JP2601087B2 - Rear wheel steering system for front and rear wheel steering vehicles - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rear wheel steering apparatus for controlling a steering angle of rear wheels based on a yaw rate generated in a vehicle.

[0002]

2. Description of the Related Art A conventional apparatus is disclosed in, for example,
As disclosed in Japanese Patent No. 4568, the rear wheel steering device is controlled based on the front wheel steering angle θf and the yaw rate YR, and the rear wheels are set to the target steering angle θr * = K ₁ · θf + K ₂ · YR (where K ₁ , K ₂ is steered controlled to a predetermined proportional constant). That is, K ₁ · θf which is the control amount of the front wheel steering angle θf.
Is the turning property of the vehicle at a high Mel direction, K ₂ · YR is yaw rate YR control component acts as a component for steering the rear wheels in the direction of suppressing the yaw rate generated on the vehicle. The front wheel steering angle θf controls the rear wheels to increase the turning performance of the vehicle to improve the small turning performance of the vehicle, and the yaw rate YR control controls the rear wheels to suppress the yaw rate, that is, the stability of the vehicle. To improve the steering stability of the vehicle.

[0003]

In the above-described conventional apparatus, the yaw rate YR control amount is determined based on the value detected by the vehicle motion state amount detecting means. However, an abnormality occurs in the vehicle motion state amount detecting means and the like. In this case, the rear wheels may be steered based on the detected abnormal value, and steering stability may be reduced. The present invention provides a front and rear wheel steering vehicle steering angle of the rear wheels is determined by the vehicle motion state quantity, in cases where there is abnormality in the detection of vehicle motion state quantity detecting means
Also, execute the appropriate control of the rear wheel steering angle to
State, that is, to maintain the four-wheel steering state .

[0004]

In order to solve the above problems BRIEF SUMMARY OF THE INVENTION, rotary steering device after the front and rear wheel steering vehicle of the present invention includes: a front wheel steering angle detected by the front-wheel steering angle detecting means, drive both motion state in wheel turning device after the front and rear wheel steering vehicle that controls the steering angle of the rear wheels based on the vehicle motion state amount detected by the amount detecting means, and the previous SL front wheel steering angle, the vehicle motion shape
A first control for calculating a steering angle of the rear wheel based on the state quantity;
Control signal calculation means, vehicle movement state quantity change rate calculation means for calculating a change rate of the vehicle movement state quantity from an output signal of the vehicle movement state quantity detection means, and an output signal of the vehicle movement state quantity change rate calculation means. Abnormality detecting means for judging whether or not the vehicle motion state is within a predetermined range, and detecting an abnormal state of the vehicle motion state amount detecting means; and detecting the abnormal state of the vehicle motion state amount detecting means by the abnormality detecting means. If
The front wheel steering angle is replaced with the first control signal calculating means.
Control signal calculation for calculating the steering angle of the rear wheel based on
Means and the vehicle motion state quantity by the abnormality detecting means.
If no abnormal state of the detecting means is detected,
1 based on the calculation result of the control signal calculation means.
The steering angle is controlled, and the vehicle operation is controlled by the abnormality detecting means.
If an abnormality of the moving state quantity detecting means is detected, the second
Of the rear wheel based on the calculation result of the control signal calculation means.
And it is characterized in the this and control means for controlling the steering angle.

[0005]

According to the device of the present invention, while the output signal of the vehicle motion state quantity change rate calculating means is a signal which can be generated during the running of the vehicle, the first control signal calculating means determines whether the front wheel steering angle and the vehicle motion are changed. The rear wheel turning angle is calculated based on the state quantity and the control means turns the rear wheel so as to have the calculated value. Also the vehicle
When the output signal of the motion state amount change rate calculating means is
If the signal cannot be obtained, the vehicle motion is detected by the abnormality detection means.
An abnormality of the state quantity detecting means is determined. In that case, the first
The second control signal calculation means is provided in place of the control signal calculation means.
Calculate the wheel turning angle. The calculation is based on the front wheel turning angle.
Calculation to determine the rear wheel turning angle.
Is no take up certain vehicle motion state quantity, Ki out to perform the wheel turning control After stabilization, the front and rear wheel steering state, that four
The wheel steering state can be continued.

