JPS62131881A - Rear wheel steering control device for front and rear wheel steering vehicle - Google Patents

Abstract

PURPOSE:To enhance the control stability of a vehicle when it receives disturbance from the road surface, by providing a means for detecting disturbance exerted to the vehicle from the road surface, and by changing the same phase rate of determined steering ratio of rear wheels. CONSTITUTION:When a road surface disturbance detecting means 4 detects disturbance of a vehicle by the road surface, and when a vehicle rectilinear moving condition detecting means 3 detects the rectilinear moving condition of the vehicle, a steering ratio changing means 5 changes the same phase rate of determined steering ratio of rear wheels with respect to front wheels to increase the same. Then, an output means 6 delivers a control signal corresponding to the determined steering ratio to a rear wheel steering mechanism B to steer the rear wheels. Accordingly, when the vehicle is subjected to disturbance from the road surface, the steering ratio is set to a value which is greater than the same phase side steering ratio during normal running, it is possible to reduce the displacement of the vehicle due to disturbance from the road surface, thereby it is possible to enhance the rectilinearity of the vehicle.

Description

[Detailed description of the invention]

[Industrial Application Field 1] The present invention relates to a rear wheel steering control device for front and rear wheel steering 111, and in particular, the ratio of the rear wheel steering angle to the front wheel steering angle (steering ratio).
This invention relates to an improvement of a rear wheel steering control device for a vehicle with front and rear wheel steering, which controls the vehicle according to the vehicle speed. [Prior Art] Conventionally, rear wheel steering control t2++ necking of front and rear wheel steered vehicles has been proposed, for example, in Japanese Patent Application Laid-Open No. 55-91457@publication and Japanese Patent Application Laid-open No. 1 & 57.
As disclosed in Publication No. 70774, when a vehicle is traveling at a speed lower than a predetermined vehicle speed value, the steering ratio is changed so that the rear wheel steering angle is in the opposite phase to the front wheel steering angle. It is proposed that the steering ratio be set to a value such that the rear wheel steering angle is in phase with the front wheel steering angle when the vehicle is running faster than a predetermined vehicle speed value. has been done. According to this rear wheel steering control device, it is possible to reduce the turning radius q of the vehicle when traveling at low speed, and it is possible to improve the turning performance of the vehicle. Furthermore, when driving at medium to high speeds, it is difficult to increase the turning radius of the vehicle to quickly and easily change lanes.

[Problems to be Solved by the Invention] However, in the conventional device described above, since the steering ratio is controlled only by the vehicle speed, the steering ratio is uniquely determined by the vehicle speed, and as a result, the steering ratio is There is a problem in that even if it is necessary to perform matching optimal rear wheel steering, the steering ratio cannot be changed. In other words, if a vehicle experiences road surface disturbance due to unevenness of the road surface while traveling straight, the vehicle will wobble, and in order to prevent this and increase the straight-line stability of the vehicle, it is necessary to increase the rear wheel steering ratio. However, the conventional rear wheel steering control device that determines the steering ratio simply based on the vehicle speed has a problem in that the steering ratio cannot be changed when a road surface disturbance occurs. In addition, in order to increase stability when traveling straight, the steering ratio is set to -(1!
