The number of patients that are waiting for heart transplants far exceed the number of available donor hearts. Left Ventricular Assist Devices are mechanical alternatives that can help and are helping several patients. They work by taking blood from the left ventricle and ejecting that blood into the aorta.
In the University of Louisville they are developing a similar device that will take the blood from the aorta instead of the ventricle. This new device is called an Artificial Vasculature Device. In this project the arterial system and AVD are modeled and a simple control algorithm for the AVD proposed.
The arteries are modeled as a tube with linear resistance and inertia followed by a chamber with linear compliance and last a tube with linear resistance. The model is identical to the 4-element Windkessel model. The values for the resistances, inertia and compliance are identified using pressure and flow measurements from the ventricle and aortic root from a healthy patient. In addition to the Windkessel model the aortic valve is also modeled. The valve is modeled as a drum that closes the aorta and the parameters identified like before. The measurements are also used to model the left ventricle by assuming it has a constant compliance profile.
The AVD is modeled using common modeling structures for servo motors and simple structures for tubes and pistons. The values for the AVD could not be measured and identified so they are fetched from preliminary motor and part specifications.
The control algorithm for the AVD uses a wanted load to create a reference aortic flow. This wanted aortic flow is then achieved by using a PI controller. With these models and controller the interaction between the arterial system and AVD is investigated.
With this preliminary understanding of the interaction further research can be made in the future to improve the understanding and improve the AVD itself.
Source: Linköping University
Author: Nyblom, Henrik
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