JPS62258867A - Rear wheel steering method for all wheel steering vehicle - Google Patents

Abstract

PURPOSE:To restrain the exhibition of abnormal behavior of a vehicle to be minimum, by using the actual angular steering speed of front wheels as an important control parameter for two sets of rear wheels, in addition to the actual steering angle of the front wheels, and the vehicle speed, so that the characteristic of frequency response for the steering of the front wheels is improved. CONSTITUTION:In an automobile having two sets of rear wheels, a control device reads a weight exerted to each wheel to calculates the vehicle mass (m), the distances lf, lr1, lr2 between the gravitational center. and the front wheels, rear front wheels and rear rear wheels, and the cornering powers Kf, kr1, kr2. Further, the control device reads a vehicle speed V, and an actual steering angles deltaf, deltar1, deltar2. Further, in accordance with the steering of the front wheels, the actual steering angle deltar1 of the rear front wheels is set to a value which is (k) time as large as deltaf where (k) is a coefficient obtained from the yawdirection rotary inertial weight I, a Laplace operator (s) and the like, and therefor, the two sets of the rear wheels are steered so that the actual steering angle deltar2 of the rear rear wheels comes to be (lr2/lr1). Thus. it is possible to avoid abnormal behavior of the vehicle during steering of the rear wheels.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention provides a vehicle having at least two sets of steerable wheels, in which at least one set of wheels is variable with respect to the steering angle of the other set of wheels. The present invention relates to a method for steering multiple sets of wheels.

In particular, the present invention relates to a method of controlling a rear wheel steering angle when the rear wheels are steered in conjunction with the steering of the front wheels in an automobile having one set of front wheels and two sets of rear wheels.

Here, the term "set of wheels" refers to left and right wheels connected by an axle if the vehicle has an axle, and refers to left and right wheels having similar functions if the vehicle does not have an axle.

[Conventional technology]

Conventional vehicle steering methods involve steering only the front wheels or rear wheels, but there are exceptions, particularly vehicles with long wheelbases, in which multiple sets of wheels can be steered to enable tight turns. This method of steering multiple sets of wheels involves mechanically or hydraulically connecting steerable wheels to each other and steering the other sets of wheels at an angle proportional to the actual steering angle of one set of wheels. This is the way to do it.

When the front and rear wheels of a vehicle are steered using this steering method, the sideslip motion changes greatly depending on the vehicle speed, and the direction of the vehicle does not turn in the turning direction intended by the driver. Problems arise, such as the lateral acceleration of the motor not matching the rotational motion.

Therefore, the steering of the rear wheels is made independent of the front wheels, which are always steered, and when steering the rear wheels, the vehicle speed is taken in addition to the actual steering angle of the front wheels as a control parameter, and the rear wheels are steered in the direction that makes the sideslip angle zero. A method for controlling the steering angle of wheels has been proposed (Reference: Japanese Patent Application Laid-open No. 11173/1983).
.

This steering method will be explained below using a model that ignores the roll of the vehicle.

Vehicle mass m, vehicle yaw direction rotational inertia mass ■, vehicle speed ■
, the longitudinal distance 1r between the front wheels and the vehicle center of gravity, the longitudinal distance lr between the rear wheels and the vehicle center of gravity, the cornering power of the front tires (sum of both left and right wheels) K', the cornering power of the rear tires (Sum of both left and right wheels) K1, actual steering angle δ2 of the front wheels, actual steering angle δ1 of the rear wheels, side slip angle β of the center of gravity of the vehicle,
Letting the sideslip angle β1 of the front wheels, the sideslip angle β1 of the rear wheels, and the vehicle yaw rate (angular velocity in the yaw direction) γ, the equation of motion is expressed as follows. The longitudinal distance between a wheel and the vehicle's center of gravity refers to the longitudinal distance between the axle and the vehicle's center of gravity if there is an axle, or the imaginary line connecting the left and right wheels if there is no axle. It refers to the same distance in the front and rear direction assuming that it is an axle.

