JPH049444B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a steering angle detection device that detects the steering angle of a steering wheel using an encoder.

<Prior art> In general, in the case of detecting the steering angle using an encoder, as shown in FIG. 1, a rotary plate 2 is attached to a steering shaft 1 connected to a steering wheel, and a A photo interrupter 4 detects a large number of slits 3 on the circumference of the steering wheel, and a pulse signal obtained by the photo interrupter 4 is sent to a counter to count up or down depending on the direction of rotation of the steering wheel. is now being detected.

However, with this type of steering angle detection device, it is not possible to obtain the absolute angle of steering;
It is not possible to recognize the straight direction of the car, that is, the neutral position. Therefore, the output of the encoder is distributed as shown in Figure 2 and constantly monitored, and the most frequent time is recognized as the neutral position. There is a problem in that it is difficult to determine the neutral position unless a considerable number of positions are taken, and the processing time after turning on the power becomes long, making it impossible to control the vehicle immediately after the start of travel.

Moreover, in such a method, the neutral position L1 on the distribution does not necessarily match the actual neutral position,
There is also the problem of variations in neutral detection accuracy.

<Objective of the Invention> An object of the invention is to shorten the processing time and to accurately detect the neutral position.

<Structure of the Invention> In order to achieve the above-described object, the present invention includes, in addition to an encoder that sends out a pulse signal for each unit rotation of the steering shaft, a neutral detection sensor that detects a neutral signal for each rotation of the steering shaft; Multiple neutral signals T from this neutral detection sensor
1, T2, and T3, and calculates the detection frequency of each of the neutral signals T1, T2, and T3 discriminated by the discrimination means, and determines the neutral signal detection position with the highest detection frequency as the true neutral position. a neutral position determining means for determining, and a rotation angle for adding and subtracting the pulse signal from the encoder according to the rotation direction and calculating the added and subtracted value into a rotation angle starting from the neutral position determined by the neutral position determining means. The steering angle is configured by a calculating means, and is capable of detecting a steering angle starting from a true neutral position.

<Examples> Examples of the present invention will be described below based on the drawings. In FIG. 3, 10 indicates a steering shaft, one end of which is connected to a steering wheel, and the other end is connected to a power steering wheel. A rotating plate 11 is mounted on the steering shaft 10, and a large number of slits 1 are formed on the circumference of the rotating plate 11.
2 are formed at equal angular intervals. Also, rotating plate 1
A notch 13 is formed at one location on the circumference of the ring. Two photo interrupters 14 and 15 are arranged circumferentially apart from each other on the circumference of the rotating plate 11, and these photo interrupters 14 and 15 are fixed to a fixed part such as a steering column. Such a photo interrupter 14 is connected to the rotating plate 1.
The light emitting element and the light receiving element are provided with two pairs of light emitting elements and light receiving elements that face each other with the slit 12 in between and are shifted in phase by 1/4 period. generates a pulse signal. Further, the photointerrupter 15 receives the light passing through the notch 13 and generates a neutral signal. The photo interrupter 15 is arranged so as to detect the notch 13 in the neutral position of the steering wheel. The rotary plate 11, slit 12, and photo interrupter 14 described above constitute an encoder that sends out a pulse signal every unit rotation of the steering shaft 10. In addition, the notch 1
3 and the photointerrupter 15 constitute a neutral detection sensor that sends out a neutral signal every time the steering shaft 10 rotates.

FIG. 4 shows the photo interrupter 14, 15.
20 is a waveform shaping circuit, and 25 is a computer. The computer 25 is composed of a steering direction determining means 21, a steering angle calculating means 22, and a neutral signal determining means 23. As shown in FIG. 5, the steering direction determining means 21 converts one period of the pulse signal from "0" to "3" by a combination of two pulse signals SS1 and SS2 generated by the encoder and shifted by 1/4 period. ” is divided into four area signals S. i.e. signal
When SS1 and SS2 are both low level, S becomes "0"; when signal SS1 is low level and SS2 is high level, S becomes "1"; when signal SS1 is high level and SS2 is low level, S is "1". In this case, S is "2"
In addition, when both the signals SS1 and SS2 are at high level, S is classified as "3".