[0006]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 2 conceptually shows the entire front and rear wheel steering vehicle according to the present invention. The front and rear wheels are steered by the front left and right wheels FW1, F
A front wheel steering device A for steering W2, and left and right rear wheels RW1, R
A rear wheel steering device B that steers W2 and an electric control device C that electrically controls the rear wheel steering device B are provided.

The front wheel steering device A has a steering wheel 11. The steering handle 11 includes a steering shaft 12, a rack and pinion mechanism 13, a relay rod 14, a left and right tie rod 15,
a, 15b and left and right knuckle arms 16a, 16b are connected to the left and right front wheels FW1, FW2, and the left and right front wheels FW1, FW2 are steered according to the rotation of the handle 11. A control valve 17 is attached to a lower portion of the steering shaft 12. The control valve 17 supplies hydraulic oil discharged from the hydraulic pump 18 and supplied through the conduit P <b> 1 in accordance with a steering torque acting on the steering shaft 12. The oil is supplied to one oil chamber of the cylinder 21 and
From the other oil chamber is discharged to the reservoir 22 via the conduit P2. The power cylinder 21 assists the steering of the left and right front wheels FW1, FW2 by driving the relay rod 14 in accordance with the supply and discharge of the hydraulic oil.

[0008] The rear wheel steering device B has a stepping motor 23, which is controlled by an electric control device C and drives the steering shaft 24 to rotate. The steering shaft 24 includes a rack and pinion mechanism 25, a relay rod 26, a left and right tie rod 27.
The left and right rear wheels RW1, RW2 are steered via the left and right knuckle arms 28a, 28b. A control valve 31 is attached to an intermediate portion of the steering shaft 24, and the valve 31 supplies hydraulic oil discharged from a hydraulic pump 32 and supplied through a conduit P <b> 3 in accordance with a steering torque acting on the steering shaft 24. The oil is supplied to one oil chamber of the power cylinder 33, and the hydraulic oil from the other oil chamber of the cylinder 33 is discharged to the reservoir 22 via the conduit P4.
The power cylinder 33 drives the relay rod 26 in accordance with the supply and discharge of the hydraulic oil, so that the left and right rear wheels RW1, RW
The steering of W2 is assisted.

The electric control device C includes a wheel speed sensor 41
a, 41b, 41c, 41d, front wheel steering angle sensor 41
e, 41f, rear wheel turning angle sensors 41g and 41h, and a yaw rate sensor 41i. Here, the yaw rate sensor 41i is a vehicle motion state amount detecting means. Wheel speed sensors 41a, 41b, 41c, 41d are left and right wheels FW.
1, FW2 and the left and right rear wheels RW1, RW2 by picking up the respective rotations, so that the respective wheels FW1, FW2, RW
1. The pickup signals having frequencies proportional to the rotation speeds Nf1, Nf2, Nr1, and Nr2 of the RW2 are output. Waveform shapers 42a, 42b, 42c, 42d are connected to these sensors 41a, 41b, 41c, 41d, respectively , and the respective shapers 42a, 42b, 42c, 42d.
d shapes the waveform of the pickup signal and outputs rotation number signals each consisting of a rectangular wave signal having a frequency proportional to each of the rotation numbers Nf1, Nf2, Nr1, and Nr2.

The steering angle sensors 41e and 41f are mounted on the steering shaft 12, respectively, and detect the rotation angles of the coaxial 12 so as to detect the steering angles θf1 and θf1 of the left and right front wheels FW1 and FW2.
Each analog signal representing θf2 is output. Analog-to-digital converters (hereinafter, referred to as A / D converters) 42e and 42f are connected to the front wheel steering angle sensors 41e and 41f, respectively. The converters 42e and 42f respectively convert the analog signals from analog to digital. Thus, each front wheel steering angle data representing the front wheel steering angles θf1 and θf2 is output. The rear wheel turning angle sensors 41g and 41h are respectively attached to the relay rods 26, and output respective analog signals representing the turning angles θr1 and θr2 of the left and right rear wheels RW1 and RW2 by detecting the displacement of the rods 26 respectively. I do. A / D converters 42g and 42h are connected to the rear wheel steering angle sensors 41g and 41h, respectively.
g and 42h are, in the same manner as the A / D converters 42e and 42f described above, digital rear wheel turnings representing the turning angles θr1 and θr2 based on the analog signals representing the rear wheel turning angles θr1 and θr2. Outputs each corner data. In addition, before each
Wheel steering angles θf1, θf2 and rear wheel turning angles θr1, θr2
Indicates positive (or negative) steering of the left and right front wheels FW1, FW2 and left and right rear wheels RW1, RW2 in the right direction (or left direction), respectively, and zero indicates zero in the left and right front wheels FW1, FW2 and left and right rear wheels RW1. , RW2 are not steered.
Further, in this embodiment, the front wheel steering angles θf1 and θf2 are detected based on the rotation angle of the steering shaft 12 and the relay rod 2
6, the front wheel steering angles θr1 and θr2 are detected based on the displacement of the relay rod 14, but the front wheel steering angles θf1 and θf2 are detected based on the displacement of the relay rod 14 and the rear wheel steering angles based on the rotation angle of the steering shaft 24. θr1 and θr2 may be detected.

