Defence of doctoral thesis in the field of Industrial Electronics and Electric Drives, M.Sc. Maksim Sokolov

The title of the thesis is Bearingless Motors: Modeling and Control
Photograph of the test setup for the prototype bearingless slice motor showing also the machine geometry.

M.Sc. Maksim Sokolov will defend the thesis "Bearingless Motors: Modeling and Control" on 21 January 2022 at 9:15 in Aalto University School of Electrical Engineering, Department of Electrical Engineering and Automation.

Opponent: Prof. Cheng Ming, Southeast University, China
Supervisor: Prof. Marko Hinkkanen, Aalto University School of Electrical Engineering, Department of Electrical Engineering and Automation

The public defense will be organized via remote technology. Follow defence:
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Thesis available for public display at:

Doctoral theses in the School of Electrical Engineering:

Press release:

Magnetically levitated electric motors

Electric motors play an integral role in the ongoing transition towards renewable energy. Paired with the variable frequency drives and intelligent control methods, they provide an efficient energy conversion mechanism that is widely used in our everyday lives and in the industry.

Although reliability is among the strong sides of electric motors, there is one part which experiences constant mechanical wear – the mechanical bearings utilized for supporting the rotating shaft. As such, the mechanical bearings require maintenance and can be a source of audible noise, vibrations, and additional friction losses – issues which are especially problematic in modern high-speed machinery.

This dissertation deals with so-called bearingless motors. In addition to the driving torque, a bearingless motor can also generate controllable radial force, which can be used to levitate the rotor, thus, eliminating any mechanical contact. However, a real-time feedback control system is required to maintain a stable and robust levitation. The complex nature of these devices results in non-trivial challenges in designing and tuning the levitation control systems.

The main focus of the dissertation is on developing mathematical models and control systems for two types of bearingless machines: rotating synchronous reluctance machines (SyRM) and linear flux-switching permanent-magnet (FSPM) machines. The proposed dynamic models are utilized as a basis for the development of model-based control systems. Analytical tuning rules for each proposed controller are presented. The applicability of the developed modeling and control methods is demonstrated with experimental results from three prototype bearingless motors including levitation, rotation, and propulsion tests.

Contact information of doctoral candidate:

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