Here, (11 and (2)) are replaced by (3) and (4)
) and the vehicle is turning steadily (dβ/d
t=0, dγ/dt=o), and solving for the sideslip angle β at the center of gravity of the vehicle, we get β− ・−・−(5). That is, (mV+ <Ktl r Kir) ) CKt1
rδf−, A, δ1)■ −CKtδf+Krδf)−(nitlt”+, 1.su■ =0 ・−・・−
・It is sufficient to satisfy (6).

In equation (6), the ratio k (=δf/δf) of the actual steering angle δf of the rear wheels to the actual steering angle δf of the front wheels is as follows.

Note that l is the distance C1r''1r) between the wheels in the longitudinal direction.

Therefore, using equation (7), find the ratio k of the actual steering angle δf of the rear wheels to the actual steering angle δf of the front wheels, and
By steering the rear wheels based on δf in one control angle,
The sideslip angle of the vehicle can be set to zero.

In other words, the actual steering angle δ1 of the rear wheels is δf = δf ・−・−・(8
), and if the mass of the vehicle and the position of the vehicle center of gravity are treated as almost constant, then the quality of the vehicle itm, the distance 1f in the longitudinal direction between the front wheels and the center of gravity of the vehicle, and the distance in the longitudinal direction between the rear wheels and the center of gravity of the vehicle 1. ,, 1 can be treated as a constant for the cornering power of the front tires and the cornering power of the rear tires, the vehicle speed ■ and the actual steering angle δf of the front wheels are detected by a sensor, and the control angle is set δf accordingly. By steering the rear wheels in this manner, the sideslip angle β at the center of gravity of the vehicle can be set to O.

In addition, if the vehicle weight is detected by the load sensors installed on the front wheels and the rear wheels, the mass m of the vehicle, the distance l1 in the longitudinal direction between the front wheels and the center of gravity of the vehicle, and the distance between the rear wheels and the center of gravity of the vehicle can be determined accordingly. distance d1r in the longitudinal direction between them, cornering power Kt of the front tires, and cornering power K of the rear tires.

This allows the rear wheels to be more accurately steered in the direction that makes the side slip angle β equal to O.

Note that when the vehicle is traveling at low speed, the front wheels and rear wheels are sheared in opposite directions, and when the vehicle is traveling at high speed, the front wheels and rear wheels are sheared in the same direction. The boundary speed varies depending on the conditions of the vehicle.

[Problem that the invention seeks to solve]

However, in this conventional method of simultaneously steering the front and rear wheels, the sideslip angle β at the vehicle center of gravity is determined assuming that the vehicle is making a steady circular turn. The sideslip angle β at the center of gravity of the vehicle changes, and the behavior of the vehicle may become unstable.

This is particularly noticeable when the center of gravity of the vehicle is biased toward the rear wheels, such as in a fully loaded large truck.

For example, in current vehicles in which only the front wheels can be steered, the vehicle direction remains approximately inside the turning arc of the vehicle (β<O). In addition, in a conventional vehicle that can steer the front and rear wheels, the sideslip angle β at the center of gravity of the vehicle becomes 0 during steady circular turning, but immediately after the front wheels are steered, the vehicle direction is outward with respect to the turning arc of the vehicle. (β〉0) or become inward (β〈O) and become unstable.

Furthermore, in the conventional vehicle capable of front and rear wheel steering, the transient response of yaw rate rises slower than that of the current vehicle, and the transient response of lateral acceleration has a more jerky rise than the current vehicle.

The present invention solves these conventional problems, and improves steering stability in a vehicle with two sets of front wheels and two sets of rear wheels. The purpose is to provide a steering method.

