JPH05310141A - Rear wheel rudder angle control device for vehicle - Google Patents

Abstract

PURPOSE:To control a rear wheel steering precisely before the completion of neutral correction of a front wheel rudder angle and prevent any side slip by suppressing the increase of a yaw rate by means the second rear wheel steering angle calculation means instead of a rear wheel steering angle calculation means when a calculation completion determining means concludes that calculation of a neutral position is not finished. CONSTITUTION:An actual yaw rate is detected by means of an actual yaw rate detector to be compared with a target yaw rate calculated from the actual yaw rate and a vehicle speed, and a rear wheel steering angle is calculated with a rear wheel steering angel calculation means, so as to drive-control a rear wheel steering means. During this sequence, a calculation completion determining means determines whether calculation of a neutral position by a neutral position calculating means is finished or not, and when the calculation of the neutral position is not finished the rear wheel steering means is controlled with the second rear wheel steering angle calculating means that calculates a rear wheel steering angle for suppressing the increase of a yaw rate on the basis of a vehicle speed and an actual yaw rate instead of the rear wheel steering angle calculating means. Then rear wheel steering is controlled by a conventional rear wheel steering angle when the neutral position calculation of front wheel steering is finished.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle rear wheel steering angle control device for steering a rear wheel in a vehicle equipped with a mechanism for steering the rear wheel so as to prevent side skid during turning. ..

[0002]

2. Description of the Related Art Conventionally, as an example of detecting the yaw rate of a vehicle and controlling the rear wheel steering angle, Japanese Patent Laid-Open No. 60-12457.
There is a technique described in Japanese Patent No. 2 publication. In this technology, the target yaw rate of the vehicle is calculated from the absolute turning angle of the front wheels of the vehicle and the vehicle speed, and the rear wheel steering angle is adjusted so that the actual yaw rate of the vehicle detected by the angular velocity sensor matches the target yaw rate. Have control.

Here, the absolute turning angle of the front wheels cannot be directly detected, and a front wheel turning amount detecting sensor is provided on the steering shaft or the like and generates a pulse signal in accordance with the turning of the front wheels. It is calculated by detecting a relative turning amount and executing a calculation by various neutral correction logics on the detected value.

In the technique described in this publication, the neutral correction logic is such that the change in the steering amount (relative steering angle) detected by the front wheel steering amount detection sensor is kept smaller than a predetermined value during a fixed traveling distance. A method was adopted in which it is determined that the vehicle is traveling straight ahead, the time is determined as a provisional neutral position, and further correction to the true neutral position is made.

[0005]

Therefore, until the neutral correction of the front wheel steering angle by the neutral correction logic is completed after the relative value of the front wheel steering amount is detected, and the front wheel steering amount can be detected as an absolute angle. Took a considerable amount of time. Therefore, in the conventional device, it is impossible to prevent the skid by the rear wheel steering control until a considerable time elapses after the engine is started. In particular, if the vehicle immediately starts to turn at a speed higher than the predetermined speed, the neutral position cannot be corrected until the turning is completed, and the rear wheels cannot be steered during this period. It was not possible to take proper measures against skidding.

In view of the above, the present invention provides a device for a vehicle in which the rear wheels can be accurately steered to prevent skid even before the neutral correction of the front wheel steering angle is completed. It was completed for the purpose of providing a rear wheel steering angle control device.