The yaw rate sensor 41i is mounted on the vehicle body, detects the rotational angular velocity of the vehicle body, and outputs an analog signal indicating the yaw rate YR of the vehicle. An A / D converter 42i is connected to the yaw rate sensor 41i.
The converter 42i performs digital-to-analog conversion of the analog signal to output digital yaw rate data representing the yaw rate YR. Note that the yaw rate YR is positive (or negative) and the vehicle turns right (or left),
That is, it indicates a yaw rate generated in the vehicle body due to right (or left) steering of the left and right front wheels FW1 and FW2.

These waveform shapers 42a, 42b, 42
c, 42d and A / D converters 42e, 42f, 42g,
A microcomputer 43 is connected to 42h and 42i, and the computer 43 includes a read-only memory (hereinafter referred to as ROM) 43b and a central processing unit (hereinafter referred to as CPU) 43 commonly connected by a bus 43a.
c, writable memory (hereinafter referred to as RAM) 43d and input / output interface (hereinafter referred to as I / O) 43e
Consists of The ROM 43b stores a program corresponding to the flowchart of FIG. 3 and, as shown in the graphs of FIGS.
The third to third coefficients K ₁ , K ₂ , and K ₃ are stored in the form of first to third tables. The details of the _{first to} third coefficients K ₁ , K ₂ , and K ₃ will be described later. CPU4
3c executes the program, and the RAM 43d temporarily stores data and flags necessary for executing the program. I / O43 waveform shaper 42a to e, 42b,
42c, 42d and A / D converters 42e, 42f, 42
g, 42h, 42 i is connected, the shaper 42a, 42
b, 42c, 42d and converters 42e, 42f, 42
g, 42h, and 42i, the front wheel steering angle data, the rear wheel turning angle data, and the yaw rate data are each taken into the microcomputer 43, and the rotation speed of the step motor 23 formed by the execution of the program is determined. The rotation control data representing the microcomputer 4
3 and has a function of storing this control data.

A driving circuit 44 is connected to the I / O 43e. The driving circuit 44 outputs a driving pulse train signal for controlling the number of rotation steps of the step motor 23 based on the supplied rotation control data.

Next, the first to third coefficients K₁, K_Two,
K_ThreeWill be described. First coefficient K₁Is a yoray
When the right sensor 41i is normal, the left and right rear wheels RW1, RW2 are moved forward.
Proportional coefficient for steering control in proportion to wheel turning angle θf
Left and right rear wheels RW1 and RW2 in the low vehicle speed range.
Steering in the opposite phase (opposite direction) to the front wheels FW1, FW2
To improve the small turning performance of the vehicle
And gradually increases from a predetermined negative value to zero as the vehicle speed V increases.
And set to zero in the middle and high vehicle speed range.
(See FIG. 4). Second coefficient K_TwoIs the yaw rate sensor 41
When the i is normal, the left and right rear wheels RW1, RW2 are set to the yaw rate YR.
This is a proportional coefficient for steering control in proportion to
Rear wheels RW1 and RW2 with respect to left and right front wheels FW1 and FW2
Steering in the same phase (same direction) to rotate the steering wheel 11
To reduce the vehicle response to low
As the vehicle speed V increases over the vehicle speed range, a predetermined positive
The value is set so as to gradually change to the value (see FIG. 5).
See). Third coefficient K_ThreeIs also the first coefficient K₁Same as left and right rear wheels
Steering control by making RW1 and RW2 proportional to the front wheel steering angle θf
The third coefficient K is_ThreeIs yo
-When an abnormality occurs in the rate sensor 41i,
In consideration of the yaw rate occurring,
To improve the turnability of the vehicle.
And the first coefficient K ₁(Refer to FIG. 4), the second coefficient K_Two(FIG. 5
) To the positive side by the correction value ΔK corresponding to the steering control by
Shift, increase vehicle speed V from low vehicle speed region to high vehicle speed region
Gradually changes from a predetermined negative value to a predetermined positive value according to
Is set to