[Means for solving problems]

A first aspect of the present invention is a method of steering the rear wheels in conjunction with the steering of the front wheels of an automobile having one set of front wheels and two sets of rear wheels, in which the two sets of rear wheels are controlled differently. ffl angle, the actual steering angle δf1 of the rear front wheels is twice the actual steering angle δf of the front wheels, and this k is D+EV2+FVs, where A=Kr (KrlIlx<it+/r+)+K
rtlr2C(lt + lfz))B = mK
, l.

C=IK.

D = K11l t (Kr+(j! t+1r+-
), and the actual steering angle δr2 of the rear wheels is .

A second invention of the present invention is a method of steering the rear wheels in conjunction with the steering of the front wheels of an automobile having one set of front wheels and two sets of rear wheels, in which the two sets of rear wheels are steered at equal control angles. , the actual steering angle δf1 of the rear wheels and the actual steering angle δr2 of the rear wheels are equal to the actual steering angle δf of the front wheels, and this k is D+EV"+FVs. However, A = Kt (K-t l□ (lf+1□) 10 Kr
zilrzC1t + 11g)) B=mKf1f C=IK.

D=Kfllf (K□(lr+Il□)+Krz(
j! r” 1rz)) +Kr+Krz(lrz
j'rυ2E=m(Kr+1, t +Krzj!r1)
2E=m(Kr1lr1+Kr2lr2)F=I
(K r+ ” K rz).

Note that the present invention is not limited to the formula shown above, and also includes cases where substantially the same effect is obtained.

[For production]

The present invention improves the frequency response characteristic for front wheel steering compared to the conventional method by using the front wheel actual steering angle speed in addition to the front wheel actual steering angle δf and vehicle speed ■ as the main control parameters for rear wheel steering. Without a feed bank, the sideslip angle β at the vehicle center of gravity can always be zero.

That is, it is possible to reduce the response delay of lateral acceleration and yaw rate to steering wheel steering, and to minimize the occurrence of unnatural behavior of the vehicle when steering the rear wheels.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a configuration diagram illustrating an embodiment of the present invention.

In Fig. 1, the input of the microcomputer l is
The outputs of the load sensor 3, vehicle speed sensor 5, front wheel steering angle sensor 7, and stroke sensor 9 are connected, and the output of the microcomputer 1 is connected to electromagnetic valves 11 and 12. The electromagnetic valves 11 and 12 are connected to a hydraulic pump 13 driven by the engine, and control the amount of oil pumped from the oil tank 15 in accordance with the output of the microcomputer 1.

Hydraulic cylinders 27.2 are connected to both ends of the rear-front shaft 21 and the rear-rear shaft 22 via torque rods 23.24.25.26.
9 is attached. The hydraulic cylinders 27, 29 each have a double configuration (27a, 27b, 29a, 29b). Hydraulic cylinders 27a, 2 controlled by electromagnetic valve 11
The displacement of 9a rotates the rear front wheel 2I, and the solenoid valve 1
The rear wheel 22 is rotated by the displacement of the hydraulic cylinders 27b and 29b controlled by the hydraulic cylinders 27b and 29b, and the actual steering angle of the rear front wheel 31.32 or the rear rear wheel 33.34 is relatively changed. . Note that the hydraulic cylinder 27a,
29a, 27b, and 29b are driven in mutually opposite directions, and the rear-front shaft 21 or the rear-rear shaft 22 rotates around its center to rotate the rear-front shaft 31.32 or the rear-rear wheel 33.34.
The actual steering angle is adjusted. Further, reference number 35 is a propeller shaft.

