JP3055310B2 - Vehicle front wheel steering angle detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a digital steering angle detection sensor which outputs a detection signal every time the steering angle of a front wheel changes by a unit angle. The present invention relates to a device for detecting a proper steering angle.

[0002]

2. Description of the Related Art Conventionally, in order to detect a front wheel steering angle of a vehicle, a rotary encoder type front wheel steering angle sensor is provided to detect a relative steering angle change amount of a front wheel.
A device for estimating and calculating a steering neutral position during a predetermined straight traveling and detecting a steering angle of a front wheel from a relationship between the neutral position and the relative steering angle change amount has been known (for example, Japanese Patent Application Laid-open No. -11608). Further, the front wheel steering angle detected by using such a sensor is determined by a side slip prevention control using a rear wheel steering device (for example, Japanese Patent Application Laid-Open No. Sho 60-124572).
No.) and four-wheel steering control (4WS).

[0003]

However, in such a conventional apparatus, the front wheel steering angle could not be detected before the calculation for estimating the neutral position was completed. Therefore, unless a considerable amount of time has elapsed since the key switch was turned on, the front wheel steering angle could not be correctly output, and the rear wheel steering control could not be performed unless the vehicle had traveled to some extent. On the other hand, 4WS, which is one of the rear wheel steering controls, is effective when trying to get out of the garage or when traveling in a narrow parking lot. However, as described above, immediately after the start, the front wheel steering angle cannot be detected, and the rear wheel steering based on the front wheel steering angle cannot be performed.Therefore, in the system using the conventional front wheel steering angle detection device, the effectiveness of the rear wheel steering control is not sufficient. There was a problem that it could not be used for

In response to such a problem, recently, until the neutral position learning of the front wheel steering angle is completed, the steering angle is detected by a potentiometer type front wheel steering angle sensor that outputs an analog signal, and the neutral position learning is completed. After that, a device for detecting the steering angle by switching to a rotary encoder type front wheel steering angle sensor has been filed by the present applicant (Japanese Patent Application No. 3-8).
5462). According to the device proposed in Japanese Patent Application No. 3-85462, effective four-wheel steering can be performed immediately after starting before the neutral position calculation is completed. Although the effect can be exhibited, the following problems have newly arisen.

The analog signal from the potentiometer type front wheel steering angle sensor is susceptible to noise and the like. In such a case, the control may be made to vibrate. Therefore, in the prior art, it is difficult to perform highly accurate rear wheel turning control with high responsiveness immediately after starting the engine.

In view of these problems, a vehicle front wheel steering angle detecting apparatus of the present invention has an object to enable a vehicle front wheel steering angle to be stably detected immediately after an engine start without becoming vibratory. I do.

[0007]

In order to achieve the above object, a vehicle front wheel steering angle detecting apparatus according to the present invention has the structure shown in FIG.
As illustrated in (A), a digital steering angle detecting means for outputting a digital signal every time the steering angle of the front wheel changes by a unit angle, and counting the digital signal of the digital steering angle detecting means, thereby obtaining the front wheel steering angle. Relative steering angle calculating means for calculating a relative steering angle, neutral position estimating means for estimating a neutral position with respect to the relative steering angle, and calculating the relative steering angle based on the estimated neutral position. An absolute steering angle converting means for converting the steering angle into an absolute steering angle, wherein the neutral position estimating means outputs an analog signal corresponding to the absolute steering angle of the front wheel as the neutral position estimating means. Type steering angle detecting means, an absolute steering angle determined from an analog signal output from the analog type steering angle calculating means when the front wheel steering angle detecting device is started, and a relative steering angle calculated by the relative steering angle calculating means. Obtains the difference between the Do steering angle, before this difference
The offset between the absolute steering angle and the relative steering angle
And a starting time estimating means for estimating the neutral position.