It is possible to make it too stiff, but this will make it difficult to bend. [Object of the Invention] The present invention has been made in order to solve the above-mentioned conventional problems, and is capable of improving steering stability even when a straight traveling frame receives road surface disturbance such as unevenness of the road surface. The purpose is to capture and provide a rear wheel steering control device for a vehicle with front and rear wheel steering. [Means for Solving the Problems 1] The present invention provides a rear wheel steering control device for a front and rear wheel steered vehicle that controls the steering ratio of 1u wheels to the front wheels to the opposite phase side at low speeds and to the same phase side at high speeds. As shown in FIG. 1, a vehicle speed detecting means 1 detects the vehicle speed, a steering ratio determining means 2 determines the steering ratio according to the detected vehicle speed, and detects the straight-ahead state of the vehicle. a vehicle road disturbance detection means 4 that detects road surface disturbance of the vehicle; and a vehicle road disturbance detection means 4 that detects road disturbance of the vehicle; a steering ratio changing means 5 for changing the in-phase ratio of the determined steering ratio to be stronger in response to the detected road surface disturbance; an output means 6 for outputting a control signal corresponding to the determined steering ratio; The above object is achieved by including a rear wheel steering mechanism B that responsively sets the rear wheel steering angle based on the determined steering ratio of 11η and steers the rear wheels. In an embodiment, the road surface disturbance detection means is configured to detect road surface disturbance based on the actual value of the road surface disturbance variation color.Furthermore, in another embodiment of the present invention, the road surface disturbance detection means is configured to detect road surface disturbance based on a vehicle wobbling component caused by a difference in external force between left and right wheels.Furthermore, in another embodiment of the present invention, the road surface disturbance detecting means detects a vibration of a vehicle body. In another embodiment of the present invention, the road surface disturbance detection means is configured to detect road surface disturbance based on road surface irregularities. Further, in another embodiment of the present invention, the road surface disturbance detection means is configured to detect road surface disturbance based on a vehicle wobbling component caused by a difference in external force between left and right wheels, a yaw rate of the vehicle body, and road surface irregularities. In another embodiment of the present invention, when the steering ratio changing means changes the in-phase ratio of the determined steering ratio to be stronger,
The system is configured to obtain a vehicle speed correction corresponding to a detected road surface disturbance, add this vehicle speed correction amount to the vehicle speed to obtain a corrected vehicle speed, and use this corrected vehicle speed to obtain and change the steering ratio. Further, in another embodiment of the present invention, when the steering ratio changing means changes the in-phase ratio of the determined steering ratio to be stronger, it calculates a steering ratio correction amount corresponding to the detected road surface disturbance, and adjusts the steering ratio accordingly. It is configured to change the fixed bond by multiplying it by the determined steering ratio. [Function] In the present invention, in the rear wheel steering control system for a front and rear wheel steering vehicle that controls the steering ratio of the rear wheels to the front wheels to the opposite phase side at low speeds and to the same phase side at high speeds, when the vehicle is traveling straight, At this time, the road surface disturbance is determined, and the in-phase ratio of the determined steering ratio is changed to be stronger in response to this road surface disturbance. Therefore, when one vehicle experiences road disturbance, by setting the steering ratio larger than the in-phase steering ratio during normal driving, the displacement of the vehicle due to road disturbance can be reduced without impairing the turning performance during normal driving. This makes it possible to improve both straight-line performance and the steering stability of the vehicle. Furthermore, when the road surface disturbance detection means is configured to detect road surface disturbance using the effective value of the road surface disturbance variation color, it is possible to accurately detect the road surface disturbance. Further, when the road surface disturbance detection means is configured to detect road surface disturbance using a vehicle wobbling component caused by a difference in external force between the left and right wheels, the road surface disturbance can be accurately and accurately grasped. Furthermore, when the road surface disturbance detection means is configured to detect road surface disturbances based on yaw rate, road surface disturbances can be easily detected when the steering wheel is not operated much. Furthermore, when the road surface disturbance detection means is configured to detect road surface disturbances based on road surface irregularities, road surface disturbances can be easily detected. Further, when the road surface disturbance detecting means is configured to detect road surface disturbance by a vehicle wobbling component caused by a difference in external force between left and right wheels, yaw 1~ by a di-A filometer, and road surface irregularities, Road surface disturbances can be accurately ascertained, and even more precise rear wheel steering control can be performed. Further, when the steering ratio changing means changes the in-phase ratio of the determined steering ratio to be stronger, it calculates a vehicle speed correction amount corresponding to the detected road surface disturbance, adds this vehicle speed correction amount to the vehicle speed to obtain a corrected vehicle speed, and calculates the corrected vehicle speed by adding this vehicle speed correction amount to the vehicle speed. If the steering ratio is determined and changed based on the corrected vehicle speed, it is possible to horizontally move the pattern of the target steering ratio Re for the m speed V shown in FIG. Yes (see dashed line B). Thereby, the in-phase steering ratio region on the high speed side can be substantially enlarged. Therefore, the straight-line stability of the vehicle when subjected to road surface disturbances can be improved. Further, when the steering ratio changing means changes the in-phase ratio of the determined steering ratio to be stronger, it determines a steering ratio correction method corresponding to the detected road surface disturbance, and changes the steering ratio by multiplying the determined steering ratio by this steering ratio correction product. The platform configured in this manner allows the steering ratio to be smoothly increased in accordance with the vehicle speed.

