Encoder system design: Strategies for error compensation

The encoder is the most used angular transducer in position control applications, such as the main axes position control of a telescope. In astronomical applications a very high precision in axes control is required. So a good encoder system design is essential to satisfy the requirements settled by the scientific goals. Today very good encoder systems (glass disk and associated readout electronics) are provided by several suppliers, with multiple readouts and error compensation capabilities to increase the reading precision and lessen the errors. Nevertheless during the lifetime of the system some unexpected errors can arise. In this paper some techniques to recognize, analyze and lessen the unavoidable encoder system error are described, with reference to some case studies.