Modelling and control design simulations of Permanent Magnet Flux-Switching Linear Bearingless Motor

For permanent magnet (PM) motor structures in rotating systems, it is typical to retain the magnets in the rotor. This constrains the rotor structure and limits applicability, e.g., for high-speed and high-temperature conditions. Flux-switching PM (FSPM) motors can overcome this limitation. Recently, the FSPM bearingless motors have been developed for special applications. The FSPM concept can be adapted to liner motors. For the linear motors, magnets or windings placed on the mover significantly decrease complexity and cost for longer distances. Still, to separate control of airgap and torque (thrust) two sets of windings or multiphase windings have been required for both rotating FSPM and linear PM machines. The linear FSPM bearingless motor solution, which integrates the magnets, winding structure and all the driving and control electronics on the mover is desired for many applications. However, because of electromagnetic unbalances the machine design is entangled with the control limitations and requirements. We reveal a modelling methodology for accurate derivation of bearingless machine dynamic and static force parameters as a function of airgap, control currents and track position in extended operational range. Model-based control simulations based on the accurate derived plant models determine the achievable machine performance and levitation limitations. The design and modelling methodology is general and can be applied to different PM bearingless motors. In the case study of linear FSPM bearingless motor the airgap control is possible in the equivalent to classical AMBs manner where it is independent from the thrust control.