Direct Torque Control Of A New Fuzzy Sliding Mode Controller,

Direct torque control (DTC) system for induction motor has got a wide attention with the advantage such as its new thought, simple control scheme, and excellent performance. In this thesis the author made a study of asynchronous motor model, designed a simulation system of DTC and analyzed the characteristics of the DTC system and the existing problems detailed.As a high-performance AC driving system, the speed controller in DTC system is always conventional PI adjuster, which can't make the system have enough quick response , the ability to restrict the noise and strong robustness to the parameters of the system. So the author designed a speed regulator based on sliding-mode control theory, which make the system has strong robustness to the parameters, excellent dynamic and steady-state performance. Simulation results show the method is effective.Variable structure control with sliding mode is a kind of nonlinear control method, which is used quite widely at present time because of its global robustness against parameters variations and external disturbance. But for the realistic system, the effect of sliding mode control can't be infinity, so the process of reaching sliding mode may be cost a lot of time , otherwise because of the inertia of the system , the chattering can't be avoid. But if eliminate the chattering, and then the system will have no robustness.For the chattering problem, a new method----using fuzzy controladjuster reaching law on-line is presented. It combines the advantages of fuzzy control and sliding mode control, as a result, the system can reach the steady-state with more quick response and the chattering can be reduced. Computer simulation results show it is correct and efficient.