| In the field of AC machines control, a strategy called variable frequency control is mostly used. As a high performance and new machines control strategy developed in 1980's, direct torque control (DTC) solves the problems that computation in vector transformation control is complex, the control characters are easily affected by the changes in machines parameters, real results of the experiments can't achieve the level of the theoretical analysis. So now direct torque control has become an emphasis and tendency in the field of AC machines control. However DTC have some bugs at low speed. Some simulation and experiment researches about this strategy are presented in the paper.Firstly, according to the mathematical model of asynchronous machines, the principle of direct torque control and fuzzy control, the theoretical and experimental analysis about approximate round track of flux is proposed in the paper. As to approximate round track, the fuzzy method of voltage vector selection is taken. We can select the proper voltage vector by the position and magnitude of stator flux as well as the magnitude of torque. In addition, the performance criterion is respectively described, and the torque ripple at low-speed is analyzed in this paper. According to a method to adjust the duty ratio coefficient, we select a torque track with adaptation fuzzy controller to simulate. The experimental results show that the control strategy proposed can acquire better control effect.Due to the direct torque control requires very high performance of Real-time, the popular microcomputer core DSP is used as controller in the design of hardware. Its high speed of running is suitable to the experiment. In the main circuit, there is a highly integrated power element: IPM as inverter, which includes seven IGBT, has high switch frequency and fault diagnosis function. IPM greatly decreases the bulk of system. The experimental results show that this control strategy proposed can acquire better control effect.
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