Research On A Brushless Direct Current Motor And Its Control System In Axial Blood Pumps

With the passage of time and the improvement of people's standard of living, heart diseases become more and more serious. Artificial heart is the important weapon on solving the problem of heart disease. The research of artificial heart has made progress continuously. Based on the research of artificial heart, axial pump is adopted in the article because it is small in size, simple in structure, integrated with pump and motor. The author designed and manufactured the stator of the motor, designed and manufactured its control system based on Digital Signal Processor (DSP). In the motor, the impeller turning with the permanent magnet rotor in the blood pump carries out its function.Firstly, in this hesis, the background, status and development trend is summarized, the progress of this issue is introduced, and then development history and trends of BLDCM are presented. Those knowledge will help readers understand the thinking and significance of the design in this thesis.The BLDCM integrated in the pump is introduced, running principle of three-teeth slotted BLDCM is analyzed. Based on works of predecessors, the author also ameliorated the stator of BLDCM, redesigned its size, shape and winding mode, and probed into its performance.Based on the mathematic and operational principle of BLDCM, the author educed its mathematic module and made its simulation module with Simulink and SimPowerSystems modules in Matlab, and carried through some simulations on the relations of PWM modulation methods and torque ripples of BLDCM, discussed how different drive circuits and PWM modulation methods affect torque ripples of the motor, and finally chose the three-phase inverter with buck converter as the drive plan.Control strategy without position sensor based on DSP is used, in which the speed and torque of the motor are controlled through double-loop control of speed and current. The main drive circuit, rotor's position detecting circuit, speed detecting circuit and drive protecting circuit based on DSP board are designed, the selection of some important electronic components and their parameters in these circuits is analyzed, the control programs, including start-up of the motor, position detecting, phase shifting and speed adjusting programs are also designed. This part is the main work of this thesis. In the end, the task uses the designed motor and the control system conducting an experiment and the experiment gets the expected results.