[0007]

A rear wheel steering angle control device for a vehicle according to the present invention made to achieve the above object is a rear wheel steering system for steering the rear wheels as illustrated in FIG. Means, vehicle speed detecting means for detecting the vehicle speed of the vehicle, front wheel turning amount detecting means for detecting the turning amount of the front wheels, neutral position calculating means for calculating the neutral position of the front wheel turning, and the calculated neutral position. Based on the position and the detected turning amount, an absolute turning angle calculating means for calculating an absolute turning angle of the front wheels, an actual yaw rate detecting means for detecting an actual yaw rate generated in the vehicle by turning, Using the calculated absolute steering angle of the front wheels and the detected vehicle speed, a target yaw rate at the time of turning of the vehicle is calculated, and the target yaw rate and the actual yaw rate are compared, and the actual yaw rate is compared. The yaw rate of the target and the yaw rate of the target A vehicle provided with a rear wheel turning amount calculating means for calculating a rear wheel turning amount required to drive the vehicle, and a rear wheel turning control means for drivingly controlling the rear wheel turning means based on the calculated rear wheel turning amount. In the rear wheel steering angle control device for use, calculation completion determining means for determining whether or not the neutral position calculation means has completed calculation of the neutral position, and calculation of the neutral position has not been completed by the calculation completion determination means. If it is determined that the rear wheel steering amount calculation unit calculates the rear wheel steering amount that suppresses the increase in the yaw rate from the vehicle speed and the actual yaw rate, instead of the rear wheel steering amount calculation unit. It is characterized by having.

According to the vehicle rear wheel steering angle control device of the present invention, the second wheel steering angle control device is used until the calculation of the neutral position of the front wheel steering is completed.
After the rear wheel steering control is performed using the rear wheel steering amount calculated by the rear wheel steering amount calculation means, when the calculation of the neutral position of the front wheel steering is completed, the rear wheel steering amount calculation means as usual calculates Rear wheel steering control is performed using the rear wheel steering amount.

Here, the second rear wheel turning amount calculating means calculates the rear wheel turning amount for suppressing the increase of the yaw rate from the vehicle speed and the actual yaw rate without using the absolute turning angle of the front wheels. Since it is a means, the control amount can be calculated even if the absolute turning amount of the front wheels is not obtained. Further, at this time, the control amount is calculated to suppress the increase of the yaw rate, so that the original purpose of preventing skid can be prevented. The reason why the skid can be performed by the control amount that does not use the front wheel steering angle is that, according to the device of the present invention, the control amount is calculated not only by the vehicle speed but also by taking into account the actual yaw rate. This is because it is possible to calculate the control amount that also reflects the magnitude of the turning amount related to the skid strength.

As a result, according to the vehicle rear wheel steering angle control device of the present invention, the rear wheels are effective as a skid prevention measure even before the calculation of the neutral position of the front wheel steering by the neutral position calculating means is completed. The steering can be controlled.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is embodied in a vehicle rear wheel steering angle control device will be described below with reference to the drawings. 2 shows the overall configuration of the apparatus, and FIG. 3 shows a block diagram of the control system. As shown in FIG. 2, the vehicle of this embodiment includes a rear wheel steering mechanism 1. A DC servo motor 2 is provided in the rear wheel steering mechanism 1.
Is attached. The DC servomotor 2 receives the electric command signal from the control device 3 and rotates in the forward and reverse directions,
The rack and pinion mechanism with hydraulic power assist is operated via the reduction gear 4. The reduction gear 4 is connected to a hydraulic power assisted rack and pinion mechanism, that is, an input shaft (a torsion bar, not shown) of the rear wheel steering mechanism 1. A pinion gear 5 is attached to the other end of the torsion bar, and the pinion gear 5 meshes with a rack 7 formed at one end of the power piston 6. Further, the torsion bar is provided with a hydraulic valve 8 whose throttle area changes according to its twist. The hydraulic valve 8 communicates with the cylinder chamber of the power piston 6 and operates the power piston 6 according to the change in the throttle area. With the above configuration, when one end of the torsion bar is rotated by the DC servomotor 2, the torsion bar is twisted, and as a result, the throttle area of the hydraulic valve 8 changes, and the hydraulic pressure is supplied in the direction to correct the torsion of the torsion bar. And move the power piston 6.

