ERROR ANALYSIS AND CHARACTERIZATION FOR OPTICAL ENCODERS

Abstract

An optical encoder is a transducer that converts mechanical motion into electrical signals and is commonly used for precise position, velocity, and direction measurements. In space ap plications, optical encoders offer significant advantages, including high precision, non-contact sensing, compactness, reliability, low power consumption, and compatibility with digital sys tems. These benefits enable accurate and reliable position sensing and control of spacecraft components, contributing to mission success, resource optimisation, and improved spacecraft performance. An absolute transmissive optical encoder with a resolution of approximately 19 bits is be ing sought for its high resolution and accuracy requirements. The output signal of this encoder exhibits various errors, including wide-angle and narrow-angle errors. Wide-angle errors are brought on by the eccentricity of the coded-disc axis of rotation, whereas narrow-angle errors are caused by spectral impurities and mismatches between sine and cosine signals. To identify and correct errors in both fine and coarse bits, fine rollover and coarse correction methods are employed. To minimize errors and enhance accuracy, several compensation techniques are uti lized, such as normalization, linear interpolation, harmonic approximation, and the ratiometric technique. The effectiveness of these techniques is evaluated through phase difference analy sis, amplitude mismatch analysis, and spectral analysis. This comprehensive approach aims to improve both accuracy and resolution