According to the vehicle front wheel steering angle detecting device,
The relative steering angle of the front wheels of the vehicle can be detected by counting the digital signals output by the digital steering angle detecting means by the relative steering angle calculating means. Although this relative steering angle is effective for knowing the amount of change in the steering angle, it is insufficient for knowing the steering state of the vehicle, and may not be used for various control processes as it is. That is, since the relative steering angle has an offset with respect to the neutral position,
It is necessary to convert to an absolute steering angle by subtracting this offset. On the other hand, the analog signal output from the analog steering angle detecting means represents an absolute steering angle, and there is no offset from the neutral position. Therefore, if the difference between the absolute steering angle and the relative steering angle is obtained, the offset of the relative steering angle with respect to the neutral position can be determined.

According to the front wheel steering angle detecting device for a vehicle according to the present invention, the starting-time estimating device uses the relationship between the analog-type steering angle detecting device and the digital-type steering angle detecting device to perform relative control at the time of starting. The difference between the perfect steering angle and the absolute steering angle ,
This difference is offset from the relative steering angle and the absolute steering angle.
And estimate the neutral position. Therefore, the absolute steering angle conversion means can convert the relative steering angle into an absolute steering angle from the time of starting. As a result, the vehicle front wheel steering angle detecting device of the present invention can detect an absolute steering angle from the start.

Here, the reason why the output of the analog type steering angle detecting means is not simply used as the detected steering angle value is that the analog signal is easily affected by noise, so that it is not suitable for high-response and high-precision control processing. This is because it may be. According to the device of the present invention, since the absolute steering angle finally detected is based on the change of the digital signal output from the digital steering angle detecting means, there is no influence of noise as in the analog signal. .

[0011] Even in the case of the analog steering angle detecting means, the influence of noise can be avoided by using a low-pass filter having a predetermined constant or more. However, it is difficult to use it for high-response control due to the influence of the low-pass filter. However, in the present invention, it can be used only to know the starting offset.

As described above, the front wheel steering angle detecting device for a vehicle according to the present invention has a remarkable effect that the absolute steering angle can be detected from the start without being affected by noise. It is better to improve as follows. In this improved type front wheel steering angle detecting device, the neutral position estimating means further calculates at least the relative steering angle calculating means as described in claim 2 and as exemplified in FIG. 1 (B). Using the relative steering angle, an estimation calculation is performed over a predetermined period of time while the vehicle is traveling, and the traveling estimation means for estimating the neutral position of the front wheel steering angle, and the estimation of the neutral position by the traveling estimation means has been completed. And a neutral position changing unit that uses the neutral position estimated by the running estimation unit to convert the absolute steering angle, instead of the neutral position estimated by the starting estimation unit. .

According to the apparatus for detecting the steering angle of a front wheel of a vehicle according to the second aspect, the in-travel estimating means performs an estimating operation for a predetermined period during the traveling to estimate the neutral position, and then the neutral position changing means. However, instead of the neutral position estimated by the starting-time estimating means, the absolute steering angle is converted by the neutral position estimated by the traveling estimating means. That is, in converting the relative steering angle into the absolute steering angle, the absolute steering angle detecting means uses the neutral position estimated by the starting-time estimating means only for a predetermined period from the time of starting, and thereafter, during traveling, The neutral position estimated by the means is used.

Since the in-traveling estimating means estimates the neutral position by the estimation calculation over a predetermined period, the neutral position is negated by the influence of the mounting error of the device and the like. On the other hand, since the starting-time estimating means uses an analog signal output from the analog-type steering angle detecting means, the mounting error of the analog-type steering angle detecting means is directly reflected. Further, as described above, it is conceivable that there is a slight shift due to the noise component. Therefore, from the standpoint of high reliability, it is better to convert the absolute steering angle using the neutral position estimated by the in-travel estimating means. The front wheel steering angle detecting device for a vehicle according to the second aspect of the present invention is configured from this point of view, and starts the steering angle detection from the start, and enables more reliable detection.

