Design and experimental evaluation of a non-contact ultrasonic motor using acoustic phase holography

Abstract Non-contact ultrasonic motors address certain limitations of conventional ultrasonic motors. However, they continue to have intricate designs and electronics. Acoustic holography has emerged as a technique for its flexibility and dynamicity in manipulating acoustic phase and amplitude patterns in the nearfield, offering a reduction in mentioned complexities. Therefore, this technique may find utility in the development of non-contact ultrasonic motors. This paper discusses a novel design for non-contact rotary ultrasonic motor using acoustic holography. Acoustic holographic technique modulates the acoustic phase to create a phase gradient, resulting in a rotary flow that drives the rotor in the interface of aqueous media and air. The motor’s performance is influenced by factors such as the acoustic pressure amplitude, the number of 0 to <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>2</mml:mn> <mml:mi>π</mml:mi> </mml:math> pitches, and the rotor’s geometry. An empirical study using the Response Surface Method (RSM) identified an optimal number of pitches for maximum rotational speed at a constant voltage. The motor torque was measured by calculating the drag forces applied to the rotor blades. It was found that the minimum output torque occurs when the stator phase pitches match the rotor blades. The ideal motor performance is achieved with eight rotor blades and six phase pitches. The motor’s top speed reached 40 rpm, and the output torque varied around 0.1 μN.m, depending on the phase pitches and rotor blades. In summary, the research highlights the potential of acoustic holography in designing a non-contact ultrasonic motor, with specific configurations yielding optimal speed and torque.