Research On Brushless DC Motor Direct Torque Control Based On DSP

The rare-earth square-wave permanent magnet brushless DC motor control system is a new type of system developed rapidly in recent years. The brushless DC motor (BLDCM) is a DC using electronic commutation instead of the mechanical commutation, so it has excellent characteristics of DC motors, such as good start and timing performance, and on the other hand it overcomes the friction disadvantages of ordinary DC motor radically with its simple brushless structure. It has been extensively used in many industrial domains, such as aviations, robots, digital machine tools, and in medical or home appliances. But the BLDCM has the disadvantages of torque pulsation, which is in the way of achieving accurate position and speed control with higher performance. This thesis research the direct torque control of square-wave brushless DC motor.In this thesis, the brushless DC motor is analyzed in detail. Taking three-phase BLDCM for example, its buildup, conduction modes and the basic running principle are introduced in this paper. Based on its mathematic model, the simulation model is established under Power System Block of MATLAB toolbox. Then double closed-loop control is adopted to simulate. Based on analyzing PMSM direct torque control thinking, mathematical models and the structure of control systems, a direct torque control scheme of brushless DC motor is given. Directly analysis the electrical model of BLDCM with the mathematical in the stator coordinates, control the flux and torque of BLDCM. Simulation studies show that the direct torque control scheme can effectively inhibit the brushless DC motor torque ripple.Based on the simulation, a DSP-based-control system has been designed. Then the control software and system debug were completed. The design of control hardware included control circuit, current sampling circuit, position detection circuit, drive and inversion circuit. Modular software design method is used.The studies of the paper have positive significance in reduce torque ripple of brushless DC motor.