The correction value ΔK is set as follows. First, an evaluation function that represents the influence of the steering of the steering wheel 11 on the turning of the vehicle during the steady turning of the vehicle, that is, the so-called “handling of the steering wheel” is considered. Then, only the steering control of the left and right rear wheels RW1 and RW2 using the first and second coefficients K ₁ and K ₂ when the yaw rate sensor 41i is normal and the third coefficient K ₃ when the sensor 41i is abnormal are calculated. A correction value ΔK is calculated such that the evaluation functions match in the case of the steering control of the left and right rear wheels RW1 and RW2 used.

The evaluation function in each of the above cases is expressed by the following equations 1 and 2, for example, using the front wheel steering angle θf _C and the yaw rate YR _C during steady turning of the vehicle. Incidentally, these front-wheel steering angle .theta.f _C and the yaw rate YR _C a variable for the derivation of the cost function, the front-wheel steering angle sensor 41e of Examples, 41f and the yaw rate sensor 4
1i are distinguished from the front wheel steering angles θf ₁ and θf ₂ and the yaw rate YR, respectively detected by 1i.

(1) Steering control of left and right rear wheels RW1, RW2 using first and second coefficients K ₁ , K ₂

[0018]

(Equation 1)

[0019] (2) When the steering control of the rear road wheels RW1, RW2 by using only the third coefficient K ₃

[0020]

(Equation 2)

Next, each YR _C / Eq.
When a third coefficient K ₃ that makes θf _C equal is obtained, and a difference between the third coefficient K ₃ and the first coefficient K ₁ , that is, a correction value ΔK is obtained, the correction value ΔK becomes as shown in the following Expression 3. .

[0022]

(Equation 3)

Then, the correction value ΔK calculated as described above
Is added to the first coefficient K ₁ to determine the third coefficient K ₃ , and RO
It is stored in M43b. Thereby, the third coefficient K ₃
The right and left rear wheels RW1 and RW2 are equivalent to the case where the yaw rate YR detected by the yaw rate sensor 41i is not used during the steady turning of the vehicle, as in the case where the detected yaw rate YR is used.
Is set to a value at which the steering control is performed, and even when the detected yaw rate YR is not used except during the steady turning of the vehicle,
The value is set to a value at which the steering control of the left and right rear wheels RW1 and RW2 is approximated when the detected yaw rate YR is used.

FIG. 3 shows the operation of the embodiment constructed as described above.
This will be described with reference to the flowchart of FIG. Ignissi
When an operation switch (not shown) is closed, the CPU 4
3c starts execution of the program in step 50,
The new yaw rate Y stored in the RAM 43d at step 51
R_NInitially set the new yaw rate data indicating “0” to “0”
You. After this initial setting, the CPU 43c proceeds to step 52
Each rotation speed signal is converted into a waveform shaper 42a, 42b, 42c, 4
2d through the I / O 43e, and input each rotation speed signal.
Left and right front wheels FW1, FW2 and left and right rear wheels RW
1, each rotation speed Nf1, Nf2, Nr1, Nr2 of RW2
Are calculated, and the calculated rotation speeds Nf1,
Each wheel FW1, FW2, Nf2, Nr1, Nr2
The traveling distance per unit time of RW1 and RW2, ie, each
First to fourth vehicle speeds V for wheels FW1, FW2₁, V_Two,
V_Three, V_FourIs calculated, and the calculated first to fourth vehicle speeds are calculated.
V₁, V_Two, V_Three, V_FourExpresses the vehicle speed V calculated based on
The vehicle speed data is stored in the RAM 43d. Of this vehicle speed V
In the calculation, the first to fourth vehicle speeds V₁, V_Two,
V_Three, V_FourOf those that show abnormal values are deleted,
Vehicle speed V₁, V_Two, V_Three, V _FourBy averaging the car
Calculate the speed V. Thus, a plurality of rotation speed signals,
From the wheel rotation speed sensors 41a, 41b, 41c, 41d
By calculating the vehicle speed V based on the pickup signal of
One of the sensors 41a, 41b, 41c, 41d
Even if an abnormality occurs, the accurate vehicle speed is calculated.