It is conceivable that the neutral position estimated by the starting-time estimating means and the neutral position estimated by the traveling-time estimating means are significantly different from each other by a certain degree or more.
As described in the above, the neutral position changing means gradually changes the neutral position used for the absolute steering angle conversion from the neutral position estimated by the starting-time estimating means to the neutral position estimated by the traveling estimating means. It is even better to have a gradual access means to change. According to the front wheel steering angle detecting device for a vehicle according to the third aspect, the steering angle can be detected from the start and the steering angle can be shifted to a more reliable steering angle detection, and the shift can be smoothly performed. It can be carried out.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a rear wheel steering device of a vehicle will be described below with reference to the drawings. In FIG. 2, a DC servo motor 2 mounted in a rear wheel steering mechanism 1 rotates in forward and reverse directions in response to a command signal from a control device 3, and passes through a reduction gear 4 to a rack-and-drive with hydraulic power assist.
The pinion mechanism, that is, one end of an input shaft (not shown torsion bar) of the steering mechanism 1 is connected. A pinion gear 5 is mounted on the other end of the torsion bar, and meshes with a rack 7 formed on one end of a power piston 6. That is, one end of the torsion bar is rotated by the motor 2, the torsion bar is twisted, the throttle area of the hydraulic valve 8 is changed, and a hydraulic pressure is supplied in a direction to correct the torsion of the torsion bar to move the power piston 6. ing.
Both ends of the power piston 6 are supported by knuckle arms 10 via tie rods 9 so as to be swingable in the left-right direction.

Accordingly, the power piston 6 moves in the direction A in the drawing.
Moves, the rear wheel 11 is steered left and right. And
When the torsion bar is no longer twisted, the throttle area of the hydraulic valve 8 becomes “0”, the hydraulic pressure for moving the power piston 6 becomes “0”, and the power piston 6 stops. Here, the rear wheel steering angle sensor 12 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 from the relationship between the position of the power piston 6 and 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. The steering mechanism 1 including the servomotor 2 and the control device 3 constitute a positioning servo system that controls the positioning of the rear wheel 11 so that the rear wheel actual steering angle matches the rear wheel steering angle command position. Reference numeral 13 denotes a hydraulic pump for supplying hydraulic pressure to the power piston 6 via the hydraulic valve 8, and reference numeral 14 denotes an oil tank.

The vehicle speed sensor 15 detects the rotational speed of the axle and outputs a vehicle speed signal corresponding to the vehicle speed V to the control device 3. The encoder type front wheel steering angle sensor 16 is formed of an increment type rotary encoder, and is provided on a steering shaft 17 as a rotating body. As shown in FIG. 3, the encoder type front wheel steering angle sensor 16 has a gear 1 having a large number of teeth with respect to a steering shaft 17.
6a is fixed and a pair of photo interrupters 16
b and 16c are disposed at the close positions, and the passage of the teeth of the gear 16a is detected by the photo interrupters 16b and 16c. The encoder type front wheel steering angle sensor 16 (photo interrupters 16b, 16c) detects the rotation of the steering shaft 17 accompanying the steering operation of the steering wheel 18 and outputs a front wheel steering angle signal corresponding to the steering angle θs to the control device 3. Output to

The output waveforms of the photointerrupters 16b and 16c when the steering wheel is turned to the right are as shown in FIG. 4, and the photointerrupters 16b and 16c when the steering wheel is turned to the left.
Is as shown in FIG. The potentiometer type front wheel steering angle sensor 34 is a potentiometer type position sensor. As shown in FIG. 6, the main body of the potentiometer is fixed to the vehicle body, the slider is fixed to the front wheel steering link 35, and the left and right stroke amount of the link is adjusted. The corresponding voltage is output. When one end is connected to 5 V and the other end is connected to 0 V as shown in FIG. 7, the output voltage of the slider becomes a voltage of 0 to 5 V according to the second front wheel steering angle θa as shown in FIG.

The 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 centered 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 (left wheel speed ωR).
The brake switch 23 is turned on during execution of ABS (anti-lock brake system) control or when a brake pedal is operated.