Power piston 6 moved in this way
Both ends of each are connected to a knuckle arm 10 via tie rods 9, respectively. The knuckle arm 10 supports the rear wheel 11 so as to be swingable in the left-right direction. Therefore, by moving the power piston 6 in the direction of arrow A in the figure, the rear wheel 11 is steered to the left and right.

At this time, the steering angle of the rear wheel 11 is controlled as a position where the twisting of the torsion bar is eliminated, the throttle area of the hydraulic valve 8 becomes "0", and the supply and discharge of the hydraulic oil to the power piston 6 is stopped. It Here, the rear wheel steering angle sensor 12 installed near the power piston 6 detects the position of the power piston 6 and outputs a signal. Based on this signal, the control device 3 obtains the rear wheel actual steering angle and also obtains the steering angular velocity from the rate of change of the rear wheel actual steering angle.
Then, the steering mechanism 1 including the servo motor 2 and the control device 3
By these, a positioning servo system for positioning and controlling the rear wheels 11 is configured so that the rear wheel actual steering angle matches the rear wheel steering angle command value. Incidentally, 13 is a hydraulic pump for supplying hydraulic pressure to the power piston 6 via the hydraulic valve 8, and 14 is an oil tank.

The vehicle speed sensor 15 is of a type that detects the rotation speed of an axle or a wheel and outputs a vehicle speed signal corresponding to the vehicle speed V to the control device 3. The front wheel steering angle sensor 16
It consists of an increment type rotary encoder,
It is provided on a steering shaft 17 as a rotated body. Then, the rotation of the steering shaft 17 accompanying the steering wheel operation of the steering wheel 18 is detected,
The front wheel steering angle signal corresponding to the steering angle (relative value) θs of the front wheels 19 is output to the control device 3. Yaw rate sensor 20
Is composed of a gyro or the like, and outputs a yaw rate signal corresponding to the rotational angular velocity (yaw rate Wa) of the vehicle centering on the center of gravity of the vehicle to the control device 3. The left wheel speed sensor 21 detects the rotation speed of the left wheel of the front wheel 19 (left wheel speed ωL), and the right wheel speed sensor 22 detects the rotation speed of the right wheel of the front wheel 19 (right wheel speed ωR). The brake switch 23 is executing ABS (anti-lock brake system) control, or
Turns on when the brake pedal is operated.

The control device 3 will be described with reference to FIG.
The control device 3 includes a microcomputer (hereinafter, referred to as a microcomputer) 24, waveform shaping circuits 25 to 28, an analog buffer 29, an A / D converter 30, a digital buffer 31, and a drive circuit 32. The waveform shaping circuits 25 to 28 waveform-shape the signals from the vehicle speed sensor 15, the left wheel speed sensor 21, the right wheel speed sensor 22, and the front wheel steering angle sensor 16 and allow the signals to be taken into the microcomputer 24.
Further, the analog buffer 29 takes in each signal from the rear wheel steering angle sensor 12 and the yaw rate sensor 20, and the A / D converter 30 performs analog / digital conversion. The digital buffer 31 latches the signal from the brake switch 23. Further, the drive circuit 32 supplies a current corresponding to the current command value signal If from the microcomputer 24 to the DC servo motor 2.

Next, the operation of the rear wheel steering angle control device thus constructed will be described. 4 shows a main processing routine of the microcomputer 24, FIG. 5 shows a vehicle speed pulse processing by a pulse signal from the vehicle speed sensor 15, and FIG. 6 shows an interrupt processing routine at every predetermined time (for example, every 5 ms). ..

As shown in FIG. 4, the microcomputer 24 is initialized at step 101 at the time of start-up, and at step 102, various processes are repeated. On the other hand, as shown in FIG. 5, in step 201, the microcomputer 24 determines the vehicle speed pulse width P from the time when the last pulse interruption occurred and the time when this interruption occurred.
Calculate and store H. Similarly, each wheel speed pulse width WPH
Is also calculated.