【Example】

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a rear wheel steering control device for a front and rear wheel steered vehicle to which the present invention is applied will be described in detail with reference to the drawings. FIG. 2 shows a 110-way steering modification A of a vehicle to which the present invention is applied, a rear wheel steering device +lI'1B, and this rear wheel steering system 1.
An electrical control device C of one structure B is shown. The front wheel steering mechanism A includes a onion and rack mechanism 11,
A pair of left and right relay rods 12a and 12b are connected to the rack portion of this mechanism 11. , the binion and rack mechanism 11 is connected to the steering shaft 13 at its binion part.
The relay rods are connected to the steering handle 14 through the relay rods 12a and 12b, and convert rotational movement of the steering handle 14 into reciprocating movement of the relay rods 12a and 12b. the left and right relay rods 12a;
The left and right relay rods 12b are connected to the left and right front wheels 16a and 116b via left and right knuckle arms 15a and 15b (not shown), respectively.
2b, the left and right front wheels 16a1°16b are steered. The rear wheel steering device HB includes a hydraulic pump 20 driven by an engine, and a hydraulic cylinder 23 to which oil discharged from the hydraulic pump 20 is applied via an l-nervo valve 21 to steer the front and rear wheels 22a122b. The hydraulic pump 20 is connected at its inlet to a reservoir 24 via a conduit P1, and at its discharge port to a servo valve 21 via a conduit P2. The servo valve 21 is connected to the hydraulic cylinder 2 at its neutral position.
The conduit P3 connected to the right chamber 23b of the hydraulic cylinder 23 is closed, and the conduit P4 connected to the left chamber 238 of the hydraulic cylinder 23 is closed. Also, when the servo valve 21 is switched to the first position,
Conduit P2 is connected to conduit P3, and conduit P4 is connected to conduit P5.
It is connected to the 1F-bar 24 via the above. When switched to the second position, conduit P2 is connected to conduit P4, and conduit P3 is connected to reservoir 24 via G pipe Ps. The switching operation of this servo valve 21 is brought about by the operation of a torque motor 21a connected to this servo valve 21, and the operation of the torque motor 21a is as follows.
It is brought about by a control signal provided by the electrical control 711 device C. The hydraulic cylinder 23 has a piston 25 housed therein.
A pair of left and right piston rods 26a and 26b are connected to each other. The left piston rod 26a connects to the rear wheel 22a via a tie rod 27a and a knuckle arm 28a.
1. :F-tied. Also, the right piston rod 26b is connected to the tie rod 27b.
, is connected to the rear wheel 22b via a knuckle arm 28b. The electric control device C includes a vehicle speed sensor 30 that picks up the rotation of a vehicle speed detection gear 16C provided on the right front wheel and generates a pickup signal with a frequency corresponding to the vehicle speed, a front wheel 16a attached to the steering shaft 13, a front wheel steering angle sensor 31 that detects a front wheel steering angle of 16b and generates an analog signal indicating a voltage value corresponding to the front wheel steering angle;
Tie ψ vertical force sensors 32a, 32 that detect the upper and lower blades of ties V attached to 6a, 16b, 22a, 22b
33a, 33b, 33c, 33d are also attached to each wheel and detect the longitudinal force of the tire. Tire longitudinal force sensors 34a, 34b, 34c, and 34d; a yaw rate sensor 35 that detects the yaw rate of the vehicle; and a yaw rate sensor 35 that detects the yaw rate of the vehicle; A road surface unevenness sensor 36 detects unevenness of the road surface by measuring the distance to the road surface using ultrasonic waves, and a road surface unevenness sensor 36 that measures the actual steering angle with respect to the target rear wheel steering angle and steers to the target steering angle. Rear wheel steering angle senna 37 for performing angle feedback control
and a microcomputer 38 that outputs a target steering angle control signal for the rear wheels by executing a program to be described later based on the signals given from each of these sensors 30 to 36, and controls the microcomputer 38. signal and
A comparator 40 outputs a difference signal from the actual steering angle signal from the rear wheel steering angle sensor 37, and a servo amplifier 41 amplifies the output signal from the comparator 40 to drive the servo valve 21. We are prepared. The micro convenience store L-938 constitutes the steering ratio determining means 2, the vehicle straight running state detecting means 3, the road surface disturbance detecting means 4, and the steering ratio changing means 5 shown in FIG. 1, and is shown in FIG. As such, the program corresponding to the flowcharts shown in FIGS. 4 and 5 and the speed Sg normal nose ΔV, steering ratio correction loss ΔR1, which will be described later, are calculated. A read-only memory (ROM) 38a that stores parameters for executing the program, a central processing unit (CPU) 38b that executes this program, and a tl programmable memory (RAM) that temporarily stores variables and flags necessary for this program. ) 38C are connected to the vehicle speed sensor 30 via a waveform shaper (not shown), as well as a front wheel steering angle sensor 31 and a tire up/down sensor 32a-.
