Absolute encoder, angle error correction device in absolute encoder, and method for correcting angle error in absolute encoder

An angle deviation correction device in an absolute encoder, the device comprising:

• a computer configured to determine, on the basis of angle information indicating an angle of a rotating body with reference to a position at a time of start-up, specifically angle information for one rotation from the time of start-up, and a predetermined coefficient, an offset value for correcting an angle deviation indicating a difference between an angle indicated by the angle information and an actual angle of the rotating body to reduce a maximum value of the angle deviation, the angle information being generated on the basis of a value of a predetermined physical quantity varying depending on a rotation of the rotating body, wherein
• the computer offsets each value of the angle deviation with reference to the position at the time of start-up according to the offset value;
• the coefficient is calculated on the basis of the angle deviation;
• the coefficient is a Fourier coefficient of the angle deviation in one of cycles predetermined;
• and
• the offset value is obtained by summing values obtained by calculating the coefficient for each of the cycles and performing an inverse Fourier transform on the coefficient.

A method for correcting an angle deviation in an absolute encoder, the method comprising:

• determining, by a computer, on the basis of angle information indicating an angle of a rotating body with reference to a position at a time of start-up, specifically angle information for one rotation from the time of start-up, and a predetermined coefficient, an offset value for correcting an angle deviation indicating a difference between an angle indicated by the angle information and an actual angle of the rotating body to reduce a maximum value of the angle deviation, the angle information being generated on the basis of a value of a predetermined physical quantity varying depending on a rotation of the rotating body;
• and
• offsetting, by the computer, each value of the angle deviation with reference to the position at the time of start-up according to the offset value, wherein the coefficient is calculated on the basis of the angle deviation;
• the coefficient is a Fourier coefficient of the angle deviation in one of cycles predetermined;
• and
• the offset value is obtained by summing values obtained by calculating the coefficient for each of the cycles and performing an inverse Fourier transform on the coefficient.