Then, as shown in FIG.
In step 300, the vehicle speed V is calculated from the vehicle speed pulse width PH stored in the vehicle speed pulse interruption processing.
In this step 300, similarly, for the left wheel speed sensor 21 and the right wheel speed sensor 22, the left and right wheel speeds ωL of the front wheels 19 are also determined by the wheel speed pulse width WPH.
, ΩR is calculated. In this embodiment, the vehicle speed sensor 1
The vehicle speed V was calculated at 5, but the vehicle speed V was (ωL + ωR) / 2.
You may ask as.

Then, the microcomputer 24 proceeds to step 400.
Then, various A / D conversion data are fetched from the rear wheel steering angle sensor 12 and the yaw rate sensor 20 via the A / D converter 30, and in step 500 the rear wheel actual steering angle θr and the actual yaw rate Wa are calculated. Further, the microcomputer 24 executes a routine for calculating the absolute steering angle θ of the front wheels in step 600. This front wheel steering angle calculation routine is shown in FIG. Further, FIG. 8 shows a control block diagram of the front wheel steering angle calculation routine of FIG. 7.

In FIG. 7, the microcomputer 24 executes step 6
In step 01, the read steering angle θs of the front wheel steering angle sensor 16 is fetched, and in step 602, the primary delay steering angle θc is calculated using the primary delay transmission characteristic. That is, the first-order lag steering angle θc is calculated by the following equation.

[0021]

[Equation 1]

The microcomputer 24 then proceeds to step 603.
Then, from the left wheel speed ωL by the left wheel speed sensor 21 and the right wheel speed ωR by the right wheel speed sensor 22, the estimated steering angle θ
Calculate p.

[0023]

[Equation 2]

At this time, the front wheel steering angle θf is as shown in FIG.

[0025]

[Equation 3]

And the turning radius R is, as shown in FIG.

[0027]

[Equation 4]

Therefore, the above equation (2) is derived using the above equations (3) and (4). However, equation (2) is θf >>
The influence of the rear wheel steering is ignored as θr. Then, in step 604, the microcomputer 24 performs low-pass filter processing on the first-order lag steering angle θc and the estimated steering angle θp. That is, the following process is executed.

[0029]

[Equation 5]

The microcomputer 24 determines the estimated steering angle θ ^* p and the front wheel steering angle θ ^* c after the low-pass filtering in step 605.
The difference (= θ ^* c−θ ^* p) is calculated as the neutral position θD. Then, the microcomputer 24 determines in step 606 whether the correction condition is satisfied. The fulfillment of this correction condition means that the driving state and the vehicle driving characteristics in which the above-mentioned first-order lag holds are linear and are in a region where an equation is applied. That is, the absolute value of the estimated steering angle θ ^* p is equal to or less than θMAX, the vehicle speed V is within the range of VLOW to VHIGH, and the brake operation is not performed by the brake switch 23 (the anti-brake lock system control is not being performed. ) When
It is assumed that the correction condition is satisfied.

If the correction condition is satisfied in step 606, the process proceeds to step 607. In step 607, the neutral position θD calculated in step 605 is averaged during T seconds to calculate θDM. If the correction condition is not satisfied in step 606, the process proceeds to step 608, and depending on the state of the correction completion flag F, the process proceeds to step 612 or the process is skipped.

After the control unit is started and the microcomputer 24 is initialized, the above-mentioned procedure is performed. In step 609, θDM is n after microcomputer initialization in step 607.
Determine if it has been calculated more than once. When it is determined that the calculation has been performed n times or more, the neutral correction completion flag F of the front wheel steering angle is set to "1" in step 610.

If it is determined in step 609 that the number of times is less than n, the process is skipped. The flag F is reset to "0" at initialization. Next, after the flag F = 1 is set in step 610, the microcomputer 24 proceeds to step 611, performs low-pass filter processing of θDM, and calculates the final neutral position θN. That is, the following process is executed.