d, Tie V left and right steering wheel 33a-cl, tire 1) η rear calendar sensor 34 a-d1 yaw rate sensor 35, road surface unevenness sensor 36, rear wheel steering angle sensor 37, analog-to-digital converter (A/D converter) not shown in the figure 18 input/output interface circuits (Ilo>38d) connected to the comparator 40 via digital-to-analog converters (D/A converters) not shown, and these ROMs.
38a, CPU38b, RAM38c, l103
8d, and a bus 38e to which the 8d are connected in common. Rear wheel steering control for vehicle 1aII R configured as above
The buying operation will be explained using the flowcharts of FIGS. 4 and 5. When the ignition switch (not shown) is opened to avoid starting the vehicle, the CPU 38b executes step 100.
At J5, listen to the execution of the program θf1, and execute step 1.
At 02, the tire upper and lower blades of the right front wheel 16b are +3
2b reads the right front wheel upper and lower blades FZ[r. Next, the process proceeds to step 104, where the front wheel upper and lower blades FZfl are read by the tire upper and lower sensor 32a of the left front wheel 16a. Next, the process proceeds to step 106, where the right rear wheel upper and lower blades FZ fr and the left front wheel upper and lower blades FZr detected in the previous steps 102 and 104 are detected.
FZfn is calculated as the absolute value of the difference from l. Next, the process proceeds to step 108, where the absolute value ΔFZfn of the difference between the front wheel upper and lower blades obtained in step 106 is averaged over a certain time [(Root
Mean 3 square ) ΔF Z fae is calculated. That is, the effective value ΔFZfa of the difference between the upper and lower blades of the left and right front wheels
is calculated using the following relationship. The effective value ΔFZfa of the difference between the upper and lower blades of the front wheel is determined by the time t
The effective values ΔF Z f sampled in
n, that is, the current effective value FZfn and the previous effective value ΔFZrn of 1f1 are determined in one routine. In addition, FIG. 6 shows the absolute value of the difference between the right front wheel upper and lower blades FZfr and the left front wheel upper and lower blades FZrλ determined in the above steps 102 and 104 and the front wheel upper and lower blades obtained in the above step 106.
7fn and the effective one-direction ΔFzfa of the difference between the upper and lower blades of the front wheel determined in step 110 is shown in a diagram with time [not shown] set horizontally by 1qb. Next, proceed to steps 110 to 116, and proceed to step 1 described above.
In the same way as 02 to 108, the effective value Δ of the difference between the In upper and lower blades
FZra (!- Stop and close. In other words, in step 110, read the right rear wheel upper and lower blades 1"Zrr, and in step 112
, read the left rear wheel upper and lower blades FZrl, and step 114
At step 116, the absolute value ΔFZrn of the difference between the upper and lower blades FZr' and Fzrl is determined, and at step 116, the effective 1 straight line ΔFZra of the difference between the upper and lower rear wheel blades is determined. The effective value of the difference between the front wheel and upper and lower blades calculated in step 116 is 8FZfa, and the effective value of the difference between the rear wheel and upper and lower blades calculated in step 116 is ΔFZra.
Based on these effective values ΔF'; l ra. ΔF Z ra is multiplied by the upper and lower blade fluctuation coefficients fiCzf and Czr, respectively, and then added to obtain the upper and lower blade disturbance ΔFZa. That is, the upper and lower blade disturbance ΔFZa is calculated from the relationship of the following equation. ΔFZa = Cz r −ΔFZra+C2r
・ ΔFZra ・ (2> In this way, the reason why the upper and lower blade disturbance ΔFZa is calculated from the difference between the upper and lower blades of the left and right wheels is to extract only the disturbance that affects one direction of the vehicle body. Next, step 120 In steps 136 to 136, the left and right force disturbance ΔFYa is calculated in the same way as the upper and lower blade disturbance ΔFZa.The processing of the program in steps 120 to 136 is the same as that in steps 102 to 118, so a description thereof will be given below. This is omitted. Next, the process proceeds to steps 138 to 154, where the longitudinal force disturbance ΔFXa of the tire is calculated. This longitudinal force disturbance ΔFXa is also
It is obtained in the same manner as the upper and lower blade disturbance ΔFZa, and the program processing in steps 138 to 154 is the same as the program processing in steps 102 to 118, so a description thereof will be omitted. Next, the process proceeds to step 156, where the tire upper and lower blade disturbance ΔFZa obtained in the above step 118 and the above step 13 are determined.
