JPH05215542A - Apparatus for detecting front-wheel steering angle of vehicle - Google Patents

Abstract

PURPOSE:To prevent the sudden change of the detected value when sensors are switched in a front-wheel-steering-angle detecting apparatus, which determines the steering angle of the front wheels based on either of a plurality of front-wheel-steering-angle sensors. CONSTITUTION:An encoder-type front-wheel-steering-angle sensor 16 and a potentiometer-type front-wheel-steering-angle sensor 34 are provided. The front- wheel steering angle is determined based on the detected value of either of the sensors, and rear-wheel steering is controlled. The front-wheel steering angle is determined at the detected value thetaa of the potentiometer-type sensor 34 before the estimating operation of the neutral position of the steering. After the estimating operation is finished, the angle is determined at the first front- wheel steering angle theta1, which is determined based on the detected value thetas of the encoder-type sensor 16 and the neutral position thetaN*. Immediately after the switching of the sensor, control is performed so that the difference thetabefore and after the switching is gradually decreased. Even when the sensors are switched in response to the vehicle speed, the front-wheel steering angle is gradually changed by the same processing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device which includes a plurality of front wheel steering angle sensors and detects a front wheel steering angle of a vehicle based on a detection signal of any one of them.

[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 change amount of a relative steering angle of the front wheels.
There has been known a device for estimating and calculating the steering neutral position during a predetermined straight running, and detecting the steering angle of the front wheels from the relationship between the neutral position and the relative steering angle change amount (for example, JP-A-61-61). -11608). In addition, the front wheel steering angle detected by using such a sensor is disclosed in, for example, JP-A-60
As described in Japanese Patent No. 124572, it has been used for skid prevention control using a rear wheel steering device.

Recently, not only such a rotary encoder type front wheel steering angle sensor, but also a potentiometer type front wheel steering angle sensor is combined with the potentiometer type front wheel steering angle sensor until the neutral position learning of the front wheel steering angle is completed. The applicant of the present invention has applied for a device for detecting the steering angle by detecting the steering angle and then switching to the rotary encoder type front wheel steering angle sensor after completion of the neutral position learning (Japanese Patent Application No. 3- 85462).

[0004]

[Patent Document 1] Japanese Patent Application No. 3-854
According to the device proposed in No. 62, effective four-wheel steering can be carried out immediately after starting before the completion of the neutral position calculation, so that the excellent action and effect aimed at by the present application can be exhibited. However, the following problems have arisen.

In this conventional apparatus, when the potentiometer type front wheel steering angle sensor is misaligned due to improper mounting or the like, when the potentiometer type sensor is switched to the rotary encoder type sensor, the detected value of the front wheel steering angle is detected. Has a problem that the vehicle control based on the front wheel steering angle (for example, the rear wheel steering control) is not effectively performed.

In view of the above problem, the present invention has been made in view of the above problem, and in the front wheel steering angle detecting device for switching the front wheel steering angle sensor to any one to determine the steering angle of the front wheel, the sensor for determining the steering angle is switched. It is an object of the present invention to provide a front wheel steering angle detecting device for a vehicle, in which the detected value does not change suddenly but changes gradually.

[0007]

In order to achieve the above-mentioned object, a vehicle front wheel steering angle detecting device according to the present invention is provided with the structure shown in FIG.
As illustrated in Fig. 2, a plurality of front wheel steering angle sensors for detecting the steering angle of the front wheels, and which of the detection values of the plurality of front wheel steering angle sensors is used to determine the front wheel steering angle according to a predetermined condition are determined. Sensor selecting means for selecting, steering angle determining means for determining the front wheel steering angle based on the detection value of the front wheel steering angle sensor selected by the sensor selecting means, and steering angle output for outputting the determined front wheel steering angle In the vehicle front wheel steering angle detection device including means, when the sensor selected by the sensor selection means is switched, the front wheel steering angle output before the switching is changed to the front wheel steering angle to be output after the switching. And gradually approaching means for gradually changing the output of the steering angle output means.

According to this vehicle front wheel steering angle detecting device,
When the sensor for determining the front wheel steering angle is switched, the approaching means gradually outputs the steering angle output means from the front wheel steering angle output before the switching to the front wheel steering angle to be output after the switching. Is gradually changed. Therefore, even if the front wheel steering angle sensor is switched under certain conditions, the output of the front wheel steering angle used as various control parameters does not suddenly change.

According to the vehicle front wheel steering angle detecting device of the present invention as described above, as the plurality of front wheel steering angle sensors, when the steering angle of the front wheels changes, the angle changes. A first front wheel steering angle sensor that outputs a signal in accordance with the steering angle, and a second front wheel steering angle sensor that outputs a signal in accordance with the steering angle of the front wheel, and at least the first front wheel as the steering angle determining means. Neutral position calculation means for estimating and calculating the neutral position of the front wheel steering angle based on the signal output from the steering angle sensor, a signal output from the first front wheel steering angle sensor, and estimation calculation by the neutral position calculation means. First front wheel steering angle calculating means for calculating a first front wheel steering angle based on the neutral position of the front wheel steering angle,
The second based on the signal output from the front wheel steering angle sensor
Second front wheel steering angle calculation means for calculating the front wheel steering angle, and an estimation calculation end determination for determining whether or not the neutral position calculation means as the sensor selection means has completed the estimation calculation of the neutral position Means and the estimation calculation end determination means selects the second front wheel steering angle sensor until it determines that the calculation of the neutral position is completed, and then determines the first front wheel steering angle sensor after the calculation of the neutral position is completed. The front wheel steering angle detection device for a vehicle is also completed, which is provided with an estimation calculation correspondence selection unit that selects the front wheel steering angle sensor.