[0034]

[Equation 6]

By this low-pass filter processing, noise added to the wheel speed is removed. Then, in step 612, the microcomputer 24 determines the steering angle θs by the front wheel steering angle sensor 16.
And the final neutral position θN (= θs−θN) is defined as the absolute steering angle θ. By the way, θMAX, VLOW, VHIGH, T
Is preset with a constant according to the vehicle.

Next, the description returns again to the main routine of FIG. After the processing of step 600, the microcomputer 24 calculates the rear wheel steering angle command value θ ^* r in step 700. Here, step 700 is executed even when the above-mentioned absolute steering angle θ has not been calculated. That is, the transition from step 600 to step 700 is not limited to after the absolute steering angle θ has been calculated.

This step 700 is the rear wheel steering angle command value.
This is a process of calculating θ ^* r. In summary, in this step 700, the rear wheel steering angle command value is calculated based on either of the two methods of calculating the rear wheel steering angle command value depending on whether the neutral correction of the front wheel steering angle sensor is completed after the engine is started. Select the steering angle command value θ ^* r.

FIG. 11 shows a flowchart of the specific processing contents. First, in step 701, the state of the front wheel steering angle neutral correction completion flag F is determined. In this determination, if F = 0, that is, it is determined that the neutral correction is not completed, the process proceeds to step 702, and the rear wheel position command value is calculated by the second rear wheel position command value calculation method peculiar to the present embodiment. To do. The second rear wheel position command value calculation method is a method of calculating the command value without using the front wheel steering angle information. For example, as shown below, only the vehicle speed V and the actual yaw rate Wa are used to calculate the rear wheel position. Calculate the command value.

[0039]

[Equation 7]

Here, θ ^* r is a command value calculated by the second rear wheel position command value calculation formula, and K2 (V) is a coefficient that changes with the vehicle speed V. An example of setting K2 (V) is shown in FIG. As shown in the figure, the coefficient K2 (V) has a value of 0 at a vehicle speed equal to or lower than a predetermined value, then increases as the vehicle speed increases, and then becomes a constant value after increasing to some extent. That is, the coefficient K2 (V) is set so that only a steering command in the same direction as the front wheel steering direction is given.

On the other hand, if it is determined in step 701 that the front wheel steering angle neutral correction completion flag F is "1",
In step 703, the rear wheel position command value is calculated based on the first rear wheel position command calculation method using the conventionally known front wheel steering angle signal. The process of step 703 will be described with reference to the flowchart of FIG. First, in step 731 which is the first process, the vehicle speed V and the absolute steering angle θ of the front wheels are
From this, the steady-state target yaw rate Ws is calculated based on the following equation (9).

[0042]

[Equation 8]

Here, Kh is a stability factor representing the understeer or oversteer characteristic of the vehicle, which is a value which is usually set in advance as a constant value. Also,
This stability factor Kh is shown in FIG.
As shown in (c), it can be determined as a function value using the vehicle speed V and the steering angle θs as parameters. 1 is the wheel base of the vehicle, and N is the steering gear ratio, which are determined from the vehicle specifications.

In the next step 732, step 731
Using the steady-state target yaw rate Ws calculated in
The final target yaw rate Wi is calculated by giving a transient characteristic determined by the transfer function H (s) shown in the equation (10).

[0045]

[Equation 9]

Here, K represents the gain at the transient time, and K
The value is set to> 0. Further, T is a time constant and s is a Laplace operator. The expression (10) is shown by the transfer characteristic of the continuous system, but in this example, it is realized by performing strict discretization by the zero-order holder.

Hereinafter, the arithmetic processing in step 732,
That is, the processing method shown in Expression (11) will be described.

