Sliding mode control of PMSM based on a novel load torque sliding mode observer

An extended sliding-mode observer of the load torque was proposed, of which the state variables were speed and load torque, in order to decrease influence of varying load torque in a permanent magnet synchronous motor (PMSM) control system. Errors between the real and the observed speed were selected as a sliding-mode hyper plane, and the observed load torque was composed of a real load torque and the filtered chattering signal. The observation error converged to zero when sliding mode occurred. A sliding-mode variable structure control (SMC). system of PMSM was designed based on the exponent reaching law, in which the observed load torque was used for feed-forward compensation. Experimental results show that the novel sliding-mode observer can estimate the load torque precisely, and the designed controller can enhance system robustness and suppress the intrinsic chattering of SMC.