JP2817244B2 - Neutral steering angle estimation device - Google Patents

Description

The present invention relates to a steering angle absolute value such as an auxiliary steering control system or an active suspension control system for assisting steering of at least one of a front wheel and a rear wheel at a front wheel steering angle. The present invention relates to a neutral rudder angle estimating device applied to a system in which is input information.

(Prior Art) As a conventional steering angle center detecting device (neutral steering angle estimating device), for example, a device described in Japanese Patent Application Laid-Open No. 59-26341 is known.

This conventional device holds the steering wheel turning angle during the traveling as a steering angle center when the change in the steering wheel turning angle during traveling is within a set range and the traveling distance during the traveling exceeds a reference value. The reference value is changed, and the reference value is changed so that the reference value after traveling a predetermined distance is larger than that at the start of traveling, that is, the response value and the accuracy are increased by making the reference value stricter according to the traveling distance. In this case, a steering angle center is obtained while achieving both.

(Problems to be Solved by the Invention) However, in such a conventional steering angle center detecting device, a steering wheel turning angle condition for calculating a steering angle center (neutral steering angle estimated value) is defined as a steering wheel turning angle. The change in the steering wheel angle is within the set range, so the steering wheel turning angle condition becomes too soft during high-speed driving where the tire slip angle is large and the steering wheel is turning due to a slight change in the steering wheel turning angle, so that straight running is maintained. In some cases, the steering angle position deviated from the original neutral position may be set as the steering angle center.

As a result, during high-speed running, an adverse effect is exerted on an applied system in which the rear wheels are steered by the rear-wheel steering control system even though the vehicle is running straight.

Further, in the conventional steering angle center detecting device, since the calculation condition of the steering angle center is gradually made stricter from the start of traveling, for example, small calculation is performed at an interchange on a highway or an introduction route at a service area exit. If the turning state continues for a long time and is set to the steering angle center that deviates from the normal neutral position, and then goes straight on the main line, the steering angle center is updated so that the stricter reference value condition for the next mileage is not satisfied. However, the steering angle center does not easily converge to the normal neutral position.

The steering angle sensor is, for example, a combination of a number of slits formed at equal intervals on the outer circumference of a disk-shaped sensor disk that rotates with the operation of the handle and an optical sensor arranged on the slit. The ON / OFF pulse signal is detected by counting the ON / OFF pulse signal due to the interruption of the light output when the steering wheel is operated.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problem, and provides a neutral steering angle estimating device that obtains a neutral steering angle estimation value without using a steering wheel neutral position sensor. The objective is to achieve both high accuracy and high neutral steering angle estimation accuracy at the same time, and to converge to the normal neutral steering angle estimated value as soon as possible when the neutral steering angle estimated value deviates from the normal value during highway driving. I do.

(Means for Solving the Problems) In order to solve the above problems, the neutral steering angle estimating apparatus of the present invention comprises a steering wheel steering angle detecting means a for detecting a steering wheel steering angle as shown in the claim correspondence diagram of FIG. A traveling distance detecting means b for detecting a traveling distance, a vehicle speed detecting means c for detecting a vehicle speed, and a steering angle by a slight steering operation to the left and right performed to maintain the straight traveling of the vehicle as a corrected steering angle. The calculation condition of the neutral steering angle estimated value that the steering angle of the steering wheel is at least the corrected steering angle range and the traveling distance in the corrected steering angle range is equal to or greater than the set traveling distance, and the corrected steering angle range is set to a large value when the vehicle speed is low Set the mileage to a short value,
As the vehicle speed increases, the value of the corrected steering angle range is reduced and the set travel distance is increased, and when the vehicle speed first reaches a high speed value equivalent to straight traveling on the highway from a low vehicle speed state, neutral steering is performed. The calculation conditions of the angle estimation value are corrected. The steering speed range is the largest value and the set travel distance is the initial condition based on the shortest value. A neutral steering angle estimated value calculating means e for calculating a neutral steering angle estimated value based on a steering wheel detected angle value obtained during traveling satisfying the vehicle speed corresponding calculation condition when the condition is satisfied. It is characterized by.

