Driving Control And Flow Measuring System Design Of A Heart Simulator

Nowadays, owing to the quickening pace of life and irregular diet, cardiac diagnosis and cardiovascular system have become the researching hotspot in domestic and overseas. Because of the complexity of cardiac structure and working mechanism, it is unlikely to operate on patients or sampling research directly. Animal experiments are faced with complex configuration, ethics and huge cost. So it is urgent to design a dynamic heart simulator system to provide a real experimental platform for the hemodynamic characteristics of the cardiovascular system, artificial heart and cardiac catheter interventional research.An actuating control and flow detection system was built based on the human cardiac physiological structure and blood pumping characteristics in this paper. The main research contents and results are as follows:Firstly, the pneumatic actuating control system was designed. The actuating device composed of motor, crank, piston rod and cylinder was designed by analyzing the pneumatic working mechanism of the cardiac phantom. On the basis of Windkessel theory, researched the blood flow of the heart and then regarded the left ventricle as elastic cavity, indentified the parameters of the driving gear and the output function. As the power source of the actuating device-motor, we used the analog voltage to control its speed, the FPGA as the machine master controller, through D/A conversion to regulate beating frequency of the simulator.Secondly, for the case that the stability and fast response characteristic of the motor would be affected under high speed or a sudden change of the speed, we designed the speed closed-loop PID controller for the motor. Using Ziegler-Nichols method which is the most commonly used engineering tuning method to identify the proportion, integral and the differential coefficient. Actuating control of the heart simulator's beating rate was realized finally.Thirdly, the transit-time ultrasonic flow detection system including the ultrasonic transmitting and receiving circuit and the software program about sequential control of the ultrasonic emission signals, the communicating control of TDC_GP2 and the PC serial communication was designed. The system realized the measurement of time difference which is only nanoseconds and the measurement of fluid flow in silicone pipeline of the heart simulatorFinally, to regulate the working state of the heart simulator and research its output characteristics more intuitively and easily, the PC measurement and control interface based LabVIEW8.6 was designed. It mainly contains the serial communication, the motor's PID parameter settings, the time difference data processing and the display of the flow curves. The performance testing experiments of whole measurement and control system was carried out. It verified that the design of the heart simulator's driving control and flow detection system is very meaningful for the research of the cardiac blood flow characteristics.The heart simulator system can simulate the contraction and relaxation vividly. We can adjust the beating rate conveniently and precisely to simulate the blood flow under different physiological environment. The blood flow changes can be detected by ultrasonic flow measurement system. It can be used for teaching demonstration, the hemodynamic characteristics of the cardiovascular system research, the performance testing of artificial heart blood pump, the development of medical imaging equipment and so on.