Antialiasing Encoder Interface With Sub-Nyquist Sampling

A technique is presented for reconstructing absolute position or angle from time-sampled outputs of incremental encoders. Unlike existing techniques, the new method is able to track analog quadrature outputs with frequency contents higher than the Nyquist frequency. The algorithm is described in detail, and both the existing and new methods are tested using a linear position sensor and a high-speed hydraulic actuator. The results from these tests demonstrate aliasing and incorrect tracking for the existing algorithm and correct tracking for the new algorithm. The technique is an excellent complement to resolution-enhancing encoder interfaces that sample raw analog encoder outputs