JPS6280158A - Vehicle steering system control device - Google Patents

Abstract

PURPOSE:To control a steering system so that a previously set and desired motion performance is always exhibited irrespective of variations in wheel load, by compensating the items of a vehicle for controlling the steering system in accordance with the loads of wheels. CONSTITUTION:A desired motion variable computing means 102 obtains a desired value of a motion variable corresponding to a turn angle of a steering wheel detected by a steering wheel turn angle detecting means 100 and a vehicle speed detected by a vehicle speed detecting means 101 in accordance with a desired vehicle model containing a previously set and desired operating performance. Further, a control amount generating means 103 delivers a control amount of a desired steering system status value for realizing the desired value of the motion variable in accordance with the desired value and the items of the vehicle. Further, a steering system status amount changing means 104 changes the steering system status value of the vehicle in accordance with the control amount. Further, a vehicle item compensating means 106 compensates the items of the vehicle used at the control amount generating means 103 in accordance with a wheel load detected by a wheel load detecting means 105.

Description

[Detailed Description of the Invention] (Industrial Application Field) This invention controls the motion performance of a vehicle to achieve a preset target motion performance by controlling the state quantity of a steering system. The present invention relates to a vehicle steering system control device, and particularly relates to a vehicle steering system control device that does not affect control accuracy even when a change in wheel load occurs.

(Prior Art) A conventional vehicle equipped with a mechanical link type steering device is configured to steer the front wheels according to the steering angle of the steering wheel, and the dynamic performance associated with steering depends on the vehicle's vehicle performance. The driving performance is determined uniformly based on specifications, and is unique to each vehicle model.

On the other hand, the applicant of the present application previously filed a patent application filed in
No. 018, Japanese Patent Application No. 188158, Japanese Patent Application No. 1881, Japanese Patent Application No. 1881-
No. 188158, etc., assuming a target vehicle with a target dynamic performance, based on the vehicle specifications and equation of motion regarding the target vehicle, target values of motion variables corresponding to the steering wheel steering angle and vehicle speed, that is, the target vehicle The steering angle of the vehicle's wheels (at least one of the front wheels or rear wheels) is determined so that the vehicle (vehicle equipped with the device) achieves the motion variable target value that represents the motion performance exhibited by the vehicle. We are proposing a device to control this.

In other words, by using this device, it is possible to freely control exercise performance.

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

That is, for example, when carrying a load equivalent to the vehicle's own weight, such as in a cargo-only vehicle, the vehicle specifications become thicker and change dramatically.

In particular, the mass, center of gravity, and moment of inertia of the vehicle fluctuate, and tire characteristics (particularly cornering power) also fluctuate due to changes in wheel loads.

However, when performing the above control, the device according to the prior application performs calculations using preset vehicle specifications of the own vehicle.
The control amount of the wheel steering angle is determined, but since the vehicle specifications of the own vehicle are fixed values, even if the actual vehicle specifications change due to the load change as described above, the control amount is performed in a constant manner, resulting in fluctuations in control accuracy.

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

The motion variable target value calculation means 102 calculates the steering angle θs1 of the steering wheel detected by the steering angle detection means 100 and the vehicle speed detection means based on a target vehicle model having preset target motion performance. 10
A target value M of the motion variable corresponding to the vehicle speed V detected in step 1 is determined.

The control amount generating means 103 generates a control amount S of the state quantity of the steering system necessary to realize the movement variable target value M based on the movement variable target value λ (and the vehicle specifications of the host vehicle).

The steering system state variable means 104 changes the state amount of the own vehicle's steering system in accordance with the control amount S.

The vehicle specification correction means 106 corrects the vehicle specifications of the own vehicle used in the control amount generation means 1 (L3) according to the wheel load of each wheel detected by the wheel load detection means 105.

(Function) Even if a large load is applied to the vehicle and the dynamic characteristics change, the wheel load detection means 105 and the vehicle specification correction means 106 estimate the load change from the change in the wheel load and adjust the automatic control system for use in control. By correcting the values of the vehicle specifications of the car to the values of the actual vehicle specifications after the load change, the steering system can be adjusted so that it always has the preset target driving performance regardless of the load change. Can be controlled.

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

The arithmetic processing device 1 is configured by a microcomputer or other electric circuit, and calculates the steering angle θ8 of the steering wheel 8 detected by the steering wheel steering angle sensor 2.
and the vehicle speed v1 of the vehicle equipped with the device of this embodiment (hereinafter referred to as "own vehicle") detected by the vehicle speed sensor 8, and the wheel load sensors 18 to 18 provided on each of the front wheels 9.10 and rear wheels 11.12.
The left front wheel load W□, the right front wheel cylinder NW2, the left rear wheel load W8, and the right rear wheel load W detected in step 16 are input, predetermined calculations are performed, and a rear wheel steering angle command value δR is output.