The control device 3 will be described with reference to FIG.
Microcomputer (hereinafter referred to as "microcomputer") 2
4, the waveform shaping circuits 25 to 28, and the analog buffer 2
9, an A / D converter 30, and a digital buffer 31
And a drive circuit 32. The waveform shaping circuits 25 to 28 include a vehicle speed sensor 15, a left wheel speed sensor 21, a right wheel speed sensor 22, and an encoder type front wheel steering angle sensor 16.
The waveform of the signal from is input to the microcomputer 24 after waveform shaping. The counter 33 is an encoder type front wheel steering angle sensor 1
The number of pulses of the signal 6 is counted, and the steering angle θs can be read from the microcomputer 24. The analog buffer 29 reads signals from the potentiometer type front wheel steering angle sensor 34, the rear wheel steering angle sensor 12, and the yaw rate sensor 20, and the A / D converter 30 performs analog / digital conversion. Digital buffer 31 is brake switch 2
3 is level-converted. 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 device having the above-described structure will be described. 10 shows a main processing routine of the microcomputer 24, FIG. 11 shows vehicle speed pulse processing based on pulse signals from the vehicle speed sensor 15 and the left and right wheel speed sensors 21 and 22, and FIG.
5 shows an interrupt processing routine executed every (s).

As shown in FIG. 10, the microcomputer 24 initializes in step 1010 at the time of starting, and performs various processes in step 1020. On the other hand, as shown in FIG. 11, in step 2010, the microcomputer 24 calculates and stores the vehicle speed pulse width from the time when the previous pulse interrupt occurred and the current interrupt occurrence time for the vehicle speed pulse and the wheel speed pulse.

Then, as shown in FIG.
In step 3000, the vehicle speed V is calculated from the vehicle speed pulse width stored in the vehicle speed pulse interruption process in step 3000. Further, signals are input from the left wheel speed sensor 21 and the right wheel speed sensor 22 to calculate the left wheel speed ωL and the right wheel speed ωR of the front wheel 19. In this embodiment, the vehicle speed V is obtained by the vehicle speed sensor 15. However, the vehicle speed V is calculated from the left and right wheel speeds ωL and ωR by (ωL + ω
R) / 2.

Then, the microcomputer 24 proceeds to step 4000.
From the potentiometer-type front wheel steering angle sensor 34, the rear wheel steering angle sensor 12, and the yaw rate sensor 20 to the A / D converter 30.
Fetches A / D conversion data via
At 0, the second front wheel steering angle θa, the rear wheel actual steering angle θr, and the actual yaw rate Wa are calculated.

Further, the microcomputer 24 determines in step 6000
Then, a routine for calculating the final front wheel steering angle (handle angle) θ and detecting a failure of the front wheel steering angle sensor is executed. This routine is shown in FIG. First, the microcomputer 24 determines in step 6010 the relative steering angle θs based on the detection signal of the encoder type front wheel steering angle sensor 16 and the absolute steering angle θa based on the detection signal of the potentiometer type front wheel steering angle sensor 34.
Are read simultaneously. That is, the value of the A / D converter 30 is read at the same time as the value of the counter 33 is read. This is because the detected value may be read while the driver is operating the steering wheel, so comparisons cannot be made unless θs and θa are guaranteed to represent values at the same timing. It is.

Next, at step 6020, it is determined whether or not the process is the first process to be executed immediately after the engine is started.
The start flag F2 is used for this determination. The start flag F2 is set so that "1" is set when the engine is started. Therefore, immediately after the engine is started, the determination in step 6020 is “NO”.

If "NO" is determined in the step 6020, the process proceeds to a step 6030. This step 6
In step 030, the steering angle θa detected by the potentiometer front wheel steering angle sensor 34 is subtracted from the steering angle θs detected by the encoder type front wheel steering angle sensor 16, and this is offset (initial value of the neutral position) θN. Set as And
Proceeding to step 6040, the start flag F2 is reset to "0". Therefore, in the next process, step 6020
At step 6030, 60
40 will be passed.

Next, the routine proceeds to step 6050, where the first-order lag front wheel steering angle θc is calculated from the steering angle θs using the first-order lag transfer characteristic. That is, the first-order delayed front wheel steering angle θc is calculated by the following equation (1).

[0030]

(Equation 1)

This is because, when the steering wheel is operated, a lateral force is generated on the wheels, a moment is generated on the vehicle, the vehicle body starts to turn, and a speed difference is generated between the left and right front wheels 19. On the other hand, a delay occurs before the speed difference occurs between the left and right front wheels 19, but by approximating this,
This is to match the phase difference with the estimated front wheel steering angle θx described below.

