High-Performance Control System For Induction Motor Based On Embedded Platform

Induction motor owns characteristics as follows:simple structure, low manufacturing cost, reliable and efficient run, maintenance-free, which is widely used in industry, agriculture, national defense, science and technology and other fields. Direct torque control technology has superior control performance, it is an AC variable speed technology comparable with vector control now. Its advantages are simple structure, good dynamic characteristics, good robustness and ease digital control, and it reduces the dependence on motor parameters. However, the problem of direct torque control are poor low speed performance and large torque ripple.For the problem of conventional direct torque control, fuzzy controller is designed based on fuzzy theory in this thesis, it will solve the pulse problem of direct torque control, so it can greatly enhance the accuracy of motor torque control, and improve the dynamic and static performance of system. Meanwhile, the speed controller of traditional AC speed control system uses conventional PI regulator, it have a greater dependence on motor parameters and the stability of system,when the system is disturbed or motor parameters change, PI controller parameters can not be adjusted in real time. A fuzzy adaptive PI controller is adopted in this thesis, it can regulate the PI controller parameters online, so it not only achieves the effect of PI controller, but also improves the adaptive capacity and the robustness of system.Stator resistance is an important parameter in direct torque control, its accuracy greatly affects accuracy of flux, so resistance identification is prerequisite; at the same time, direct torque control must introduce speed feedback in order to get high-performance speed control. However, in practice, the installation of speed sensor not only increases system cost and complexity of motor, but also reduces reliability of system, so it is necessary to make speed identification. The theory based on model reference adaptive is applied in this paper, it devises the interactive MRAS identifier, through the exchange of reference model and adjustable models, it will complete the identification of stator resistance and speed.Basing on fuzzy adaptive theory and parameter identification theory, we use Matlab/Simulink software to establish simulation model of adaptive fuzzy direct torque control system, and build simulation model of parameter identification, then the feasibility of method can be verified in line with simulation results.