Based on the tire lateral force disturbance ΔFYa obtained in step 6 and the tire longitudinal force disturbance ΔFXa obtained in step 154, these disturbances ΔFZa% ΔFYa and ΔFXa are multiplied by correction coefficients Gz, Cy, and OX, respectively. The total tire disturbance ΔF is determined by adding the total tire disturbance ΔF. That is, the total tire disturbance ΔF is calculated from the relationship of the following equation. ΔF=Cz −ΔFZa +Cy −ΔFYa+Cx−
ΔFXa-<3> Next, the process proceeds to step 158, where the yaw rate sensor 35 reads the yaw rate φd. Next, the process proceeds to step 160, where the yaw rate φd detected in the previous step 158 is
The absolute value φdn of is calculated. Next, the process proceeds to step 162, where the effective value φda of the yaw rate is calculated from the absolute value φdn of the yaw rate obtained in step 160 described above from the relationship of the following equation. φda −(Σφdn)/l −(4)x,
L Next, the process proceeds to step 164, where the output road surface height xt is read from the road surface unevenness sensor 36. Next, the process proceeds to step 166, where the absolute value Xfn of the road surface height Xf detected in step 164 is calculated. Next, proceed to step 168;
Calculate the effective value of the road surface height from the absolute value Xfn of the road surface height obtained in step 166 above from the relationship of the following formula: xra=(ΣXrn) /l (5) Answer Proceeding to step 170, these are calculated based on the total tire disturbance ΔF obtained in step 156, the effective yaw rate φda obtained in step 162, and the effective road surface height fj*Xra obtained in step 168. Numeric value Δ
Road surface disturbance M[ is calculated by multiplying F1φda and Xfa by correction coefficients Cf, Cφ, and Cxa, respectively, and then adding them. That is, the road surface disturbance M' is calculated from the following relationship: Mf = (J - ΔF + Cφ · φda + Cxa - xfa
(6) Next, the process proceeds to step 172, where the vehicle speed ■ is read from the vehicle speed sensor 30. Next, the process proceeds to step 174, and the front wheel steering angle θ'' is read from the front wheel steering angle sensor 31. Next, the process proceeds to step 176, where the front wheel steering angle θ'' obtained in step 174 is the predetermined value of the front wheel steering angle. It is determined whether or not it is smaller than θfc.If it is determined to be positive in this step 176, that is, if it is determined that the vehicle is traveling straight, the process proceeds to step 178.In step 178, the above step It is determined whether the road surface disturbance M[ obtained in step 170 is larger than the road surface disturbance limit value Mrc. If it is determined to be positive in this step 178, that is, it is determined that the road surface disturbance Mf is larger than the limit value Mfc. If so, it is determined that it is necessary to change the steering ratio, and the process proceeds to step 180. In step 180, based on the road surface disturbance Mr obtained in step 170, the road surface disturbance M" shown in FIG. The vehicle speed change ΔV is calculated from the map data of
The steering ratio correction MΔR is calculated based on the map data of t is reset to the time required to have a constant τ.Next, the process proceeds to step 186, where the speed correction amount ΔV obtained in step 180 is added to the vehicle speed detected in step 172, and this corrected vehicle speed v A target steering ratio RC is calculated from 1ΔV based on the steering ratio pattern shown in FIG. The set steering ratio Rn is calculated by multiplying the steering ratio correction period ΔR.Next, the process proceeds to step 190, and in order to smoothly switch the set steering ratio Rn obtained in step 188, the previous set steering ratio Rn is calculated. -+ and the target steering ratio Re with a certain time constant τ, using the following equation: Rn -Rn-++ (Rc Rn-+) (1-Q
(7) Next, the process proceeds to step 192, where the set steering ratio Rn obtained in step 190 is multiplied by the front wheel steering angle θ, and the rear wheel steering angle θr is calculated as 0. Next, the process proceeds to step 194. The control signal corresponding to the rear wheel steering angle θ" calculated in step 192 is sent to the comparator 4.