The front wheels 9 and 10 are steered to a steering angle corresponding to the steering angle of a steering wheel 8 by a mechanical link type steering device 6 similar to that of a conventional vehicle.

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 5. This rear wheel steering device 5 controls the hydraulic steering device 7 by changing the oil pressure applied to the hydraulic steering device 7 in accordance with the rear wheel steering angle command value δR input from the arithmetic processing device 1. (Details are substantially the same as those described in Japanese Patent Application No. 188158/1983).

As the wheel load sensors 18 to 16, suspension stroke sensors are used to detect the amount of displacement of the suspension of each of the wheels 9 to 12.

FIG. 8 and FIG. 4 are flowcharts showing the processing executed by the arithmetic processing device 1 when the arithmetic processing device 1 is configured using a microcomputer.

The process shown in the figure is repeatedly executed at predetermined time intervals, and initialization is performed when the ignition switch is turned on.

In the process of step 21, both data of the steering wheel steering angle θS inputted from the wheel steering angle sensor 2 and the vehicle speed ■ inputted from the vehicle speed sensor 8 are read.

In the process of step 22, by calculation regarding a target vehicle model having a preset target motion performance,
A target value of a motion variable corresponding to the above-mentioned steering wheel steering angle θ8 and vehicle speed ■, that is, a target value of yaw angular acceleration ¥ is calculated.

The above target vehicle model is a simulation model in which a vehicle with target dynamic performance is set using vehicle specifications and a motion equation, and the steering wheel steering angle θ8 is used as a variable.
By giving and vehicle speed V, the motion state of the target vehicle model corresponding to these θS and V is determined, and the yaw angular acceleration at this time is set as the target value ¥.

Note that the calculation of the above-mentioned yaw angular acceleration target value V is the same as the method of finding a solution from the equation of motion of a normal vehicle (
(Please refer to Japanese Patent Application No. 188158/1988 for specific calculation formulas).

Next, in step 28, the vehicle specifications of the own vehicle that have been corrected by a separate routine shown in FIG. 4 are read. In this example, quality of own vehicle #M1 yaw moment of inertia of the center of gravity of the own vehicle Iz1 distance between the front axle of the own vehicle and the center of gravity LF-, distance between the rear axle of the own vehicle and the center of gravity LR1 of the own vehicle Front wheel cornering power KBr 1 The rear wheel cornering power KRO value of the host vehicle is corrected. This correction process will be described later.

In the next step 24, calculations are performed to determine the rear wheel steering angle of the own vehicle that is necessary for the own vehicle to realize the yaw angular acceleration target value V obtained in the above step 22.

In this calculation, a simulation model (hereinafter referred to as "own vehicle model") that has the driving performance of the own vehicle is set according to the vehicle specifications of the own vehicle, and the above yaw angular acceleration target value is substituted into this own vehicle model. By doing this (in addition, using the steering wheel steering angle θ8 and wheel 7v), what value is the rear wheel steering angle when the yaw angular acceleration of the own vehicle model is ¥?
・It is something that asks for something. This calculation is also shown in the aforementioned Japanese Patent Application No. 188158/1982.

Among the vehicle specifications of the own vehicle used here, the mass M of the own vehicle
1 Yaw moment of inertia at the center of gravity of your vehicle 1 Distance between your vehicle's front axle and center of gravity LF1 Distance between your vehicle's rear axle and center of gravity LR1
The corrected value read in step 28 is used as the front wheel cornering power KF1 of the own vehicle and the rear wheel cornering power KRO value of the own vehicle. Other vehicle specifications of your vehicle are:
For example, a value at the time of shipment of the vehicle is stored in advance as a fixed value in a memory, and this is read out and used for calculation.

Then, in step 25, the rear wheel steering angle command value is output to the rear wheel steering device 5.

The rear wheel steering device 5 supplies the hydraulic pressure required to adjust the actual steering angle of the rear wheels 11.12 to the rear wheel steering angle command value 7R to the hydraulic steering device I11.7.

As a result, the actual steering angle of the rear wheels 11, 12 becomes equal to the rear wheel steering angle command value 7RK, and the actual yaw angular acceleration of the host vehicle at this time becomes equal to the yaw angular acceleration target value γ. In other words, the target driving performance can be achieved by the own vehicle.

