System Dynamics Modelling of Ncku Electro-Hydraulic Total Artificial Heart

The establishment of a dynamic model is critical for a successful design of a long-term implantable total artificial heart (TAH). The TAH currently under design in National Cheng Kung University (NCKU) is a pulsatile device driven by an electro-hydraulic actuation system. Modular approach has been adopted in the system design which includes modules such as impeller, switching valve, stepping and torque brush-less DC motors, blood chambers, artificial valves, and shunt flow mechanism, etc. Each module has been modelled using subsystem performance maps, fluid dynamic conservation laws, and/or electromagnetic and circuit equations. To close this TAH hydraulic loop, the Utah Circulation Model (UCM) was employed to represent the cardiovascular system to he connected with. Bronchial shunt flow was accounted for by interconnecting a branch between the pulmonary arterial and aortic lumped elements in the UCM circuit. Critical parameters of the TAH system were identified using experimental data obtained from the subsystem rig test results. This integrated TAH and physiological circulation system results in a non-linear dynamic system of 1 5 state variables. The evaluation of the TAH subsystem has been conducted to gain insightful information for components improvement. Closed-loop simulations of the coupled TAH and UCM system reveal in detail many useful understandings of how TAH and human cardiovascular system interact under both healthy and pathologic conditions. The influence of TAH shunt design was also studied to see whether the present TAH can deliver differential cardiac outputs as required by the human physiology.