According to the vehicle front wheel steering angle detecting device of the present invention, the first front wheel steering angle sensor detects the front wheel steering angle sensor since the calculation of the neutral position of the front wheel steering is completed, such as immediately after the engine of the vehicle is started. During the period when the front wheel steering angle cannot be determined using the value, the front wheel steering angle is determined and output based on the detection value of the second front wheel steering angle sensor that does not require such neutral position correction. After the neutral position calculation is completed, the front wheel steering angle is determined and output based on the detection value of the first front wheel steering angle sensor. Then, when such switching of the sensor, the approaching means is operated gradually,
The output of the front wheel steering angle does not change suddenly.

Therefore, according to the apparatus of the second aspect, various controls based on the front wheel steering angle can be executed immediately after the engine is started. After the neutral position calculation is completed, the first front wheel steering angle sensor capable of highly accurate steering angle detection without being affected by noise or the like can be used to execute accurate control. When the sensors are switched in accordance with the neutral position calculation, the front wheel steering angle is smoothly changed, so that problems such as destabilization of control are not caused.

The present invention is not limited to solving such a problem immediately after the engine is started, and further, as described in claim 3, the front wheel steering of the vehicle according to claim 1 or claim 2 described above. The angle detection device further includes a driving state detecting means for detecting a driving state of the vehicle, and the sensor selecting means is any one of the plurality of front wheel steering angle sensors according to the driving state detected by the driving state detecting means. It is also completed as a front wheel steering angle detection device for a vehicle, characterized by comprising a driving state correspondence selection means for selecting.

According to the vehicle front wheel steering angle detecting device of the third aspect, the condition of the operating state of the vehicle, for example, whether or not the vehicle speed is a certain value or more, whether the steer is steered, and other Any one of the plurality of front wheel steering angle sensors can be used based on various driving condition conditions. Therefore, it is possible to arrange the sensors suitable for the control in various operating states and perform the control in conformity with the operating state. Further, according to the detection device of the present invention, in such control, there is no possibility of causing a sudden change in control when the operating state is switched.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a rear wheel steering system of a vehicle will be described below with reference to the drawings. In FIG. 2, a DC servomotor 2 mounted in the rear wheel steering mechanism 1 receives a command signal from the control device 3 and rotates in the forward and reverse directions.
It is connected to one end of an input shaft (a torsion bar (not shown)) of the pinion mechanism, that is, the steering mechanism 1. A pinion gear 5 is attached to the other end of the torsion bar and meshes with a rack 7 formed at 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 hydraulic power 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 a knuckle arm 10 via tie rods 9 so as to be swingable in the left-right direction.

Therefore, the power piston 6 is moved in the direction A in the figure.
The rear wheel 11 is steered to the left or right by moving the. And
When the torsion bar is not 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 servo motor 2 and the control device 3 constitute a positioning servo system for positioning and controlling the rear wheels 11 so that the actual rear wheel steering angle coincides with the rear wheel steering angle command position. 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 detects the rotation 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 composed of an increment type rotary encoder, and is provided on a steering shaft 17 as a rotated body. This 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 as shown in FIG.
6a is fixed and a pair of photo interrupters 16 are provided.
b and 16c are arranged at close positions, and the photointerrupters 16b and 16c detect the passage of the teeth of the gear 16a. The encoder-type front wheel steering angle sensor 16 (photointerrupters 16b, 16c) detects the rotation of the steering shaft 17 associated with the steering wheel 18 steering wheel operation, and outputs a front wheel steering angle signal corresponding to the steering angle θs. Output to.

The output waveforms of the photo interrupters 16b and 16c when the handle is rotated to the right are as shown in FIG. 4, and the photo interrupters 16b and 16c when the handle is rotated to the left.
The output waveform of 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 potentiometer main body is fixed to the vehicle body, the slider is fixed to the front wheel steering link 35, and the lateral stroke amount of the link is adjusted. The corresponding voltage is output. When one end is connected to 5V and the other end is connected to 0V as shown in FIG. 7, the output voltage of the slider becomes a voltage of 0 to 5V 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 about 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 when ABS (anti-lock brake system) control is being executed or when the 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, A / D converter 30, and 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 signal from is waveform-shaped and is taken into the microcomputer 24. The counter 33 is an encoder type front wheel steering angle sensor 1
The number of pulses of the signal of 6 is counted so that the steering angle θs can be read from the microcomputer 24. Further, the analog buffer 29 reads each signal 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. The digital buffer 31 is the brake switch 2
The signal from 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 system thus constructed will be described. FIG. 10 shows a main processing routine of the microcomputer 24, FIG. 11 shows vehicle speed pulse processing by pulse signals from the vehicle speed sensor 15 and the left and right wheel speed sensors 21 and 22, and FIG. 12 shows every predetermined time (for example, 5 m).
An interrupt processing routine executed every s) is shown.

As shown in FIG. 10, the microcomputer 24 is initialized at step 1010 at the time of startup, and various kinds of processing are performed at 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 at which the previous pulse interrupt occurred for the vehicle speed pulse and the wheel speed pulse and the time at which this interrupt occurred.