Further, the steering direction determining means 21 is adapted to determine the steering direction of the steering wheel based on the current area signal and the previous area signal, and this will be described below with reference to the flowchart shown in FIG. explain. In FIG. 6, S indicates the current area signal, and OS indicates the previous area signal.
First, in step 30, it is determined whether S and OS are the same, and if YES, the program returns with the assumption that the steering wheel is stopped. If NO, proceed to steps 31 and subsequent steps, in step 31 check whether S is ``0'', in step 32 check whether S is ``1'', and in step 33 check whether S is ``2'' are determined, and if neither of these is the case, S is recognized as "3" in step 34.
If S is determined to be “0” in step 31,
Proceeding to step 35, it is determined whether the OS is "1". If YES, it is determined that the direction of rotation of the steering wheel is normal (clockwise), and in step 39, 1 is added to the rotation angle THETA stored in the memory of the computer 25.
If the determination result in step 35 is NO, it is determined that the direction of rotation of the steering wheel is reverse (counterclockwise), and in step 40, 1 is subtracted from the rotation angle THETA stored in the memory. Similarly, if S is determined to be "1" in step 32, the OS is determined to be "0" in step 36.
If it is determined in step 33 that S is "2", it is determined in step 37 whether OS is "0", and in step 34 it is determined that S is "3". ”, it is determined in step 38 whether the OS is “1”, and depending on the determination result, the rotation angle THETA stored in the memory is changed in step 39 or step 40 as described above. The contents of are added or subtracted.

Next, the steering angle calculating means 22 and the neutral signal determining means 23 will be explained according to the flowchart shown in FIG. Based on the interrupt signal every Nmsec, it is determined in step 50 whether it is a neutral signal from the photo interrupter 15 or not. If the signal is not a neutral signal, calculation processing of the rotation angle THETA is executed according to the flowchart described above. If it is determined in step 50 that the signal is a neutral signal, the neutral signal T1 is determined in steps 52 and 53.
If it is neither of these, it is recognized as a neutral signal T3 in step 54. That is, T1 is the first neutral signal detected after power is turned on, and T2 is the neutral signal T1.
When the steering shaft 10 rotates once in the left (right) direction from the detection position (rotation angle THETA =
360°), and T3 is a neutral signal detected when the steering shaft 10 further rotates one turn to the left (right) from the neutral signal T2 detection position (rotation angle THETA = 720°) or When rotating twice in the (left) direction (rotation angle THETA = -
It is a neutral signal detected in 360°). step 52
If it is determined that the signal is the neutral signal T1, one is added to the memory counter C1 at step 55. Similarly, if it is determined at step 53 that the signal is the neutral signal T2, 1 is added to the memory counter C2 at step 56, and if it is recognized at step 54 that it is the neutral signal T3, then 1 is added to the memory counter C2 at step 57. 1 is added to the memory counter C3. step
58, the memory counters C1, C2, C
It is determined whether the maximum value Cmax of 3 exceeds the set value M, and if NO, the position of the maximum value of the memory counters C1, C2, C3 is determined as the true neutral position, and then The contents of the rotation angle THETA are stored in memory as CENTER. In step 60, CENTER stored in the memory as described above is subtracted from THETA calculated in the flowchart shown in FIG. 6, and the result is output as the steering angle A with the true neutral position as the starting point. Note that step 58 above
If it is determined in step 61 that the maximum value Cmax of the memory counters C1, C2, C3 exceeds the set value M, the memory counters C1, C3 are
The contents of 2 and C3 are each modified to 1/2 to prevent the contents of the memory counter from exceeding the set value.

