Sensorless Control Of Blood Pump Motor In Artificial Heart

Heart failure has become a serious disease threat to human life and health, the artificial heart is an important means for the treatment of heart failure. Artificial heart need to meet the requirements of small size and high reliability, so the pump device in the artificial heart- brushless DC motor need to adopt a sensorless control technology. This paper takes the maglev artificial heart prototype developed by CH Biomedical,Inc. as the research object, design a drive system for the prototype based on sensorless brushless dc motor control method.Firstly, the paper introduces the background and development of the artificial heart generally. For the motor type used in artificial heart, the paper overviews brushless dc motor and permanent magnet synchronous motor sensorless control method respectively.Secondly, the paper introduces the working principle of brushless dc motor and rotor position detection technology based on back emf zero test principle. At starting stage, back emf is too small to commutate accurately, we use pre-position starting method as the starting method for the blood pump motor. In addition, in view of the back emf waveform in the artificial heart blood pump motor is sine distribution, to eliminate the commutation torque ripple existing in square-wave driving, accordingly reduce noise, improve efficiency, this paper conducts simulation research of the sensorless control of permanent magnet synchronous motor technology in the sine wave driving mode. Based on the analysis of permanent magnet synchronous motor vector control and sliding mode variable structure control theory, using sliding mode observer to achieve sensorless control of permanent magnet synchronous motor. For chattering problem in the sliding mode control, the paper introduces saturation function instead of switching function and feeds the back emf estimation back to the observer to suppress the chattering. Matlab/Simulink simulation results verify the accuracy of the sliding mode observer to estimate speed and rotor position.Then design the artificial heart blood pump motor driven system based on microprocessor STM32F103ZET6. Hardware circuit including: power and its drive circuit, back emf detection circuit, the bus voltage testing and overvoltage protection circuit, current sampling and overcurrent protection circuit and power supply circuit. For software implementation aspects, gives the flow chart of main program and key subprogram, including: the pre-position starting subroutine, AD sampling interrupt subroutine, commutation subroutine according to the back emf.Finally, this paper sets up the artificial heart test platform in the imitation of human blood circulation system, and then test the drive system with the prototype. The blood pump motor speed response is tested under the condition of no-load and pulsating load. The preliminary experimental results show that the artificial heart can run smoothly under the pulsating load which simulates heartbeat, the control goal is achieved and lay the foundation for further experiments.