Speed ripples reduction of a non-linear loaded synchronous motor through fuzzy algorithms commutation

The main objective of this paper is to show that fuzzy logic can be used for three different reasons at the same time: providing a powerful control law with high dynamic performances and robustness first; for nonlinear phenomena minimisation; and for algorithms soft commutation. This paper first presents an efficient onsite tuning strategy for a fuzzy logic PI controller, which is devoted to the speed control of a permanent magnet synchronous motor. This onsite tuning strategy is based on the experimental designs methodology. The obtained experimental results combine a high performances level with a very good robustness on an industrial benchmark. However, due to a static friction torque angular nonuniformity on the considered electromechanical system, some speed ripples appear during the steady-state. In this paper, the authors propose to take into account this nonlinear phenomenon in order to reduce the resulting speed ripples as much as possible without any torque compensation strategy and without reducing the performances of the control law on the chosen benchmark. Therefore, two fuzzy rules tables are proposed, one designed to act near the steady-state operating point and to reduce the speed ripples, another designed to act at some distance of this point. To avoid sharp modifications in the control value applied to the system, a fuzzy algorithms commutation between these two tables is proposed. Parameters of this algorithm commutation are tuned using a simplex optimisation algorithm. The provided experimental results show a significant reduction of the speed ripples without any alteration of the general system response.