Observer-based load disturbance compensation for motor drive with DSP implementation

Abstract

The paper presents a methodology to make the load torque disturbance compensation based on the normal state observer. First, a state feedback controller is designed to achieve a satisfied speed command tracking performance. Then a multi-purpose state observer is constructed to observe the motor states (current and speed), as well as to provide the disturbance compensation. Since the variable of load torque is beyond the motor system state space model, some observation error will be inevitably existed in the observed states. Based on the demonstrated mathematics derivation, the state observation error feedback can be isolated from the exact state feedback. Such a state observation error feedback actually constructs some kind of feedforward compensation for the load disturbance. If the observer gain is picked up appropriately, then the effect of the load torque variation can be considerably compensated, such that the system performance deviation will be greatly attenuated. Both MATLAB/Simulink simulation and dSPACE DSP-based implementation have confirmed its effectiveness in the permanent magnetic synchronous motor (PMSM) drive system.