[0048]

[Equation 10]

First, the equation (11) is discretized at sampling intervals h (period of the timed interrupt processing shown in FIG. 6). In the description below, the input of the transfer function H (s) is u (s) and the output is y (s). When the equation (11) is converted into the state equation expression, it becomes as follows. That is,

[0050]

[Equation 11]

Therefore,

[0052]

[Equation 12]

Is obtained. When this equation (13) is discretized,

[0054]

[Equation 13]

Here, since h and T are known constants, e
^{-h / T} can be treated as a constant. Therefore, x, e
The output y (s) of the transfer characteristic H (s) can be calculated by appropriately calculating ^{-h / T} , K and calculating the equation (14). That is, u = Ws and y = Wi are set, and the final target yaw rate Wi can be calculated from the steady-state target yaw rate Ws by calculating the equation (14).

In the next step 733, the actual yaw rate Wa calculated in step 500 of FIG.
The error ΔW from the target yaw rate Wi calculated in step (15)
Calculate according to the formula.

[0057]

[Equation 14]

In step 734, the rear wheel steering angle command value first term θ ^* r1 is calculated from the error ΔW calculated in step 733 and the vehicle speed V calculated in step 300 according to the equation (16).
To calculate.

[0059]

[Equation 15]

Here, F (ΔW, V) is a function having the yaw rate error ΔW and the vehicle speed V as parameters, and FIG.
As shown in (a), a two-dimensional map is searched and calculated. Generally, when the vehicle speed is in the medium speed range, the yaw rate gain shown in the equation (9), that is, the ratio of the yaw rate to the front wheel steering angle, becomes high. Therefore, as shown in FIG. The term θ ^* r1 is set to be large in the low speed range, small in the medium speed range, and gradually increase in the high speed range with respect to the vehicle speed V. Further, the rear wheel steering angle command value first term θ ^* r1 is set proportionally to the yaw rate error ΔW. The yaw rate error ΔW
Is extremely small (ΔW ≦ ΔW0), θ ^* r1 = 0
And Also, the rear wheel steering angle command value first term θ ^* r1 is as shown in FIG.
As shown in FIG. 4 (b), the yaw rate error ΔW may be simply calculated.

Subsequently, when the routine proceeds to step 735, the front / rear wheel steering ratio K1 which gives the rear wheel steering amount by an amount proportional to the front wheels.
Calculate (V). This is calculated by performing a map search for a predetermined value according to the vehicle speed V as shown in FIG. As can be seen by comparing FIG. 16 and FIG. 12, in the processing by the first calculation method, the rear wheels are steered even in the reverse phase of the front wheel steering.

In the next step 736, the front wheel steering angle θ is multiplied by K1 (V) to calculate the rear wheel steering angle command value second term θ ^* r2. That is, the calculation of θ ^* r2 = K1 (V) · θ is executed. Then, in step 737, the final rear wheel steering angle command value θ ^* r is calculated. That is, θ ^* r = θ ^* r1 + θ ^*
Perform the operation of r2.

As described above, in step 703 of FIG. 11, the rear wheel steering angle command value is calculated using the front wheel steering angle signal. Note that the processing in step 703 is not limited to the contents described above, and for example, steps 735 to 7 in FIG.
The rear wheel steering angle command value may be calculated by the known front wheel proportional control in which the rear wheel is steered by an amount proportional to the front wheel described in reference numeral 36.

FIG. 17 shows a rear wheel control block diagram realized in step 703. The steady-state target yaw rate determined in consideration of the yaw rate gain, that is, the steady-state target yaw rate Ws, which is determined from the front-wheel steering angle, that is, the front-wheel steering angle θ and the vehicle speed V, is calculated by the equation (9), and the steady-state target yaw rate Ws is calculated. The signal that has passed through the first-order transfer function H (s) shown in equation (10) is used as the input, and the final target yaw rate Wi is set as the final target yaw rate Wi. Calculate the steering angle command first term θ ^* r1. Here, this first-order transfer characteristic H (s) determines the characteristic correction during the turning transition of the vehicle. Further, the rear wheel steering angle command second term θ ^* r2 determined from the front and rear wheel steering angles is added as a feedforward term.

