JPS622123A - Position detector - Google Patents

Abstract

PURPOSE:To enable adjustment in a fine operation range without complicating the construction, by varying the resolution of a rotary angle detection of a non-contact digital absolute encoder as required according to the range of rotation. CONSTITUTION:A rotary disc which is turned in linkage with a rotating shaft to form a non-contact digital absolute encoder is provided with slits 39a-39d together with a light emitting receiving element or the like so as to increase the number of detection signal bits in a concentrical fashion sequentially near each other's boundaries. Consequently, the detection signal is generated corresponding to fine variations in the angle of rotation at the area near the limit position of the rotation range to change the resolution as required according to the angle of rotation. This enables adjustment satisfactorily in a fine operation range without increasing the number of bits more than necessary as well as complicating the construction.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a position detector used in industrial equipment such as robots and NC machine tools.

Background of the Invention In recent years, position detectors for robots, NC machine tools, etc., have appeared that combine multiple sensors into one unit in order to save wiring. 1031
An example of this is introduced in 29, which controls the position of equipment without installing a position detector.It uses an incremental rotary encoder (hereinafter referred to as an "encoder") that detects the rotation angle of a rotating shaft, and a and an input shaft, a reducer section that decelerates the rotational speed of the input shaft and outputs it to the output shaft, and a rotating shaft that is coupled to the output shaft of this reducer section. It has a potentiometer that outputs a corresponding voltage.

The conventional position detector mentioned above will be explained below with reference to the drawings.

FIG. 2 shows a horizontal positioning device equipped with a conventional position detector configured as described above.

The rotation of the motor 1 is transmitted to the pole screw 2, and the rotational motion is converted into a linear motion along the slide shirt 3b, causing the slider 4 to move linearly. 10 is a stopper that mechanically restricts the movement of the slider. A position detector configured as described above is connected to the shaft of the motor 1.

Figure 3 shows a conventional position detector with the above-mentioned configuration.
is a rotating shaft supported by bearings 16a and 16b. The light emitted from the light emitting element 17 passes through the rotating slit plate 18 attached to the rotating shaft 15 and the fixed slit plate 19, enters the light receiving element 2°, is converted into an electrical signal, and is converted into an electrical signal by the circuit on the printed circuit board 21. It is processed and output as an encoder signal. A pinion 22 is attached to the rotating shaft 16, and the rotation of the rotating shaft 15 is reduced in speed by a gear 23 and transmitted to the shaft 24 of the potentiometer. A brush attachment plate 25 is attached to the shaft 24, and a brush 26 is attached to the brush attachment plate 25. The brush 26 slides on a resistor 27 and outputs a potentiometer signal.

Furthermore, a shielding plate 28 is provided between the encoder section and the reduction gear to prevent dust from entering the encoder section.

FIG. 4a shows the output signal of the encoder. The A signal generates a pulse signal N times at equal intervals during one revolution of the rotary shaft of the encoder. The B signal generates a pulse signal N times during one rotation while maintaining a constant phase difference with respect to the A signal. The Z signal is a pulse signal with a width equivalent to one period of the A signal.
Only one pulse occurs at the same position during one rotation.

Figure 4 shows the output signal of the potentiometer.

The rotation of the potentiometer is reduced by a reduction gear, and a reduction ratio is set so that the rotation of the potentiometer does not exceed an electrically effective angle of the potentiometer.

The output of the potentiometer is input to a comparator circuit shown in FIG. 5, and DC voltage levels a and b are determined.

The θ side mitt signal C0 is compared with C2d, e, f, q, and h to detect the limit of operation on the C) side from the origin, and detects the position where the speed of the slider 4 is reduced just before passing the origin position. Slow down signal C8, origin signal C○, ■ side mitt signal CH that detects the limit of operation on the ■ side from the origin
is output as Figure 4C shows CL according to the rotation angle of the potentiometer.

Each signal of C8 and C02CH is shown.