Step 60 following step 6050
At 60, the following equation (2) is obtained from the left wheel speed ωL obtained by the left wheel speed sensor 21 and the right wheel speed ωR obtained by the right wheel speed sensor 22.
Calculates the estimated front wheel steering angle θx.

[0033]

(Equation 2)

At this time, as shown in FIG. 14, the front wheel steering angle θf is expressed by the following equation (3).

[0035]

(Equation 3)

As shown in FIG. 15, the turning radius R is expressed by the following equation (4).

[0037]

(Equation 4)

The above equation (2) is derived using these equations (3) and (4). However, equation (2) ignores the influence of rear wheel steering as θf >> θr. Then, in order to remove the noise of the first-order lag front wheel steering angle θc calculated in step 6050 and the estimated front wheel steering angle θx calculated in step 6060, the microcomputer 24 determines in step 6070 the first-order lag front wheel steering angle θc and the estimated front wheel steering angle θx. Low-pass filter processing is performed, and the LPF first-order lag front wheel steering angle θc
^* And the LPF estimated front wheel steering angle θx ^* are obtained. That is, the processing represented by the following equation (5) is executed.

[0039]

(Equation 5)

Next, in step 6080, the microcomputer 24 calculates the difference (= θc ^* −θx ^* ) between the LPF estimated front wheel steering angle θx ^* and the LPF first-order lag front wheel steering angle θc ^* as the neutral position θD. Then, the microcomputer 24 proceeds to step 609.
At 0, it is determined whether or not the correction condition is permitted. Satisfaction of the correction condition means that the driving state and the vehicle driving characteristic in which the first-order lag is satisfied are in a linear and equational region. That is, if the absolute value of the LPF estimated front wheel steering angle θx ^* is equal to or less than θMAX and the brake operation is not performed by the brake switch 23 (the antilock brake system is not being controlled), the correction condition is satisfied. I do.

If the correction condition is satisfied, the microcomputer 24 increments the value of the counter C1 at step 6100. This counter C1 is set to 0 in the initialization processing in step 1010. Next, step 60
To remove the noise at the neutral position θD calculated at 80,
The microcomputer 24 performs a low-pass filter process in step 6110, and outputs the LPF neutral position θD ^*, which is the final neutral position ^.
Is calculated. That is, the processing of the following equation (6) is executed.

[0042]

(Equation 6)

By the low-pass filter processing, noise added to the wheel speed is removed. Next, step 6120
Then, it is determined whether or not the value of the counter C1 is equal to or more than a predetermined value n. This is for judging whether or not the filtering of the neutral position .theta.D is sufficiently effective in the low-pass filter processing in step 6110. C1
If it is determined to be <n, it means that the value of the LPF neutral position θD ^* has not yet been sufficiently filtered and the reliability is poor. Therefore, in step 6120, “N
If “O” is determined, the process jumps to step 6150 to calculate the absolute steering angle θ from the offset θN obtained in step 6030 and the steering angle θs detected by the encoder type front wheel steering angle sensor 16.

On the other hand, if it is determined in step 6120 that C1 ≧ n, it means that the value of the LPF neutral position θD ^* has been sufficiently filtered and has reliability. Therefore, thereafter, it is possible to calculate the front wheel steering angle using the highly reliable LPF neutral position θD ^* in the same manner as in step 6150. However, in this embodiment, this L
Instead of switching to the PF neutral position θD ^* , the process proceeds to step 6130, and this highly reliable LPF neutral position θD ^*
Is reflected in the offset .theta.N. That is, the processing of the following equation (7) is executed.

[0045]

(Equation 7)

Here, L in steps 6070 and 6110
In the PF calculation, the filter constants b and c are determined mainly for the purpose of matching by noise elimination.
In the LPF calculation in 30, if the reference of the neutral position changes suddenly, the driver may feel uncomfortable. Therefore, the filter constant k is determined from the viewpoint of a smoothing process for removing this.

Then, from step 6130 to step 6
After proceeding to 140 to clear the counter C1, proceed to step 6150. By clearing the counter C1 in step 6140, step 6130 is executed after filtering is repeated a predetermined number of times in step 6110 again. Thus, immediately after the start, the offset θN obtained from the difference between the steering angle θs detected by the encoder type front wheel steering angle sensor 16 and the steering angle θa detected by the potentiometer type front wheel steering angle sensor 34 gradually becomes the neutral position by the estimation calculation. It approaches the θD itself.