The equation of motion of the present invention system is as follows: vehicle quality Jim, vehicle yaw direction rotational inertia mass ■, vehicle speed V, longitudinal distance between the front wheels and the vehicle center of gravity! 2. Distance in the longitudinal direction between the rear front wheels and the vehicle center of gravity #1. Distance in the longitudinal direction between the rear wheels and the center of gravity of the vehicle1. ．． 2. Cornering power of front tires (sum of left and right wheels) Kf, 1i! is the cornering power of the front tires (sum of the left and right wheels) K11, the cornering power of the rear tires (sum of the left and right wheels) K, 2, the actual steering angle of the front wheels δ2
, the actual steering angle δf of the rear front wheels, the actual steering angle δr2 of the rear wheels, the detected slip angle β of the center of gravity of the vehicle, the side slip angle β2 of the front wheels, the tested belly angle βr1 of the rear front wheels, the side slip angle β1□ of the rear wheels, If the vehicle's yaw rate (angular velocity in the yaw direction) is γ, then ゛However,
Represented by i.

Conditions in which the sideslip angle β at the center of gravity of the vehicle is set to O irrespective of the value of the actual steering angle δf of the front wheels by substituting formulas 00 or 0 into formulas (9) and 001 and performing Laplace transform. Finding the formula, ■ CmVKtlt Kt (Kr+'r+(j!r+
j! r+)■ +Krzzj'rz(j!r+1rz)) I Kt
s) δf(S)Kr+Jr+(lr-1□))+I
Kr1s) δ1□(s)zO- (2).

Note that the steering of the rear front wheels and the rear rear wheels is based on the rear front axle and rear rear axle steering in this example (actual steering angle of the rear wheels = actual steering angle of the rear axle). The present invention can also be practiced with other steering methods as long as they can be steered.

Here, the actual steering angle δf1 of the rear front wheels and the actual steering angle δf of the rear wheels
2 is shown in two ways, and control equations for the rear front wheels and the rear rear wheels with respect to the actual steering angle δf of the front wheels in each case are determined.

The first control equation assumes that the vehicle is running at an extremely low speed and the turning radius is sufficiently large, so that the actual steering angle of the rear and front wheels is δ1. Assuming that the actual steering angle δf2 of the rear wheels is sufficiently small, the following relationship holds true as shown in FIG.

In this case, the actual steering angle δ of the rear and front wheels is relative to the actual steering angle δf of the front wheels.
If we calculate the ratio of f1 to 1 (= δf, (s)/δf (s)), then A= Kt (Krrlrr(lt +i!t+)+
KrzlrtClt" 7!rz)) B = m K
t l t Ct IKt . Therefore, the actual steering angle δ of the front wheels at this time
The ratio of the actual steering angle δ2□ of the rear wheels to f is 2 (=δ−Z
(S)/δt (s)) becomes.

The second control equation shows that when the vehicle is running at high speed, even if the actual steering angle δr1 of the rear front wheels and the actual steering angle δr2 of the rear wheels are controlled to be equal, it is sufficient to satisfy the conditional expression (2). can be met. That is, δr+=δf2...
In the case of OB, the ratio of the actual steering angle δfl of the rear front wheels to the actual steering angle δf of the front wheels is (=δf, (s)/δt (s)
), however, A=-Kt (Kr+lr+C1t+j!r+)"Kr
zlf□(A'r"j!rg))3 = m K t
It t C=IK.

D=11! r (Kr1(1t + j!r+)+K
rz(j2r+j!rg))+Kr+Krg(j!rz
zr+)2E=m(Krt'r++Krz1rt)
It is sufficient to set F = I (Kr+''Krz). Therefore, the actual steering angle δ of the front wheels at this time
The ratio of the actual steering angle δ1□ of the rear wheels to f is 2 (= δf−
(s)/δt(s)) is k2 =,
, -----・- (to).

Note that the embodiment shown in FIG. 1 is a configuration for realizing the first control equation, and in order to realize the second control equation,
The solenoid valves 11 and 12 are similarly controlled and the hydraulic cylinders 27a,
27b, 29a, and 29b may be driven simultaneously, but it is also possible to simultaneously control the rear-front shaft 21 and the rear-rear shaft 22 to the same control angle using one left and right hydraulic cylinder. In this case, only one system of solenoid valves is sufficient.

