Design of a Cardiovascular Flow Mimicking Pump
Brake, Christopher F.
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In vitro testing is an important part of the development of new cardiovascular prosthesis designs. One important aspect of simulating the cardiovascular system is properly modeling the pulsatile flow created by the heart. To test prosthesis' effect on the blood flow and the vessels themselves, it must be possible to reproduce the complex, time varying flow generated by the heart. Therefore, there is a need for a pump that is capable of delivering complex, time varying flows that can be easily adapted to mimick waveforms in a range of vessels. A novel pump has been developed that can output a wide variety of complex pulsatile waveforms at physiologically relevant flows. The design uses a linear actuator to drive a piston pump. With closed loop velocity reference tracking of a piston head, the flow can be accurately controlled. A prototype pump was constructed as a proof of concept for the design. The prototype showed that basic linear control theory is insufficient to achieve accurate velocity control. The friction characteristics of the pump are the main source of nonlinearity in the system. The next step was to apply a LuGre model based friction compensator. Since the pulsatile flow in cardiovascular systems frequently oscillates around the zero velocity point, adequate friction compensation is critical to achieve accurate flow control. The pump has been used to output two waveforms so far. For a first attempt the results are encouraging, but the control system needs improvement to better track reference waveforms. The continued development of this novel cardiovascular mimicking pump has potential to provide a pump that fills the current gap in the available products.