Thereafter, in step 6160, the front wheel steering angle θa detected by the potentiometer type front wheel steering angle sensor 34 and the step 6150 are used to diagnose the failure of the encoder type front wheel steering angle sensor 16 or the potentiometer type front wheel steering angle sensor 34. Is compared with the final front wheel steering angle θ. That is, it is determined whether or not the absolute value | θ−θa | of the difference between the two is greater than a predetermined value ε. Absolute value of the difference | θ−θ
If a | is larger than the predetermined value ε, it is determined that the encoder type front wheel steering angle sensor 16 or the potentiometer type front wheel steering angle sensor 34 has failed, and the failure flag F1 is turned on in step 6170.

As described above, after calculating the final front wheel steering angle θ and detecting the failure of the front wheel steering angle sensor at step 6000, the following processing is performed to steer the rear wheels. In step 7000, it is determined whether the encoder type front wheel steering angle sensor 16 or the potentiometer type front wheel steering angle sensor 34 is determined to have failed in step 6000 by determining whether the failure flag F1 is on.

If the failure flag F1 is off at step 7000, it is determined that the encoder type front wheel steering angle sensor 16 and the potentiometer type front wheel steering angle sensor 34 are normal. Then, in step 7010, a rear wheel steering angle command value θr ^* is calculated to steer the rear wheels.

First, a target yaw rate Ws is calculated from the following equation (8) based on the vehicle speed V and the final steering angle θ of the front wheels.

[0052]

(Equation 8)

Then, the difference ΔW (= Wa−Ws) between the actual yaw rate Wa and the target yaw rate Ws is calculated, and the rear wheel steering angle command value θr ^* is calculated by the following equation (9).

[0054]

(Equation 9)

On the other hand, at step 7000, the failure flag F1
Is ON, it is determined that at least one of the encoder type front wheel steering angle sensor 16 and the potentiometer type front wheel steering angle sensor 34 is out of order. Then, the processing of steps 7021 to 7023 is performed to perform the safety processing of the rear wheel steering angle.

In steps 7021 to 7023, control is performed to add or subtract the rear wheel steering angle command value θr ^* by △ θr in order to gradually reduce the rear wheel steering angle to zero.
First, in step 7021, the rear wheel steering angle command value θ
Compare r ^* with 0. If the rear wheel steering angle command value θr ^* is larger than 0, the steering angle of the rear wheel is gradually reduced to 0, so in step 7022, the rear wheel steering angle command value θr ^* is subtracted by △ θr. . If the rear wheel steering angle command value θr ^* is less than 0, the steering angle of the rear wheel is gradually increased to 0, and therefore, in step 7023,
The rear wheel steering angle command value θr ^* is added by △ θr. If the rear wheel steering angle command value θr ^* is 0, the rear wheel steering angle is 0, and no processing is performed.

Next, in step 8000, the microcomputer 24 performs a generally known rear wheel steering positioning servo calculation based on the rear wheel steering angle command value θr ^* and the rear wheel actual steering angle θr to eliminate the difference between the two. Step 90
At step 00, the current command value signal If is calculated and output to the drive circuit 32 to drive the servomotor 2.

In the present embodiment, the encoder type front wheel steering angle sensor 16 corresponds to digital type steering angle detecting means, the counter 33 corresponds to relative steering angle calculating means, and steps 6050 to 6060 in the flowchart of FIG.
80 corresponds to the running estimation means, step 6150 corresponds to the absolute steering angle conversion means, the potentiometer front wheel steering angle sensor 34 corresponds to the analog steering angle detection means, and steps 6020 to 6040 correspond to the starting estimation means. Equivalent to. Step 6130 is a neutral position changing means and corresponds to a gradually approaching means.

