JPS60205211A - Steering angle detection apparatus of steering shaft - Google Patents

Abstract

PURPOSE:To accurately detect a neutral position by shortening a processing time, by providing an encoder and a nutral position detecting sensor which respectively send out a pulse signal at every unit rotation of a steering shaft and a neutral position signal at every one rotation. CONSTITUTION:A rotary plate 11 having a large number of slits 12 on the circumference thereof and a notch 13 formed to the periphery thereof at one place is attached to a steering shaft 10. Photo-interruptors 14, 15 are further arranged to the circumference of the rotary plate 11 so as to be spaced apart to each other. An encoder and a neutral position detecting sensor, which respectively send out a pulse signal at every unit rotation of the shaft 10 by the rotary plate 11, the slits 12 and the photointerruptor 14 and a neutral position signal at every one rotation of the shaft 10 by the notch 13 and the photointerruptor 15, are constituted. By this mechanism, a real neutral position is detected by reduced sampling and a steering angle can be accurately detected within a short time.

Description

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

<Prior art> In the case where the steering angle of the steering wheel is detected by using an encoder in -m, as shown in FIG. A photo interrupter 4 detects a large number of slits 3 formed on the circumference, and a pulse signal obtained by the photo interrupter 4 is caused to count up or down in a counter depending on the direction of rotation of the steering wheel, thereby detecting the steering angle. It is supposed to be done.

However, in this type of steering angle detection device, it is not possible to obtain the absolute steering angle, and therefore it is not possible to recognize the straight direction of the vehicle, that is, the neutral position. Therefore, the output of the encoder is distributed as shown in Figure 2 for lightning monitoring, and the most frequent time is recognized as the neutral position. If the number is quite large, it will be difficult to determine the neutral position, and the processing time after the power is turned on will be long, leading to the problem that it will not be possible to control the vehicle immediately after the start of travel.

Moreover, in such a method, there is a problem that the neutral position 1 on the distribution does not necessarily match the actual neutral position, resulting in variations in neutral detection accuracy.

<Object of the Invention> An object of the present invention is to shorten the processing time and to be able to accurately detect the neutral position.

<Structure of the Invention> In order to achieve the above-mentioned object, the present invention provides a neutral detection sensor that sends out a neutral signal for each rotation of the steering shaft in addition to an encoder that sends out a pulse signal for each unit rotation of the steering shaft. Among the plurality of neutral signals from the neutral detection sensor, the most frequent position is determined to be the true neutral position, and the steering angle can be detected starting from this true neutral position.

<Example> Embodiments of the present invention will be described below based on the drawings.

In FIG. 3, 10 indicates a steering shaft;
A steering wheel is connected to one end of the steering shaft 10, and a power steering wheel is connected to the other end. A rotating plate 11 is mounted on the steering shaft 10, and a large number of slits 12 are formed on the circumference of the rotating plate 11 at equal angular intervals. Furthermore, a notch 13 is formed at a location on the circumference of the rotating plate 11.

Two photointerrupters 14.15 are arranged circumferentially apart from each other on the circumference of the rotating plate 11, and these photointerrupters 14.15 are fixed to a fixed part such as a steering column. The photointerchanger 14 includes two pairs of light-emitting elements and light-receiving elements that face each other with the rotary plate 11 in between and are shifted in phase by 1/4 period, and receives the light passing through the slit 12 and directs the steering shaft. A pulse signal is generated every 1° unit rotation. Further, the photo interlayer 15 receives the light passing through the notch 13 and generates a neutral signal. The photointerrupter 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 photointerrupter 14 described above constitute an encoder that sends out a pulse signal every unit rotation of the steering shaft 10. In addition, the notch 13 and the photo interlayer 1
5 constitutes a neutral detection sensor that sends out a neutral signal every time the steering shaft 10 rotates once.

FIG. 4 shows the processing circuits of the photo interpolators 14 and 15. In the figure, 20 is a waveform shaping circuit, and 25 is a computer. , neutral signal discrimination means 23
It is composed of C.

As shown in FIG. 5, the steering direction determining means 21 determines one period of the pulse signal from "0" to "3" by a combination of two pulse signals SSI and SS2 generated by the encoder and shifted by 174 periods. It is divided into four area signals S. That is, when the signals SSI and SS2 are both low level, S becomes "0", and when the signal SSI is low level, S becomes "0".
When S2 is high level, S is connected to rlJ, and the signal SSI
is high level and SS2 is low level, S is "2".
”, when both the signals SSI and SS2 are at high level, S is classified as “3”.

Further, the steering direction determining means 21 is configured to determine the steering direction of the steering wheel based on the current area signal and the previous area signal, and this will be explained below with reference to the flowchart shown in FIG. In FIG. 6, S indicates the current area signal, and O8 indicates the previous area signal.