0 to control the steering of the rear wheels. Next, the process returns to step 102 mentioned above. Further, if it is determined in step 176 that the front wheel steering angle θ[ is equal to or greater than the predetermined value θ[C, it is determined that the vehicle is not traveling straight, and the process proceeds to step 196. Further, if it is determined that the above-mentioned step 178 is negative, that is, if it is determined that the road surface disturbance M[ is equal to or less than the limit fi (JMfc), it is determined that there is no need to change the steering ratio, and the process proceeds to step 196. In step 196, the vehicle speed correction amount Δ■ is set to zero, and the process then proceeds to step 198, where the steering ratio correction b1ΔR is set to 1, and the process proceeds to step 186. Therefore, the program of steps 176, 178, 196, and 198 Due to this process, the vehicle is not in a straight-line state, and
When the road surface disturbance is small, the steering ratio is not modified based on the road surface disturbance. As can be understood from the above operation description, according to this embodiment, the total tire disturbance ΔF, the effective yaw rate value φda,
The road surface height effective value Xfa is calculated, the road surface disturbance Mr is calculated based on this, it is determined whether the steering ratio needs to be changed based on this road surface disturbance Mf, and the steering ratio is changed. If necessary, the steering ratio is changed to become larger based on the road surface disturbance Mf. Therefore, the steering ratio can be corrected in response to road surface disturbances caused by road surface irregularities, etc., and straight-line stability when road surface disturbances are encountered can be improved. In particular, in this embodiment, when calculating the road surface disturbance Mf, the total tire disturbance ΔF, the yaw rate effective value φda, and the road surface height effective value Xfa are obtained, and the calculation is performed using these values. Mf can be determined with high accuracy, and even more precise rear wheel steering control can be performed. Furthermore, in this embodiment, by setting the time constant τ when changing the set steering ratio Rn, the steering ratio can be smoothly changed, and the rear wheels can be smoothly steered. Figure 10 shows vehicle speed ■ and road surface disturbance Mf on the same time axis.
It is a diagram showing the relationship between the equipment steering ratio Rn and the equipment steering ratio Rn. This first
As is clear from Figure 0, when the vehicle speed V is constant and the road surface disturbance M' fluctuates, when the road surface disturbance IVH exceeds the road surface disturbance limit value MfC, the steering ratio Rn changes to the road surface disturbance M. In the above embodiment, the road surface disturbance Mr is determined based on the total tire disturbance ΔF, the yaw rate effective value φda, and the road surface height effective value Xfa. , road surface disturbance M
Although f is determined with high accuracy, the present invention is not limited to this, and the road surface disturbance Mf is determined by the total tire disturbance ΔF, the effective yaw rate value φda, and the effective road surface height value X[
The groove bottom may be determined by one or two of a, and the groove bottom may be a WI element. Further, in the above embodiment, the total tire disturbance ΔF was determined from the upper and lower edges of the tire, the lateral force, and the longitudinal force, but the present invention is not limited to this, and the total tire disturbance ΔF is It may be determined by any one or two of the upper and lower blades of the tire, the lateral force, and the frontal force. In other words, the total tire disturbance ΔF may be determined by setting one or two of the correction coefficients Cz, Cy, and Cx in equation (3) of step 156 to zero and J5<. good. Further, in the above embodiment, the tire depth disturbance ΔF is determined using a vertical force sensor, a lateral force sensor, and a longitudinal force sensor, but the present invention is not limited to this, and other methods may be used. For example, it may be determined by a sensor such as a suspension displacement sensor, a vehicle body vertical acceleration sensor, or a tire vertical acceleration sensor that outputs an output according to the unevenness of the road surface. In addition, in the above embodiment, when calculating the effective value, (
1), (71), and (5), the present invention is not limited thereto, and the root mean square value may be used as shown below. For example, the effective value of the difference between the upper and lower blades of 11j in step 108 △
Taking the case of finding FZfa as an example, the following equation is obtained. ΔFZra= & n /l −<8. )

【Effect of the invention】

As explained above, according to the present invention, the excellent effect of improving steering stability even when the straight traveling surface receives road surface disturbance is achieved.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the main structure of a rear wheel steering control device for front 1!2 wheel steering 1i according to the present invention, and FIG. 2 is a rear wheel steering control for a front wheel steering vehicle according to the present invention. Figure 3 is a block diagram showing the configuration of the microcomputer in the embodiment; , Figures 4 and 5 are flowcharts showing the operation of the microcomputer in the same embodiment, and Figure 6 shows the difference between the upper and lower blades of the left and right front wheels and the upper and lower blades of the left and right front wheels on the same time axis in the same example. FIG. 7 is a diagram showing the relationship between the absolute value of and the effective value of the difference between the upper and lower blades of the left and right front wheels. FIG. FIG. 9 is a diagram showing the relationship between road surface disturbance and steering ratio correction m in the same embodiment, and FIG. 10 is a diagram showing the relationship between the target steering ratio and the vehicle speed in the same embodiment. It is a diagram showing the relationship between vehicle speed, road surface disturbance, and steering ratio in the example on the same time axis. A... Front wheel steering (4 mechanisms, B... contact wheel steering mechanism, C... electrical control device) , 11... Binion and rack (some, 16a, 16
b-... Front wheel, 21... Servo valve, 22a, 22b... Rear wheel, 23... Hydraulic cylinder, 30... Heavy speed sensor, 31... Front wheel steering angle sensor, 32a, 32b, 32c, 32d - Vertical force sensor, 33a, 33b, 33c, 33d =.
