Robust PM synchronous motor servo drive with variable-structure model-output-following control

A variable-structure model-output-following controller is proposed in which only output from the plant is needed in the variable-structure control law to enhance the robustness of the control system. The position control of a permanent-magnet synchronous motor servo drive using the proposed control strategy is illustrated. First, an integral-proportional (IP) position controller is systematically designed according to the prescribed drive specifications of command tracking. To allow the specifications to be maintained under operating conditions, the state-space model of the systematically designed inner IP speed loop in the nominal case is chosen as the reference model. Then the proposed controller based on variable-structure control theory is designed and added in the inner speed loop to preserve the control performance. Simulation and experimental results show that the proposed control approach results in an accurate model-following characteristic and is robust with regard to plant parameter variations and external load disturbance