Absolute encoder, signal processing method, program, driving apparatus, and industrial machine

Patent metadata

Field	Value
Publication number	US-9417102-B2
Application number	US-201414554803-A
Country	US
Kind code	B2
Filing date	Nov 26, 2014
Priority date	Nov 29, 2013
Publication date	Aug 16, 2016
Grant date	Aug 16, 2016

Abstract

An absolute encoder includes a scale with a plurality of marks of various types arranged with a space and a period. A detector includes a plurality of elements arranged along a direction corresponding to the aforementioned arrangement, and detects a partial plurality of marks. A signal processor performs amplitude quantization with respect to each period of periodic signals with a plurality of periods output from the detector to generate a data string. First position data having a resolution of the period is generated. The signal processor obtains a plurality of thresholds for the quantization respectively corresponding to a plurality of periodic signals of the periodic signals with the plurality of periods based on a plurality of representative values respectively obtained from the periodic signals with the plurality of periods.

First claim

What is claimed is:

1. An absolute encoder comprising:
a scale in which a plurality of marks including a plurality of types of marks are arranged with a space therebetween and at a period;
a detector including a plurality of elements arranged along a direction corresponding to a direction in which the plurality of marks are arranged, and configured to detect a partial plurality of marks of the plurality of marks by the plurality of elements; and
a signal processor configured to perform quantization of an amplitude with respect to each period of periodic signals with a plurality of periods output from the detector to generate a data string, and generate, based on the data string, first position data which represents an absolute position of the scale or the detector, and has a resolution of the period,
wherein the signal processor is configured to obtain a plurality of thresholds for the quantization respectively corresponding to a plurality of periodic signals of the periodic signals with the plurality of periods based on a plurality of representative values obtained from the periodic signals with the plurality of periods.

2. The absolute encoder according to claim 1 , wherein the signal processor is configured to obtain smoothed data by smoothing the periodic signals with the plurality of periods, and obtain the plurality of thresholds by using the plurality of representative values selected from the smoothed data.

3. The absolute encoder according to claim 2 , wherein the smoothing includes obtaining, with respect to a specified element of the plurality of elements, a total sum of outputs from elements, of the plurality of elements, including the specified element.

4. The absolute encoder according to claim 2 , wherein the signal processor is configured to select the plurality of representative values from the smoothed data based on information on a phase of a signal, with at least one period, of the periodic signals with the plurality of periods.

5. The absolute encoder according to claim 4 , wherein the signal processor is configured to select, as the plurality of representative values, a plurality of higher representative values and a plurality of lower representative values of values, of the smoothed data, respectively corresponding to specified phases of the signal of the periodic signals with the plurality of periods.

6. The absolute encoder according to claim 5 , wherein the signal processor is configured to represent the plurality of higher representative values with a first regression equation, and represent the plurality of lower representative values with a second regression equation, and obtain the plurality of thresholds based on the first regression equation and the second regression equation.

7. The absolute encoder according to claim 6 , wherein the signal processor is configured to obtain each of the plurality of thresholds by averaging a value acquired by the first regression equation and a value acquired by the second regression equation.

8. The absolute encoder according to claim 5 , wherein the specified phases are phases at which the signal of the periodic signals with the plurality of periods have extremum values.

9. The absolute encoder according to claim 4 , wherein the signal processor is configured to generate a plurality of phase signals having phases different from each other based on the signal with the at least one period, and obtain the information on the phase based on the plurality of phase signals.

10. The absolute encoder according to claim 4 , wherein the signal processor is configured to obtain second position data with a resolution higher than a resolution of the period based on the information on the phase.

11. The absolute encoder according to claim 10 , wherein the signal processor is configured to generate data representing an absolute position by connecting the first position data and the second position data respectively as higher bits and lower bits.

12. The absolute encoder according to claim 2 , wherein the signal processor is configured to quantize the plurality of representative values respectively corresponding to the plurality of thresholds respectively based on the plurality of thresholds to generate the data string.

13. The absolute encoder according to claim 1 , wherein the absolute encoder is configured as a rotary encoder.

14. A driving apparatus comprising:
a movable part;
an absolute encoder according to claim 1 configured to measure an absolute position relating to a motion of the movable part; and
a driving device configured to perform driving relating to the motion of the movable part based on an output of the absolute encoder.

15. An industrial machine comprising the driving apparatus according to claim 14 .

16. A signal processing method for an absolute encoder including
a scale in which a plurality of marks including a plurality of types of marks are arranged with a space therebetween and at a period;
a detector including a plurality of elements arranged along a direction corresponding to a direction in which the plurality of marks are arranged, and configured to detect a partial plurality of marks of the plurality of marks by the plurality of elements; and
a signal processor configured to perform quantization of an amplitude with respect to each period of periodic signals with a plurality of periods output from the detector to generate a data string, and generate, based on the data string, first position data which represents an absolute position of the scale or the detector, and has a resolution of the period, the method comprising a step of:
obtaining a plurality of thresholds for the quantization respectively corresponding to a plurality of periodic signals of the periodic signals with the plurality of periods based on a plurality of representative values obtained from the periodic signals with the plurality of periods.

17. A program for causing a computer to execute the signal processing method according to claim 16 .

Assignees

• Canon Kk

Inventors

• Uozumi Takayuki

Classifications

• G01D5/24476

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

• G01D5/34715

  Scale reading or illumination devices · CPC title

• G01D5/34707

  Scales; Discs, e.g. fixation, fabrication, compensation · CPC title

• G01D5/3473

  Circular or rotary encoders · CPC title

• H03M1/00

  Analogue/digital conversion; Digital/analogue conversion (conversion of analogue values to or from differential modulation H03M3/00) · CPC title