Design Of The Direct Torque Control For Asynchronous Motor Based On DSP

The Direct Torque Control(DTC) is an another high performance AC Servo-control method after the Vector Control. The Direct Torque Control attracts more and more attention due to its direct control method,rapid reponse system,good robustness,excellent static and dynamic characteristics.The paper presents the development of AC Servo-control technology and then analyzes the basic principle and the basic framework of asynchronous motor direct torque control. It presents the arithmetic equation of flux and torque in stator coordinate by mathematical deduction according to the arithmetic model of the asynchronous motor. It deduces u-i flux model and i-n flux model, and the proper area and features of these two models are analyzed, then presents a u-n model which is suitable in all speed area. Futhermore,after the analysis of the state of converter switches, the dual closed loop control of flux and torque is discussed. The paper presents a mixed torque adjusted metheod,which is combined with the hexagon stator flux trace method and round stator flux trace. It adjusts torque with Bang-Bang control.A typical AC-DC-AC general voltage source frequency converter is used in the main circuit.IRFP460 of ST Corporation is the core componet of the main circuit,which is a N-Channel Power MOSFET with antiparallel diode.DSP(TMS320LF2407A) of TI Corporation which includes DSP control circuit, source circuit,sampling circiut, is used as the core-processing chip of the digital control system. It integrates many special modules in motor control system, and decrease peripheral instruments labor. The software of the system is developed through Assmeble Language,which includes A/D sampling, flux model,model switch and speed PI adjuster,etc.At the end of this paper, the performance of the whole system is analyzed briefly. The results of the experiment show that the control methods described in this paper can achieve good control performance, rapid response,strong reliability,which can be broadly applied in industrial field.