Robust speed controller for a PMSM drive

A robust speed controller based on mixed sensitivity is presented to improve the speed control performance of the PMSM servo system. Selecting suitable state variables and choosing appropriate weighting functions, the state equation of the system is built and the vibration of system is quantitatively described. Then the robust control problem comes down to the solution of Riccati equation. Changing the parameter of the weighting functions can get the desired parameters of the robust controller. Simulation results demonstrate that compared with conventional PI control, the robust controller can reduce the speed ripple and has good attenuation to disturbance of load impact. Simulation results also show that there is a trade-off between the dynamic performance and the robustness. There should be a comprise between rise time, overshot of speed response and robustness to inertia.