JPS63149265A - Actual rear wheel steering angle control device for vehicle - Google Patents

Abstract

PURPOSE:To prevent the rear section of a vehicle body from projecting outward in a turning direction during turning, by performing a computation relating to the motion of the vehicle so as to obtain a desired actual rear wheel angle which is to cause the rear point on the vehicle to follow the locus of motion of the front point, and the moving locus of the front point. CONSTITUTION:There is provided a desired actual rear wheel angle computing means 103 for performing computation relating to the motion of a vehicle in accordance with output signals from a front actual steering angle detecting means 101 and a vehicle speed detecting means 102, and the locus of the motion of the front one of two points which are aligned in the longitudinal direction, so as to obtain a desired actual rear wheel steering angle with which the rear one of the two point is to follow the locus of the motion of the front point. Further, there is provided a motion locus computing means 104 for computing the further motion locus of the front point in accordance with the output signals from the detecting means 101, 102, and thus obtained motion locus of the front point is stored in a memory means 105. Further, a rear wheel steering means 105 is controlled so as to allow an actual rear wheel steering angle to correspond to the desired actual rear wheel steering angle.

Description

Detailed Description of the Invention (Field of Industrial Application) This invention reduces the inner wheel difference between the front and rear wheels by controlling the actual steering angle of the rear wheels of a vehicle that can steer both the front and rear wheels. The present invention relates to a rear wheel actual steering angle control device for a vehicle that reduces the size of the steering angle and prevents the rear part of the vehicle body from protruding outward when turning.

2 (Prior Art) As such a conventional control device, for example, there is one previously proposed by the present applicant in Japanese Patent Application No. 143842/1982.

This device stores traveling direction data for each predetermined distance movement of a predetermined point A at the front of the vehicle body, that is, the movement locus of point A, and stores the traveling direction data of point A at a predetermined point B at the rear of the vehicle body. Extract the data, and based on this traveling direction, the actual steering angle of the front wheels at that point, and the yaw angle of the vehicle body, the actual rear wheel steering angle that causes point B to move in the traveling direction of point A at this point. The target value is determined by geometric calculation, and the rear wheel steering angle is controlled so that the actual rear wheel steering angle corresponds to the determined rear wheel actual steering angle target value. Point B at the rear of the vehicle follows the movement trajectory of point A at the front of the vehicle body, thereby reducing the difference between the inner wheels of the front and rear wheels during turning to reduce the turning radius and preventing the rear of the vehicle from protruding outward when turning. It functions as expected.

(Problems to be Solved by the Invention) By the way, in the above-mentioned conventional device, since the rear wheel actual steering angle target value is determined by geometric calculation, when driving at an extremely low speed, the vehicle body is positioned at point B at the rear of the vehicle body. Although the movement trajectory of point A at the front can be traced well, as the vehicle speed increases, sideslip etc. occur as a result.

This causes an error in the rear wheel actual steering angle target value, causing the point B to move away from the locus of movement of the point A, resulting in a problem that the turning radius cannot be made sufficiently small.

The present invention provides a control device that advantageously solves these problems.

(Means for Solving the Problems) As shown in FIG. 1, the vehicle rear wheel actual steering angle control device of the present invention includes a front actual steering angle implementing means 101 for detecting the actual steering angle of the front wheels; , a vehicle speed detection means 102 that detects the vehicle speed, and the detected actual steering angle of the front wheels and the vehicle speed, and two points that are aligned with each other in the longitudinal direction of the vehicle and maintain predetermined relative positions with respect to the vehicle and each other. After calculating the vehicle motion based on the movement locus of the front point, and calculating the rear wheel actual steering angle target value that causes the rear point of the two points to follow the movement locus of the front point. A wheel actual steering angle target value calculating means 103 performs calculations related to the motion of the vehicle based on the detected actual front wheel steering angle and vehicle speed, and the determined rear wheel actual steering angle target value,
a movement trajectory calculation means 104 for calculating a further movement trajectory of the point ahead; and a movement trajectory calculation means 104 for storing the movement trajectory of the calculated point ahead, and transmitting the stored movement trajectory to the rear wheel actual steering angle target value calculation means. A movement trajectory storage means 105 for outputting the output, and a rear wheel steering means 106 for making the actual steering angle of the rear wheels correspond to the target value of the rear wheel actual steering angle for the vehicle, which includes a rear wheel steering means for making the rear wheels correspond. It's getting better.

