The Research And Design Of BLDCM Current Peak Controller Based On DSP

Brushless DC motor(BLDCM)has advantages of high efficiency,simple control,large starting torque and wide speed range.The mechanical properties of BLDCM is similar to traditional DC motor.The traditional DC motor changes the phase by brush and commutation and its maintenance cost is high.But BLDCM changes the phase by electronic commutation instead of mechanical commutation,so BLDCM also has the advantage of low maintenance cost.After decades of development,BLDCM and its control technology are becoming more mature.Its application is also more and more extensive.The basic structure of BLDCM is introduced,including the body of motor,position sensor and inverter.The operation principle of six-phase asymmetrical BLDCM that is studied in the thesis is expounded.The mathematical model of BLDCM is established and the equivalent circuit of BLDCM is gotten.Then the operating characteristic of six-phase asymmetrical BLDCM in the six-phase working state and three-phase working state is analysed.Current peak control strategy is introduced and current peak controller is designed for 22kW six-phase asymmetrical BLDCM that is studied in the thesis.The simulation model of control system is built by PLECS simulation software.Through the analysis of the simulation results,the feasibility of the current peak control is verified and the controller is optimized.An improved PI control method is proposed and the dynamic characteristics of the control system are improved.Hardware and software are designed for the current peak controller that is studied in the thesis.The hardware design of the thesis includes the circuit design of the main circuit,the circuit design of the detection part,the circuit design of the driving part,the circuit design of the current comparison circuit,the circuit design of the protection part and the circuit design of thyristor trigger circuit.The software design of the thesis is based on DSP and CPLD.DSP is the master chip and TMS320F28335 DSP of TI is selected.CPLD is the logic chip and it assists DSP.The main program is designed firstly.Then the CPU timer program,the rotor position detection program,the driver program,the speed measurement program,the detection program and SPI program are designed.Finally,the hardware and the software that are designed in the thesis are tested by experiment.The experimental results show that the current peak controller designed in the thesis can control motor stably and reliably and the current waveform of the motor is ideal square wave.