Then, as shown in FIG.
In step 4, the vehicle speed V is calculated from the vehicle speed pulse width stored in the vehicle speed pulse interruption processing in step 3000. Furthermore, 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 wheels 19. In the present embodiment, the vehicle speed V is obtained by the vehicle speed sensor 15, but the vehicle speed V is calculated from the left and right wheel speeds ωL and ωR by (ωL + ω)
It may be obtained as R) / 2.

The microcomputer 24 then proceeds to step 4000.
From the potentiometer type front wheel steering angle sensor 34, rear wheel steering angle sensor 12, yaw rate sensor 20 to A / D converter 30
A / D conversion data is fetched via, and step 500
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 executes step 6000.
Then, a routine for calculating the final front wheel steering angle (steering wheel angle) θ and detecting a failure of the front wheel steering angle sensor is executed. This routine is shown in FIG. Further, FIG. 14 shows a control block diagram of the routine shown in FIG.

First, in step 6010, the microcomputer 24 reads the steering angle θs of the encoder type front wheel steering angle sensor 16. On the other hand, when the steering wheel is operated, a lateral force is generated in the wheels, a moment is generated in the vehicle, and when the vehicle body starts to turn, a speed difference is generated between the left and right front wheels 19. There is a delay before the speed difference occurs in the front wheels 19, but in order to approximate this, in step 6020, the primary delay front wheel steering angle θc is calculated from the steering angle θs using the transfer characteristic of the primary delay. That is, the first-order lag front wheel steering angle θc is calculated by the following equation (1).

[0026]

[Equation 1]

The microcomputer 24 then proceeds to step 6030.
Then, the estimated front wheel steering angle θx is calculated by the following equation (2) 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.

[0028]

[Equation 2]

At this time, as shown in FIG. 15, the front wheel steering angle θf is expressed by the following equation (3).

[0030]

[Equation 3]

Further, as shown in FIG. 16, the turning radius R is expressed by the following equation (4).

[0032]

[Equation 4]

The above equation (2) is derived using these equations 3 and 4. However, in the equation (2), the influence of the rear wheel steering is ignored by setting θf >> θr. And step 602
In order to remove noise of the first-order lag front wheel steering angle θc calculated at 0 and the estimated front-wheel steering angle θx calculated at step 6030, the microcomputer 24 at step 6040 performs low-pass filter processing of the first-order lag front wheel steering angle θc and the estimated front-wheel steering angle θx. And the LPF first-order lag front wheel steering angle θc ^* and LP
F Estimate front wheel steering angle θx ^* is obtained. That is, the following equation (5)
The process represented by is executed.

[0034]

[Equation 5]

The microcomputer 24 executes the LPF in step 6050.
Estimated front wheel steering angle θx ^* and LPF first-order lag front wheel steering angle θc
The difference from ^* (= θc ^* −θx ^* ) is calculated as the neutral position θD. Then, the microcomputer 24 determines in step 6060 whether the correction condition is permitted. 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, 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 control is not in progress), the correction condition is satisfied. To do.

If this correction condition is satisfied, the microcomputer 24 increments the value of the counter C1 in step 6070. This counter C1 is set to 0 in the initialization processing of step 1010. Next, step 60
To remove the noise of the neutral position θD calculated in 50,
The microcomputer 24 performs low-pass filter processing in step 6080, and finally determines the LPF neutral position θ N ^* which is the neutral position ^.
To calculate. That is, the processing of the following expression (6) is executed.

[0037]

[Equation 6]

By this low-pass filter processing, noise added to the wheel speed is removed. Next, Step 6090.
Then, it is determined whether or not the value of the counter C1 is greater than or equal to the predetermined value n. This is to determine whether or not the filtering of the neutral position θ D is sufficiently effective in the low pass filter processing of step 6080. C1
If it is judged that ≧ n, the LPF is sufficiently filtered.
It is determined that the value of the neutral position θ N ^* is reliable, and it is time to switch from the potentiometer type front wheel steering angle sensor 34 to the encoder type front wheel steering angle 16, and the process proceeds to step 6120.

At step 6120, it is judged at step 6121 whether the flag F2 = 0.
It is determined whether to proceed to. This flag F2 is set to F2 = 1 at the initialization of step 1010. Therefore, when the microcomputer 24 is started, the first step 612 is performed.
When executing 0, NO is determined and step 612 is executed.
I will proceed to 1.

In step 6121, the first front wheel steering angle θ1 is calculated based on the first front wheel steering angle θs and the LPF neutral position θN ^*, which are expressed as a relative angle change amount, by the following equation (7).
Calculate from

[0041]

[Equation 7]

In step 6122, the steering angle difference Δθ which is the difference between the second front wheel steering angle θa and the first front wheel steering angle θ1 is calculated from the following equation (8).

[0043]

[Equation 8]

When the steering angle difference Δθ is calculated, step 61
23, the flag F2 = 0 is set. This step 61
When the microcomputer 24 is activated by the processing of 23 and the step 6120 is executed for the second time and thereafter, the determination is YES, and the processing of the steps 6121 to 6123 is not performed and the processing proceeds to the step 6124.

