JPS62235820A - Displacement transducer - Google Patents

Abstract

PURPOSE:To improve the reproducibility of position by storing the information being the correspondence between a phase difference actually counted and the absolute angle of a reference origin detection slit in a memory in advance and applying the home position return based on the information. CONSTITUTION:When an LED 7 projects light between slits 31,32 at application of power for a robot or the like, a motor 4 is driven clockwise (direction A) and stops by a detection signal from a home position detecting circuit 10 when a home position signal detector 9 detects the slit 32. A phase counter circuit 14 obtains the phase difference between an inputted waveform signal fS and a reference waveform signal fR and gives the resulting signal to a microprocessor 15. The reference waveform signal fR is a waveform signal obtained in closing any of switches 111, 112 m-. The microprocessor 15 finds out an absolute angle from a table in a memory 151 based on the phase difference signal from the phase counter circuit 14. This is the turning position of a code disk 1 at the present point of time and then the home position returning is finished.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application 1] The present invention relates to improvements in displacement transducers used in robot arms and the like.

[Prior Art] A robot arm is provided with a displacement transducer to detect its joint angle. Incremental displacement transducers lose positional information when the power is turned off.
When the power is turned on, a return-to-origin operation is required.

Conventionally, as an incremental type displacement transducer, the present applicant's Special Issue No. al159-79564 application III
There was something written in. This displacement transducer will be outlined below.

Third. The figure is a block diagram of a code plate of such a displacement converter.

In the figure, a code plate 1, which is a one-turn disc, is provided with an angle detection slit 2 and a reference origin detection slit 3. The angle detection slits 2 are arranged in the circumferential direction at a pitch corresponding to the angle Δθ. The reference origin detection slits 3 are arranged in the circumferential direction at the same pitch as the angle detection slits 2. ! ! Although 31 of the quasi-origin detection slits 3 are in phase with the angle detection slit 2, 32.3
3, the phase shift with respect to the angle detection slit 2 increases linearly with δ and 2δ.

With such a displacement converter, the code plate 1 is rotated in a fixed direction when the power of the robot, etc. is turned on, and the slit 3 for detecting the reference origin is rotated.
The rotation will stop when one of the two is detected. , when the reference origin detection slit 31 is detected, the phase shift from the origin position is 0゛, but the reference origin detection slit 32
If Δθ is equivalent to 360 degrees of electrical angle, the phase shift from the origin is (δ/Δθ)×3
It becomes 60°. Thereafter, the angle is detected using this phase shift as an offset.

[Problems to be Solved by the Invention] However, in such a displacement converter, the reference origin detection slit 31.3 due to interpolation error, eccentricity error, etc. of the code plate 1.
Since the phase shift of 2.33 does not actually change linearly, there is a problem that position reproducibility deteriorates.

The present invention has been made in order to eliminate the above-mentioned problems, and it is an object of the present invention to realize a displacement transducer that has good position reproducibility and has a short return-to-origin operation time.

Means for Solving Problem L] The present invention provides the following features: A code plate serving as a rotating disk has angle detection slits arranged at a predetermined pitch, and a phase difference for the angle detection slits. An optical type that forms arranged reference origin detection slits, detects one of the reference origin detection slits in an origin return operation, and performs displacement conversion taking into consideration the phase difference between the detected slit and the angle detection slit. In the displacement converter, a memory is provided that stores information that associates the actually counted phase difference with the absolute angle of the reference origin detection slit that produces this phase difference, and the information in this memory is used to perform displacement conversion. This is a characteristic displacement transducer.

[Example] Hereinafter, the present invention will be explained using the drawings.

FIG. 1 is a block diagram of an embodiment of a displacement transducer according to the present invention. Components in FIG. 1 that are the same as those in FIG. 3 are given the same reference numerals.

In the figure, 4 is a motor that rotates the code plate 1, and 5 is a motor 4.
This is a motor drive circuit that drives the.