(Function) According to the device configured as described above, the rear wheel actual steering angle target value, in which the rear point follows the movement trajectory of the front point, and the movement trajectory of the front point, are determined based on the movement trajectory of the front point. Since it is determined by calculation, even if the vehicle speed increases and the vehicle skids, the error in the rear wheel actual steering angle target value can be made extremely small.
This allows the rear point to always reliably follow the locus of the front point.

(Example) Hereinafter, an example of the present invention will be described in detail based on the drawings.

FIG. 2 shows a first embodiment of the rear wheel actual steering angle control device for a vehicle according to the present invention.
FIG. 3 is a block diagram showing the configuration of the embodiment using functional blocks, and FIG. 3 is a schematic diagram showing the positional relationship between a point A as a front point and a point B as a rear point.
As shown in FIG. 3, point A is set at the front end position of the vehicle 8 on the longitudinal central axis (this is the X axis) of the vehicle 8 to be controlled, while point B is similarly set at the front end position of the vehicle 8. It is set at the rear end position of the vehicle 8 on the x-axis. Here, the y-axis is
It is assumed that the center of gravity G of the vehicle 8 is orthogonal to the X-axis on the vehicle plane, the X-axis has a positive direction toward the front of the vehicle, and the y-axis has a positive direction toward the left of the vehicle. In addition, here we use the orthogonal coordinate system X
- A Y coordinate system is set, and its X-axis and Y-axis coincide with the above-mentioned X-axis and y-axis when the ignition switch of the vehicle 8 is turned on.

1 in FIG. 2 indicates the actual steering angle δ2 of the front wheels 9, 9 steered by the steering handle (not shown) of the vehicle 8 shown in FIG. 2 is a normal steering angle sensor as the front actual steering angle implementing means 101 which detects and outputs from the angle, and vehicle speed detecting means 102 which detects and outputs the vehicle speed V of the vehicle 8 to be controlled. Here, the output signals of these sensors 1 and 2 are input to an arithmetic processing unit 3 constituted by a normal microcomputer having a CPU and memory.

This arithmetic processing device 3 includes rear wheel actual steering angle target value calculation means 10
It functions as a rear wheel actual steering angle target value calculation section 4 as a rear wheel actual steering angle target value calculation section 3, a movement trajectory calculation section 5 as a movement trajectory calculation means 104, and a data storage section 6 as a movement trajectory storage means 105. The wheel actual steering angle target value calculation unit 4 calculates the inputted front wheel actual steering angle δ.

and vehicle speed ■, and the fourth output from the data storage section 6.
The n-th moving direction of point A with respect to the current and past X-axes shown in the figure, that is, the direction immediately before point B ψA(n)
and the data of the current yaw angle ψ of the vehicle 8 with respect to the , the rear wheel actual steering angle target value δ8, which is the moving direction at the past position of point A, is determined. Here, the movement trajectory calculation section 5 calculates the vehicle speed from the inputted front wheel actual steering angle δ and vehicle speed V, and from the rear wheel actual steering angle target value δ calculated by the rear wheel actual steering angle target value calculation section 4. The yaw angle ψ of the vehicle 8 with respect to the X axis after traveling a predetermined distance from the current position by calculating the vehicle model expressed as a balance equation of the forces acting on the vehicle 8. . 8 and the direction of movement ψ, (0) to the point with respect to the The movement locus of point A and the current yaw angle ψ of the vehicle 8 with respect to the X-axis are stored as data. Incidentally, when storing ψA(1) and ψ here, their values are stored as the above-mentioned ψA(0) and ψ, .