In steps 6124 to 6126, since the steering angle difference Δθ gradually approaches 0, the steering angle difference Δθ is changed to Δd.
Only the addition or subtraction processing is performed. First, in step 6124, the steering angle difference Δθ is compared with 0. If the steering angle difference Δθ is greater than 0, the final front wheel steering angle (steering wheel angle) θ calculated in step 6127 is gradually decreased to reach the first front wheel steering angle θ1, and therefore in step 6125, The steering angle difference Δθ is subtracted by Δd. If the steering angle difference Δθ is less than 0, the final front wheel steering angle θ is gradually increased to reach the first front wheel steering angle θ1, so in step 6126, the steering angle difference Δθ is added by Δd. .. If the steering angle difference Δθ is 0, the second front wheel steering angle θa and the first front wheel steering angle θ1 are the same, so no processing is performed.

Then, in step 6127, the following equation (9)
From this, the final front wheel steering angle θ is calculated.

[0047]

[Equation 9]

Step 6120 to Step 6127
By performing the processing of (1), the final front wheel steering angle θ is gradually increased from the second front wheel steering angle θa by Δd by the first front wheel steering angle θ.
You can take one. Then step 613
At 0, the second front wheel steering angle θa is compared with the final front wheel steering angle θ obtained in step 6120 in order to diagnose the failure of the encoder type front wheel steering angle sensor 16 or the potentiometer type front wheel steering angle sensor 34. That is, the absolute value of the difference between the two |
It is determined whether or not θ−θa | is larger than a predetermined value ε.
If the absolute value | θ−θa | of the difference between the two 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 is in failure, and the failure flag is determined in step 6140. Turn on F1.

On the other hand, if it is determined in step 6090 that C1 <n, it is determined that the filtering of the neutral position θD is not sufficiently effective, and in step 6100, the second front wheel steering angle θa is changed to the final front wheel steering. Let the angle be θ. Therefore, when the neutral position is not calculated when the vehicle starts, the second front wheel steering angle θa detected by the potentio-type front wheel steering angle sensor 34 is set as the final front wheel steering angle θ.

At step 6000, the final front wheel steering angle θ
After calculating and the failure detection of the front wheel steering angle sensor, the following processing is performed to steer the rear wheels. In step 7000, it is determined whether or not the encoder-type front wheel steering angle sensor 16 or the potentiometer-type front wheel steering angle sensor 34 is determined to be faulty in step 6000 depending on whether the fault flag F1 is on.

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

First, the target yaw rate Ws is calculated from the vehicle speed V and the final steering angle θ of the front wheels by the following equation (10).

[0053]

[Equation 10]

Then, the difference ΔW (= Wa-Ws) between the actual yaw rate Wa and the target yaw rate Ws is calculated, and the following equation (1)
In 1), the rear wheel steering angle command value θr ^* is calculated.

[0055]

[Equation 11]

On the other hand, in step 7000, the failure flag F1
If 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, since the steering angle of the rear wheels is gradually brought to 0, control is performed to add or subtract the rear wheel steering angle command value θr ^* by Δθr.
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 greater than 0, the steering angle of the rear wheels is gradually reduced to zero, and therefore, in step 7022, the rear wheel steering angle command value θr ^* is subtracted by Δθr. . If the rear wheel steering angle command value θr ^* is less than 0, the steering angle of the rear wheels is gradually increased to zero.
The rear wheel steering angle command value θr ^* is added by Δθr. If the rear wheel steering angle command value θr ^* is 0, the steering angle of the rear wheels is 0, and no processing is performed.

Next, in step 8000, the microcomputer 24 performs a generally known rear wheel steering positioning servo calculation on the basis of the rear wheel steering angle command value θr ^* and the rear wheel actual steering angle θr to eliminate the difference therebetween. Based on this calculation result, step 90
The current command value signal If is calculated at 00 and is output to the drive circuit 32 to drive the servo motor 2.

In this embodiment, the encoder-type front wheel steering angle sensor 16 corresponds to the first front wheel steering angle sensor, and step 6010 in the flowchart of FIG.
.About.6050 correspond to the neutral position calculating means, and step 61
21 corresponds to a first front wheel steering angle calculation means, the potentiometer type front wheel steering angle sensor 34 corresponds to a second front wheel steering angle sensor, and step 6090 corresponds to an estimation calculation determination means.
Steps 6122 to 6127 correspond to the gradually approaching means. Further, step 6090 also corresponds to the sensor selection means and the neutral operation correspondence selection means. Then, steps 6100 and 6127 correspond to the steering angle determination means, and the processing corresponding to the steering angle output means in the processing of step 7010 in the flowchart of FIG. 12 is executed.

As described above, in the present embodiment, the steering angle difference Δθ is Δd by the processing of steps 6120 to 6126.
Since it will approach 0 one by one, step 612
The final front wheel steering angle θ calculated in 7 also approaches the first front wheel steering angle θ1 from the second front wheel steering angle θa by Δd. Therefore, even when it is determined in step 6090 that it is time to switch from the potentio-type front wheel steering angle sensor 34 to the encoder-type front wheel steering angle sensor 16, the second front wheel steering angle θa is rapidly changed to the first front wheel. The conventional problem that the front wheel steering angle detection value changes suddenly without being switched to the steering angle θ1 is solved (see FIG. 17).

In this embodiment, the encoder type front wheel steering angle sensor 16 and the potentiometer type front wheel steering angle sensor 3 are mounted on the vehicle.
4, the potentiometer type front wheel steering angle sensor 34 detects the steering angle of the front wheels before the neutral position θ D is low-pass filtered a predetermined number of times. This allows
The steering angle of the front wheels can be detected even before the neutral position of the steering wheel is calculated.

