Analysis and Comparison of Different Control Strategies for a Ventricular Assist Device
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Tipus de documentProjecte/Treball Final de Carrera
Condicions d'accésAccés restringit per decisió de l'autor
The aim of this thesis is to make a comparison between different methodologies to control a Ventricular Assist Device. To find these control trajectories, are defined several objectives that are interesting to study. The objectives that are calculated are the minimization of the flow though the pump cannula, the minimization of the left ventricular work, minimization of the wall stress in the left ventricle and the optimal speed trajectory that fulfills a proper cardiac output with the lowest energy consumption. The obtained trajectories must satisfy two constraints: Backflow through the VAD cannula is not allowed and the cardiac output has to be 5 l/min. Each method consists in different procedures. The first case, and defined as standard, is to actuate the pump with a current that provides a constant speed. This solution is compared with the ones obtained with other procedures, that always provide better trajectories that minimize the objective parameters. Some of the trajectories to evaluate have been obtained using a non-linear optimization program, which minimizes the objective functions. The trajectories obtained with this method are trajectories which optimally minimize the objective functions. Another procedure consisting in a sine wave speed input control has been implemented. This procedure calcules all the sine wave speed trajectories that meet the desired cardiac output. This sine waves are designed using two parameters, a relation between the mean and the amplitude, and the phase shift. The feasible solutions that minimize the objectives, are studied and compared with the other solutions. As expected, the optimal solutions always provide the better solutions. However, with a sine wave input control also significantly minimizes the objective functions. At last, the optimal solutions are tested in a hybrid mock circulation, in order to assure that the results are experimentally reproducible.