A new improved method of motor speed identification for direct torque control of the asynchronous motor

Two speed estimators are designed respectively for direct torque control system of the asynchronous motor in this paper. One is MRAC identification model with high-pass and low-pass filter part based on traditional MRAC theory, besides, an improved u-n magnetic chain observer method has been adopted. We employ improved u-n magnetic chain observation method to get magnetic chain, enhance accuracy of the magnetic chain calculation, and overcome the limitation of pure integral magnetic chain calculation. Computer simulations are made in the high-speed section and low-speed section respectively. Simulation results prove that the improved method enhances identification precision and control performance of the whole system, and overcome fluctuates of the torque and motor speed. The other is the motor speed identification method based on neural network. This method not only needn´t model on control objects, but also can overcome the effect of the changing parameters and improve the robustness of the system by ANN´s learning and self-optimizing abilities. In addition, a new improved direct torque control (DTC) method based on the speed identification is proposed in this paper, and it has a better control performance, higher identification precision and practical significance. Finally, we adopt TMS320F240 digital signal processor to build relevant equipment system, and the validity of this method has been demonstrated by the experiment results.