Moreover, in this embodiment, when the carrying load of the own vehicle changes, the vehicle specifications of the own vehicle used in step 24 are adjusted so that the vehicle specifications of the own vehicle are the same as the actual vehicle specifications that have changed due to this load change. By correcting the specifications, even if the live load changes,
Steering can always be done with the same motion characteristics. In other words, regardless of changes in live load, the accuracy of achieving the target motion performance is always the same.

Next, the process of correcting the vehicle specifications of the own vehicle in accordance with the above-mentioned change in payload will be explained with reference to the flowchart shown in FIG. 4.

In step 81, the output of the vehicle speed sensor 8 is read to determine whether the vehicle speed is v-0, that is, whether the vehicle is stopped. Here, when ■>01, that is, it is determined that the vehicle is running, the vehicle specifications of the own vehicle are not corrected. This is because the wheel loads applied to each wheel vary when the vehicle is running, so in order to accurately determine the wheel loads, it is necessary to do so while the vehicle is stopped.

When it is determined that the vehicle is stopped, step 8
2, each data of the left front wheel load W, the right front wheel load W2, the left rear wheel load W3, and the right rear wheel load W detected by each wheel load sensor 18 to 16 is read.

Then, in the next step 88, the vehicle specifications of the own vehicle are corrected based on the above-mentioned read wheel loads W□ to W. This correction process is performed as follows.

First, the quality iM of the own vehicle is determined by the sum of the loads on each wheel. Therefore, M=1mi, Wl°-(11) is performed to determine the quality of the own vehicle Hy, and this value is temporarily stored.

Next, depending on the change in the center of gravity G, the distance L between the front axis and the center of gravity is
Since F and the distance LR between the rear axis and the center of gravity change, these LF and LR'a' are determined.

As is clear from Figure 5, the wheelbase of your vehicle is set to L.
Then, . Here, if we approximate our own vehicle as a two-wheel steered vehicle, we get
It is sufficient to consider the wheel loads of the front and rear wheels on the left side of the vehicle, as in equation (2) above, but if you want to find a more accurate value, you can find LF using the calculation: i:1". Good. 00 in the figure is the center of gravity when not loaded.

Also, the distance LR between the rear axle and the center of gravity is LR=L Lp
WL&'! in Figure 5 is the live load.

Next, the calculation for determining the yaw moment of inertia z of the own vehicle will be explained.

Now, the wheel load of each wheel when there is no live load W, is
In the order of left front wheel 9, right front wheel 10, left rear wheel 11, and rear wheel 12,
Assuming W SW 1W SW , the increase in the wheel load of each wheel when the live load W is added is ΔW = w, -w□. ... (
5)ΔW2””2”20
... (6) ΔW8=W8-W8o・-f7) 3w4=w, -w,. ---
(81, and 1, Mi □ΔW = W, ... (9)
It is. Therefore, as shown in Fig. 6, if the distance between the center of gravity Gw of the live load WL and the vehicle center of gravity 0 is LW1~ and the distance between the front axle is LW = Lg Llr... (
11).

The yaw moment of inertia of the own vehicle at this time, E2, is calculated by dividing the yaw moment of inertia of the own vehicle when it is not loaded by 2°, and the yaw moment of inertia of the loaded object is zw, then z - zo
It is determined by 10IZW 10WLLW - (12). Here, '■zw is expressed as follows. However, m: Mass of minute volume dV e: Distance from the center of gravity of the loaded object to minute volume dV.

Here, freight vehicles (trucks, tank lorries, etc.)
In this case, the cargo is often of one type, and its density can be assumed to be constant, and the shape of the cargo is approximately determined by the shape of the cargo compartment or deck. 'IZW is determined by the mass W of the load and the shape factor of 1 (a constant determined by the shape of the cargo compartment, loading platform, tank, etc.) = w, ・Ko... (14
).

Therefore, in step 88, according to the above equation (14),
Find 2. In other words, W can be found using the formula 91 mentioned above, and K1 can be stored in advance in memory for each purpose during the production process, or 4F can be stored in memory according to the type of load at the time of order. Just do it like this.

Next, determination of the front wheel cornering power Ky and the rear wheel cornering power KR will be explained.

The tire sideslip angle β and the front wheel cornering power KF - the rear wheel cornering power KH have a relationship as shown in FIG. 7, and as the wheel load W increases, the slope of the characteristic curve increases. That is, as the wheel load W increases, the cornering power also increases.