[0025] After the process of step 25, CPU43c vinegar
Before wheel steering angle θf1 In step 53, each represent front-wheel steering angle data the A / D converter 42e of Shitaefu2, read via respective I / O43e from 42f, the front-wheel steering angle θf based on this read both the steering angle data And calculates the front wheel steering angle data representing the calculated front wheel steering angle θf as RA
It is stored in M43d. In calculating the front wheel steering angle θf, if one of the front wheel steering angles θf1 and θf2 indicates an abnormal value, the other front wheel steering angle θf1 ( or θf2) is adopted as the front wheel steering angle θf, and both front wheels are used. If both the steering angles θf1 and θf2 indicate normal values, the average value of the front wheel steering angles θf1 and θf2 is adopted as the front wheel steering angle θf. By calculating the front wheel steering angle θf based on the plurality of front wheel steering angle data, that is, the output signals from the front wheel steering angle sensors 41e and 41f, an abnormality occurs in one of the front wheel steering angle sensors 41e and 41f. Also, the accurate front wheel steering angle θf is calculated. Next, the CPU 43c
In step 54, the rear wheel turning angle θ from the A / D converters 42g and 42h is
The rear wheel turning angle θr is calculated based on the rear wheel turning angle data representing r1 and θr2, respectively, and the rear wheel turning angle data representing the calculated rear wheel turning angle θr is stored in the RAM 43d.

After the processing of step 54, the CPU 43c stores the old yaw rate Y stored in the RAM 43d in step 55.
Old yaw rate data representing R _0, is updated by the new yaw rate data representing be stored new yaw rate YR _N in the RAM43d. Next, in step 56, the CPU 43c reads the yaw rate data representing the yaw rate YR detected by the yaw rate sensor 41i from the A / D converter 42i via the I / O 43e, and stores the read yaw rate data in the RAM 43d. By storing the yaw rate data as a new yaw rate YR _N
Is set to the detected yaw rate YR.

After the processing in step 56, the CPU 43c determines in step 57 whether or not the yaw rate sensor 41i is abnormal.

This step 57 corresponds to the vehicle momentum change rate calculating means and the abnormality detecting means of the present invention, and in this embodiment, the change rate of the output value of the yaw rate sensor 41i (the difference between the output values at a constant sampling time). Is monitored to distinguish an electrical abnormality due to a failure of the yaw rate sensor 41i from a change in the output value of the yaw rate sensor 41i due to the behavior of the vehicle and detect an abnormal state of the yaw rate sensor 41i. In particular,
The difference between the new yaw rate YR _N set in the old yaw rate YR ₀ and step 56 updated in step 55 is calculated, the difference is determined to be abnormal if Kose the predetermined range may be the vehicle running, otherwise If it is normal, it is determined.

If no abnormality has occurred in the yaw rate sensor 41i, the CPU 43c determines "NO" in step 57, and calculates a target rear wheel turning angle θr * in step 58. Note that the calculation in step 58 is
Corresponding to one of the control signal computing means. In the calculation in step 58, the RAM 43
d based on the vehicle speed data stored in d.
The first and second coefficients K ₁ and K ₂ (FIGS. 4 and 5) are derived with reference to the first and second tables in 43b, and the derived first and second coefficients K ₁ and K ₂ and Step 53 above,
The front wheel steering angle θ stored in the RAM 43d by the process of 56
based on the front-wheel steering angle data and the new yaw rate data representing respectively f and new yaw rate YR _N, performs operations of 4.

[0030]

Equation 4 θr * = K ₁ · θf + K ₂ · YR _N

After calculating the target rear wheel turning angle θr *, CP
U43c determines in step 59 that the target rear wheel turning angle θ
The target rear wheel turning angle θ is calculated by executing the calculation of θr * −θr based on r * and the rear wheel turning angle data representing the rear wheel turning angle θr stored in the RAM 43d by the processing of step 54.
A steering angle difference θr * -θr between r * and the rear wheel steering angle θr is calculated, and rotation control data for the step motor 23 corresponding to the steering angle difference θr * -θr is output to the I / O 43e. . The I / O 43e stores the rotation control data until new rotation control data is supplied, and at the same time, the driving circuit 4
4 is output.

