Improved velocity estimation for low-speed and transient regimes using low-resolution encoders

This paper presents a new estimation method, entitled the asynchronous sampling pulse method (ASPM), for determining velocity in systems with low but variable speeds, and/or with low-resolution encoders. The ASPM forces the estimator procedure to synchronize with the actual encoder pulse input, thus eliminating encoder positioning error independent of target velocity variations. This method is based on using an auxiliary sampling period to measure the time interval between the moment of encoder input and the control sampling instant, and its precision is shown to be dependent only on this auxiliary sampling period. Thus, the ASPM improves over existing methods in which estimator performance is dependent on both target acceleration and encoder resolution. Simulation and experimental results are used to verify the method.