Further, in this embodiment, the second front wheel steering angle θ
It is determined whether or not the absolute value | θ−θa | of the difference between a and the final front wheel steering angle θ is larger than the predetermined value ε. Accordingly, it is possible to detect that the encoder type front wheel steering angle sensor 16 or the potentiometer type front wheel steering angle sensor 34 is out of order.

In the embodiment described above, the front wheel steering angle is determined and output based on the detection signal of the encoder-type front wheel steering angle sensor 16 after the neutral position calculation is completed. On the other hand, even after the neutral position calculation is completed and the detection signal of the encoder-type front wheel steering angle sensor 16 becomes usable, the front wheel steering angle sensors 16 and 34 are switched based on the predetermined parameter related to the driving state. A second embodiment will be described in which the rear wheel steering control that matches the driving state is performed.

The second embodiment basically has the same system hardware configuration as that of the above-described embodiment, and the main routine is the same as that shown in FIG. 12, but the final routine corresponding to step 6000 in this main routine. The difference is that the calculation routine of the front wheel steering angle θ is configured as follows. The final steering angle θ calculation routine peculiar to the second embodiment is shown in FIGS.
It is configured as shown in. 18 to 2
The control block diagram of the 0 routine is as shown in FIG.

Steps 6010-6 of this calculation routine
080 is the above-mentioned embodiment (hereinafter, referred to as the first embodiment)
The description is omitted because it is exactly the same as. Step 6200 following these steps 6010 to 6080
Then, it is determined whether the vehicle speed V detected by the vehicle speed sensor 15 exceeds a predetermined value Vo (for example, 40 km / h). If the determination in step 6200 is "YES", the flow jumps to step 6300 to determine whether or not the value of the counter C1 is equal to or greater than the predetermined value n. This step 6
Reference numeral 300 is a step for determining whether or not the encoder-type front wheel steering angle sensor 16 has become usable after the neutral position calculation has been completed similarly to the processing of step 6090 in the first embodiment.

When it is determined to be "NO" in step 6200, the process proceeds to step 6210, and it is determined whether or not the switching flag F3 is set to "1". The switching flag F3 is a flag indicating whether or not the determination of the front wheel steering angle by the potentiometer type front wheel steering angle sensor 34 is currently being executed. When the switching flag F3 is "0", it means that the potentio-type front wheel steering angle sensor 34 is not currently in control, and when it is "1", the potentio-type front wheel steering angle sensor 34 is currently in control. Means that. Note that "1" is set immediately after the engine is started.

When the determination at step 6210 is "NO", that is, at present, the potentiometer type front wheel steering angle sensor 34 is used.
If it is not under control by step 622,
The current value θi determined as the front wheel steering angle at 0 is stored as the previous value θi−1, and the current detected value θa of the potentiometer type front wheel steering angle sensor 34 is stored as the current value θi. Then, in the following step 6230, the steering angle difference Δθ between the previous value θi−1 and the current value θi is calculated, and the flow proceeds to step 6240 to set the switching flag F3 to “1”. Therefore, the calculation of the steering angle difference Δθ in step 6230 is executed only in the first process in which the vehicle speed V becomes equal to or lower than the predetermined value Vo.

On the other hand, in step 6210, "YE
If it is determined to be "S", that is, if the control by the potentiometer type front wheel steering angle sensor 34 is already being performed, the routine proceeds to step 6250, where the current potentiometer type front wheel steering angle sensor 34 is operated. The detected value θa of is stored as the current value θi. Then, these steps 6240
Or, following step 6250, step 6260
Perform the following processing.

In steps 6260 and below, step 62
In order to gradually bring the steering angle difference Δθ calculated in 40 closer to 0, processing for adding or subtracting the steering angle difference Δθ by Δd is performed. First, in step 6260, the steering angle difference Δθ
Is compared with 0. If the steering angle difference Δθ is larger than 0, the process proceeds to step 6280 through step 6270, and the steering angle difference Δ
If θ is smaller than 0, the process proceeds to step 6280 via step 6275, and if the steering angle difference Δθ is 0, the process directly proceeds to step 6280.

At step 6270, the steering angle difference Δθ is subtracted by Δd, and at step 6275, the steering angle difference Δθ is reversed by Δd.
Just add. Then, in step 6280, a value obtained by adding the steering angle difference Δθ to the current value θi is calculated as the final front wheel steering angle θ. Therefore, if the steering angle difference Δθ is 0, the final front wheel steering angle θ is the current value θi itself, and the steering angle difference Δθ is
If is not 0, it becomes an intermediate value between the current value θi and the last front wheel steering angle θ up to the previous time.

Steps 6260 to 6280
This process is a process for preventing a sudden change in the final front wheel steering angle θ associated with the switching of the front wheel steering angle sensor, and includes steps 6124 to 6127 in the above-described embodiment. Similar to processing. As will be described later, this step 6260 to step 6
The processing of 280 is performed not only when the encoder type front wheel steering angle sensor 16 is switched to the potentiometer type front wheel steering angle sensor 34, but also when the potentiometer type front wheel steering angle sensor 3 is used.
Even when switching from 4 to the encoder-type front wheel steering angle sensor 16 is performed, it acts as a configuration for preventing a sudden change in the final front wheel steering angle θ.

