Research Of Control System For Brushless DC Motor Based On DSP

Brushless DC motor(BLDC)is a new type of motor which emerges with the development of permanent magnet and power switching technology.It uses electronic commutation instead of the mechanical commutation and maintains the superior speed performance of DC motor while overcoming friction,spark and other weak points of the mechanical commutation process.With these advantages,it is applied in all walks of life.Therefore,the research on the control system of BLDC is of great significance and value.The thesis introduces the structure and working principle of BLDC and studies the speed control methods after establishing the mathematical model of BLDC.From all the speed control methods,we choose PWM modulation.The thesis also makes a research on the traditional PID control and fuzzy control algorithm.Considering the non-linear and multivariable characteristics of BLDC,a new control algorithm combined PID control to fuzzy control is proposed to reach the control requirement.In MATLAB,we build a model of the double closed loop control system of BLDC and simulate it.The results proved the advantage of the fuzzy PI control over traditional PI control.Finally,a hardware platform was built with TMS320F28335 processor as the control core,combine with drive circuit,inverter circuit,sampling circuit and isolation circuit.On the basis of simulation and hardware system,we designed the software of the control system by using C and assemble program language in integrated development environment CCS.The software realized the generation of PWM,the current detection,the calculation of rotational speed,the update for the PWM duty cycle.After completing joint debugging of hardware and software for system,experiment is implemented.Compared to traditional control system,the fuzzy PI control system has advantages of quicker response,smaller overshoot and stabler performance.Then summaries for the whole design are given and options for subsequent work are put forward finally.