(Operation) When the vehicle speed is low immediately after the start of traveling of the vehicle, the vehicle speed corresponding calculation condition setting means d determines that the steering angle of the steering wheel is at least within the corrected steering angle range and the traveling distance in the modified steering angle range is equal to or greater than the set traveling distance. As the calculation condition of the steering angle estimated value, a condition is set such that the corrected steering angle range is a large value and the set traveling distance is a short value. In the neutral steering angle estimated value calculating means e,
When the steering angle detection value obtained from the steering angle detection means a and the travel distance obtained from the travel distance detection means b satisfy the low vehicle speed corresponding calculation condition, the steering wheel obtained during running satisfying this condition is satisfied. A neutral steering angle estimated value is calculated based on the detected steering angle value.

When the vehicle speed gradually increases after a while from the start of vehicle running, the vehicle speed corresponding calculation condition setting means d decreases the value of the corrected steering angle range as the vehicle speed increases, and increases the set travel distance to a longer value. In the neutral steering angle estimated value calculating means e, the neutral steering angle estimated value is calculated based on the steering wheel angle detected value obtained during traveling satisfying the increasingly strict vehicle speed corresponding calculation condition. Done.

Therefore, when the vehicle speed is low immediately after the start of traveling, the neutral steering angle estimated value is set early and with good response because the corrected steering angle range is large and the set traveling distance is short and the vehicle speed is low.
When driving at medium or high speeds after a while from the start of driving, the steering angle range is strictly set so that the corrected steering angle range becomes smaller and the set traveling distance becomes longer as the vehicle speed corresponding calculation condition becomes higher, so the neutral steering angle The estimated value is gradually set with high accuracy.

When the vehicle speed firstly reaches a high speed value corresponding to the straight running of the highway from the low vehicle speed state, the calculation condition of the neutral steering angle estimated value is the largest in the corrected steering angle range. The set traveling distance is set to the initial condition based on the shortest value, and the neutral steering angle estimated value calculating means e immediately thereafter calculates the neutral steering angle estimated value when the soft initial condition is satisfied.

Therefore, for example, when a small turning state is continuously performed for a long time at an interchange of a highway or an introduction path of a sirth area exit, the steering wheel is deviated from a steering angle center deviated from a normal neutral position, and then the vehicle travels straight on the main line. The neutral steering angle estimated value is immediately calculated according to the mild calculation condition, and the neutral steering angle estimated value converges to the normal neutral position early.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 2 is a diagram showing the overall configuration of a four-wheel steering vehicle equipped with a rear-wheel steering control system to which the neutral steering angle estimating device of the embodiment is applied.

 First, the configuration will be described.

In FIG. 2, 1L and 1R are left and right front wheels, 2L and 2R are left and right rear wheels,
3 is a handle. The front wheels 1L, 1R can be steered by a steering wheel 3 via a steering gear 4, respectively, and the rear wheels 2L, 2R
R can be steered by the rear wheel steering actuator 5, respectively.

The rear wheel rudder actuator 5 is a spring center type hydraulic actuator. When hydraulic pressure is supplied to the chamber 5R, the rear wheels 2L and 2R are steered to the right by a steering angle proportional to the pressure, respectively.
When supplying hydraulic pressure to L, the rear wheels 2L,
It is assumed that each 2R is turned to the left.

An electromagnetic proportional rear wheel steering control valve 6 for controlling hydraulic pressure to the actuator chambers 5L, 5R is provided, and the valve 6 is configured such that variable throttles 6a, 6b, 6c, 6d are connected in a bridge manner. , Reservoir 8 and actuator chamber
Oil paths 9 and 10 from 5L and 5R are connected respectively.

The control valve 6 further includes solenoids 6L and 6R. When the solenoids 6L and 6R are OFF, the control valves 6 each have a variable throttle 6R.
a, 6b and 6c, 6d are fully opened, both actuator chambers 5L, 5R are in a non-pressure state, and the drive current with dither for solenoid 6L or 6R
When turned on by I _L ^* or I _R ^* , the variable throttle 6c, 6d or 6a, 6b is throttled to an opening corresponding to the current value, and the drive current I _L ^* or I _R ^* with dither is supplied to the actuator chamber 5L or 5R. The hydraulic pressure according to the value shall be supplied. As described above, this hydraulic pressure steers the rear wheels 2L, 2R in the corresponding directions by an angle corresponding to the value.