As described above, in the present embodiment, the offset θN between the steering angle θa detected by the potentiometer type front wheel steering angle sensor 34 and the steering angle θs detected by the encoder type front wheel steering angle sensor 16 when the engine is started is determined. Since this is used as the initial value of the neutral position to calculate the final steering angle θ, the rear wheel turning control can be performed immediately after the vehicle starts. Therefore, when trying to get out of the garage or when traveling in a narrow parking lot, the rear wheels can be steered, and driving with a small turn can be realized.

In particular, Japanese Patent Application No. Hei.
The difference from No. 85462 is that the signal used by the encoder type front wheel steering angle sensor 16 is used before the end of the neutral position estimation calculation. And
Due to this difference, according to the present embodiment, there is no concern about the influence of noise which is a problem in the potentiometer type front wheel steering angle sensor 34, and the rear wheel steering control does not become oscillating. As a result, highly responsive and highly accurate rear wheel steering control can be performed.

In this embodiment, when the neutral position estimating operation is completed, the result θD of the estimating operation is used. Then, instead of simply switching the neutral position, the configuration is such that the estimated value θD is reflected in the offset θN and the θN LPF calculation is performed so that the influence of the estimated value θD gradually becomes stronger. There is no sudden change.

Here, since the estimated value θD is a result of the neutral position estimating operation over a predetermined period, it is a highly reliable value. Therefore, the configuration in which the offset .theta.N is used immediately after key-on, but the estimated value .theta.D is used after the estimation calculation is completed, guarantees more reliable control.

The front wheel steering angle detecting device for a vehicle according to the embodiment has been described above. However, the front wheel steering angle detecting device of the present invention is not limited to the above-described embodiment. Deformable. Steps 7021 to 7021 in the flowchart of the first embodiment
In 7023, when the front wheel steering angle sensor failed, control was performed to gradually reduce the rear wheel steering angle to zero. Alternatively, as shown in steps 7026 to 7028 in FIG. Alternatively, the rear wheel steering angle may be returned to zero when the vehicle speed becomes zero.

The neutral position calculated in each of the above embodiments
θD is the LPF estimated front wheel steering angle θx ^* And LPF first order delay
Front wheel steering angle θc^* (= Θc^* -Θx^* ) Calculated from
However, the encoder type front wheel steering angle sensor 16
Are sequentially averaged.
Thus, the neutral position θD may be calculated.

In the above embodiment, a configuration is adopted in which the offset θN gradually approaches the estimation calculation θD when the neutral position estimation calculation is completed. However, a configuration in which the switching is performed directly without using such a configuration may be adopted. This is because the deviation from the estimated value is not large if the mounting accuracy of the potentiometer type front wheel steering angle sensor 34 is sufficiently reliable.

In the above embodiment, the offset θ N estimated at the start in step 6030 is not used as it is, but steps 6080 to 6110
Although the configuration is such that the neutral position θD ^* is gradually changed to the neutral position estimated and calculated in the above, the configuration may be such that the offset value at the time of starting is used as it is. This is because there is no particular problem if the mounting accuracy of the potentiometer type front wheel steering angle sensor 34 is sufficiently high.

In the above embodiment, steps 6020 to 6020
At step 6040, the neutral position θN is determined by the first single value.
As shown in steps 8010 to 8040 shown in FIG. Thus, it is possible to prevent the neutral position at start from having an error due to noise of the analog steering angle detecting means.

[0068]

As described above in detail, according to the front wheel steering angle detecting device of the present invention, not only the digital steering angle detecting means but also the analog steering angle detecting means is provided, and the starting time estimating means is used for starting. Since the neutral position can be estimated from the time, the absolute steering angle can be detected immediately after starting. In addition, since the absolute change in the detected steering angle with time is based on the result of counting the digital signals output from the digital steering angle detection means, it is not affected by noise. As a result, according to the front wheel steering angle detection device of the present invention, an absolute steering angle that is not affected by noise can be detected from the start.

According to the front wheel steering angle detecting device of the second and third aspects of the present invention, the vehicle further includes a traveling estimating means, and after the neutral position estimating calculation is completed there, based on the neutral position. Because it was configured to detect the absolute steering angle,
While satisfying the first object of the present invention of detecting the absolute steering angle from the time of starting, the absolute steering angle is finally determined in a highly reliable manner not affected by the mounting error of the device. Can be detected.

