Rotational Speed Control Strategy Of Permanent Axial Blood Pump In Large Gap

As the core component of the artificial heart, the main function of the blood pump was to realize the blood pump function instead of the natural heart. So the control method of the blood pump system was the primary problem for the clinical application of the artificial heart.According to the study on magnetic drive technology of blood pump, the rotational speed of blood pump, which had a directory relationship with the human physiological state, was the primary control parameter of system. However, the control strategy of blood pump lacked depth study, and the startup process stability, the speed control rapidity and the operation stationarity could be all improved. Besides, there were some other problems of system, such as high energy lose, serious heat and bulky driving device. The relationship of the cotrol parameters (current, frequency and driver program), the performance parameters (torque and power) and the output state parameters (speed, flow and pressure) lacked depth research.In this paper, taking the rapid and stable speed control and the safety and reliable monitor of the operation parameters as the target, and throughing researching on drive characteristics, energy lose, torque-frequency and torque-angle, the control strategy of blood pump was proposed, to realize the feedback control of the blood pump and to provide a reference for adaptive control system.The main contents and conclusions:1. Design of the blood pump feedback control systemAccording to the human physiological regulatory mechanisms and the strock volume (SV) of different physiological state (different pressure), the blood pump feedback control system was established. Then taking the flow as the feedback control parameter, the automatic adjustment of the output flow under different pressure was realized.2. Establishment of the energy loss mathematical model of magnetic driver system According to the eddy current loss, hysteresis loss and copper loss, the energy loss mathematical model of the magnetic driver system was established. Then the influence law of the core shape on iron loss was simulated. The results show that the core shape had little influence on hysteresis loss and has5%influences on eddy current loss of the asymmetrical core shape.3. The magnet states control methods based on torque-angle characteristicsAccording to the voltage-current equation, the mathematical model of the torque-frequency and torque-angle characteristics was established. Through researching the affection of frequency, the magnet states control method was proposed, which could obtain the maximum magnetic drive torque.4. The control methods of the startup current based on torque-frequency characteristicsAccording to the mathematical model of the energy loss and the torque-frequency characteristics, the minimum energy loss control method of the startup current was proposed. Then based on the dynamic model of the startup process, the speed control method of blood pump for rapid response was proposed. The experimental results show that the blood pump could reach the rated output power within2s.5. The control methods for constant power outputAccording to the stable operation process of blood pump, the control methods for constant power output under different coupling distance was presented, which could realize the constant power output under different coupling distance. Then based on the formula of the magnet state deviation angles, the maximum touque control method was proposed, to improve9.5%of the maximum torque.