Flux observer of induction motor based on “assumed inherent sensor” inversion

In induction motor vector control system, the obtaining of accurate rotor flux is of essential significance. Based on the “assumed inherent sensor” reverse principle, a new method for observing flux is proposed. It firstly assumes that there exists a subsystem inside the induction motor, whose inputs are just the to-be-estimated variables while outputs the measurable variables and establishes the mathematical model of the subsystem. Then it analyzes the reversibility of the subsystem according to inverse system theory, and establishes the flux observer inverse model. Compared with traditional observation method, the proposed method provides a precise mathematical model with high measurement accuracy for observing flux. Simulation results show that: the inverse method of observation is extremely robust to changes of the rotor resistance and load and can achieve an accurate observation of the rotor flux.