Next, the operation of detecting the steering angle A will be explained. When the rotating plate 11 is rotated together with the steering shaft 10 by operating the steering wheel, a pulse signal is generated every time the slit 12 is detected by the photo interrupter 14.
The contents of the memory storing the rotation angle THETA are added or subtracted according to the steering direction. Furthermore, each time the steering shaft 10 rotates once, the notch 13 on the rotating plate 11 is detected by the photo interrupter 15 and a neutral signal is generated. By the way, when the car is stopped, the orientation of the tires is not constant, and therefore the rotation angle obtained by the output of the encoder starts from the position of the steering wheel when the power is turned on.

As shown in Figure 8, the power is turned on in state P0, where the steering wheel is turned almost all the way to the left, and the steering wheel is operated over time as shown by the solid line. T1 is determined based on the neutral signal of , and 1 is added to the memory counter C1. A second neutral signal is then generated based on that steering direction.
2, and 1 is added to the memory counter C2. Each time the neutral signals T1, T2, and T3 are determined in this way, 1 is added to the memory counters C1, C2, and C3, respectively, in steps 55 to 57 of FIG.
is added. However, since the steering wheel is normally operated to the right or left beyond the actual neutral position, the signal T2 generated at the actual neutral position
becomes the largest, and the content of C2 among the memory counters becomes the largest. Therefore, in step 59,
The output THETA from the encoder when the neutral position T2 is determined is stored as CENTER, and by subtracting CENTER from THETA in step 60, the steering angle A starting from the true neutral position is determined.

This steering angle A is displayed on a display device provided in the driver's seat, or is used as a control input for controlling the steering force of the power steering device.

<Effects of the Invention> As described above, the present invention includes, in addition to the encoder that detects the rotation angle of the steering shaft, a neutral detection sensor that generates a neutral signal for each rotation of the steering shaft. Distinguish multiple neutral signals, calculate their frequencies, determine the most frequent position as the true neutral position, and determine the relative rotation angle obtained by the encoder as the rotation starting from the true neutral position. Since it is configured to calculate angles, it is possible to detect the true neutral position with a small number of samplings, and the steering angle can be accurately detected in a short processing time after power is turned on.

[Brief explanation of drawings]

Figure 1 is a diagram showing a conventional steering angle detection device, Figure 2 is a diagram showing a conventional steering angle detection device.
3 shows a steering angle detection device according to an embodiment of the present invention, FIG. 4 is a control circuit diagram thereof, FIG. 5 is an output waveform diagram of an encoder, and FIG. FIG. 6 is a flowchart of the steering direction determining means, FIG. 7 is a flowchart of the steering angle calculation means, and FIG. 8 is a diagram for explaining the operation of the present invention. 10... Steering shaft, 11... Rotating plate, 12... Slit, 13... Notch, 14,1
5...Photo interrupter, 21...Steering direction discrimination means, 22...Steering angle calculation means, 23...Neutral signal discrimination means, 25...Computer.

Claims (1)

[Claims] 1. An encoder that detects the steering angle of the steering wheel and has a rotating plate that rotates in synchronization with the steering shaft and sends out a pulse signal for each unit rotation that is sufficiently smaller than one rotation of the rotating plate, and an encoder that detects the steering angle of the steering shaft. A neutral detection sensor that detects a neutral signal every rotation, and a plurality of neutral signals T1, T2, T3 from this neutral detection sensor (however,
T1 is the first neutral signal detected after power-on, T
2 is a neutral signal detected at an angular position 360° different from T1, and T3 is a neutral signal detected at an angular position 360° different from T1 or T2), and a means for discriminating a neutral signal detected at an angular position 360° different from T1 or T2, Each neutral signal T
1, T2, and T3, and determines the neutral signal detection position with the highest detection frequency as the true neutral position; A steering angle detection device for a steering wheel, comprising: a rotation angle calculation means for calculating the added and subtracted values into a rotation angle starting from the neutral position determined by the neutral position determination means.