Magnetic bearing for heart pumps

• Main Author: Lim, Hao Wei
• Other Authors: Tegoeh Tjahjowidodo
• Format: Final Year Project
• Language: English
• Published: Nanyang Technological University 2020
• Subjects: Engineering::Mechanical engineering::Prototyping
• Online Access: https://hdl.handle.net/10356/136884
• Institution: Nanyang Technological University

Due to the inherent benefits of a magnetic bearing over the common contact bearings, it was worth studying how the magnetic bearing system could be used in heart pumps which would aim to have as little maintenance as possible. In the second generation of the Ventricular Assist Device (VAD), there has been issues with wear due to the usage of contact bearings. In the third generation VAD, some designs have opted for the use of magnetic bearings while the rest have chosen to use journal bearings. In a recent study, evidence of clotting blood has been discovered and were deemed to be the result of the tight spaces in journal bearings. With the high costs of a heart transplant, the VAD seems to be the way forward for patients that suffer from heart failure and hence continuous improvements and reviews should be made to improve the performance of its future iterations. The objective of the project was to study existing magnetic levitation systems and develop a proof of concept for a magnetic bearing to be used in a heart pump. This report covers the work that the author has done which includes studies on the components in a simple magnetic levitation system and three designs of prototypes which were considered and subsequently by the author. In the first prototype, which had a suspending design, but the electromagnetic forces were not strong enough to attract the magnet. In the second prototype, the author decided to follow a repelling model and experimented the use of electromagnets as the main source of electromagnetic forces. In the third prototype, the author kept the repelling model and attempted to build a similar design to the Levitron Revolution. The mathematical model was derived and proved that the system could be built using the parts and parameters selected. The use of rectifying diodes as a safety feature due to flyback voltage was discussed. Three recommendations were also proposed. Halbach arrays has shown that magnetic flux density could be concentrated on a specified pole area. The sensor resolution tracking the position of the levitating magnet was vital in allowing for a system response for each minute movement. Temperature of the coil was also an important parameter to be tracked to ensure the magnetic performance of the system.