Research On Small Linear Inertial Ultrasonic Motor Driven By Standing Waves

Ultrasonic motors,characterized by their simple structure,rapid response,and absence of electromagnetic interference,have been extensively employed in recent years across various domains,including precision positioning,adaptive focusing in optical systems,and medical devices.However,when implemented in confined spaces,e.g,smartphones,PCs,and other space-sensitive electronic products,ultrasonic motors typically fail to deliver sufficient driving force due to spatial constraints,resulting in low rotor movement speeds and overall compromised performance,thereby limiting the applicability of linear ultrasonic motors.To address these challenges,this study proposes a miniature inertial ultrasonic motor based on standing-wave drive,composed of piezoelectric ceramics,bimetallic reeds,guide rods,and rotors.The preloading force between the stator and the rotor is supplied by the rotor’s structure,rendering the motor’s structure more compact.The working principle of the inertial linear ultrasonic motor is analyzed.Based on the contact model between the stator and rotor,the conditions for the rotor’s motion are determined,and the rotor’s movement process is analyzed in conjunction with the driving electrical signal.Grounded on the standing-wave drive principle,a bimetallic reed-based ultrasonic inertial linear motor is proposed.First,the finite element model of the linear motor’s stator is established,and the stator’s resonance frequency and corresponding resonance modes are calculated using the finite element method.Next,the stator’s working mode and frequency are determined based on the rotor’s motion state.Subsequently,the stator structure of the linear motor is optimized via finite element calculations.The amplitude and vibration velocity of the linear motor’s stator are computed and compared under different metal reed thicknesses,heights,metal reed-to-guide rod diameters,and guide rod lengths to determine the stator’s structural parameters.A prototype of the bimetallic reed linear ultrasonic motor is fabricated,and an experimental system for testing the vibration characteristics of the ultrasonic motor stator is established.A Doppler vibrometer is employed to measure the vibration velocity of the guide rod tip at the linear motor stator under varying metal reed thicknesses,heights,guide rod diameters,and guide rod lengths.Additionally,the relationship between the stator amplitude and voltage is measured,and the accuracy of the finite element model is validated by comparing the experimental and computational results.A test platform for the output performance of the bimetallic reed linear ultrasonic motor is constructed,and the relationships between the driving voltage,driving frequency,preloading force,and rotor movement velocity are measured,ultimately determining the motor’s maximum no-load speed and maximum load capacity.