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