Returning to the explanation of the flow chart of FIG. In step 704 following step 702 or 703, when the first rear wheel position command and the second rear wheel position command are switched, the front wheel steering angle neutral correction completion flag F is changed so that sudden steering does not occur in the rear wheel. It is determined whether or not, that is, immediately after the command calculation method is changed. If it is detected that the command calculation method has just been switched,
Go to step 705. In step 705, it obtains a command value θ ^* ri-1 calculated before switching, and a command value theta ^* ri calculated after switching, the difference △ theta ^* r generated by the switching of the command value calculation method. Then, in the following step 706, the difference Δθ ^* r is set to the offset value θ ^* ro.
ffset and at step 707 this offset value θ ^* ro
ffset is added to this command value θ ^* ri.

On the other hand, if it is determined in step 704 that it is not immediately after switching the calculation method, step 708
To the absolute value of the offset value θ ^* roffset by a predetermined amount d.
Only reduce. This reduction processing is (| θ ^* roffset |
If -d) is negative, it is guarded by "0".

That is, in this embodiment, step 70
Immediately after the calculation method of the rear wheel command value is switched by the processing of 4 to step 708, the value calculated by the new calculation method is not immediately set, but the value itself calculated by the new calculation method is changed over time. To approach. This control prevents the occurrence of sudden turning while following a new calculation method.

As described above, in step 700 shown in the interrupt processing routine of FIG. 6, either the first or the second calculation method is performed depending on whether the neutral position correction of the front wheel turning angle is completed. The rear wheel command value is calculated based on Then, the microcomputer 24 compares the rear wheel command value θ ^* r with the actual rear wheel position θr in step 800, and performs a generally known rear wheel positioning servo calculation to eliminate the difference between them.
Based on the result of this calculation, the current command value If is calculated in step 900 and output to the drive circuit 32 to drive the servo motor 2.

As described above, according to the present embodiment, even when the neutral position correction of the front wheel steering angle is not completed, such as immediately after the start, the rear wheel position command value is calculated based on the second calculation method. It can be calculated. At this time, the rear wheels are not steered in the opposite phase direction, but the rear wheels are steered only in the in-phase direction. Moreover, the rear wheel position command necessary for steering the rear wheels is calculated based on the vehicle speed V and the actual yaw rate Wa, and the tendency is that the higher the vehicle speed, the greater the steering in the in-phase direction.
The larger the actual yaw rate Wa, the larger the steering amount in the in-phase direction. Therefore, even if the amount of steering of the front wheels is unknown, there is no side slip such that the actual yaw rate Wa that is currently occurring increases, and if side skid is currently occurring, the side slip is reduced. The rear wheel steering control is executed as the control of.

After the neutral correction is completed, the control for matching the actual yaw rate with the target yaw rate is executed as in the conventional case, and the occurrence of skidding can be prevented. After the completion of the neutral correction, the steering control is executed not only in the in-phase direction but also in the anti-phase direction at the low speed, and a sharp turning at the low speed can be realized.

Further, according to the present embodiment, when switching between these two calculation methods, the control is shifted gradually according to the calculated value using only the new calculation method by using the offset value. When performing the switching control, it is possible to realize stable control without causing sudden turning.

Although one embodiment of the present invention has been described in detail above, the present invention is not limited to this embodiment and can be realized in various modes without departing from the scope of the invention. Is.

[0073]

As described in detail above, according to the vehicle rear wheel steering angle control device of the present invention, the rear wheels are steered even before the neutral correction of the front wheel steering angle is completed. Measures can be taken to prevent skidding.

As a result, the engine starts immediately after starting,
Even when the vehicle starts to turn at a speed higher than a predetermined speed, it is possible to appropriately prevent the sideslip during the turning. And, even though the front wheel steering angle is controlled in this way, the rear wheel steering amount is calculated by using the vehicle speed and the actual yaw rate so as to suppress the increase in the yaw rate. Does not increase skidding.

