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Abstract

In industrialized countries cardiovascular diseases are the major cause of death. The last clinical therapy option for some patients, suffering from terminal heart diseases, is donor heart transplantation. As the available number of donor organs is decreasing, many patients die while waiting for a transplant. For this reason Ventricular Assist Devices (VADs), which can mechanically support the human heart to achieve a sufficient perfusion of the body, are under development. For an implantable VAD, design constraints have to be deduced from the physiological conditions in the human body. In case of a VAD drive, these constraints are for example dimensions, electric losses, which might result in an overheating of blood, and a long durability. Therefore a hybrid permanent magnet hydrodynamic bearing is designed in this paper, which works passively and contactless. Based on Finite Element simulations of magnetic fields, various permanent magnet topologies are studied in terms of axial forces and stiffness.
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Abstract

Total Artificial Hearts (TAHs) are required for the therapy of terminal heart diseases as heart transplants are only a limited option due to the available number of donor hearts. For implantation TAHs have to meet constraints regarding its dimensions, weight, perfusions and electrical losses. An innovative linear driven TAH is presented, which meets all constraints except weight. Therefore the geometry of the linear drive is optimised to reduce its weights while simultaneously limiting the electrical losses as much as possible. In order to calculate the losses, this paper introduced a combined calculation chain consisting of FEM simulations and analytical equations. Based on this chain the linear drive is optmised by the method of parameter variations. The results yield a hierachic order of parameters which are most suitable for the weight reduction of the drive for low losses. By this the weight of the linear drive is reduced by 25%. As the allowable loss limit is not exceeded yet, room for further weight reduction achieved by an optimisation of the axial geomtry parameters is given.
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