6 and 7 are LEDs that project light into the angle detection slit 2 and the reference origin detection slit 3, and 8 and 9 are angle signal detectors and reference origin signal detectors that detect the light that has passed through the slits 2 and 3.

10 is a reference signal detection circuit, and a reference origin signal detector 9
The light detected is output as a detection signal.

11 is a scanning circuit which scans the output of each light receiving element of the angle signal detector 8 by sequentially closing switches 111, 1', 12, . . . using a shift register (not shown). The output of the scanning circuit 11 is passed through a low-pass filter 12 and an amplifier 13.
The signal is applied to the phase counting circuit 14 via the following.

The phase counting circuit 14 counts the phase difference between the reference origin detection slit 3 and the angle detection slit 2 based on the supplied counting clock signal, and outputs a phase difference signal. In addition, the phase counting circuit 14 uses a clock (hereinafter referred to as CLOCK).
is given to the scanning circuit 11, and the scanning circuit 11 receives the given C.
On the evening of LOCK, switch 111 based on the timing,
112... is opened.

Reference numeral 15 denotes a sub-means, for example, a microprocessor, which contains a phase difference between the angle detection slit 2 and the reference origin detection slit 3 (hereinafter simply referred to as phase difference), and a reference origin detection slit that produces this phase difference. Memory 1 that measures and stores table information that corresponds to absolute angles in advance.
51 are provided. The memory 151 is a non-volatile memory such as an EEPROM (Electrically
Erasable Programmable R
OM) etc. An example of stored information is shown in FIG.

This information is expressed in the number of pulses.

Note that the memory 151 may be located outside the microprocessor 151. The microprocessor 15 calculates the memory 15 based on the phase difference given from the phase counting circuit 14.
1 to read the absolute angle of the reference origin detection slit 3,
An angle command signal based on this is given to the motor drive circuit 5.

With this kind of displacement transducer, when turning on the power of a robot, etc., L
When the ED7 is projecting light between the slits 31 and 32, the motor 4 rotates clockwise (six directions) and the reference origin signal is detected! ! 19 detects the slit 32, it is stopped by the detection signal from the reference origin detection circuit 10.

The phase counting circuit 14 receives the input waveform signal S at this time.
The phase difference between and the reference waveform signal f is determined and sent to the microprocessor 15. Here, the reference waveform signal fR is the switch 1
This is a waveform signal obtained when any one of 11, 112-... is closed.

Microprocessor 15 finds the absolute angle from a table in memory 151 based on the phase difference signal from phase counting circuit 14. This is the current rotational position of the code plate 1. This completes the return-to-origin operation.

Since this position will be used as a reference from now on, the absolute angle found will be an offset.

[Effects] According to the present invention, information that associates the actually counted phase difference with the absolute angle of the reference origin detection slit is stored in advance in the memory, and the origin return operation is performed based on this information. As a result, position reproducibility is improved. Further, since the origin return operation is completed by simply rotating the code plate until the nearest reference origin detection slit is detected, the time required for the operation can be known.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of an embodiment of a displacement converter according to the present invention, FIG. 2 is a diagram showing an example of information stored in the memory of the displacement converter of FIG. 1, and FIG. It is a block diagram of the code plate of a converter. 1... Code plate, 2... Angle detection slit, 3...
・Slit for standard origin detection, 6, 7...LED, 8・
・・Reference origin signal detector, 9 ・・Angle signal detector, 1
5 = control means, 151--memory.

Claims (1)

[Claims] A code plate serving as a rotating disk includes angle detection slits arranged at a predetermined pitch and reference origin detection slits arranged with a phase difference with respect to the angle detection slits. An optical displacement converter that detects one of the reference origin detection slits during the origin return operation and performs displacement conversion taking into consideration the phase difference between the detected slit and the angle detection slit, was used to actually count A displacement converter comprising a memory storing information that associates a phase difference with an absolute angle of a reference origin detection slit that produces this phase difference, and performs displacement conversion using the information in this memory.