Oil passages 9 and 10 between the electromagnetic proportional rear wheel steering control valve 6 and the rear wheel steering actuator 5 (oil passages before and after the cut valve 20 are respectively 9-1, 9-2 and 10-1, 10- 2)
A cut valve 20 having a solenoid on-off valve structure is inserted in the middle of the process.

The cut valve 20 is a normally closed type, and the ignition OF
A time F or during failure, when the solenoid drive current I _F is not supplied to the solenoid 20a is between the oil passage 9-1, 9-2 and 1
Blocked between 0-1,10-2 is when being performed rear wheel steering control properly, when the solenoid drive electric I _F is supplied, while the oil passage 9-1, 9-2 And between 10-1 and 10-2.

When the quad valve 20 is closed, a failure occurs when the microcomputer runs out of control, a sensor error occurs, or the solenoids 6L, 6R of the control valve 6 are disconnected or short-circuited. Lights up.

The drive current with dither I _L ^* or I _R ^* is applied to the control valve solenoids 6L and 6R, and the cut valve solenoid is
Or by applying the solenoid driving current I _F to 20a, the warning lamp 2
The rear wheel steering control unit 30, which applies an ON-OFF signal to 1, includes a steering wheel angle sensor 40 for detecting a steering wheel direction and a steering wheel angle θ as sensors for providing input information, and a vehicle speed for detecting a vehicle speed V. The sensor 42, an ignition switch 43 and the like are connected.

And, in this rear wheel steering control unit 30,
As shown in the block circuit diagram of FIG. 3, the internal circuits include an A / D converter 30a, a neutral steering angle estimated value calculation circuit 30b, a backup memory 30c, a front wheel steering angle calculation circuit 30d, and a rear wheel steering angle calculation circuit 30e. , D / A converter 30f, θ _R -I conversion circuit 30g,
It has a dither setting circuit 30h, a solenoid drive circuit 30i, an abnormality detection circuit 30j, a fail-safe circuit 30k, a solenoid drive circuit 30l, and a display drive circuit 30m.

As shown in FIG. 4, the steering angle sensor 40 is provided with a steering shaft 50 which is circuited together with the steering wheel 3.
And two sets of discs arranged at half-pitch intervals corresponding to the steering angle detecting slits 51a formed at intervals of several degrees over the entire circumference of the sensor disc 51 fixed to the sensor disc 51. Diode and photo IC (first sensor unit 40
a) and the second sensor section 40b).

The steering angle θ is detected by counting the number of pulses corresponding to the amount of turning of the steering wheel.
As shown in the figure, both sensor units are used when turning right and turning left.
The turning direction is detected by the difference in the phase difference between the output pulse waveforms from the 40a and 40b.

 Next, the operation will be described.

(A) Neutral steering angle estimated value calculation processing operation FIG. 7 is a flowchart showing the flow of the neutral steering angle estimated value calculation processing operation started from the time when the ignition switch 43 is turned ON.

First, in step 70, the rear wheel turning control is prohibited until the start command of the rear wheel turning control is output to step 80.

In step 71, the neutral steering angle estimated values θ _C1 , θ _C2 , θ _C3 and the stored neutral steering angle estimated value θ set during the previous traveling are set.
_CM is reset.

In step 72, the set high vehicle speed value was set when the previous process was started.
Be less than V _4, set in the current process startup speed faster V ₄
It is judged whether it is above or not.
Proceed to the normal neutral steering angle estimation calculation processing operation after 73, YES
In the case of, the process proceeds to the initialization processing operation of the neutral steering angle estimation calculation after step 88.

The setting high vehicle speed value V ₄ is set to, for example, vehicle speed corresponding straight running of the highway, such as 90 km / h.