8, and the memorized ψA(1) to ψA(n
) values are sequentially replaced (shifted).

The rear wheel actual steering angle target value δ8 calculated by the rear wheel actual steering angle calculation unit 4 is:
Here, the rear wheel steering device 7 is also used.

This rear wheel steering device 7 controls the steering angle of the rear wheels 10.10 so that the actual steering angle of the rear wheels 10.10 shown in FIG. 3 matches the rear wheel actual steering angle target value δ7. For example, a hydraulic control device that changes the supplied hydraulic pressure according to an input electric signal, and a hydraulic steering device that operates an actuator to steer the rear wheels 10.10 using the hydraulic fluid supplied from the hydraulic control device. (For details, the present applicant previously published Japanese Patent Application Laid-Open No. 61-6767.
Please refer to it as it is written in No. 0).

5 and 6 are flowcharts showing arithmetic processing programs executed by the above-mentioned arithmetic processing device 3. Below, along with an explanation of these flowcharts, the operation of the device in this example will be explained.

The program shown in FIG. 5 is an initial setting program, and is executed each time the ignition switch is turned on and each time the vehicle 8 is stopped.

In step 11, the current position A (1) of point A on the X-Y coordinate system and the past position (
X at n-1) passing positions A(2) to A(n)
The initial value data of the movement directions ψA(1) to ψa(n) of point A relative to the axis are all stored as O in the memory.

Here 5. dx is a distance C1x = -) that divides the entire length of the vehicle 8 into an arbitrary integer number n, or an integer part of L/n.

Then, in the next step 12, the initial value data of the yaw angle ψ from the X axis of the vehicle 8 is stored as O in the memory.

By executing such a program, when the vehicle 8 starts, it is possible to move the point B straight to the position of the point A before starting,
It is possible to reliably prevent the rear part of the vehicle body from protruding outward during turning and coming into contact with a wall surface or the like.

The program shown in FIG. 6 is an actual steering angle control program, and this program is executed every time the vehicle 8 travels the distance ΔX.

In this program, first, in step 21, the detected values of the front wheel actual steering angle δ and the vehicle speed V are input, and then in the next step 22
, the moving direction data ψ of the past position A (n) of point A in front of the thin plate (n-1) from the current position A (1) of point A
, (n), that is, the past movement direction data to the point immediately before point B and the current yaw angle ψ of the vehicle 8 are retrieved from the memory.

Continuing (in step 23, based on the above δ2.■, ψA(n) and ψ, the rear wheel actual steering angle target value δ8 is determined using the following formula.

However, the mass eKF of the vehicle 8; the front wheel equivalent cornering power KR of the vehicle 8; the rear wheel cornering power LF of the vehicle 8; the distance LR from the center of gravity G of the vehicle 8 to the front axle; Distance to axle L8; Wheelbase (LH = Ly + LR) b
is the distance from the center of gravity G of the vehicle 8 to the point B.

Therefore, this step 23 is performed by the rear wheel actual steering angle target value calculation section 4.
corresponds to

The above equation (1) can be derived from the balance equation of the forces acting on the vehicle 8 as follows.

In other words, is the balance of forces acting on the vehicle 8 the estimated value of the yaw rate at the center of gravity? and for the X axis, it can be expressed by the following equation.

■ On the other hand, the target traveling direction β with respect to the X axis in which point B should travel
= is determined by the following formula % formula % (4), and in order for point B to move in this direction β-,
Assuming that the actual steering angle of the rear wheels 10.10 is δ, the sideslip angle β8 at point B with respect to the X axis should be expressed by the following equation. Therefore, from equations (4) and (51), the following equation is obtained, and by combining this equation (6) and the above equations (21 and (31), equation (1) is derived.

The rear wheel actual steering angle target value δ thus obtained is output to the rear wheel steering device 7 in the next step 24.

