High-Speed Stability in Shaft-Free MEMS Traveling Wave Motors Using Magnetic Constraint

The micro-electro-mechanical systems traveling wave motor (MEMS TWM) based on lead zirconate titanate (PZT) thin films holds significant potential for applications in micro-actuators, owing to its compact size, batch manufacturing capability, and ease of integration with existing microelectronic systems. Traditional MEMS TWM designs typically relied on a central shaft bearing to limit the in-plane translational movement of the rotor. However, the presence of a shaft inevitably introduced frictional contact between the rotor and the bearing, which led to undesirable energy loss, increased wear, and reduced rotational stability, especially at high speeds. To overcome these limitations, this study proposes a novel shaft-free design for MEMS TWMs that employs magnetic constraints to stabilize the rotor without physical contact. The design parameters of the magnetic constraint mechanism were carefully optimized through finite element analysis to ensure effective confinement while minimizing disturbance to the vibration mode of the stator. A precise assembly process was developed, enabling the successful fabrication of the proposed motor. Experimental validation demonstrated that the magnetically constrained, shaft-free design achieved a significant improvement in high-speed rotational stability, reducing rotational instability to just 4.6% at 13,024 rpm, thereby confirming its feasibility and performance advantages for future MEMS TWM applications.