The stability analysis of the position control system with disturbance observer for induction machine drive

The design of the position-tracking control system for induction machine drive is presented. The system consists of direct-axis current PI (proportional-plus-integral) regulator, quadrature-axis current PI regulator, a position loop feedback PD (proportional-plus-derivative) controller and a disturbance observer (DOB). The stability conditions of the position control system with DOB for induction machine drive are given in frequency domain and time domain respectively. The position-tracking performance has been examined by experiments under the external disturbance. The performance of the system with DOB plus PD has been compared with PD. The results show that DOB plus PD has a better ability to deal with the external disturbance. Through experiments, speed measurement delay-dependent stability of the system has been studied. The conclusion is that the DOB plus PD can also handle large inertia load variations.