As a result, point B moves from the current position B(1) in the direction in which point A moved in the past at the nearest position in front of it, that is, point B follows the movement trajectory of point A. In addition, the steering angle of the rear wheels 10.10 can be controlled.

Next, in step 25, the above equation (2) is applied.

(3) and γ=? , β=β, and the current yaw rate γ and side slip angle β of the vehicle 8 are determined by giving δF + rM and V to the vehicle model expressed by the following equation obtained by replacing β=β.

however, It is.

Then, in step 26, from the time Δtl required to travel the predetermined distance/X, the current yaw angle ψ, and the current yaw rate γ obtained in step 25, the following formula % formula % (8) , the yaw angle ψ, .
, , and the above-mentioned current yaw rate γ and side slip angle β, the moving direction ψA of point A when the vehicle 8 next moves by ΔX is determined by the following equation expressing the geometrical relationship between these.
Find (0). Here, a indicates the distance from the center of gravity G to the point A.

Therefore, these steps 25 to 27 correspond to the movement trajectory calculation section 5.

Thereafter, in step 28, the data in the memory is sequentially replaced (shifted) as shown below, ψA(n-1
) ψA(n) ψ^(n-2)
ψA(r+-1)ψA(1)
ψA(2) In the subsequent steps 29 and 30, the above ψA(0) and ψ7- are stored in the memory as the data of ψA(1) and ψ at the next time this program is executed (during ΔX running), Return after that.

Therefore, these steps 28 to 30 are performed in the data storage section 6.
corresponds to

According to the device of this example described above, the rear wheel actual steering angle target value δ
8 and the direction of movement of point A are performed using a balance equation for the forces acting on the vehicle 8, so even if the vehicle speed increases, the movement trajectory of point A to point B can always be traced with high precision. This can be traced to the vehicle 8 when the vehicle speed increases.
The turning radius of the vehicle can be made sufficiently small.

FIG. 7(a) and FIG. 8(a) show the vehicle speed V
= 10km/h, and in the figure, P indicates the trajectory of point A and Q indicates the trajectory of point B, respectively. From these figures as well, the effects of the device of this example described above are clear. In addition, Fig. 7 (bl and 8
Figure (b) shows six changes in the actual steering angle δ1 of the front and rear wheels of a vehicle equipped with the device of this example and a vehicle equipped with the conventional device.

Next, an apparatus according to a second embodiment of the present invention will be explained here.

In the device of the second embodiment, in the movement trajectory calculation unit 5 shown in FIG. 2 of the device of the first embodiment, the vehicle 8 is The following equation of motion that indicates the state of motion is
Lr H7)/V)-2 *'LR(δ*-(V
y-LR-r)/V), and here these equations (10),
The following 2V derived from (11), = 2eKr (δy-(Vy+Lp HT)/V
l /M+2* (δ*-(Vy-LRHr)/V
) /M-V ・rυ Te=213KF-LF (δr-(Vy+LFIT
)/V ) /Iz-2KR' LR(δ*-(Vy
-L++ -y)/V)/Iz and the following equation (16): Find the current yaw rate γ and sideslip angle β.

In addition, vy: lateral speed of the vehicle 8 ■y; Lateral translational acceleration of vehicle 8 ■2; Yaw moment of inertia of vehicle 8 It is.

According to this device, since the calculation for determining the moving direction of point A is performed using the equation of motion of the vehicle, the moving trajectory of point A can be determined more accurately, and as a result, even more precise control than the first embodiment can be performed. It can be carried out.

FIG. 9(a) shows the test results of running a vehicle equipped with the device of the second embodiment at a vehicle speed of 10 kn+/h, or FIG.
b) is the actual steering angle δ1 of the front and rear wheels at that time. Each shows the state of change of δ8, and P and Q in the figure are points A.

The movement trajectory of B is shown. This figure also shows that the second
It is clear that the apparatus of this embodiment can realize more precise control than the conventional apparatus as well as the apparatus of the first embodiment.