In step 73, the condition for calculating the neutral steering angle value at the time of high speed is determined. When YES, the process proceeds to step 84 and thereafter, and when NO, the process proceeds to step 74.

Here, V ₃ is a high-speed vehicle speed condition, for example, 70 km / h
Is set to

theta ₃ is faster when the corrective steering angle condition, for example, is set to 6 ° (deg).

L ₃ is a high-speed during the continuous running distance condition while satisfying the high-speed condition and fixes the steering angle condition, for example, is set to 37.5 m.

Then, the vehicle speed V calculated by another flowchart
, The corrected steering angle θ _S , the continuous running distance L, and the high-speed calculation conditions V ₃ , θ ₃ , L ₃ are compared, and V ≧ V ₃ , θ ₃ ≦ θ
₃ , it is determined whether the three conditions of L ≧ L ₃ are simultaneously satisfied.

Note that in this operation condition determination, when satisfied that the vehicle speed condition correction steering angle condition at the same time, the right maximum steering angle theta _MAX of the steering angle theta and left maximum steering angle theta _MIN is set by another flow, If either the vehicle speed condition or the modified steering angle condition is not satisfied, the rightward maximum steering angle θ
_MAX and the maximum leftward steering angle θ _MIN are cleared.

In step 74, the conditions for calculating the neutral steering angle value at the time of middle speed are determined. When YES, the process proceeds to step 81 and later, and when NO, the process proceeds to step 75.

Here, V ₂ is a medium speed vehicle speed condition, for example, 50 km / h
Is set to

theta ₂ is a medium-speed correction steering angle condition, for example, 8 ° (de
g) is set.

L ₂ is a continuous running distance condition when fast in the state that satisfies the corrective steering angle condition and vehicle speed conditions, for example, is set to 25 m.

Then, the vehicle speed V calculated by another flowchart
And the corrected steering angle θ _S and the continuous traveling distance L are compared with the high-speed calculation conditions V ₂ , θ ₂ , and L ₂ , respectively, and V ≧ V ₂ , θ _S ≦ θ
₂ , it is determined whether the three conditions of L ≧ L ₂ are simultaneously satisfied.

Note that in this operation condition determination, when satisfied that the vehicle speed condition correction steering angle condition at the same time, the right maximum steering angle theta _MAX of the steering angle theta and left maximum steering angle theta _MIN is set by another flow, If either the vehicle speed condition or the modified steering angle condition is not satisfied, the rightward maximum steering angle θ
_MAX and the maximum leftward steering angle θ _MIN are cleared.

In step 75, the conditions for calculating the neutral steering angle value at low speed are determined. When the result is YES, the process proceeds to step 76 and thereafter, and when the result is NO, the process returns to step 72.

Here, V ₁ is a vehicle speed condition at low speed, for example, 30 km / h
Is set to

theta ₁ is a low speed correction steering angle condition, for example, is set to 10 ° (deg).

L ₁ is a low speed during the continuous running distance condition while satisfying the corrective steering angle condition and vehicle speed conditions, for example, it is set to 12.5 m.

Then, the vehicle speed V calculated by another flowchart
, The corrected steering angle θ _S , the continuous travel distance L, and the high-speed calculation conditions V ₁ , θ ₁ , L ₁ are compared, and V ≧ V ₁ , θ _S ≦ θ
_It is determined whether the three conditions of ₁ and L ≧ L ₁ are simultaneously satisfied.

Note that in this operation condition determination, when satisfied that the vehicle speed condition correction steering angle condition at the same time, the right maximum steering angle theta _MAX of the steering angle theta and left maximum steering angle theta _MIN is set by another flow, If either the vehicle speed condition or the modified steering angle condition is not satisfied, the rightward maximum steering angle θ
_MAX and the maximum leftward steering angle θ _MIN are cleared.

When all of the low-speed operation conditions in step 75 are satisfied, the process proceeds to step 76, in which a low-speed neutral steering angle is estimated by the following equation, which calculates the average value of the maximum right steering angle θ _MAX and the maximum left steering angle θ _MIN. The value θ _C1 is calculated.

