Mode Optimization of Microelectromechanical-System Traveling-Wave Ultrasonic Motor Based on Kirigami

Area of Science:

• Mechanical Engineering
• Materials Science
• Acoustics

Background:

• High-quality traveling waves in stators are essential for the stability and efficiency of traveling-wave ultrasonic motors (TUSMs).
• Anisotropic elasticity in stators causes modal splitting and shape distortion, leading to significant traveling wave distortion.
• Existing methods struggle to effectively mitigate these issues, hindering TUSM performance.

Purpose of the Study:

• To propose and investigate a novel mode optimization method using kirigami patterns to suppress modal splitting and shape distortion in TUSM stators.
• To analyze the impact of kirigami-based optimization on the traveling wave characteristics, specifically focusing on orthogonal modes with even and odd nodal diameters.
• To demonstrate the effectiveness of the proposed method in improving the quality of traveling waves for enhanced TUSM operation.

Main Methods:

• Kirigami patterns were designed on the inner boundary of the stator using linear interpolation.
• An optimization model was established for orthogonal modes with even and odd nodal diameters.
• An extended Nelder-Mead Simplex Algorithm, featuring derivative-free and bound constraints, was employed for optimization.

Main Results:

• Optimization significantly improved the mode shape of orthogonal modes with odd nodal diameters, making them closer to a sine-style wave (e.g., B13 mode distortion reduced to 0.003).
• Intrinsic frequency matching was successfully maintained post-optimization.
• For orthogonal modes with even nodal diameters, both frequency splitting (e.g., B14 mode reduced from 380 Hz to 1 Hz) and shape distortion (as low as 0.004) were substantially suppressed.

Conclusions:

• Kirigami-based mode optimization is an effective strategy for suppressing modal splitting and shape distortion in TUSM stators.
• The proposed method enhances traveling wave quality by improving mode shapes and reducing frequency splitting, leading to better TUSM stability and efficiency.
• This approach offers a promising solution for developing high-performance traveling-wave ultrasonic motors.