Adaptive Load Torque Observer for Permanent Magnet Synchronous Motor Based on a Modified Compound Sliding Mode Reaching Law

For the sake of enhancing the disturbance suppression ability of permanent magnet synchronous motor (PMSM) systems, an adaptive load torque observer (LTO) based on a modified compound sliding mode reaching law (MCSMRL) for disturbance feedforward compensation is proposed in this article. Firstly, a LTO is designed based on a integral sliding surface and the exponential reaching law to achieve load torque estimation and feedforward compensation. Besides, in order to reduce the chattering of the load torque estimated by the conventional LTO, a MCSMRL is proposed to reconstruct an adaptive LTO. The stabilities of the proposed MCSMRL and the LTO have been proven through the Lyapunov stability theory. Finally, the numerical simulation results for PMSM systems show that the proposed approach has better performance in load torque observation and suppression.