As shown in equation Q9, the system of the present invention uses the front wheel actual steering angle speed in addition to the front wheel actual steering angle δf and the vehicle speed ■ as the main control parameters for rear wheel steering.

Therefore, the value of 1 is determined by the formula Qlf (to), and the value of 2 is determined by the formula (5) and (to), and the control angle (δr+) of the rear front wheels is set to kI6t, and the control angle of the rear wheels is By steering the vehicle with the angle (δr□) set to 2δf, the sideslip angle β at the center of gravity of the vehicle can always be set to O even in a transient state.

FIG. 3 is a flowchart illustrating the operation according to the first control formula of the system of the present invention.

The microcomputer reads the weight applied to each wheel from the load sensor provided on each wheel, and calculates the vehicle mass m, the digit 1 of the vehicle center of gravity, and the longitudinal distances M1f, lf, and j between each wheel and the vehicle center of gravity. 'rt, cornering power Kt of each wheel, K-KrZ are calculated. Furthermore, the vehicle speed V is read from the vehicle speed sensor, the front wheel actual steering angle δf is read from the front wheel steering angle sensor, and the front wheel actual steering angular velocity is calculated. Furthermore, the rear front wheel actual steering angle δ1 is determined from the stroke sensor. and the rear wheel actual steering angle δf,2. Here, the control angle of the rear front wheels (ktδt) and the control angle of the rear front wheels (kzδF) are calculated.

Next, first, the rear front wheel actual steering angle δ1. and 1 for the control angle of the rear and front wheels.
δf is compared, and when the rear front wheel actual steering angle δ□ is equal to the control angle and δf, the rear front wheel steering is stopped, and when they are not equal, the rear front wheel actual steering angle δf is adjusted to 1, and the rear front wheel steering is adjusted so that the rear front wheel actual steering angle is 1 or δf. to steer.

Next, in the same way, compare the actual rear wheel steering angle δr2 and the control angle of the rear rear wheels by δ, and find that the actual rear wheel steering angle δrt is equal to the control angle 2δ.
When it is equal to f, the rear rear wheel steering is stopped, and when it is not equal, the rear rear wheels are steered so that the actual rear wheel steering angle δf2 becomes 2δf.

By repeating this control flow, it is possible to perform transiently stable simultaneous steering of the front wheels, rear front wheels, and rear rear wheels, thereby improving steering stability.

FIG. 4 is a flowchart illustrating the operation according to the second control formula of the present invention system.

This control method controls the steering of the rear front wheels and rear rear wheels to the same actual steering angle at the same time. Therefore, the following description will be made assuming that the actual steering angle of the rear front wheels or the rear rear wheels is δf.

The microcomputer reads the weight applied to each wheel from the load sensor installed on each wheel, and calculates the vehicle quality (1 m), the position of the vehicle center of gravity, the distance H1t in the longitudinal direction between each wheel and the vehicle center of gravity, lr-l1rt, and each The cornering power Kt of the wheel, KrlfK,2 is calculated. Furthermore, the vehicle speed V is read from the vehicle speed sensor, the front wheel actual steering angle δf is read from the front wheel steering angle sensor, and the front wheel actual steering angular velocity is calculated.

Furthermore, the rear wheel actual steering angle δf is read from the stroke sensor.

Here, the rear wheel control angle (kδf) is calculated, the rear wheel actual steering angle δ7 is compared with the rear axle control angle δf, and the rear wheel actual steering angle δf is calculated.
When the control angle is equal to δf, the rear wheel steering is stopped, and when the control angle is not equal to the rear wheel actual steering angle δf, the rear wheel steering is stopped.6. Steer the rear wheels so that

By repeating this control flow, it is possible to perform transiently stable simultaneous steering of the front wheels, rear front wheels, and rear rear wheels, thereby improving steering stability.