Following the processing of step 6280, step 6285, step 6290 and step 6295.
Are the steps 6090 and 613 in the previous embodiment.
The same processing as 0 and step 6140 is executed.
That is, after the neutral position learning of the encoder-type front wheel steering angle sensor 16 is completed in steps 6290 and 6295, a failure diagnosis of the encoder-type front wheel steering angle sensor 16 or the potentiometer-type front wheel steering angle sensor 34 is performed.

On the other hand, in step 6200, "YE
If it is determined to be “S”, the above-described step 6210 is performed.
-Step 6250 is not executed but it jumps to step 6300, and it is judged whether the value of the counter C1 is a predetermined value n or more. This step 6300 is a step for determining whether or not the encoder-type front wheel steering angle sensor 16 has become usable after the neutral position calculation has been completed similarly to the processing of step 6090 in the above-described embodiment.

The determination of "YES" in step 6300 means that the neutral position calculation for the encoder-type front wheel steering angle sensor 16 is completed. Therefore,
If “YES” is determined in step 6300,
Proceeding to step 6310, the first front wheel steering angle θ1 is calculated based on the first front wheel steering angle θs and the LPF neutral position θN ^* which are expressed as a relative angle change amount. This step corresponds to step 6121 in the previous embodiment.

In the following step 6320, the switching flag F
It is determined whether 3 is “0”. This is to determine whether or not it is time to switch the sensor from the potentiometer type front wheel steering angle sensor 34 to the encoder type front wheel steering angle sensor 16.

If "NO" is determined in this step 6320, that is, if the sensor switching timing is just reached, the current value θi determined as the front wheel steering angle in step 6330 is changed to the previous value θi-1. Then, the current first steering angle θ1 is stored as the current value θi. Then, in the following step 6340, the previous value θi-
The steering angle difference Δθ between 1 and the current value θi is calculated, and step 63
In step 50, the switching flag F3 is set to "0".

On the other hand, in step 6320, "YE
If it is determined to be “S”, that is, if the control by the encoder-type front wheel steering angle sensor 16 is already being performed, the process proceeds to step 6360, and the current first steering angle θ1 is set. The current value θi is stored. And
Subsequent to these step 6350 or step 6360, step 6260 and subsequent steps described above are executed. That is, even when the sensor is switched from the potentiometer type front wheel steering angle sensor 34 to the encoder type front wheel steering angle sensor 16, the final front wheel steering angle θ is prevented from changing suddenly.

On the other hand, if it is determined "NO" in step 6300, that is, if the vehicle speed V exceeds the predetermined value Vo but the neutral position calculation is not completed, the process proceeds to step 6400. In step 6400, similarly to step 6320, it is determined whether the switching flag F3 is “0”. Then, in this step 6400, "N
If it is determined to be “O”, that is, if the vehicle speed V is immediately after it exceeds the predetermined value Vo, step 6410 is performed.
Then, the current final front wheel steering angle θ is stored as the steering angle difference Δθ. Then, in the subsequent step 6420, the switching flag F3 is set to "0", and the processing proceeds to step 6430 and the subsequent steps. On the other hand, in step 6400, “YE
If it is determined to be “S”, the process immediately proceeds to the processing of step 6430 and thereafter.

In Step 6430 and the following steps, Step 64
In order to gradually bring the steering angle difference Δθ calculated in 20 closer to 0, a process of adding or subtracting the steering angle difference Δθ by Δd is performed. That is, steps 6260, 6270, 6275
First, in step 6430, the steering angle difference Δθ
Is compared with 0, and if the steering angle difference Δθ is larger than 0, the steering angle difference Δθ is subtracted by Δd in step 6440, and the process proceeds to step 6450. Conversely, if the steering angle difference Δθ is smaller than 0, In step 6445, the steering angle difference Δθ is added by Δd, and then the process proceeds to step 6450. If the steering angle difference Δθ is 0, the process immediately proceeds to step 6450. In this step 6450,
The steering angle difference Δθ currently obtained is set as the final front wheel steering angle θi.

As described above, according to the second embodiment, the detection signal of the potentiometer type front wheel steering angle sensor 34 for detecting the absolute steering angle is obtained in the low speed operation state where the vehicle speed V is the predetermined value Vo or less. Based on the above, the final front wheel steering angle θ is determined. On the other hand, in a high-speed driving state in which the vehicle speed V exceeds the predetermined value Vo, the final front wheel steering angle θi is determined based on the detection signal of the encoder-type front wheel steering angle sensor 16 which detects the relative steering angle. Therefore, in the low speed operation state in which the large steering angle reverse phase control needs to be performed in the four-wheel steering control, the detection signal of the encoder-type front wheel steering angle sensor 16 is not used.

Here, the encoder type front wheel steering angle sensor 1
The neutral position θ N used in calculating the first steering angle θ1 based on the detection signal of No. 6 is not always the first time it is used, but is normally corrected when the correction condition is satisfied. Target. However, at low speeds, this correction condition is generally not satisfied, so that the neutral position calculation result cannot be corrected. The first front wheel steering angle θ1 is calculated based on the neutral position obtained a long time before such neutral position correction cannot be performed.
However, the error may increase depending on the case.