In particular, according to the front wheel steering angle detecting device of the third aspect, it is possible to detect the steering angle from the start and to shift to a more reliable steering angle detection. Moreover, this transition can be performed smoothly.

[Brief description of the drawings]

FIG. 1 is a diagram corresponding to a claim illustrating the configuration of a front wheel steering angle detecting device of the present invention.

FIG. 2 is an overall configuration diagram illustrating an overall configuration of a rear wheel steering device according to an embodiment.

FIG. 3 is a sectional view showing a sectional configuration of a rotary encoder.

FIG. 4 is an explanatory diagram of output waveforms of the photointerrupters 16b and 16c when the steering wheel is turned right.

FIG. 5 is an explanatory diagram of output waveforms of the photointerrupters 16b and 16c when the steering wheel is turned to the left.

FIG. 6 is an explanatory diagram showing an attached state of a potentiometer type front wheel steering angle sensor.

FIG. 7 is an explanatory diagram showing front wheel steering angle detection by a potentiometer type front wheel steering angle sensor.

FIG. 8 is a graph showing a relationship between a voltage output by a potentiometer type front wheel steering angle sensor and a steering wheel angle.

FIG. 9 is an electrical configuration diagram showing an electrical configuration of the rear wheel steering device according to the embodiment.

FIG. 10 is a flowchart illustrating a main processing routine of a microcomputer.

FIG. 11 shows a vehicle speed sensor and left and right wheel speed sensors 21,
12 is a flowchart illustrating a vehicle speed pulse process based on a pulse signal from the control unit 22;

FIG. 12 is a flowchart showing an interrupt processing routine executed at predetermined time intervals.

FIG. 13 is a flowchart illustrating a calculation of a front wheel steering angle and a failure detection routine of a front wheel steering angle sensor.

FIG. 14 is an explanatory diagram at the time of steering.

FIG. 15 is an explanatory diagram at the time of steering.

FIG. 16 is a flowchart showing a modification.

FIG. 17 is a flowchart showing another modified example.

[Explanation of symbols]

 3 Control device 15 Vehicle speed sensor 16 Encoder type front wheel steering angle sensor 21 Right wheel speed sensor 22 Left wheel speed sensor 33 Counter 34 Potentiometer type front wheel steering angle sensor

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-2-218909 (JP, A) JP-A-4-242111 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01B 21/00-21/32

Claims (3)

(57) [Claims] 1. Digital steering angle detecting means for outputting a digital signal each time the steering angle of the front wheel changes by a unit angle; and relative steering of the front wheels by counting the digital signal of the digital steering angle detecting means. Relative steering angle calculating means for calculating an angle; neutral position estimating means for estimating a neutral position with respect to the relative steering angle; and absolute steering of the relative steering angle based on the estimated neutral position. An absolute steering angle converting means for converting an angle into an angle, wherein the neutral position estimating means outputs an analog signal according to an absolute steering angle of the front wheel as the neutral position estimating means. And an absolute steering angle determined from an analog signal output from the analog steering angle calculating means and a relative steering angle calculated by the relative steering angle calculating means when the front wheel steering angle detecting device is started. Obtains the difference between the angular, the the relative absolute steering angle of this difference
A starting-time estimating means for estimating the neutral position as an offset with respect to a steering angle. 2. The vehicle control apparatus according to claim 1, wherein the neutral position estimating means further performs an estimation calculation over a predetermined period during vehicle running by using at least a relative steering angle calculated by the relative steering angle calculating means, and calculates a front wheel steering angle. A traveling estimating means for estimating the neutral position, and a neutral position estimated by the traveling estimating means in place of the neutral position estimated by the starting estimating means after the estimation of the neutral position by the traveling estimating means is completed. 2. A front wheel steering angle detecting device for a vehicle according to claim 1, further comprising: a neutral position changing unit that uses the neutral position for converting an absolute steering angle. 3. The neutral position changing means gradually changes the neutral position used for absolute steering angle conversion from the neutral position estimated by the starting estimating means to the neutral position estimated by the traveling estimating means. 3. The front wheel steering angle detecting device for a vehicle according to claim 2, further comprising a gradually approaching means for performing the operation.