Correction value derivation apparatus, displacement amount derivation apparatus, control apparatus, and correction value derivation method

A correction value derivation method for deriving a correction value used in correction of a displacement amount derived based on an encoder signal indicating a change in position of a movable portion as a target, comprising:

• deriving a detected displacement amount of the movable portion based on the encoder signal;
• deriving a detected displacement velocity based on the detected displacement amount derived in the deriving the detected displacement amount;
• calculating an average displacement velocity by calculating an average of detected displacement velocities derived in the deriving the detected displacement velocity over ½N of one period of a change in displacement velocity indicated by the encoder signal, wherein N is a positive integer;
• and
• deriving the correction value based on a difference between the detected displacement velocity and the average displacement velocity.

A non-transitory computer-readable storage medium storing a program for deriving a correction value used in correction of a displacement amount derived based on an encoder signal indicating a change in position of a movable portion as a target, said program controlling a computer to function as:

• a displacement amount derivation unit configured to derive a detected displacement amount of the movable portion based on the encoder signal;
• a displacement velocity derivation unit configured to derive a detected displacement velocity based on the detected displacement amount derived by said displacement amount derivation unit;
• an average displacement velocity calculation unit configured to calculate an average displacement velocity by calculating an average of detected displacement velocities derived by said displacement velocity derivation unit over ½N of one period of a change in displacement velocity indicated by the encoder signal, wherein N is a positive integer;
• and
• a correction value derivation unit configured to derive the correction value based on the detected displacement velocity and the average displacement velocity.