That is, the rotational motion of the motor 1 is converted into a linear motion of the slider 4, and while the slider 4 makes one reciprocation, the potentiometer built in the conventional position detector also makes one reciprocation, and its output is input to the comparator. When the slider 4 reaches a predetermined position, output signals CL, C8, and C02CH are generated, and the position of the slider 4 can be detected separately from the encoder's A and B signals.

Further, as shown in FIG. 4d, the position is detected by performing a logical product of the output signal of the comparator and the two signals of the encoder.

Problems to be Solved by the Invention However, in the above conventional example, 1. The resistance value of the resistor changes over time due to wear of the resistor 27, or the contact resistance changes due to wear of the contact portion between the resistor 27 and the brush 26. However, it is difficult to obtain a stable output signal over a long period of time.

2. Depending on the direction of rotation, the contact angle of the brush 26 with the resistor 27 changes slightly, resulting in a slight positional error.

It had such drawbacks.

In addition, attempts have been made to apply non-contact digital absolute encoders as a measure to solve the above problems, but digital requires a large number of pits to increase resolution, and the encoder This method has problems such as higher processing costs and more complex signal processing.

Means for Solving the Problems In order to solve the above problems, the position detector of the present invention uses a non-contact digital absolute encoder for generating a rotation angle detection signal in accordance with the rotation of a rotating shaft. A Liut encoder is applied, and the rotation angle detection signal of the non-contact digital absolute encoder corresponds to a finer rotation angle change in a region corresponding to the vicinity of the limit position of the rotation range of the rotary shaft than in other regions. It is set to occur.

Function As described above, the present invention uses a non-contact digital absolute encoder that uses a non-contact sensor to output the output signal for detecting the rotation angle of the rotating shaft. This problem is solved, a stable output signal can be obtained over a long period of time, and no position error occurs due to the direction of rotation. Furthermore, since the position resolution is unevenly set so that it is high only in the portion corresponding to the vicinity of the operating range limit position, fine adjustment of the operating range is possible with a smaller number of bits. A position detector according to an embodiment of the invention will be described with reference to the drawings.

FIG. 1 shows a position detector which is an embodiment of the present invention, 29 is a rotating shaft, 30a and 30b are bearings that support the rotating shaft 29, 31 is a light emitting element, 32 is a rotating slit plate, 33 34 is a fixed slit plate, 34 is a light receiving element, and 36 is a printed circuit board for electrically processing the signal of the light receiving element 34. The above components constitute an incremental encoder.

36a is a pinion fixed to the rotating shaft 29, and 3eb is a gear meshing with the pinion 35.The pinio/36a and the gear 36b constitute a reducer with the rotating shaft 29 as an input shaft, and the rotation of the rotating shaft 29 is decelerated. and is output to the output shaft 37. The above configuration is completely the same as the conventional example. 38 is a rotating slit plate fixed to the output shaft 37, and as shown in FIG. 6, it has a first slit 39a, a second slit 39b,
A third slit) 39a and a fourth slit) 39d are provided to form a total of 4-bit gray code. 4 is a light emitting element, 41 is a fixed slit plate, and 42 is a slit plate 3.
There are four light receiving elements provided corresponding to each of the eight pits. 43 is a printed circuit board for electrically processing the signal of the light receiving element 42, and the signal of the light receiving element 42 is thereby outputted as a 4-pit binary code. That is, the rotating slit plate 38, the light receiving element 42, and the printed circuit board 43 constitute an absolute encoder.

FIG. 7 shows the output signal of the incremental encoder and the output signal of the absolute encoder in this embodiment. As for the input signal, pulse signals are generated N times at equal intervals during one rotation of the rotating shaft 29. The B signal generates a pulse signal N times during one rotation while maintaining a constant phase difference with respect to the A signal.

