|
Abstract:
|
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. |
