Modeling and control of transition dynamics in a two-piston toroidal blood pump
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Ventricular Assist Devices (VADs) are becoming more and more popular as a treatment option for patients with weak or failing hearts, and this has made research into the analysis and control of VADs more necessary. This thesis is a study of the modeling and control of transition dynamics of the pistons in the TORVAD, a toroidal VAD developed by Windmill Cardiovascular Systems, Inc. (WCS, Inc., Austin, TX). The main objective of this thesis is to design a model-based control strategy for trajectory tracking in the transition phase of the TORVAD with minimal oscillations in the control voltages provided to the motors. A bond graph-based hybrid model of the pump is designed for better understanding of the fluid-mechanical coupling in the TORVAD, as well as performance comparison of the designed controllers. Using a simplified version of the pump model as the nominal plant, a model-based cascaded controller is designed and compared with an error-based PID control strategy. Results for specified testing trajectories, and a preliminary robustness analysis of the two control strategies are presented, and the cascaded control strategy is shown to generate control voltages which are much less oscillatory than that of the PID control strategy.