Measurement and compensation of errors in absolute encoder using dual absolute encoder system

Abstract

The dual absolute encoder (DAE) system is a measurement system for a motion control system that comprises two absolute encoders and one reduction mechanism. In terms of accuracy and measuring range, DAE is superior to ordinary dual encoder systems, which comprise one incremental encoder, one absolute encoder, and a reduction mechanism. In this study, we focus on the error measurement and compensation using DAE system. There have been many studies to measure and compensate for the errors in measuring systems. However, this typically demands high precision equipment to measure the errors, and attaching and detaching the equipment affects the errors. We measured the errors in the absolute encoder by using the DAE systems solely. The measured errors are modeled using harmonic functions and compensated for by using the modeled errors. The experimental results reveal that the maximum errors and mean absolute errors decrease by one-seventh and one-twelfth, respectively, after error compensation. As a result, we can compensate the errors in the encoders with the encoder system, itself. Additionally, the modeled errors in a DAE system are observed to remain constant even when changing the reduction ratios between two absolute encoders. Once the errors are measured and modeled in the DAE system, the modeled errors can be applied to a DAE system with a different reduction ratio for error compensation.