The sideslip angle β at the vehicle center of gravity of the vehicle according to the present invention becomes approximately 0 degrees immediately after the vehicle enters a turn, so that the vehicle can stably enter a turn. Furthermore, the rise of the vehicle yaw rate T and the vehicle lateral acceleration at the moment the vehicle enters a turn is faster than that of the current vehicle and the conventional vehicle capable of front and rear wheel steering.
1. Therefore, in the method of steering the rear wheels in conjunction with the steering of the front wheels of the present invention, the sideslip angle β at the vehicle center of gravity, the vehicle yaw rate γ, and the vehicle lateral acceleration have been sufficiently solved and It can be seen that the movement is stable even in a transient state.

In addition, in this example, the approximate control conditions (actual steering angle δ1□ of the rear front wheels and rear wheel Actual steering angle δ1
．． It was shown that rear wheel control is performed by determining the ratio of the actual steering angle of the rear wheels to the actual steering angle of the front wheels. That is, in one vehicle, when the vehicle is traveling at low speed, the condition of formula (to) is used, and when the vehicle is traveling at high speed, the condition of formula (08%) is used for control.

Next, the frequency response characteristics of the method of the present invention are shown, and the front wheel serpent (
The following describes how much the phase delay in vehicle behavior with respect to steering wheel operation has been improved compared to current vehicles and conventional vehicles capable of front and rear wheel steering. Note that the Bode diagram shown below was created based on calculations.

The calculation conditions are a general 10 ton truck constant volume, a vehicle speed of 80 km/hour, and a large snake frequency of the front wheels of 0.0 IHz.
~10112. Therefore, a second controlled a mallet is used.

FIG. 5 is a frequency characteristic diagram of the actual steering angle of the rear wheels relative to the actual steering angle of the front wheels.

FIG. 6 is a frequency characteristic diagram of the sideslip angle at the center of gravity of the vehicle with respect to the actual steering angle of the front wheels.

FIG. 7 is a frequency characteristic diagram of the yaw rate of the vehicle with respect to the actual steering angle of the front wheels.

FIG. 8 is a frequency characteristic diagram of the lateral acceleration of the vehicle with respect to the actual steering angle of the front wheels.

In FIGS. 5 to 8, the horizontal axis represents the front wheel actual steering angular velocity (llz), the upper row of the vertical axis represents the gain, and the lower row represents the phase. Further, the broken line shows the frequency characteristics of a current vehicle in which only the front wheels can be steered, the dashed line shows the frequency characteristics of a conventional vehicle in which front and rear wheels can be steered, and the solid line shows the frequency characteristics of a vehicle in which front and rear wheels can be steered according to the method of the present invention.

〔Effect of the invention〕

As explained above, the present invention improves steering stability by reducing the delay in response of the vehicle's lateral acceleration and yaw rate to steering wheel steering, thereby making it possible to avoid unnatural behavior of the vehicle when steering the rear wheels. can. In addition, since it is possible to reduce the minimum turning radius and further reduce the sideslip angle at the center of gravity of the vehicle to O, there is an excellent effect of minimizing tire wear.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram illustrating an embodiment of the present invention. FIG. 2 is a diagram explaining the conditions of the first control equation. FIG. 3 is a flowchart illustrating the operation according to the first control formula of the system of the present invention. FIG. 4 is a flowchart illustrating the operation according to the second control formula of the method of the present invention. Figure 5 shows the frequency of the actual steering angle of the rear wheels relative to the actual steering angle of the front wheels!
Number characteristic diagram. FIG. 6 is a frequency characteristic diagram of sideslip angle at the center of gravity of the vehicle with respect to the actual steering angle of the front wheels. FIG. 7 is a frequency characteristic diagram of vehicle yaw rate with respect to front wheel actual steering angle. FIG. 8 is a frequency characteristic diagram of the lateral acceleration of the vehicle with respect to the actual steering angle of the front wheels. l...Microcomputer, 3...Load sensor,
5...Vehicle speed sensor, 7...Front wheel actual steering angle sensor, 9.
... Stroke sensor, 11.12 ... Solenoid valve, 13
...Hydraulic pump, 15...Oil tank, 21...
・Rear-front axis, 22...Rear-rear axis, 23.24.25.26
・) Lucrosodo, 27a, 27b, 29a129b...
・Hydraulic cylinder, 31.32...Rear front wheel, 33.34
... Rear wheel, 35... Propeller shaft.