The drive circuit 44 outputs a drive pulse train signal corresponding to the rotation control data to the step motor 23 to control the rotation of the motor 23. With this rotation control,
A step motor 23 drives the steering shaft 24 to rotate, and the coaxial 2
In response to the rotation of No. 4, the left and right rear wheels RW1, RW2 are steered to the target rear wheel turning angle θr *. These left and right rear wheels RW1, RW2
During the steering, the steering torque acts on the steering shaft 24, so that the power cylinder 33 assists the steering of the rear wheels RW1, RW2.

After the processing of step 59, the CPU 43c
Returns the program to step 52, and thereafter, returns to step 5
The circulation process consisting of 2-59
The steering control of W1 and RW2 is continued to the target rear wheel turning angle θr * determined by the processing of step 58.

In this state, the vehicle is started and the steering wheel 11 is turned to turn the front left and right wheels FW1, FW2.
, The rear left and right wheels RW1 and RW2 become the front wheel steering angle θf by the steering and the yaw rate Y generated in the vehicle body.
Target rear wheel steering angle θr determined in accordance with the R _N and the vehicle speed V
* (= K ₁ · θf + K ₂ · YR _N ). In this case, in the low vehicle speed region, the left and right rear wheels RW1, RW2
The sign of the control component K ₁ · θf is opposite to that of the front wheel steering angle θf. As a result, in this region, the left and right rear wheels R
W1 and RW2 are steered in opposite phases to the left and right front wheels FW1 and FW2, and the small turning performance of the vehicle is improved. In the middle and high vehicle speed range, the left and right rear wheels RW1, RW2 is positive or negative sign of the control component K ₂ · YR _N is the same as that of the front-wheel steering angle .theta.f. Thus, in this region, the left and right rear wheels RW1,
The RW2 is steered in the same phase with respect to the left and right front wheels FW1 and FW2, and the response of the vehicle to the rotation of the steering wheel 11 is reduced, so that the steering performance is improved.

If an abnormality occurs in the yaw rate sensor 41i during the circulation process consisting of steps 52 to 59, the CPU 43c determines "YES" in step 57, and in step 60, the target rear wheel turning angle θr *. Is calculated. The processing in this step 60 corresponds to the second control signal operation.
Corresponding to the Sante stage. In this calculation, we derive a third coefficient number K3 (Fig. 6) by referring to the third table in ROM43b based on the vehicle speed data representing the vehicle speed V stored in RAM43d by the processing in step 52, and the derived based on the front-wheel steering angle data representative of the front-wheel steering angle θf is stored in RAM43d by the processing of the third engagement number K3 and the step 53, to perform the calculation of the number 5.

[0036]

[Number 5] θr * = _{K 3} · θf

After calculating the target rear wheel turning angle θr *, CP
In step 59, the U43c sets the left and right rear wheels RW1, RW2 to the target rear wheel turning angle θr * (= K ₃ · θ) in the same manner as described above.
The steering control is performed in f). And the vehicle motion state quantity sensor 4
As long as the abnormality continues to occur in 1i, the CPU 43c
Continues the circulation processing consisting of steps 52 to 57, 60, and 59, and continues the steering control of the left and right rear wheels RW1, RW2 . That is, the four-wheel steering state is continued. In this case, the third coefficient K _3, as shown in FIG. 6, is set to a negative in a low vehicle speed range, and therefore is positively set at medium to high vehicle speed region, the target rear wheel steering angle [theta] r * The sign of (K ₃ · θf) is opposite to that of the front wheel steering angle θf in the low vehicle speed range. As a result, the left and right rear wheels RW1, RW2 are steered in the opposite phase to the left and right front wheels FW1, FW2 in the low vehicle speed region, so that the dominance of the steering wheel 11 is improved and the minimum turning radius is increased.
Is suppressed as much as possible, and the inner ring difference is suppressed as much as possible.
Such as, along with the maneuverability performance of the vehicles is improved, after the left and right
Wheels RW1, RW2 left and right front wheels FW1 at high vehicle speed region in the
The steering is performed in the same phase as the FW 2, and the response of the vehicle to the rotation of the steering wheel 11 is reduced, and the steering stability is improved.

As described above, according to the present embodiment, the rate of change of the output value of the yaw rate sensor 41i is calculated in step 57, and if the rate of change is outside the predetermined range that can be assumed during the running of the vehicle, the detection means sets the yaw rate The sensor 41i detects that it is above or not, and proceeds to step 60 where the yaw rate sensor 4
1i based on the front wheel steering angle θf without taking in the output value of 1i.
Of performing the calculation of the target rear wheel steering angle [theta] r *, abnormal yaw rate sensor 41i occurs, also the yaw rate of the abnormal value is outputted, it is controlled on the basis of the abnormal value is performed is prevented.