In step 77, it is determined whether or not the high-speed neutral steering angle estimated value θ _C3 has already been calculated in step 84. In step 78, the medium-speed neutral steering angle estimated value θ has already been calculated in step 81.
It is determined whether _C2 has been calculated.

If the high-speed neutral steering angle estimated value θ _C3 or the medium-speed neutral steering angle estimated value θ _C2 has already been calculated, the routine proceeds to step 72 without updating the neutral steering angle estimated value and then to step 72. to return, when high speeds neutral steering angle estimated value theta _C3 is the calculation of the medium speed during the neutral steering angle estimated value theta _C2 is not completed, the process proceeds to step 79, low speed neutral steering angle estimating obtained in step 76 The value θ _C1 is set as the stored neutral steering angle estimation angle θ _CM .

In step 80, the start command of the rear wheel steering control is outputted by the set of storage the neutral steering angle estimated value theta _CM.

On the other hand, if all of the medium-speed calculation conditions in step 7 are satisfied, the process proceeds to step 81, in which a neutral value at the middle speed is calculated by the following formula for calculating an average value of the maximum right steering angle θ _MAX and the maximum left steering angle θ _MIN. The estimated steering angle θ _C2 is calculated.

In step 82, whether done so already calculated fast during the neutral steering angle estimated value theta _C3 in step 84 is determined already, if the calculation of the high speed at the neutral steering angle estimated value theta _C3 is done so, neutral The process returns to step 72 via step 80 without updating the steering angle estimated value, and if the high-speed neutral steering angle estimated value θ _C3 has not been calculated, the process proceeds to step 83, where the medium speed obtained in step 81 is calculated. The hourly neutral steering angle estimated value θ _C2 is set as the stored neutral angle estimated value θ _CM .

Further, when satisfying all the high-speed time operation condition of step 73, the process proceeds to step 84, a high speed during the neutral steering angle according to the following equation for obtaining the average value of the right maximum steering angle theta _MAX and left maximum steering angle theta _MIN The estimated value θ _C3 is calculated.

In step 85, whether done so already calculated fast during the neutral steering angle estimated value theta _C3 in step 84 is determined already, if the calculation of the high speed at the neutral steering angle estimated value theta _C3 is done so, step _Proceeding to 86, a high _- speed neutral steering angle estimated value θ _c3 is calculated by adding and averaging the previous high-speed neutral steering angle estimated value θ _C3i-1 and the current high-speed neutral steering angle estimated value θ _C3i .

When the calculation of the estimated value of the neutral steering angle θ _C3 at high speed is the first, the process proceeds from step 85 to step 87, and
If the high-speed neutral steering angle estimated value θ _C2 obtained in step 84 is set as the stored neutral steering angle estimated value θ _CM , and if the high-speed neutral steering angle estimated value θ _C3 has already been calculated, step 85 → step 86 → Proceeding to step 87, the high-speed neutral steering angle estimated value θ _C2 obtained in step 86 is updated and set as the stored neutral steering angle estimated value θ _CM .

On the other hand, when the initialization vehicle speed condition of step 72 is satisfied, the process proceeds to step 88, where the neutral steering angle estimated values θ _C1 , θ _C2 , θ
_C3 is reset, and the calculation of the low-speed neutral steering angle estimated value θ _{C1 under} the weak initial condition is started again.

Therefore, the neutral steering angle estimation calculation processing operation has the following features.

Immediately after the vehicle starts running, the low-speed neutral steering angle estimated value θ _C1 is set as the stored neutral steering angle estimated value θ _{CM under} the weakest low-speed neutral steering angle estimated value calculation condition, and thereafter, the stricter steps are performed.
74 The medium speed neutral steering angle estimated value calculation condition is satisfied, the medium speed neutral steering angle estimated value θ _C2 is set as the stored neutral steering angle estimated value θ _CM , and the strict step 73 high speed neutral steering angle estimation Value calculation condition is satisfied, and the high-speed neutral steering angle estimated value θ _C3 is set as the stored neutral steering angle estimated value θ _CM. Since the estimated value θ _CM is not updated, the stored neutral steering angle estimated value θ _CM is set with good responsiveness immediately after the start of traveling, and when traveling at medium / high speed after a while from the traveling start, The stored neutral steering angle estimated value θ _CM is gradually set with high accuracy.