In this embodiment, the characteristics of the neutral position correction in the encoder type front wheel steering angle sensor 16 are also taken into consideration, and the encoder type front wheel steering angle sensor is operated in the low speed operation state where the reliability of the neutral position θ N is not reliable. The front wheel steering angle is not determined using the detection signal of the 16th wheel. In other words, the encoder-type front wheel steering angle sensor 16 that is adopted in the expectation of highly accurate steering angle detection is used only in a state where the highly accurate detection as expected can be performed. On the other hand, regarding the potentiometer type front wheel steering angle sensor 34, even if the calculation of the neutral position is completed for the first time, if the vehicle speed V exceeds the predetermined value Vo, the use thereof is also prohibited. This is a feature of the example. This is because the potentiometer-type front wheel steering angle sensor 34 is generally apt to contain noise, and therefore smooth control may not be possible when used under high-speed operation that requires highly accurate four-wheel steering control such as small steering angle in-phase control. Because there is. That is, in the case of high-speed operation, since the steering is performed at a small steering angle, the influence of noise may be noticeable, and good control may not be achieved. Therefore, the potentiometer-type front wheel steering angle sensor 34 should not be used. I did. On the contrary, in the low speed operation state, even if there is such noise, it is a region where the four-wheel steering control of the large steering angle reverse phase control is mainly performed, so it is safe to ignore such noise. Alternatively, since responsiveness is not required, a low-frequency low-pass filter can be adopted to remove noise, and there is no problem. Therefore, the detection signal of the potentiometer-type front wheel steering angle sensor 34 is used in a low speed operation state. To use.

As described above, in this embodiment, the small steering angle in-phase control and the large steering angle anti-phase control are executed depending on the vehicle speed, and the reliability of each control is improved. It is possible to execute the four-wheel steering control without deteriorating the reliability by selecting a sensor that matches the driving state without using a sensor having a low value. Then, when the condition of the operating state is switched, the front wheel steering angle is gradually changed so that the detected value of the front wheel steering angle does not suddenly change based on the difference in the characteristics of the sensors.

In the second embodiment, the vehicle speed sensor 15 corresponds to the driving state detecting means, the process of step 6200 corresponds to the driving state correspondence selecting means, and the step 626.
The processing from 0 to step 6280 corresponds to the gradually approaching means. Although the front wheel steering angle detection device for a vehicle as an embodiment has been described above, the front wheel steering angle detection device of the present invention is not limited to the above embodiment, and can be modified as follows without departing from the spirit thereof. is there.

In steps 7021 to 7023 of the flowchart of the first embodiment, when the front wheel steering angle sensor fails, control is performed so that the rear wheel steering angle is gradually reduced to 0. However, as another method, step 7026 in FIG. ~ 70
As shown in 28, a method of fixing the rear wheel steering angle at that position and returning the rear wheel steering angle to 0 when the vehicle speed becomes 0 may be used.

Neutral position calculated in each of the above embodiments
θD is the LPF estimated front wheel steering angle θx ^* And LPF primary delay
Front wheel steering angle θc^* Difference (= θc^* -Θx^* ) Calculated from
However, the encoder type front wheel steering angle sensor 16
The first detected front wheel steering angle θs detected by
Alternatively, the neutral position θD may be calculated.

In each of the above embodiments, the steered angle difference Δθ is obtained, and the steered change of the front wheel steered angle is prevented by gradually decreasing or increasing the steerable angle difference Δθ. A configuration is adopted in which a large weighting factor is applied to the steering angle, this weighting factor is gradually reduced over time, and conversely, the weighting factor of the front wheel steering angle that should be output after switching is increased. Of course, you can do that.

In the second embodiment, the vehicle speed is used as the driving state for the sensor switching determination, but the steering angle may be used as the sensor switching reference. In this case, after the neutral position calculation is completed, as a general rule, the rear wheel steering is performed based on the first front wheel steering angle θ1 described above.
The second front wheel steering angle θa is used when the front wheel steering angle θ1 exceeds a predetermined value, and when the second front wheel steering angle θa is less than the predetermined value when the second front wheel steering angle θa is used, the first front wheel steering angle is again set. The control may be such that the steering angle is switched to the angle θ1, and the gradual approach means may be made to function in order to prevent a sudden change in the steering angle detection value during these switchings.

In the first embodiment, the potentiometer type front wheel steering angle sensor is always used before the neutral position calculation is completed, but if the vehicle speed is equal to or higher than the predetermined value even before the neutral position calculation is completed. The front wheel steering angle detection using the potentiometer type front wheel steering angle sensor may be prohibited. The difference from the second embodiment is that the encoder type front wheel steering angle sensor is used after the first neutral position calculation is completed. In the second embodiment, when the neutral position correction that is constantly performed cannot be performed for a considerable period of time, the fact that the detection value of the encoder-type front wheel steering angle sensor may be used may be unreliable. This is because in general control, it is often sufficient without considering that much. However, if you control using the detection value of the potentiometer type sensor, there may be a problem of noise at high speed,
This is effective when you want to prevent it.

In the second embodiment, in consideration of the fact that the detection signal of the potentiometer type front wheel steering angle sensor 34 is likely to contain noise, it is configured not to be used at all during high speed traveling where the small steering angle in-phase control should be performed. , As shown in FIG.
"0" was input in the control block diagram of "C1 ≧
The configuration is such that “θa” is input to the block representing the “n” switch, and the front wheel steering angle is calculated using the detection signal of the potentiometer-type front wheel steering angle sensor 34 regardless of the vehicle speed before the neutral position estimation calculation is completed. It does not matter if it is configured to do so. This is because there is no problem if the noise of “θa” can be sufficiently removed by using a filter or the like.

