High-performance position detection and velocity adaptive measurement for closed-loop position control

This paper presents a new solution for processing the pulses from an optical encoder attached to a motor shaft, and deriving the rotational speed information. An adaptive method allows the evaluation of the motor rotational speed with very good accuracy even at very low speeds. The adaptation also of the sampling period, according to the instant rotational speed, results in better response times at medium or high rotational speeds. The measurement accuracy at low speeds using the proposed method is improved, compared to currently known methods. Another significant advantage of using the proposed circuit is that it can be implemented in specific hardware, thus, reserving the full computational power of the controlling digital signal processor (DSP) for high-level control tasks and for future software expansions.