Robust speed tracking of networked PMSM servo systems with uncertain delay

When a Permanent Magnet Synchronous Motor (PMSM) closes its feedback loop over a digital network, uncertain network-induced delays could degrade its performance. The torque disturbance is another source to harm the performance of PMSM. This paper proposes a robust controller design method to reduce and quantify the effects of the delay and torque disturbance. By introducing an efficient controller structure, we transform the originally nonlinear PMSM model into a linear one. Then we design a controller robust against the feedback delay and the torque disturbance. A sufficient conditions for the robust stability is given in the form of matrix inequalities. Moreover, an upper bound on the H-∞ performance of the PMSM is provided to quantitatively measure the robustness against the uncertain feedback delays and torque disturbance. Simulations were done to verify the correctness and effectiveness of the obtained results.