Study On The Digital Control System For Brushless DC Motor Using DSP

Permanent magnet brushless DC motor (PMBLDCM) has extensive applications in industrial environments due to its excellent performances. This paper discusses the speed control system for BLDCM using TMS320LF2407 DSP.In the paper, the development of BLDC motor control in our country and abroad is summarized first, and the control methods of BLDC motor as well as the structure and characteristics of TMS320LF2407 DSP is introduced in brief.In the area of hardware design, the system uses TMS320LF2407 DSP as microprocessor, and uses intelligent power module (IPM) as inverter, which is drived by high-speed optocouplers. And the signal-sampling circuits of the position, current, speed are also designed. The whole system's hardware has a very compact structure and can operate with high reliability.Adopting simultaneously the C and assemble language, the software development is based on the CCS2000 integrated development environment. For less occupancy of system resources and more precision, the decimal fraction in DSP is realized by the Q representation. The system software involves five main modules: initialization module, phase-changing module, current-regulating module, speed-regulating module and timer interrupt module. Only onegeneral-purpose timer Tl is used in the software to achieve such functions as PWM output, the production of signal collecting time-sequence and speed loop and current loop period, etc.In designing system controller, the parameters of plant are first recognized. Then, according to the classical control theory and the transfer function model of BLDC motor, controllers are designed and realized in order from inner loop (current-loop) to outer loop (speed-loop).The three-phase model of the BLDC motor is analyzed using MATLAB6.1. In additional, the load torque observer is simultaneously employed to achieve the feedforward compensation for the required unknown load torque. Based on the state feedback, the speed control system is set up, and the simulation waveforms are also given in the paper. This simulations analysis indicates that this control system has a highly robust performance under the load torque disturbance.The experimental waveforms of currents and voltages are showed in the paper. It can be seen than experimental results are relatively perfect. Through the study of the project, the following conclusions can be made:1. My careful writing results from many references to the literature of BLDC motor.2. TMS320LF2407 DSP, which has powerful performance, can help simplify hardware structure and increase system reliability when used in sensorless control system for permanent magnet brushless DC motor.3. IPM has such advantages as high integration level, high reliability, simple driving control circuit and small hardware size etc., which shows that it is a perfect switch element. But the protection of devices should still be attached importance to.4. The overall design abides by the principles considering security, reliability, simplicity and practicality, and the control scheme has considerable guiding significance to practical products.In conclusion, proved by experiments, the control scheme presented and designed in the paper is feasible and the control system studied in the paper meets the requirements of design task.