Incidentally, the apparatus of the present invention may also represent the moving locus of point A by the coordinates of point A at every predetermined time Δt2, and an example in which this is done will be described below as a third embodiment.

The device in this example has a 10th processor in the arithmetic processing device 3 in FIG.
The arithmetic processing program shown in the figure and FIG. 11 is executed, and the other configurations are the same as in the first embodiment.

The program shown in FIG. 10 is an initial setting program, and when the ignition switch is turned on,
It is executed when the vehicle 8 is stopped and when the vehicle 8 has been traveling straight for a predetermined period of time.

In step 31, the current position of point A in the X-Y coordinate system (1) and the past (n-1)
The initial value data of the coordinates of the passing positions A' (2) to A'' (n) are stored as follows. Note that ΔX is the distance that divides the total length into n pieces as in the first embodiment. do.

A(1) = (-b+n-Δx, 0)8'(2)
= (-b+(n-1)Δx, 0)A' (3)
= (-b+(n-2)Δx, 0)A(n)
= (-b+Δx, 0) ''' Also, in this step 31, initial value data of the coordinates of the current position B(1) of point B in the X-Y coordinate system is stored as follows.

B(1) = (-b, 0) Furthermore, these A(1), A''(2) to A'(n),
The coordinates of B(1) are determined from the positional relationship shown in FIG.

Then, in the next step 32, the initial value data of the yaw angle ψ from the X-axis of the vehicle 8 is stored as 0.

According to such processing, it is possible to prevent the rear part of the vehicle body from protruding outward when turning, similar to the program shown in FIG. - Flow can be prevented.

The program in Figure 11 is an actual steering angle control program,
This program is executed every predetermined time Δt2 only while the vehicle 8 is running.

In this program, first, in step 4I, the actual front wheel steering angle δ and the vehicle speed ■ are input, and then in step 42, Δ
Determine whether t2・V is smaller than ΔX, and as a result, Δ
If tt -V is smaller than ΔX or equal to Jx, that is, if the vehicle speed V is low or medium, in step 43, A(
1) to (n-1) Coordinate data A of point A of deflection (n)
(= (XA (n) , YA (n) )) and
Current coordinate data of point B B(1)(・(XB(1),
VB(1))) and the current yaw angle ψ of the vehicle 8 are retrieved from the memory, and in the subsequent step 44, the past coordinates (position) of the immediately preceding point A are set to point B using the following equation.
In order to move point B to A(n), that is, to make point B follow the movement locus of point A, the moving direction θ of point B with respect to the X axis is determined.

On the other hand, as a result of the judgment in step 42, Δt2·ν is A
If it is larger than x, proceed to step 45 and set A(1)
Coordinate data AC1) (=(
XA(1), YA(1))) and the above B(1) and ψ, and in the subsequent step 46, in the same way as step 44, point B is calculated from the past coordinates A( Find the moving direction θ of point B to move to /.Here, l is the integer part of the value of L/, dtz・V, and by the processing of steps 45 and 46, the vehicle speed Even in this case, the past coordinates of point A immediately before point B can be used as the moving target of point B.

Since θ obtained in this way corresponds to ψA(n) in the first and second embodiments, in the subsequent step 47,
In equation (1) in step 23 of FIG. 6, ψA(n)
By using this θ instead of , the rear wheel actual steering angle target value δ
In the next step 48, this δ value is output to the rear wheel steering device 7. As a result, here, the rear wheel 10.1 The steering angle can be controlled.

In step 49, in the same way as step 25 in FIG.
Then, the current yaw rate T and sideslip angle β are determined by equation (7), and in the next step 5o, the yaw angle ψζ after Δt2 has elapsed from the current time is estimated using the following equation. Here, the integration on the right side of equation (18) may be performed as Δt2·γ using the rectangular integration method used in step 26 of the first embodiment, or may be performed using other methods.