[0039]

According to the present invention, when the output signal of the vehicle motion state amount change rate calculating means is normal , the first control signal
The calculating means calculates the value based on the front wheel steering angle and the vehicle motion state quantity.
And the rear wheel turning angle is calculated and controlled based on the calculated value.
Means steer the rear wheels. In addition, the vehicle motion state quantity change rate performance
If the output signal of the calculating means is a signal that cannot be
If the abnormality detection means detects
Always is determined. In that case, the first control signal calculation means
Instead, the second control signal calculation means calculates the rear wheel turning angle.
You. In that calculation, the rear wheel turning angle is calculated based on the front wheel turning angle.
And therefore abnormal vehicle motion conditions
Set the rear wheel turning angle to an appropriate value without taking
Steering stability by continuing wheel steering state, that is, four-wheel steering state
Property can be maintained favorably. For example, in the low vehicle speed range
The left and right rear wheels are steered in opposite phases to the left and right front wheels.
This improves the steering wheel's dominance and minimizes rotation.
The radius is suppressed as much as possible and the inner ring difference is suppressed as much as possible.
The turning performance of the vehicle is improved. Also, for example
For example, in the middle and high vehicle speed range, the left and right rear wheels are in phase with the left and right front wheels.
By performing the steering control, the steering wheel rotation
The response of the vehicle to the vehicle is reduced, and the steering stability is improved .

[Brief description of the drawings]

FIG. 1 is a diagram corresponding to the configuration of the invention described in the claims.

FIG. 2 is an overall schematic diagram of a front and rear wheel steering vehicle to which the rear wheel steering device according to the present invention is applied.

FIG. 3 is a flowchart of a program executed by the microcomputer of FIG. 2;

FIG. 4 is a diagram illustrating a change characteristic of a parameter for turning control of a rear wheel with respect to a vehicle speed;

FIG. 5 is a diagram showing a change characteristic of a parameter for steering control of a rear wheel with respect to a vehicle speed.

FIG. 6 is a diagram showing a change characteristic of a parameter for steering control of a rear wheel with respect to a vehicle speed.

[Explanation of symbols]

A: front wheel steering device B: rear wheel steering device C: electric control device (control means) FW1, FW2: front wheel RW1, RW2: rear wheel 41a, 41b, 41c, 41d. · Wheel rotation speed sensors 41e, 41f · · · Front wheel steering angle sensors 41g · 41h · · · Rear wheel steering angle sensors 41i · · · Yaw rate sensors (vehicle motion state quantity detection means) 43 · · · Microcomputer 43a · · · Bus 43b Read only memory (ROM) 43c Central processing unit (CPU) 43d Write only memory (RAM) 43e Input / output interface (I / O)

Claims (1)

(57) [Claims] 1. A front wheel steering angle detected by the front-wheel steering angle detecting means, the front and rear wheels to control the steering angle of the rear wheels based on the vehicle motion state quantity detected by the vehicle both motion state quantity detecting means steering in wheel turning device after the car, before based and pre SL front wheel turning angle, the said vehicle motion state quantity
First control signal calculating means for calculating a turning angle of the rear wheel, vehicle motion state quantity change rate calculating means for calculating a change rate of the vehicle motion state quantity from an output signal of the vehicle motion state quantity detecting means, Abnormality detecting means for judging whether or not the output signal of the vehicle motion state amount change rate calculating means is within a predetermined range in which the vehicle can travel, and detecting an abnormal state of the vehicle motion state amount detecting means; When the abnormal state of the vehicle motion state amount detecting means is detected by the first control signal calculating means,
Instead of the step, the steering angle of the rear wheel is set based on the front wheel steering angle.
Second control signal calculating means for calculating, and the vehicle motion state amount detecting means by the abnormality detecting means
If no abnormal state is detected, the first control
The steering angle of the rear wheel is calculated based on the calculation result of the signal calculation means.
Controlling the vehicle motion state quantity by the abnormality detection means.
When an abnormality of the detection means is detected, the second control signal is output.
The steering angle of the rear wheel is controlled based on the calculation result of the signal calculation means.
Wheel turning device after the front and rear wheel steering vehicle, characterized that you have a Gosuru control means.