Therefore, when the vehicle is running at a high speed in which the tire slip angle is large and the vehicle is in a turning state due to a slight change in the steering wheel angle, the corrected steering angle condition becomes very severe, so that the stored neutral position substantially matches the original neutral position for maintaining the straight running. The estimated steering angle θ _CM is set, and the desired rear wheel turning control can be obtained during high-speed running.

When the vehicle speed first reaches a high vehicle speed value corresponding to the straight running of the highway from the low speed state, the vehicle speed corresponding calculation condition is initialized, and thereafter, when the least sweet low vehicle speed corresponding calculation condition is satisfied, The low speed neutral steering angle estimated value θ _C1 is set as the stored neutral steering angle estimated value θ _CM .

Therefore, for example, when a small turning state is continuously set for a long time on a highway interchange or a service area exit introduction road and the like, and is set to the stored neutral steering angle estimated value θ _CM which is deviated from the normal neutral position, and thereafter, the vehicle travels straight on the main line , The low speed neutral steering angle estimated value θ _C1 is immediately calculated under the mild calculation condition, and the stored neutral steering angle estimated value θ _CM is updated and set.
Storage neutral steering angle estimated value theta _CM converges prematurely neutral position normal to maintain the vehicle running straight.

(B) Rear wheel steering control and fail-safe operation FIG. 8 is a flowchart showing the flow of the rear wheel steering control operation and the fail-safe operation performed after the rear wheel steering control start command is output in FIG.

In step 90, it is determined whether or not a failure command output when any abnormality is detected by the abnormality detection circuit 30j is output.If the fail command is not output, the rear wheel steering control operation after step 91 is performed. When the fail command is output, the fail-safe operation from step 97 is performed.

* Rear wheel turning control operation In step 91, the steering wheel angle θ, the vehicle speed V, and the stored neutral steering angle estimated value θ _CM (including the fixed stored neutral steering angle estimated value θ _MAX ) are read.

In step 92, the front-wheel steering angle theta _F is calculated by the following equation, steering angle theta and a storage neutral steering angle estimated value theta _CM.

_{θ F = | θ-θ CM} | In step 93, the target rear wheel steering angle theta _R is calculated based on the vehicle speed V and the front wheel steering angle theta _F.

In step 94, the target rear wheel steering angle theta _R is converted into a drive current I _L or I _R by pre-given theta _R -I characteristic table.

In step 95, is output to the predetermined amplitude, driving with dithered by adding a dither by frequency current I _L ^* or I _R ^* control valve solenoids 6L or 6R in the drive current I _L or I _R obtained in step 94 .

In step 96, a solenoid drive current _IF is output to the valve solenoid 20a by an ON signal for opening the cut valve 20.

* The fail-safe operation step 97, the solenoid drive current by OFF signal to close the cut valve 20 to the valve solenoid 20a I _F
Is output.

In step 98, a lighting signal (ON) is output to the alarm lamp 21.

In step 99, the elapsed time [Delta] T from the fail-safe command checks whether it is a predetermined time [Delta] T _O (e.g. 150 msec), the dither of the solenoid 6L or 6R of the control valve 6 in Step 100 When turned [Delta] T ≧ [Delta] T _O A command to turn off the attached drive current I _L ^* or I _R ^* is output.

Thus, in the rear wheel steering control operation, for example, as shown in FIG. 9, and turning control of the rear wheels in the opposite phase for a moment to the front-wheel steering angle theta _F, then turning control to the in-phase first-order-advance of When phase inversion control is performed, the rise of the yaw rate is improved by positively applying the generation of cornering force in the yaw generation direction, and after sufficient yawing is obtained, the rear wheels are turned to the same phase. By suppressing the increase in yaw rate by steering, it is possible to suppress the occurrence of a vehicle side slip angle, and it is possible to obtain turning performance that achieves both high responsiveness and steering stability.

