Error-compensation of angular displacement measurement based on posteriori error fitting

In the aerospace, military, and industrial fields, which have strict requirements on the volumes of devices, photoelectric encoders require not only a reduction in the size and weight of the outer diameter, but also improvements in the measurement accuracy. In this study, an error compensation method for photoelectric encoders was investigated. The error model parameters were determined based on a posteriori error-fitting method, and then depth error compensation was performed for a small photoelectric encoder. First, the main factors that affect the angle measurement error of the photoelectric encoder were analyzed, and the long-and short-period error models were established. Then, a posteriori error-fitting error compensation algorithm was proposed. Finally, a small photoelectric encoder was tested to verify the performance of the proposed error compensation algorithm. The test results demonstrate that the proposed posteriori error-fitting compensation method can significantly reduce the angle measurement error of the photoelectric encoder. We utilized an encoder to verify this method. The accuracy before compensation is 22.48", and that after compensation is 5.82". This approach employs a posteriori error compensation method, which can directly compensate the encoder error without considering the sizes of the error factors, and possesses the advantages of high efficiency and accurate compensation. The product precision is considerably improved when the photoelectric encoder is mass produced. © 2019, Science Press. All right reserved.