Claims (2)

[Claims] (1) In a method of simultaneously steering the rear wheels in conjunction with the steering of the front wheels of an automobile having one set of front wheels and two sets of rear wheels, the actual steering angle δ_r_1 of the rear and front wheels of the rear wheels is defined as the actual steering angle δ_r_1 of the rear wheels of the rear wheels. The angle δ_f is multiplied by k, and this k is k=(A+BV^2-CVs)/(D+EV^2+FV
s) However, A=-K_f{K_r_1l_r_1(l_f+l_r
_1)+K_r_2l_r_2(l_f+l_r_2)
}B=mK_fl_f C=IK_f D=(K_fl_f{K_r_1(l_f+l_r_1
)+K_r_2(l_f+l_r_2)l_r_2/l
_r_1}E=m(K_r_1l_r_1+K_r_2
[l_r_(2^2)/l_r_1])F=I(K_r
_1+K_r_2 [l_r_2/l_r_1]),
The actual steering angle δ_r_2 of the above rear wheels is δ_r_2=(
l_r_2/l_r_1) δ_r_1. A rear wheel steering method for an all-wheel steered vehicle. Where, m is the mass of the vehicle, I is the rotational inertial mass of the vehicle in the yaw direction, V is the vehicle speed, l_f is the longitudinal distance between the front wheels and the vehicle center of gravity, and l_r_1 is the longitudinal distance between the rear front wheels and the vehicle center of gravity. distance, l_r_2 is the distance in the longitudinal direction between the rear rear wheels and the center of gravity of the vehicle, K_f is the cornering power of the front tires (sum of both left and right wheels), K_r_1 is the cornering power of the rear front tires (sum of both left and right wheels), K_r_2 is the cornering power of the rear rear tires (sum of both left and right wheels), and s is the Laplace operator. (2) In a method of simultaneously steering the rear wheels with the steering of the front wheels of an automobile having one set of front wheels and two sets of rear wheels, the actual steering angle δ_r_1 of the rear front wheels of the rear wheels and the rear wheels of the rear wheels are as follows: The actual steering angle δ_r_2 of the rear wheels is equal to the actual steering angle δ of the front wheels.
__f is k times, and this k is k=(A+BV^2-CVs)/(D+EV^2+FV
s) However, A=-K_f{K_r_1l_r_1(l_f+l_r
_1)+K_r_2l_r_2(l_f+l_r_2)
}B=mK_fl_f C=IK_f D=K_fl_f{K_r_1(l_f+l_r_1)
+K_r_2(l_f+l_r_2)}+K_r_1K
_r_2(l_r_2-l_r_1)^2E=m(K_
r_1l_r_1+K_r_2l_r_2)F=I(K
_r_1+K_r_2) A rear wheel steering method for an all-wheel steering vehicle. Where, m is the mass of the vehicle, I is the rotational inertial mass of the vehicle in the yaw direction, V is the vehicle speed, l_f is the longitudinal distance between the front wheels and the vehicle center of gravity, and l_r_1 is the longitudinal distance between the rear front wheels and the vehicle center of gravity. distance, l_r_2 is the distance in the longitudinal direction between the rear rear wheels and the center of gravity of the vehicle, K_f is the cornering power of the front tires (sum of both left and right wheels), K_r_1 is the cornering power of the rear front tires (sum of both left and right wheels), K_r_2 is the cornering power of the rear rear tires (sum of both left and right wheels), and s is the Laplace operator.