Absolute position detecting device and method

Patent metadata

Field	Value
Publication number	US-10145709-B2
Application number	US-201615223527-A
Country	US
Kind code	B2
Filing date	Jul 29, 2016
Priority date	Mar 4, 2016
Publication date	Dec 4, 2018
Grant date	Dec 4, 2018

Abstract

An absolute position detecting device and method are provided. The absolute position detecting device utilizes the incremental magnetization on a magnetic encoding ruler with two different pole widths, such that elliptical Lissajous curves may be obtained by magnetoresistive sensors. The absolute position may be obtained by determining the region of the signals on the ellipses read by the magnetoresistive sensors.

First claim

What is claimed is:

1. An absolute encoder, comprising:
a magnetic encoding ruler, comprising:
a first magnetic path on which a plurality of first magnetic poles with opposite polarities are successively arranged, wherein a length of each of the plurality of first magnetic poles is a first pole width;
a second magnetic path, parallel to the first magnetic path, on which a plurality of second magnetic poles with opposite polarities are successively arranged, wherein a length of each of the plurality of second magnetic poles is a second pole width, and the first pole width and the second pole width are different from each other;
a first magnetoresistive sensor disposed adjacent to the first magnetic path to detect magnetic fields of the first magnetic path and to generate a first magnetoresistive signal;
a second magnetoresistive sensor disposed adjacent to the second magnetic path to detect magnetic fields of the second magnetic path and to generate a second magnetoresistive signal; and
a processor electrically connected to the first and the second magnetoresistive sensors to respectively receive the first and the second magnetoresistive signals;
wherein the absolute encoder is configured to output the first and the second magnetoresistive signals;
wherein the lengths of north/south poles of the plurality of the second poles comprise second to Nth pole widths, and the lengths of the second to N th pole widths are different from each other;
wherein when the magnetic encoding ruler moves relative to the first and the second magnetoresistive sensors along a longitudinal direction of the magnetic encoding ruler, the processor is configured to generate a first elliptical pattern according to the first magnetoresistive signal and a second elliptical pattern according to the second magnetoresistive signal, and to generate a unique relation of the first elliptical pattern and the second elliptical pattern.

2. The absolute encoder of claim 1 , further comprising a database electrically connected to the processor, the database storing absolute position information, and the absolute position information respectively defining relationships between positions on the first and the second elliptical patterns and positions on the magnetic encoding ruler;
wherein after the processor is configured to generate the first and the second elliptical patterns, the processor is further configured to compare the first and the second elliptical patterns with the absolute position information to obtain the absolute position on the magnetic encoding ruler.

3. The absolute encoder of claim 2 , wherein the first magnetoresistive signal comprises a first A-phase signal and a first B-phase signal, the second magnetoresistive signal comprises a second A-phase signal and a second B-phase signal, and the processor is configured to generate the first elliptical pattern according to the first A-phase signal and the first B-phase signal, and to generate the second elliptical pattern according to the second A-phase signal and the second B-phase signal.

4. The absolute encoder of claim 2 , wherein the plurality of first magnetic poles and the plurality of second magnetic poles are arranged along the longitudinal direction of the magnetic encoding ruler.

5. An absolute position detecting device adapted to detect an absolute position of an object, comprising:
a magnetic encoding ruler, comprising:
a first magnetic path on which a plurality of first magnetic poles with opposite polarities are successively arranged, wherein a length of each of the plurality of first magnetic poles is a first pole width;
a second magnetic path, parallel to the first magnetic path, on which a plurality of second magnetic poles with opposite polarities are successively arranged, wherein a length of each of the plurality of second magnetic poles is a second pole width, and the first pole width and the second pole width are different from each other;
a sensor module adhered to the object, comprising:
a first magnetoresistive sensor disposed adjacent to the first magnetic path to detect magnetic fields of the first magnetic path and configured to generate a first magnetoresistive signal; and
a second magnetoresistive sensor disposed adjacent to the second magnetic path to detect magnetic fields of the second magnetic path and to generate a second magnetoresistive signal;
a processor electrically connected to the first and the second magnetoresistive sensors to respectively receive the first and the second magnetoresistive signals, wherein when the object moves relative to the magnetic encoding ruler, the processor is configured to generate a first elliptical pattern according to the first magnetoresistive signal, and to generate a second elliptical pattern according to the second magnetoresistive signal, and to calculate the absolute position of the object according to the first and the second elliptical patterns;
wherein the lengths of north/south poles of the plurality of the second poles comprise a second to Nth pole widths, and the lengths of the second to Nth pole widths are different from each other;
wherein the absolute position of the object is generated according to a unique relation of the first and the second elliptical patterns.

6. The absolute position detecting device of claim 5 , further comprising a database electrically connected to the processor, which stores absolute position information, the absolute position information respectively defining relationships between positions on the first and the second elliptical patterns and positions on the magnetic encoding ruler; and
wherein after the processor is configured to generate the first elliptical pattern and the second elliptical pattern, the processor is further configured to compare the first elliptical pattern and the second elliptical pattern with the absolute position information to obtain the absolute position of the object on the magnetic encoding ruler.

7. The absolute position detecting device of claim 5 , wherein the first magnetoresistive signal comprises a first A-phase signal and a first B-phase signal, the second magnetoresistive signal comprises a second A-phase signal and a second B-phase signal, and the processor is configured to generate the first elliptical pattern according to the first A-phase signal and the first B-phase signal, and to generate the second elliptical pattern according to the second A-phase signal and the second B-phase signal.

8. The absolute position detecting device of claim 5 , wherein the plurality of first poles and the plurality of second poles are arranged along a longitudinal direction of the magnetic encoding ruler.

9. A method of detecting an absolute position adapted to the absolute position detecting device of claim 5 , comprising following steps of:
adhering an object to the sensor module;
moving the object relative to the magnetic encoding ruler, the first magnetoresistive sensor and the second magnetoresistive sensor respectively outputting the first magnetoresistive signal and the second magnetoresistive signal;
receiving the first magnetoresistive signal and the second magnetoresistive signal by the processor, and generating a first elliptical pattern according to the first magnetoresistive signal and a second elliptical pattern according to the second magnetoresistive signal, respectively; and
calculating the absolute position of the object on the magnetic encoding ruler according to the first and the second elliptical patterns by the processor;
wherein lengths of north/south poles of the plurality of the second poles comprise a second to Nth pole widths, and the lengths of the second to Nth pole widths are different from each other;
wherein the absolute position

Assignees

• Univ Nat Tsing Hua

Inventors

• Lin Cheng-Yi
• Hsiao Heng-Sheng
• Wang Sheng-Ching
• Chin Tsung-Shune
• Sung Cheng-Kuo
• Chang Jen-Yuan

Classifications

• G01D5/2452 Primary

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