making a steady sideslip angle at the center of gravity of the own vehicle always near zero regardless of changes in vehicle speed. a steering gear ratio target value calculating means for calculating a target value of the steering gear ratio for the vehicle by calculation using the vehicle specifications of the own vehicle; a steering gear ratio variable means that sets the steering gear ratio to a value corresponding to the vehicle speed V and the steering angle of the steering wheel based on the steering gear ratio target value and the vehicle specifications of the own vehicle used by the steering gear ratio target value calculation means. Also, a rear wheel steering angle target value calculating means for calculating a target value of the rear wheel steering angle such that the sideslip angular acceleration of the center of gravity of the own vehicle is always near zero; 1. A vehicle steering system control device comprising: rear wheel steering means for steering rear wheels.