・Left and right force dead υ°, 34, a, 34b, 34c,
34d -... Longitudinal force sensor, 35... Yaw rate sensor, 36... Road surface unevenness sensor, 37... Rear wheel steering angle sensor, 38... Microcomputer, 40... Comparator, 41... ·servo amplifier.

Claims (8)

[Claims] (1) A rear wheel steering control device for a front and rear wheel steered vehicle that controls the steering ratio of the rear wheels to the front wheels to the opposite phase side at low speeds and to the same phase side at high speeds, comprising a vehicle speed detection means for detecting vehicle speed; Steering ratio determining means for determining the steering ratio according to vehicle speed; Vehicle straight-ahead state detecting means for detecting a straight-ahead state of the vehicle; Vehicle road surface disturbance detecting means for detecting road surface disturbance of the vehicle; and The vehicle straight-ahead state detecting means. a steering ratio changing means for increasing the in-phase ratio of the determined steering ratio in response to the road disturbance detected by the road disturbance detecting means when a straight-ahead state of the vehicle is detected; and a rear wheel steering mechanism that sets a rear wheel steering angle based on the determined steering ratio in response to the control signal and steers the rear wheels. Rear wheel steering control device for front and rear wheel steered vehicles. (2) The rear wheel steering control device for a front and rear wheel steered vehicle according to claim 1, wherein the road surface disturbance detection means is configured to detect road surface disturbance based on an effective value of a road surface disturbance change. (3) The front and back of claim 1 or 2, wherein the road surface disturbance detection means is configured to detect road surface disturbance based on a vehicle wobbling component caused by a difference in external force between left and right wheels. Rear wheel steering control device for wheel steering vehicles. (4) The rear wheel steering control device for a front and rear wheel steered vehicle according to claim 1 or 2, wherein the road surface disturbance detection means is configured to detect road surface disturbance based on the yaw rate of the vehicle body. (5) The rear wheel steering control device for a front and rear wheel steered vehicle according to claim 1 or 2, wherein the road surface disturbance detection means is configured to detect road surface disturbance based on unevenness of the road surface. (6) The road surface disturbance detection means detects a vehicle wobbling component caused by a difference in external force between the left and right wheels and a yaw rate of the vehicle body;
A rear wheel steering control device for a front and rear wheel steered vehicle according to claim 1 or 2, wherein the device is configured to detect road surface disturbance based on unevenness of the road surface. (7) When changing the in-phase ratio of the determined steering ratio to be stronger, the steering ratio changing means obtains a vehicle speed correction amount corresponding to the detected road surface disturbance, and adds this vehicle speed correction amount to the vehicle speed to obtain a corrected vehicle speed. A rear wheel steering control device for a front and rear wheel steered vehicle according to any one of claims 1 to 6, wherein a steering ratio is determined and changed based on the corrected vehicle speed. (8) When changing the in-phase ratio of the determined steering ratio to be stronger, the steering ratio changing means obtains a steering ratio modification amount corresponding to the detected road surface disturbance, and multiplies the determined steering ratio by this steering ratio modification amount. A rear wheel steering control device for a front and rear wheel steered vehicle according to any one of claims 1 to 6, which is modified.