Rotation angle detection apparatus having function of detecting entry of foreign substance based on frequency characteristic of signals

• US 10,066,971 B2
• Filed: 08/29/2016
• Issued: 09/04/2018
• Est. Priority Date: 08/31/2015
• Status: Active Grant

• Current Assignee: Fanuc Corporation
• Original Assignee: Fanuc Corporation
• Inventors: Nishioka, Akira, Odaka, Shunichi, Imai, Keisuke
• Primary Examiner(s): Le, Que T
• Assistant Examiner(s): Bennett, Jennifer
• Application Number:
  US15/249,854
• Publication Number:
  US 20170059366A1
• Time in Patent Office: 736 Days
• CPC Class Codes: G01D 5/24461 by redundancy or plausibility
• CPC Class Codes: G01D 5/24471 Error correction
• CPC Class Codes: G01D 5/34715 Scale reading or illumination devices
• CPC Class Codes: G01D 5/3473 Circular or rotary encoders

Abstract

A rotation angle detection apparatus includes a rotator having a track unit to detect the rotation angle of a rotation axis; a detection unit disposed in correspondence with the track unit; a rotation angle calculation unit for calculating the rotation angle of the rotation axis based on signals generated by the detection unit; a rotation speed calculation unit for calculating the rotation speed of the rotation axis; and an abnormality detection unit for detecting an abnormality. The abnormality detection unit includes a frequency analyzing unit for calculating the frequency characteristic of the signals; a storage unit for storing the number of the signals per revolution of the rotator; a signal frequency calculation unit for calculating a signal frequency; and a determination unit for detecting the abnormality in the detection apparatus, when the frequency characteristic includes a component of a higher order than the signal frequency.

Claims

1. A rotation angle detection apparatus comprising:

a rotator and a track, the rotator configured to rotate the track around a rotation axis;

a detector disposed in correspondence with the track; and

a processor configured to;

calculate a rotation angle of a rotation axis based on signals generated by the detector;

calculate the rotation speed of the rotation axis based on the signals; and

detect an abnormality based on the signals, by;

calculating a frequency characteristic of the signals;

storing the signals generated from the track per revolution of the rotator;

calculating a signal frequency that is the product of the stored signals and the calculated rotation speed; and

detecting the abnormality, when the frequency characteristic includes a component of a higher order than the signal frequency.