Also, in the fail-safe operation, the hydraulic pressure is cut by the cut valve 20, and thereafter, the rear wheel is gradually returned to the neutral position by utilizing the oil leak at the cut valve 20, so that when the fail occurs, Sudden change in vehicle behavior is prevented.

Although the embodiment has been described with reference to the drawings, the specific configuration, control contents, and the like are not limited to this embodiment.

For example, in the embodiment, the neutral steering angle estimating device applied to the rear wheel steering control system is shown as an example, but an auxiliary steering control system, an active suspension control system, and the like that perform steering control of both front and rear wheels during front wheel steering. Of course, any system that uses a steering angle absolute value as input information and requires a neutral steering angle estimation device can be applied to other systems.

(Effects of the Invention) As described above, according to the first aspect of the present invention, in the neutral steering angle estimating device for obtaining the neutral steering angle estimating device without using the steering wheel neutral position sensor, the corrected steering angle range The calculation condition of the neutral steering angle estimated value that the mileage at the vehicle is equal to or more than the established mileage, the correction steering angle range is set to a large value when the vehicle speed is low, and the set mileage is set to a short value. The value of the range is reduced and the set traveling distance is increased to a longer value.When the vehicle speed first reaches a high speed value equivalent to straight traveling on an expressway from a low vehicle speed state, the calculation condition of the neutral steering angle estimation device is corrected. Because the angle range is the largest value and the set traveling distance is the initial condition with the shortest value,
It is possible to achieve both high responsiveness at low-speed driving and high neutral steering angle estimation accuracy at high-speed driving, and to perform early operation when the neutral steering angle estimation value deviates from the normal value during highway driving. Thus, the effect of converging to the normal neutral steering angle estimated value can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram corresponding to claims of a neutral steering angle estimating device of the present invention, and FIG. 2 is an overall configuration of a four-wheel steering vehicle equipped with a rear wheel turning control system to which the neutral steering angle estimating device of the present invention is applied. FIG. 3 is a block circuit diagram of a rear wheel turning control unit of a rear wheel turning control system. FIG. 4 is a diagram showing a steering wheel steering angle sensor. FIGS. 5 and 6 are right views of a steering wheel steering angle sensor. FIG. 7 is a flowchart showing a steering angle pulse signal at the time of turning and left turning, FIG. 7 is a flowchart showing a flow of a neutral steering angle estimated value calculation processing operation, and FIG. 8 is a flow of a rear wheel turning control operation and a fail safe operation. FIG. 9 is a time chart showing an example of the rear wheel steering control. a steering wheel steering angle detecting means b running distance detecting means c vehicle speed detecting means d vehicle speed corresponding calculation condition setting means e neutral steering angle estimated value calculating means

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Claims (1)

(57) [Claims] 1. A steering angle detecting means for detecting a steering angle of a steering wheel, a traveling distance detecting means for detecting a traveling distance, a vehicle speed detecting means for detecting a vehicle speed, and a left and right direction for maintaining the straight running of the vehicle. Assuming that the steering angle due to slight steering of the steering wheel is the corrected steering angle, the neutral steering angle estimated value calculation condition that at least the steering wheel angle is within the corrected steering angle range and the traveling distance in the corrected steering angle range is equal to or greater than the set traveling distance When the vehicle speed is low, the corrected steering angle range is set to a large value, and the set traveling distance is set to a short value.As the vehicle speed increases, the value of the corrected steering angle range is reduced, and the set traveling distance is set to a long value. When the vehicle first reaches a high speed value equivalent to straight traveling on the highway from the low vehicle speed state, the calculation condition of the neutral steering angle estimated value is modified to the initial condition by the value with the largest steering angle range and the shortest set traveling distance. You When the steering angle and the traveling distance obtained by the detection satisfy the vehicle speed corresponding calculation condition, the neutral steering is performed based on the steering wheel angle detection value obtained during traveling satisfying the vehicle speed corresponding calculation condition. A neutral steering angle estimating device comprising: a neutral steering angle estimated value calculating means for calculating an angle estimated value.