Design Of Direct Torque Control Speeding System Based On DSP For Corless Disk Type PMSM

The disk type PM synchronous motor has high power density and excellent dynamic performance at the same output power or shaft torque. Considering abundant rare earth in China, research on this kind of motor shows great meaning to the development of high performance motor and its driving system.The aim of our study is to design a set of specialized driving system for disk type PMSM that makes full use of its advantage in structure and dynamic performance. Direct torque control method is used by the designed system due to its fast torque response, although it is still in a stage of theoretical study to control PMSM with DTC strategy. This paper proposed to execute DTC on a coreless disk type PMSM to get very fast dynamic torque response. Such work has been done by no one until our study begin.The research of this paper includes the following contents: first of all, the structure characters of coreless disk type PM motor are introduced. The mathematic model of prototype is built according to the results of magnetic circuit analysis and attributes calculation. Then the emphasis is put on theoretical discussion of PMSM DTC. It is mathematically proven that the increase of electromagnetic torque in a permanent magnet motor is proportional to the increase of the angle between the stator and rotor flux linkages. Therefore, the fast torque response can be obtained by adjusting the rotating speed of the stator flux linkage as fast as possible. To improve the steady-state behavior, our design substitutes Space Vector PWM for traditional hysteresis PWM. It leads to the reduction of torque ripple and switching losses of power transistors.Finally, the speeding driving system is designed based on theoretical analysis and computer simulation. High performance hardware with a DSP core is used to match requirements of software programming. Experimental results shows that the coreless disk type motor DTC system has extremely fast torque response and satisfying dynamic performance, and its torque ripple in steady-state is much smaller than normal DTC system.