Electronic absolute position encoder

Patent metadata

Field	Value
Publication number	US-9683869-B1
Application number	US-201514966379-A
Country	US
Kind code	B1
Filing date	Dec 11, 2015
Priority date	Dec 11, 2015
Publication date	Jun 20, 2017
Grant date	Jun 20, 2017

Abstract

An electronic absolute position encoder comprises a scale, a detector and a signal processing configuration. The scale comprises a signal modulating scale pattern including a first periodic pattern component having a spatial wavelength λ 1 , and a second periodic pattern component having a spatial wavelength λ 2 . The detector comprises a set of first wavelength sensing elements comprising a first filtering subset of first wavelength sensing elements and a second filtering subset of first wavelength sensing elements including complementary pairs of sensing elements spaced apart by an integer number times 180 degrees of the spatial wavelength λ 2 . The detector comprises a set of second wavelength sensing elements comprises a first filtering subset of second wavelength sensing elements and a second filtering subset of second wavelength sensing elements including complementary pairs of sensing elements spaced apart by an integer number times 180 degrees of the spatial wavelength λ 1 .

First claim

The invention claimed is:

1. An electronic absolute position encoder, the electronic absolute position encoder comprising:
a scale extending along a measuring axis direction and including a signal modulating scale pattern comprising a first periodic pattern component as a function of position along the scale having a spatial wavelength λ 1 , and a second periodic pattern component as a function of position along the scale having a spatial wavelength λ 2 ;
a detector comprising sensing elements arranged along the measuring axis direction, the sensing elements comprising:
a set of first wavelength sensing elements configured to provide a first set of detector signals which respond to the signal modulating scale pattern; and
a set of second wavelength sensing elements configured to provide a second set of detector signals which respond to the signal modulating scale pattern; and

a signal processing configuration that determines an absolute position of the detector along the scale based on detector signals provided by the detector,
wherein:
the set of first wavelength sensing elements comprises:
a first filtering subset of the set of first wavelength sensing elements that each span across the first and second pattern components; and
a second filtering subset of the set of first wavelength sensing elements that each span across the first and second pattern components;
wherein the first and second filtering subsets of the set of first wavelength sensing elements are arranged such that each sensing element of the first filtering subset forms a complementary pair with a sensing element in the second filtering subset that is spaced apart from it along the measuring axis direction by an integer number times 180 degrees of spatial phase difference in terms of the spatial wavelength λ 2 ; and

the set of second wavelength sensing elements comprises:
a first filtering subset of the set of second wavelength sensing elements that each span across the first and second pattern components; and
a second filtering subset of the set of second wavelength sensing elements that each span across the first and second pattern components;
wherein the first and second filtering subsets of the set of second wavelength sensing elements are arranged such that each sensing element of the first filtering subset forms a complementary pair with a sensing element in the second filtering subset that is spaced apart from it along the measuring axis direction by an integer number times 180 degrees of spatial phase difference in terms of the spatial wavelength λ 1 .

2. The electronic absolute position encoder of claim 1 , wherein:
the signal processing configuration is configured to process the first set of detector signals to provide first wavelength spatial phase measurement signals wherein signal components due to the second periodic pattern component are suppressed, and to process the second set of detector signals to provide second wavelength spatial phase measurement signals wherein signal components due to the first periodic pattern component are suppressed.

3. The electronic absolute position encoder of claim 2 , wherein:
the signal processing configuration is configured to process the first wavelength spatial phase measurement signals and determine a spatial phase measurement for the set of first wavelength sensing elements relative to the spatial wavelength λ 1 , and to process the second wavelength spatial phase measurement signals and determine a spatial phase measurement for the set of second wavelength sensing elements relative to the spatial wavelength λ 2 .

4. The electronic absolute position encoder of claim 1 , wherein:
the sensing elements in each complementary pair of the set of first wavelength sensing elements are spaced apart at K1*180 degrees of spatial phase difference in terms of the spatial wavelength λ 2 , where K1 is an integer; and
the sensing elements in each complementary pair of the set of second wavelength sensing elements are spaced apart at K2*180 degrees of spatial phase difference in terms of the spatial wavelength λ 1 , where K2 is an integer.

5. The electronic absolute position encoder of claim 4 , wherein K1 and K2 are even integers.

6. The electronic absolute position encoder of claim 5 , wherein:
the signal processing configuration is configured to provide a difference signal between signals arising in the sensing elements of each complementary pair;
the difference signals of the set of first wavelength sensing elements provide first wavelength spatial phase measurement signals wherein signal components due to the second periodic pattern component are suppressed;
the difference signals of the set of second wavelength sensing elements provide second wavelength spatial phase measurement signals wherein signal components due to the first periodic pattern component are suppressed; and
the signal processing configuration is configured to process the first wavelength spatial phase measurement signals and determine a spatial phase measurement for the set of first wavelength sensing elements relative to the spatial wavelength λ 1 , and to process the second wavelength spatial phase measurement signals and determine a spatial phase measurement for the set of second wavelength sensing elements relative to the spatial wavelength λ 2 .

7. The electronic absolute position encoder of claim 1 , wherein:
the set of first wavelength sensing elements is configured to provide detector signals corresponding to N spatial phases spaced apart at 360/N degrees of spatial phase difference in terms of the spatial wavelength λ 1 ; and
the set of second wavelength sensing elements is configured to provide detector signals comprising a second set of N detector signals corresponding to N unique spatial phases spaced apart at 360/N degrees of spatial phase difference in terms of the spatial wavelength λ 2 .

8. The electronic absolute position encoder of claim 7 , wherein N=3.

9. The electronic absolute position encoder of claim 7 , wherein N=4.

10. The electronic absolute position encoder of claim 7 , wherein:
the first filtering subset of the set of first wavelength sensing elements comprises N sensing elements spaced a distance λ 1 /N apart; and
the first filtering subset of the set of second wavelength sensing elements comprises N sensing elements spaced a distance λ 2 /N apart.

11. The electronic absolute position encoder of claim 1 , wherein:
the scale comprises a cylindrical shape having a cylinder axis aligned parallel to the measuring axis direction with the first periodic pattern component formed as notches or grooves arranged along the scale and the second periodic pattern component formed as notches or grooves arranged along the scale; and
the sensing elements comprise loops which encircle the scale.

12. The electronic absolute position encoder of claim 11 , wherein the first and second periodic pattern components comprise notches formed in respective first and second tracks along the scale.

13. The electronic absolute position encoder of claim 1 , wherein:
the scale comprises a flat substrate comprising a first material; and
the first periodic pattern component and the second periodic pattern component are formed from a second material fabricated on or embedded in the flat substrate, the second material having a different magnetic property than the first material.

14. The electronic absolute position encoder of claim 1 , wherein:
the scale comprises a first flat substrate that extends along the measuring axis direction and the first periodic pattern component and the second periodic pattern component are formed a

Assignees

• Mitutoyo Corp

Inventors

• Kapner Daniel John

Classifications

• G01D5/2452

  incorporating two or more tracks having an (n, n+1, ...) relationship · CPC title

• G01D5/2497 Primary

  Absolute encoders (G01D5/2454 takes precedence) · CPC title

• G01D5/20 Primary

  by varying inductance, e.g. by a movable armature · CPC title

• G01D5/2006 Primary

  by influencing the self-induction of one or more coils (G01D5/22 takes precedence) · CPC title