Eccentricity calculating method, rotary encoder, robotic arm and robot apparatus

Patent metadata

Field	Value
Publication number	US-10514255-B2
Application number	US-201715695365-A
Country	US
Kind code	B2
Filing date	Sep 5, 2017
Priority date	Sep 30, 2016
Publication date	Dec 24, 2019
Grant date	Dec 24, 2019

Abstract

The present invention provides: a rotary encoder checking an eccentricity state of a scale by sensor units; and related matters. The scale moves, relatively to the sensor units, around a rotational axis line. The pair of sensor units are arranged opposite to each other sandwiching the rotational axis line C 0 therebetween. A processing system acquires output signals from each of the sensor units, at a plurality of rotation angles at which the scale has moved relatively to the sensor units. The processing system determines first phase information based on the output signal obtained from the sensor unit, and second phase information based on the output signal obtained from the sensor unit. The processing system determines eccentricity information based on a differential value between any one of the first phase information and the second phase information and an average value of the first phase information and the second phase information.

First claim

What is claimed is:

1. A detecting method for detecting eccentricity information of an encoder,
wherein the encoder has a scale in which a pattern is arranged, and has a pair of sensor units that read the pattern of the scale,
wherein the scale moves, relatively to the pair of sensor units, and
the pair of sensor units are arranged so as to be opposite to each other sandwiching a rotational axis line therebetween,
the detecting method comprising:
acquiring an output signal from each sensor unit of the pair of sensor units, in a plurality of rotation angles by which the scale has been moved relatively to the pair of sensor units;
determining first information based on the output signal that has been obtained from one of the pair of sensor units, and second information based on the output signal that has been obtained from the other one of the pair of sensor units;
determining an average value of the first information and the second information;
determining a differential value between any one of the first information and the second information and the average value; and
detecting the eccentricity information, based on the differential value.

2. The detecting method according to claim 1 , wherein the eccentricity information is an eccentricity quantity from an amplitude of a periodic fluctuation component.

3. The detecting method according to claim 2 , further comprising:
extracting the periodic fluctuation component by a Fourier analysis or least-square method.

4. The detecting method according to claim 2 , wherein the angle range in which the scale rotates is smaller than 360 degrees, and components other than the angle range in the periodic fluctuation component are determined by extrapolation processing.

5. The detecting method according to claim 1 , wherein, an angle range in which the scale rotates is 360 degrees or larger.

6. The detecting method according to claim 1 , wherein the pattern comprises:
a first track having a plurality of first marks that are arranged around a center line, and
a second track that is arranged outside of the first track, and has second marks which are arranged, and of which the number is different from that in the first track, and
each of the pair of sensor units reads the first track and the second track.

7. The detecting method according to claim 1 , wherein the encoder is an absolute type.

8. An encoder system comprising:
a scale in which a pattern is arranged;
a pair of sensor units that read the pattern of the scale,
wherein the scale moves relatively to the pair of sensor units, and
the pair of sensor units are arranged so as to be opposite to each other sandwiching a rotational axis line therebetween; and
a processing unit that outputs signals of the scale for the pair of sensor units, based on output signals obtained from the pair of sensor units,
wherein the processing unit:
acquires an output signal from each sensor unit of the pair of sensor units, at a plurality of rotation angles to which the scale has been moved relatively to the pair of sensor units;
determines first information based on the output signal that has been obtained from one of the pair of sensor units, and second information based on the output signal that has been obtained from the other one of the pair of sensor units;
determines an average value of the first information and the second information;
determines a differential value between any one of the first information and the second information and the average value; and
detects eccentricity information, based on the differential value.

9. The encoder system according to claim 8 , wherein the encoder system is an absolute type.

10. A robotic arm comprising:
a pair of links that are connected to each other by a joint; and
the encoder according to claim 8 ,
wherein in the encoder, the scale is arranged in one of the pair of links, and the pair of sensor units are arranged in the other one of the pair of links.

11. A robot apparatus comprising:
the robotic arm according to claim 10 ; and
a warning unit that issues warning according to the eccentricity information.

12. The robot apparatus according to claim 11 , wherein the warning unit emits different colors according to the eccentricity information, as the warning.

13. The robot apparatus according to claim 12 , wherein the warning unit has a plurality of lamps which emit light of different colors, respectively.

14. The robot apparatus according to claim 11 , further comprising:
a display unit which displays the eccentricity information thereon.

15. A robot apparatus comprising:
the robotic arm according to claim 10 ; and
a display unit which displays the eccentricity information thereon.

16. An imaging apparatus comprising:
rotation driving mechanisms; and
the encoder according to claim 8 .

17. A non-transitory computer-readable recording medium storing a computer readable control program for operating a computer to execute a detecting method for detecting eccentricity information of an encoder,
wherein the encoder has a scale in which a pattern is arranged, and has a pair of sensor units that read the pattern of the scale,
wherein the scale moves, relatively to the pair of sensor units, and
the pair of sensor units are arranged so as to be opposite to each other sandwiching a rotational axis line therebetween,
the program comprising code to execute:
acquiring an output signal from each sensor unit of the pair of sensor units, in a plurality of rotation angles by which the scale has been moved relatively to the pair of sensor units;
determining first information based on the output signal that has been obtained from one of the pair of sensor units, and second information based on the output signal that has been obtained from the other one of the pair of sensor units;
determining an average value of the first information and the second information;
determining a differential value between any one of the first information and the second information and the average value; and
detecting the eccentricity information, based on the differential value.

Assignees

• Canon Kk

Inventors

• Horiguchi Haruhiko

Classifications

• G01D5/24476

  Signal processing (G01D5/2448 - G01D5/24495 take precedence) · CPC title

• G01D5/24471

  Error correction · CPC title

• G01D5/34

  the beams of light being detected by photocells · CPC title

• G01D5/36

  Forming the light into pulses · CPC title

• G01D5/12

  using electric or magnetic means (G01D5/06 takes precedence) · CPC title