An Alternative Hybrid Super-Twisting Differentiator for a Motor Control System

Motor actuators require accurate estimates of the velocity. When a velocity sensor is not available, the speed must be obtained by numerically differentiating the position signal. Several differentiators are proposed in the literature, all of them returning signals which are affected, at different levels, by noise and time delays. This paper proposes an alternative version of the so-called Hybrid Super Twisting Differentiator (HSTD) recently proposed in the literature. The novel HSTD, whose stability is investigated in the paper, changes its behaviour depending on the operating conditions of the system, in order to reduce noise and time delays. It is particularly suited for motor applications: as proven in the paper by means of an experimental test bench, it estimates the velocities better than alternative differentiation techniques.