2022/09/30 by Silvan Viëtor, Viëtor, Silvan G., Spronck, Jo W. +4
Engineering · Materials Science · #Electric Motor Design and Analysis #FOS: Electrical engineering #Magnetic Bearings and Levitation Dynamics #Magnetic Properties and Applications #Systems and Control (eess.SY) #electronic engineering #information engineering
paper · pdf · doi:10.48550/arxiv.2210.00142
openalex publication_date 2022/09/30 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
Actuator self-heating limits the achievable force and can cause unwanted\nstructural deformations. This is especially apparent in quasi-static actuation\nsystems that require the actuator to maintain a stable position over an\nextended period. As a solution, we use the concept of a Tunable Magnet. Tunable\nmagnets rely on in-situ magnetization state tuning of AlNico to create an\ninfinitely adjustable magnetic flux. They consist of an AlNiCo low coercivity\npermanent magnet together with a magnetizing coil. After tuning, the AlNiCo\nretains its magnetic field without further energy input, which eliminates the\nstatic heat dissipation. To enable implementation in actuation systems, the\nAlNiCo needs to be robustly tunable in the presence of a varying system\nair-gap. We achieve this by implementing a magnetization state tuning method,\nbased on a magnetic circuit model of the actuator, measured AlNiCo BH data and\nair-gap flux feedback control. The proposed tuning method consists of 2 main\nsteps. The prediction step, during which the required magnet operating point is\ndetermined, and the demagnetization step, where a feedback controller drives a\ndemagnetization current to approach this operating point. With this method\nimplemented for an AlNiCo 5 tunable magnet in a reluctance actuator\nconfiguration, we achieve tuning with a maximum error of 15.86 "mT" and a\nminimum precision of 0.67 "mT" over an air-gap range of 200 "\μm". With this\ntuning accuracy, actuator heating during static periods is almost eliminated.\nOnly a small bias current is needed to compensate for the tuning error.\n