Sequential delay-free strategy for sliding mode position observer considering analog and digital implementations of PMSM drives

This paper proposes a sequential delay-free strategy to avoid side effects of the delays arising from both analog and digital implementations of permanent magnet synchronous machine (PMSM) drives on the accuracy of sliding mode position observers used in the high-speed conditions. First, after establishing the sliding mode observer (SMO) used for position estimation, the principles of the analog delay, low-pass filter (LPF) delay and execution delay together with their impacts are presented at length, posing the necessity of investigating the delay-free techniques. Then, novel current-based, position-based and speed-prediction-based compensation strategies are developed to deal with the three kinds of delays, respectively. Because the proposed compensation strategies are achieved based on the direct signal compensation theories, they are simple to be understood and implemented in practice. Third, the implementation sequence of the sequential delay compensation-based SMO is illustrated clearly. Thanks to the proposed delay compensation approaches, not only the position estimation accuracy but also the current regulation process of the closed-loop control can be improved. Finally, experiment is conducted on a three-phase 8000 rpm PMSM to verify the effectiveness of the proposed delay compensation-based SMO algorithms.