[Brief description of drawings]

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

FIG. 2 is a schematic configuration diagram of a rear wheel steering angle control device according to an embodiment.

FIG. 3 is a configuration diagram of a control system in the apparatus of the embodiment.

FIG. 4 is a flowchart of a main routine in the embodiment.

FIG. 5 is a flowchart of vehicle speed pulse processing in the embodiment.

FIG. 6 is a flowchart of an interrupt process for a rear wheel steering control process in the embodiment.

FIG. 7 is a flowchart of a neutral position correction logic according to the embodiment.

FIG. 8 is a control block diagram of a neutral position correction logic in the embodiment.

FIG. 9 is an explanatory diagram at the time of steering in the embodiment.

FIG. 10 is an explanatory diagram at the time of steering in the embodiment.

FIG. 11 is a flowchart of a rear wheel position command calculation process in the example.

FIG. 12 is a rear wheel position command calculation process in the embodiment,
It is explanatory drawing of the coefficient K2 (V) at the time of using a 2nd calculation method.

FIG. 13 is a characteristic diagram showing a method of setting the stability factor Kh in the first calculation method in the embodiment.

FIG. 14 is a characteristic diagram of a rear wheel steering angle command value calculation method according to the first calculation method in the embodiment.

FIG. 15 is a detailed flowchart of processing for calculating a rear wheel position command by the first calculation method according to the embodiment.

FIG. 16 is a rear wheel position command calculation process in the embodiment,
It is explanatory drawing of the coefficient K1 (V) at the time of using a 1st calculation method.

FIG. 17 is a control block diagram of a first calculation method according to the embodiment.

[Explanation of symbols]

1 ... Rear wheel steering mechanism, 2 ... DC servo motor, 3
... Electric control device, 4 ... Reduction gear, 5 ... Pinion gear, 6 ... Power piston, 7 ... Rack, 8 ... Hydraulic valve, 9 ... Tie rod, 10.
..Knuckle arm, 11 ... rear wheel, 12 ... rear wheel steering angle sensor, 15 ... vehicle speed sensor, 16 ... front wheel steering angle sensor, 17 ... steering shaft, 18
... Steering wheel, 19 ... Front wheel, 20 ...
..Yaw rate sensor, 21 ... left wheel speed sensor, 2
2 ... right wheel speed sensor, 23 ... brake switch, 24 ... microcomputer, 25-28 ... waveform shaping circuit, 29 ... analog buffer, 30 ... A / D converter, 31 ... ..Digital buffer, 32 ... Driving circuit

Claims (1)

[Claims] 1. A rear wheel steering means for steering the rear wheels, a vehicle speed detecting means for detecting a vehicle speed of the vehicle, a front wheel steering amount detecting means for detecting a steering amount of the front wheels, and a neutral position of the front wheel steering. A neutral position calculating means for calculating the absolute steering angle of the front wheels based on the calculated neutral position and the detected turning amount; Using the actual yaw rate detection means for detecting the actual yaw rate that occurs in the above, the calculated absolute steering angle of the front wheels and the detected vehicle speed, the target yaw rate during turning of the vehicle is calculated, Rear wheel steering amount calculation means for comparing the target yaw rate and the actual yaw rate, and calculating the rear wheel steering amount necessary for matching the actual yaw rate with the target yaw rate, and the calculated rear wheel steering. Based on the quantity, the rear wheel steering In a vehicle rear wheel steering angle control device including a rear wheel steering control means for driving and controlling a gear, calculation completion determination means for determining whether or not the neutral position calculation by the neutral position calculation means is completed, When the calculation completion determining means determines that the calculation of the neutral position is not completed, the rear wheel steering amount that suppresses an increase in the yaw rate from the vehicle speed and the actual yaw rate instead of the rear wheel steering amount calculating means. A rear wheel steering angle control device for a vehicle, comprising: a second rear wheel turning amount calculating means for calculating