Levitation and driving performance of a non-contact rotation actuator excited by near-field ultrasonic energy

To address friction induced in the assembly of disk-shaped precision components, a non-contact rotation actuator driven by ultrasonic energy has been developed based on near-field acoustic levitation technology and non-contact drive principles. The actuator can levitate the rotor and drive the rotor to rotate. The theoretical model for the levitation mechanics and rotation driving mechanics of the non-contact rotation actuator is developed based on a nonlinear acoustic theory and ideal gas thermodynamics with analysis of the influence of key structural and dynamic parameters on levitation force and driving torque. Analysis of the levitation mechanics model revealed that the levitation force increases with vibration amplitude but decreases with levitation height. The rotation driving mechanics model demonstrated that maximum driving torque is achieved when the inclination angle of the cross section reaches 45°. Acoustic characteristics of the ultrasonic transmitter have been performed, elucidating the driving mechanism through acoustic pressure and acoustic streaming analysis. Experimental results on levitation force demonstrate an inverse proportional relationship between levitation height and levitation force. Experimental investigations of rotation driving force revealed optimal actuation performance at the resonant frequency of 20.21 kHz under constant excitation voltage. Additionally, the rotational speed is found to increase with rising excitation voltages when operating under fixed frequency conditions. Under an excitation condition of 225 Vp-p and a frequency of 20.21 kHz, the rotor achieved a maximum rotational speed of 3145 rpm while generating a peak torque output of 1.238 mN m. The experimental results substantiate the validity of the theoretical model and the practicality of the proposed design.