A Realization Of Speed Sensor-less Direct Torque Control System Based On DSP

The strategy of Direct Torque Control is one of the variable frequency speed control scheme, which was developed in 1985 by Prof. Depenbrock and which was one of high performance control of Induction motor drives after Vector Control. The merits of DTC lie in the simplicity of the control structure , fast torque response , better robustness and being more prone to digital control. Although DTC have made fast progress in recent year, it has disadvantage in the theory and performance that not good at low speed operation and having serious pulsating torque .Aim at the DTC's blemish mentioned above and the direction of DTC technique development, the dissertation put great emphasis on the work as follows, with an eye to exalt DTC system function:(1) A new speed-flux observer of an induction motor is proposed to enhance the accuracy of flux observing, which is an adaptive closed-loop flux observer and different from the traditions. A new adaptive speed-observation-way is deduced out according to the Popov's stability theories;(2) To improve the performance of DTC at low speed operation, we have to exalt the accuracy of the stator flux estimation and a new way of BP neural network based on extended PIDBP algorithm is given to estimate and tune the stator resistance of an induction motor to increase the accuracy of the stator flux estimation;(3) Digital signal processor is adopted to realize digital control. An device of Direct Torque Control system is designed for experiment using TMS320LF2407 chip produced by TI company ;(4) Bring up a distributed Direct Torque Control system based on SERCOS bus, SERCOS stand for Serial Real Time Communication System agreement which is most in keeping with synchronous with moderate motor control;(5) The basic design frame of the hardware and software of the whole control system is given here and some concrete problem in the experiments is described here in detail.