In order to detect the origin of the incremental encoder, the Z signal generates only one pulse during one rotation, which has a width equivalent to one cycle of the A signal. When the output signal of the absolute encoder is expressed in hexadecimal, it is output as shown in FIG. At this time, the rotation of the absolute encoder is decelerated by a speed reducer, and when this embodiment is used in a horizontal positioning device as shown in FIG. The reduction ratio is set so that the encoder corresponds to a little less than one rotation, and within the maximum operating range, the absolute encoder output corresponds uniquely, and the same signal will not appear twice. do not have.

In this embodiment, the origin signals are two signals immediately after the output of the absolute encoder changes from 1 to 0. If you want to change the origin position, count the Z signals after the absolute encoder output changes from 1 to 0, and set the nth Z signal as the origin, or vice versa. The origin may be determined by counting the Z signal after the change from 1 to 1.

A limit signal that sets the limit position of the robot's operating range (hereinafter referred to as "limit J") is determined by arbitrarily selecting a change point in the output of the absolute encoder.

Generally, when setting a limit signal so that the robot does not interfere with surrounding obstacles, the signal near the area corresponding to the limit, that is, the limit position of the rotation range of the rotating shaft 15, is set as follows.
It is necessary to maintain high resolution in other areas as well. Therefore, in this embodiment, the rotation angle detection signal of the absolute encoder is set to be generated in response to a finer rotation angle change in the area where the limit is set than in other areas, thereby reducing the number of bits. The number allows fine limit adjustment.

In this embodiment, the absolute encoder is a 4-bit encoder, but it is not necessary to limit the encoder to 4 bits. Although both the incremental encoder and the absolute encoder are of optical type, this is just an example, and other non-contact digital encoders such as magnetic type may also be used.

Effects of the Invention As described above, the present invention applies a non-contact digital absolute encoder as an absolute encoder that generates a rotation angle detection signal according to the rotation of a rotating shaft.
The problems of contact-type absolute encoders, such as changes in the resistance value of the resistor over time due to wear, changes in contact resistance, and errors due to differences in rotation direction, are eliminated, and stable output signals can be obtained over a long period of time. This is because the rotation angle detection signal of the non-contact digital absolute encoder is set to be generated in response to minute changes in the rotation angle in an area corresponding to the limit of the rotation range of the rotating shaft, and in other areas as well. , it is possible to finely adjust the operating range with a very small number of bits, and its industrial value is considerable.

[Brief explanation of drawings]

FIG. 5 is a diagram showing a horizontal positioning waveform equipped with a position detector in an embodiment. FIG. 5 is a diagram showing a comparator circuit that inputs the output of the position detector. FIG. FIG. 7, which is a plan view of the absolute encoder rotating slit plate, is a diagram showing the output signal of the same position detector. 1...Motor, 2...Ball screw, 3
a, 3b...Slide shaft, 4...
・Slider, 1°...stopper, 14...
...Position detector, 29... Rotation axis, 3Qa
, 30b...bearing, 31...light emitting element, 32...rotating slit plate, 33...
...Fixed slit plate, 34... Light receiving element, 3
6... Printed circuit board, 36a... Binion, 36b... Gear, 37... Output shaft, 38... Rotating slit plate, 40・・・・・・
・Light emitting element, 41...Fixed slit plate, 42・
. . . Light receiving element, 43 . . . Printed circuit board. 40- Starting plan 4f-11 side fixed, To7 42-Aozanju) 43--7° Rishito 1 (↓Flash 2nd flash)
f-motor No. 3 Fig. 4fA
C.C. ``This 3・Figure 5 f Chinshi 3 meter staff number 6 Figure 3Qa
--+ 1 slit, 79b--su 2II 3Qc--one year old 3 -I horse---sweet 4 ・Fig.

Claims (1)

[Claims] It consists of a rotating shaft and a non-contact digital absolute encoder that generates a rotation angle detection signal according to the rotation of the rotating shaft, and the rotation angle detection signal of the non-contact digital absolute encoder detects the limit of the rotation range of the rotating shaft. A position detector that is set to respond to a rotation angle change that is smaller in a region corresponding to the vicinity of the position than in other regions.