Self-Calibration of On-Axis Rotary Encoders

This paper presents a new self-calibration method for rotary encoders mounted on precision axes of rotation. By measuring encoder pulse widths in the time domain, the angular distance corresponding to each pulse is automatically derived from the spindle free-response dynamics. This method has three distinctive features: 1) instant calibration of the encoder error map without need for an angle measurement instrument; 2) wide applicability to general encoders without requiring multiple read-heads; 3) in-place calibration on the target rotary axis rather than the axis of another calibration system. Experiments and simulations have been conducted to characterize the calibration repeatability and accuracy.