First, in step 30, it is determined whether S and O8 are the same, and if YES, the program returns as if the steering wheel is stopped. In the case of No, the process proceeds to steps 31 and subsequent steps, in which it is determined whether S is rOJ in step 31, whether S is "1" in step 32, and whether S is "2" in step 33.
'', and if it is neither of these, it is recognized in step 34 that S is 13''. If S is determined to be "0" in step 31, the process proceeds to step 35, where it is determined whether O8 is "1". If YES, it is determined that the rotation direction 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. Also step 35
If the determination result is NO, it is determined that the rotation direction of the steering wheel is reverse (counterclockwise rotation), and in step 40, the rotation angle T HE stored in the memory is determined.
Subtract 1 from TA. Similarly, in step 32, S
If it is determined that is rlJ, it is determined in step 36 whether O3 is "0", and if it is determined in step 33 that S is "2", then in step 37 It is determined whether O3 is rOJ, and if S is recognized as "3" in step 34, it is determined in step 38 whether O3 is "1", and according to the determination result, Step 39 as described above.
Alternatively, in step 40, the contents of the rotation angle THETA stored in the °ζ memory are added or subtracted.

Next, the steering angle calculating means 22 and the neutral signal determining means 2
3 will be explained according to the flowchart shown in FIG. N
Based on the interrupt signal for each m5ec, it is determined in step 50 whether or not the signal is a neutral signal from the photointerrupter 15. If the signal is not a neutral signal, the rotation angle THETA is calculated according to the flowchart described above. If it is determined in step 50 that it is a neutral signal, it is determined in steps 52 and 53 whether it is a neutral signal T1 or T2, and if it is neither of these, it is recognized as a neutral signal T3 in step 54. Ru. If the steering knob 52 determines that the signal is the neutral signal Tl, 1 is added to the memory counter C1 in step 55. Similarly, if it is determined in step 53 that it is the neutral signal T2, then in step 56 the memory counter C
If the neutral signal T3 is recognized in step 54, 1 is added to the memory counter C3 in step 57. In step 58, the maximum value Cm of the memory counters C1, C2, C3 is
It is determined whether aX exceeds the set value M, and if No, the memory counters C1,
The position of the maximum value of C2 and C3 is determined as the neutral position of the tool, and the rotation angle 'I'11 E 'FA at that time is determined as C
Store in memory as ENTER. In step 60, THE
CENTE stored in memory as described above from TA
R is subtracted and the result is output as a steering angle starting from the true neutral position. Note that in the stainless steel 15B, the maximum value Cma of the memory counters C1, C2, and C3
If it is determined that x has exceeded the set value M, the contents of memory counters C1, C2, and C3 are each revised to 1/2 in step 61 to prevent the contents of the memory counters from exceeding the set value. ing.

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, and the rotation angle THE is changed depending on the steering direction.
The contents of the memory storing the TA are added or subtracted. Furthermore, each time the steering shaft lO is rotated once, the notch 13 on the rotary plate ll is detected by the photointerrupter 15, and a neutral signal is generated. By the way, when the car is stopped, the orientation of the tires is not constant, so 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 the PO state with the steering wheel turned almost all the way to the left, and as time passes the steering wheel is operated as shown by the solid line. T1 is determined by the first neutral signal, and 1 is added to the memory counter CI. Subsequently, the second neutral signal is determined to be 'r2' based on the steering direction, and I' is added to the memory counter C2.

In this way, the neutral signals TI, T2 . Each time T3 is determined, 1 is added to each of the memory counters C1, C2, and C3 in steps 55 to 57 in FIG. 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 is the largest, and the content of C2 of the memory counter is the largest. Become. Therefore step 5
At step 9, the output THETA from the encoder when the neutral signal T2 is determined is stored as CENTER, and at step 60, by subtracting CENTF and R from THETA, the steering operator 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 provides a neutral detection sensor that generates a neutral signal every rotation of the steering shaft in addition to an encoder that detects the rotation angle of the steering shaft, and Distinguish multiple neutral signals, calculate their frequencies, determine the most frequent position as the true neutral position, and convert the relative rotation angle obtained by the encoder to the rotation angle starting from the true neutral position. Since it is configured to perform calculations, the true neutral position can be detected with a small number of samplings, and the steering angle can be accurately detected in a short processing time after the power is turned on.

[Brief explanation of the drawing]

FIG. 1 shows a conventional steering angle detection device, FIG. 2 shows its output distribution, FIG. 3 shows a steering angle detection device according to an embodiment of the present invention, and FIG. 4 shows a steering angle detection device according to an embodiment of the present invention. The control circuit diagram thereof, FIG. 5 is an output waveform diagram of the encoder, 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 showing the flowchart of the steering angle calculation means. It is a figure for detailed explanation. 10... Steering shaft, 1]... Rotating plate, 12... Slit, 13... Notch, 14.15.
... Photo interoperator, 21... Steering direction determining means, 22... Steering angle calculating means, 23... Neutral signal determining means, 25... Computer. Patent applicant Toyoda Machine Tool Co., Ltd. Figure 4 Figure 5 Figure 6 Figure 8

Claims (1)

[Scope of Claims] [1] An encoder that detects the steering angle of a steering wheel and has a rotary plate that rotates in synchronization with a steering shaft and sends out a pulse signal every unit rotation of the rotary plate; A neutral detection sensor that sends out a neutral signal every rotation of the shaft, means for discriminating multiple neutral signals from the neutral detection sensor, and calculating the frequency of each neutral signal discriminated by this discriminating means to find the most frequent one. neutral position determining means for determining a high position as a true neutral position;
and a rotation angle calculation means for inputting and counting signals from the encoder and calculating a rotation angle starting from the neutral position determined by the foot means for calculating the neutral position. Detection device.