Simulation of Pole Slip Control in an Axial Flux Magnetic Gear with Changeable Transmission Ratios using Stateflow and Simulink

Magnetic gears (MG) demonstrate substantial developments over the years and is seen as a potential direct alternative for conventional mechanical gears due to their contactless torque transmission. Although it offers increased reliability and reduced maintenance, the contactless nature of magnetic gears also makes it prone to pole slipping when the load torque exceeds the transmitted torque. While this prevents potential damage to the MG, it also causes a loss of output speed, which would ultimately reduce the driven rotor to a standstill. In conventional automotive vehicles, gearboxes with multiple transmission ratios are used to vary the transmitted torque and output speed according to operating conditions. Based on a similar concept, a prototype MG with two switchable transmission ratios has been proposed in an earlier study. In the present work, the study focuses on the development of a control system that regulates gear ratio switching to prevent slipping, thus aiming to address an inherent limitation of MGs. This paper presents a simulation study of the MG switching transmission ratio control system. Developed via Simulink and State flow, the system starts with high gear ratio (1:2). After two seconds, the load was increased until it exceeded the transmitted torque and initiated slipping. The system then switches to the lower gear ratio (4:1). It was observed that slipping stopped, and the driven rotor starts rotating steadily again. Simulation results demonstrate that driven rotor speed, which dropped sharply during slipping, regains stabilization at approximately 80rad/s after the gear ratio switch. In contrast, the non-changeable ratio system failed to recover from slipping with rotor speed reducing to zero. The simulation results provide evidence for the effectiveness of dynamic gear ratio switch control in maintaining stable and safe operation and preventing unwanted pole slipping from occurring in MG systems.