In the subsequent step 51, the coordinates A(1
), , , B(1)n, , and in the next step 52, the coordinate data of point A in the memory is sequentially shifted as shown below.

8 (n-1) -1111--→ A (n) ^(n
-2) A(n-1) A(2) -1→A(3) A(1) --1---→A(2) After that, in step 53 and step 54, the above A(1) , 1. lol
, B(1), , and ψwatm are expressed as A(1), B(1) at the next execution of this program (after Δt2)
) and ψ in memory, and then returns.

The apparatus of the third embodiment, which is controlled by the program described above, can also provide the same effects as the first embodiment. In addition, step 49 in the program of FIG.
The calculations for determining γ and β may be performed using the equation of motion regarding the vehicle 8 as in the second embodiment, and in this case, the same effects as in the second embodiment are produced.

(Effects of the Invention) Thus, according to the rear wheel actual steering angle control device for a vehicle of the present invention, even if the vehicle speed increases and the vehicle skids, etc., the error in the desired rear wheel actual steering angle target value is extremely reduced. Therefore, the rear point can always reliably follow the trajectory of the front point, and the turning radius can be made sufficiently small even when the vehicle speed increases.

[Brief explanation of the drawing]

FIG. 1 is a conceptual diagram of a rear wheel actual steering angle control device for a vehicle according to the present invention, FIG. 2 is a block diagram showing the configuration of a first embodiment of the present invention in functional blocks, and FIG. 3 is a diagram showing the first embodiment of the invention. FIG. 4 is an explanatory diagram showing the movement locus of point A in the first embodiment. FIGS. Flowchart 1 showing the program executed by the device 3, FIGS. 7 and 8 are operation explanatory diagrams showing the test results of the device of the first embodiment and the conventional device, and FIG. 9 is a flowchart of the program executed by the device 3. 10 and 11 are flowcharts showing a program executed by the arithmetic processing unit 3 in the third embodiment of the present invention. 101--Front actual steering angle execution means 102--Vehicle speed detection means 103-Rear wheel actual steering angle target value calculation means 104-Travel trajectory calculation means 105--Travel trajectory storage means 106--Rear wheel steering Means 1 - Steering angle sensor 2 -
・Vehicle speed sensor 3--Arithmetic processing unit 4--Rear wheel actual steering angle target value calculation section 5--Movement trajectory calculation section 6--Data storage section 7-
・-Rear wheel steering device 8-Vehicle 9・-Front wheels 10-Rear wheel ψA(1) ・Current moving direction of one point A ψA(n)
-・-Past moving direction ψ of (n-1) detailed point A from the present...Current yaw angle (with respect to the X axis) of the vehicle 8 A(1
) --- Current coordinates (position) A (n) of point A --- Past coordinates of point A (n-1) from the present B (1) ---
Current coordinates of point B Figure 2 Figure 7 (a) (b) Figure 8 (a) (b) Figure 9 (a) (b)

Claims (1)

[Scope of Claims] 1. Front actual steering angle implementing means for detecting the actual steering angle of the front wheels; Vehicle speed detecting means for detecting the vehicle speed; The detected actual steering angle of the front wheels and the vehicle speed; Based on the movement locus of the forward point of the two points that are aligned with each other in the direction and maintain a predetermined relative position with respect to the vehicle and each other, calculations regarding the movement of the vehicle are performed, and the backward point of the two points is rear wheel actual steering angle target value calculation means for calculating a rear wheel actual steering angle target value such that the point follows the movement trajectory of the point in front; the detected actual front wheel steering angle and vehicle speed; a movement trajectory calculation means for calculating a further movement trajectory of the point ahead by calculating the movement of the vehicle based on the actual wheel steering angle target value; and rear wheel steering means for controlling the actual steering angle of the rear wheel based on the stored movement locus so that the actual steering angle of the rear wheel corresponds to the obtained rear wheel actual steering angle target value. A rear wheel actual steering angle control device for vehicles.