Rotary encoder

Patent metadata

Field	Value
Publication number	US-2018231402-A1
Application number	US-201815895288-A
Country	US
Kind code	A1
Filing date	Feb 13, 2018
Priority date	Feb 14, 2017
Publication date	Aug 16, 2018
Grant date	—

Abstract

A rotary encoder may include a magnet, a magnetic sensor, and a control part configured to calculate a rotation position of the rotor body based on an output signal outputted from the magnetic sensor. The control part includes a temperature detecting section configured to detect temperature of the magnetic sensor, an offset voltage calculation section configured to calculate an offset voltage of the magnetic sensor based on the output signal from the magnetic sensor, and a storage section which stores a slope and an intercept of a primary approximate expression calculated by a relationship between temperatures previously detected by the temperature detecting section and the offset voltages previously calculated by the offset voltage calculation section. The control part executes offset voltage estimate processing based on the slope and the intercept stored in the storage section and correction processing which corrects the output signal from the magnetic sensor.

First claim

What is claimed is:

1 . A rotary encoder structured to detect a rotation position of a rotor body with respect to a fixed body, the rotary encoder comprising:
a magnet which is provided in one of the fixed body and the rotor body; a magnetic sensor part which is provided in the other of the fixed body and the rotor body so as to face the magnet and is structured to detect a magnetic field change of the magnet; and a control part configured to calculate a rotation position of the rotor body based on an output signal outputted from the magnetic sensor part accompanied with rotation of the rotor body; wherein the control part comprises:
a temperature detecting section configured to detect temperature of the magnetic sensor part;
an offset voltage calculation section configured to calculate an offset voltage of the magnetic sensor part based on the output signal from the magnetic sensor part; and
a storage section configured to store a slope and an intercept of a primary approximate expression which is calculated by a relationship between temperatures previously detected by the temperature detecting section and the offset voltages previously calculated by the offset voltage calculation section;
wherein the control part is configured to perform:
offset voltage estimate processing which estimates an offset voltage of the magnetic sensor part from current temperature of the magnetic sensor part detected by the temperature detecting section based on the slope and the intercept which are stored in the storage section; and
correction processing which corrects the output signal from the magnetic sensor part based on the estimated offset voltage; and
wherein the control part is configured to calculate a rotation position of the rotor body by using a corrected output signal.

2 . The rotary encoder according to claim 1 , wherein when a total sum of the temperatures previously detected is “A”, a total sum of the offset voltages previously calculated is “B”, a total sum of products of the temperatures previously detected and the offset voltages previously calculated is “C”, and a total sum of squares of the temperatures previously detected is “D”, the slope “a” and the intercept “b” are given by:
a =( C−AB )/( D−A 2 ), and
b =( DB−CA )/( D−A 2 ).

3 . The rotary encoder according to claim 2 , wherein the control part is configured such that, in a case that a difference between the offset voltage calculated by the offset voltage calculation section at a predetermined temperature and the offset voltage estimated at the predetermined temperature is not less than a predetermined value, the control part updates the intercept stored in the storage section based on the difference.

4 . The rotary encoder according to claim 3 , wherein
the magnet comprises a plurality of magnets, the magnetic sensor part comprises a plurality of magnetic sensor parts, and the control part is configured to calculate a rotation position of the rotor body based on a plurality of the output signals of the plurality of the magnetic sensor parts and executes the offset voltage estimate processing and the correction processing for the plurality of the magnetic sensor parts.

5 . The rotary encoder according to claim 4 , wherein
the plurality of the magnets comprises a first magnet in which one “N”-pole and one “S”-pole are disposed in a circumferential direction of the rotor body, and a second magnet in which a plurality of “N”-poles and a plurality of “S”-poles are alternately disposed in the circumferential direction of the rotor body, the plurality of the magnetic sensor parts comprises at least one magnetic sensor part which faces the first magnet, and a magnetic sensor part which faces the second magnet, the plurality of the magnetic sensor parts comprises:
a first magneto-sensitive element which is disposed so as to face a magnetized face of the magnet and is structured to output an “A”-phase signal in a sine wave shape accompanied with rotation of the rotor body; and
a second magneto-sensitive element which is disposed so as to face the magnetized face of the magnet and is structured to output a “B”-phase signal in a sine wave shape having a phase difference of 90° with respect to the “A”-phase signal accompanied with rotation of the rotor body.

6 . The rotary encoder according to claim 5 , wherein the offset voltage calculation section is configured to perform:
forming a Lissajous waveform on a rectangular coordinate system based on the “A”-phase signal and the “B”-phase signal; selecting successive three points from a plurality of points equally dividing circumference of the Lissajous waveform; and calculating the offset voltage of at least the one magnetic sensor part corresponding to the first magnet based on an intersecting point of perpendicular bisectors of two line segments formed by connecting successive two points of selected three points.

7 . The rotary encoder according to claim 5 , wherein the offset voltage calculation section is configured to perform:
forming a Lissajous waveform on a rectangular coordinate system based on the “A”-phase signal and the “B”-phase signal; specifying four points which are located in vicinities of four intersecting points of the Lissajous waveform and the coordinate axes; and calculating the offset voltage of the magnetic sensor part corresponding to the second magnet based on a predetermined value, the predetermined value being added to or subtracted from at least one of the “A”-phase signal and the “B”-phase signal so that the four points specified are substantially equally separated from an origin of the coordinate axes.

8 . The rotary encoder according to claim 5 , wherein each of the magneto-sensitive elements comprises a magneto-resistance effect element.

9 . The rotary encoder according to claim 2 , wherein
the magnet comprises a plurality of magnets, the magnetic sensor part comprises a plurality of magnetic sensor parts, and the control part is configured to calculate a rotation position of the rotor body based on a plurality of the output signals of the plurality of the magnetic sensor parts and executes the offset voltage estimate processing and the correction processing for the plurality of the magnetic sensor parts.

10 . The rotary encoder according to claim 9 , wherein
the plurality of the magnets comprises a first magnet in which one “N”-pole and one “S”-pole are disposed in a circumferential direction of the rotor body, and a second magnet in which a plurality of “N”-poles and a plurality of “S”-poles are alternately disposed in the circumferential direction of the rotor body, the plurality of the magnetic sensor parts comprises at least one magnetic sensor part which faces the first magnet, and a magnetic sensor part which faces the second magnet, and the plurality of the magnetic sensor parts comprises:
a first magneto-sensitive element which is disposed so as to face a magnetized face of the magnet and is structured to output an “A”-phase signal in a sine wave shape accompanied with rotation of the rotor body; and
a second magneto-sensitive element which is disposed so as to face a magnetized face of the magnet and is structured to output a “B”-phase signal in a sine wave shape having a phase difference of 90° with respect to the “A”-phase signal accompanied with rotation of the rotor body.

11 . The rotary encoder according to claim 1 , wherein the control part is configured such that, in a case that a difference between the offset voltage calculated by the offset voltage calculation section at a predetermined temperature and the offset voltage estimated at the predetermined temperature is not le

Assignees

• Nidec Sankyo Corp

Inventors

• Okumura Hirokatsu
• Saito Yutaka
• Joko Hitoshi

Classifications

• G01D5/24485 Primary

  using other sensors · CPC title

• G01D5/24476 Primary

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

• G01D5/24495

  using previous values · CPC title

• G01D5/2451

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

• G01D5/2497 Primary

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