Chattering Suppression for DSP Based Sliding Mode Current Control of PM DC Drives

This paper investigates several chattering suppression methods for DSP based implementation of sliding mode control (SMC). It concentrates on the 'equivalent-control-dependent' and 'state-dependent' gain adjustment methods proposed in recent theoretical studies, and tests the effectiveness of these proposals for current regulation of PM DC drives. The well-known observer-based method was also used for purposes of comparison. Additionally, increasing sampling rate was examined to determine how it affects the amplitude of discretization chattering. These methods may exhibit unsatisfactory results when performed separately, and so various combinations of these methods are tested to find the best solution for chattering elimination. Discontinuous control signal averaging, which is a common chattering reduction technique, is made possible while the system is online by the use of a tunable low-pass filter (LPF). Experimental results demonstrating the effectiveness of each method as well as a combined chattering elimination method are presented and discussed.