[0091]

As described in detail above, according to the front wheel steering angle detecting device of the present invention, in the front wheel steering angle detecting device for switching the plurality of front wheel steering angle sensors to determine the steering angle of the front wheel, When the sensor for determining the steering angle is switched, the detected value does not change suddenly but gradually changes.Therefore, when performing various controls using such detected values of the front wheel steering angle, the value of the control parameter It does not cause unstable control due to sudden changes in.

Particularly, according to the vehicle front wheel steering angle detecting device of the second aspect, various controls based on the front wheel steering angle can be executed immediately after the engine of the vehicle is started, and the first characteristic is different. Even when the sensor is switched to the front-wheel steering angle sensor, the front-wheel steering angle is smoothly changed, so that problems such as instability of control are not caused. That is, according to the device of the second aspect, there is an effect that the front wheel steering angle is immediately output immediately after the engine is started and the front wheel steering angle is not suddenly changed.

Further, according to the vehicle front wheel steering angle detecting device of the third aspect, the sensors suitable for the control in various driving states are provided and the control in accordance with the driving state is performed. In addition to such an effect, a further excellent effect that a sudden change in control is not caused when the operating state is switched is also exhibited.

[Brief description of drawings]

FIG. 1 is a claim correspondence diagram illustrating the configuration of a front wheel steering angle detection device of the present invention.

FIG. 2 is an overall configuration diagram showing an overall configuration of a rear wheel steering system 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 photo interrupters 16b and 16c when the handle rotates to the right.

FIG. 5 is an explanatory diagram of output waveforms of the photo interrupters 16b and 16c when the handle rotates to the left.

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

FIG. 7 is an explanatory diagram showing detection of a front wheel steering angle 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 system according to the embodiment.

FIG. 10 is a flowchart showing a main processing routine of the microcomputer.

FIG. 11 shows a vehicle speed sensor and left and right wheel speed sensors 21,
6 is a flowchart showing a vehicle speed pulse process based on a pulse signal from 22.

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

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

FIG. 14 is a control block diagram of FIG. 13.

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

FIG. 16 is an explanatory diagram at the time of steering.

FIG. 17 is a characteristic diagram showing a change in front wheel steering angle in the example.

FIG. 18 is a flowchart showing a part of a front wheel steering angle calculation routine and a front wheel steering angle sensor failure detection routine.

FIG. 19 is a flowchart showing a part of a front wheel steering angle calculation and a front wheel steering angle sensor failure detection routine.

FIG. 20 is a flowchart showing a part of a front wheel steering angle calculation routine and a front wheel steering angle sensor failure detection routine.

FIG. 21 is a control block diagram of FIGS. 18 to 20.

FIG. 22 is a flowchart showing a modified example.

FIG. 23 is a control block diagram showing another modification.

[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 34 potentiometer type front wheel steering angle sensor

Claims (3)

[Claims] 1. A plurality of front wheel steering angle sensors for detecting a steering angle of a front wheel, and which one of the plurality of front wheel steering angle sensors is used to determine a front wheel steering angle according to a predetermined condition. Sensor selecting means, a steering angle determining means for determining a front wheel steering angle based on a detection value of a front wheel steering angle sensor selected by the sensor selecting means, and a steering angle output means for outputting the determined front wheel steering angle. In the front wheel steering angle detection device for a vehicle including: When the sensor selected by the sensor selection means is switched, the front wheel steering angle output before the switching is changed to the front wheel steering angle to be output after the switching. A front wheel steering angle detecting device for a vehicle, comprising: a gradually approaching means for gradually changing an output of the steering angle output means. 2. The front wheel steering angle detecting device for a vehicle according to claim 1, wherein the plurality of front wheel steering angle sensors output a signal according to a change in a steering angle of the front wheels when the front wheel steering angle changes. A front wheel steering angle sensor, and a second front wheel steering angle sensor that outputs a signal according to the front wheel steering angle, and as the steering angle determination means, at least a signal output from the first front wheel steering angle sensor. Neutral position calculation means for estimating and calculating the neutral position of the front wheel steering angle based on the above, a signal output from the first front wheel steering angle sensor, and a neutral position of the front wheel steering angle estimated and calculated by the neutral position calculation means. A first front wheel steering angle calculating means for calculating a first front wheel steering angle, and a second front wheel steering angle for calculating a second front wheel steering angle based on a signal output from the second front wheel steering angle sensor. In front of 2 Steering angle calculation means, and as the sensor selection means, an estimated calculation end determination means for determining whether or not the neutral position calculation means has finished estimating the neutral position, and the estimated calculation end determination means are neutral. The second front wheel steering angle sensor is selected until it is determined that the position calculation is completed,
A front wheel steering angle detection device for a vehicle, comprising: an estimation calculation correspondence selection unit that selects the first front wheel steering angle sensor after determining that the calculation of the neutral position has been completed. 3. The front wheel steering angle detecting device for a vehicle according to claim 1, further comprising a driving state detecting means for detecting a driving state of the vehicle, wherein the sensor selecting means includes the driving state detecting means. A front wheel steering angle detecting device for a vehicle, comprising: driving state correspondence selecting means for selecting one of the plurality of front wheel steering angle sensors according to the detected driving state.