Incremental Optical Encoder Error Modeling and Compensation for Accurate Speed Acquisition in Non-Stationary Conditions

Instantaneous angular speed (IAS) signals are widely used in motor control and fault detection. However, incremental optical encoders inevitably suffer from engraving and subdivision errors during manufacturing and installation, resulting in reduced accuracy of angle measurement and calculated IAS signals. Existing error compensation methods have limitations such as low efficiency and inapplicable for nonstationary conditions. To address above issues, an error model is developed to reveal the relationship between these errors and IAS signal fluctuations. Subsequently, a novel error compensation approach is proposed to reduce the engraving and subdivision errors while considering the disturbances of both the servo motor and the mechanical system. To verify the accuracy of the error model and the feasibility of the error compensation method, simulation analysis and actual experiments were carried out on an rotary vector (RV) reducer test rig. The experimental results that the proposed error compensation method can eliminate approximately 53.52% of the encoder errors, and can be executed in real-time.