Modeling and Single-Variable-Based Axial Force Balance Control of Conical PMSM for Electric Aircraft Propulsion System

Permanent magnet synchronous motor (PMSM) and propeller direct-drive systems are widely used in electric aircraft due to their lightweight and high-efficiency structure. During flight, the thrust generated by the propeller is transmitted to the motor bearings through the rotating shaft, leading to increased bearing wear and consequently affecting the service life of the electric propulsion system. This paper proposes an axial force balance control strategy by considering the characteristics of permanent magnet synchronous conical motors. Firstly, to address the lack of mathematical models for axial forces in conical PMSMs (CPMSMs), a mathematical modeling method is proposed. Based on the characteristics of the mathematical model, a simplified method using the fundamental wave of magnetic potential is presented. To solve the control complexity caused by multivariate influences on axial forces, a Single-Variable-Based model predictive axial force control (SVB-MP-AFC) is proposed, along with a state smooth switching method to reduce bearing wear and improve system stability. Finally, simulations and experiments verify the accuracy of the mathematical model and the effectiveness of the control strategy.