Therefore, the relationship between wheel load and cornering power is determined in advance by
It is stored in the memory as a data table or function, and by lookup processing of this data table or calculation of the function, the front wheel cornering power KF is calculated from the front wheel loads W□, W2, and the rear wheel cornering power is calculated from the rear wheel load "81" 4. Find KR.

The relationship between wheel load and cornering power has a characteristic as shown in FIG. 8, for example, when it is assumed that the linearity of cornering power with respect to tire sideslip angle β is sufficient.

In addition, in the above embodiment, an example was shown in which the rear wheel steering angle is controlled as the state bone of the steering system as a control target, but in addition to this, it is possible to control both the front wheel steering angle and the rear wheel steering angle ( Special request 1977
(Already proposed in Patent Application No. 9-188158), and one that controls the steering gear ratio (Already proposed in Patent Application No. 1988-?3L39)
The present invention can be similarly applied to a device that controls a steering system using a self-vehicle model such as the following.

Further, in the above embodiment, an example was shown in which the vehicle specifications of the own vehicle are corrected while the vehicle is stopped, but this is only performed when the ignition switch is turned on.

I'll do it. You can even run a 5K. In this case, instead of the process in step 81 in FIG. 4, a process for determining that the ignition switch has been switched from OFF to ON may be executed.

By doing so, the processing time can be reduced and used for other processing. In particular, in luggage-only vehicles, when load changes occur, it is mainly due to the loading and unloading of luggage, and the engine is usually stopped when loading and unloading luggage, so the above-mentioned process is necessary. It is valid to do so.

(Effects of the Invention) As explained in detail above, the present invention detects the wheel load of each wheel and corrects the vehicle specifications of the own vehicle used for controlling the steering system according to this wheel load. For example, even if a large load is applied to the vehicle and the dynamic characteristics change, the vehicle specifications of the own vehicle used for control will be changed to the actual vehicle specifications after the load change in accordance with the change in dynamic characteristics. can be corrected to the same value.

As a result, the steering system can be controlled so that it always has the preset target motion performance regardless of load changes.
Steering can always be performed with the same motion characteristics regardless of load changes.

[Brief explanation of drawings]

FIG. 1 is a block diagram of the present invention; FIG. 2 is a block diagram of an embodiment of the present invention; FIGS. Figure 6 is a diagram showing the movement of the center of gravity and wheel load during loading; Figure 6 is a diagram showing the center of gravity of the loaded object and its relationship; Figure 7 is a characteristic diagram showing the relationship between tire sideslip angle and cornering power; FIG. 8 is a characteristic diagram showing the relationship between wheel load and cornering power. 100...Handle steering angle detection means 101...Vehicle speed detection means 102...Motion variable target value calculation means 108...Controlled amount generation means 104...Steering system state quantity variable means 105...Wheel load Detection means 106...Vehicle specification correction means 1...Arithmetic processing device 2...Handle steering angle sensor 8...Vehicle speed sensor 5...Rear wheel steering device 7.
...Hydraulic steering device 9.10...Front wheels 11, 12...Rear wheels 18-16...Wheel load sensor θS...Handle steering angle V...Vehicle speed 6B'' Rear wheel steering angle command Value... Yaw angular acceleration target value, W□...
Left front wheel load W2...Right front wheel load W8...Left rear wheel load W,...Right rear wheel load Patent applicant Nissan Motor Co., Ltd. f-,,+- Representative patent attorney Hidei Sugimura Akatsuki, i'i
:, 1゛ This Figure 5 Figure 6

Claims (1)

[Claims] 1. Based on a target vehicle model having a steering wheel steering angle detection means for detecting a steering angle of a steering wheel, a vehicle speed detection means for detecting a vehicle speed, and a preset target motion performance, a motion variable target value calculating means for calculating a target value of a motion variable corresponding to the steering angle of the steering wheel and the vehicle speed; and realizing the motion variable target value using the determined motion variable target value and vehicle specifications of the host vehicle. a control amount generating means for generating a control amount of the state amount of the steering system necessary for the control, a steering system state amount variable means for changing the state amount of the own vehicle's steering system in accordance with the control amount; wheel load detection means for detecting the wheel load of the wheels; and vehicle specification correction means for correcting the vehicle specifications of the host vehicle used by the control amount generation means according to the detected wheel loads of the respective wheels. A vehicle steering system control device comprising: 2. The vehicle steering system according to claim 1, wherein the vehicle specification correction means corrects the vehicle specifications in accordance with the wheel load when the ignition switch is turned on or when the vehicle is stopped. System control device.