Abstract
A novel U-shaped piezoelectric ultrasonic motor that mainly focused on miniaturization and high power density was proposed, fabricated, and tested in this work. The longitudinal vibrations of the transducers were excited to form the elliptical movements on the driving feet. Finite element method (FEM) was used for design and analysis. The resonance frequencies of the selected vibration modes were tuned to be very close to each other with modal analysis and the movement trajectories of the driving feet were gained with transient simulation. The vibration modes and the mechanical output abilities were tested to evaluate the proposed motor further by a prototype. The maximum output speed was tested to be 416 mm/s, the maximum thrust force was 21 N, and the maximum output power was 5.453 W under frequency of 29.52 kHz and voltage of 100 Vrms. The maximum output power density of the prototype reached 7.59 W/kg, which was even greater than a previous similar motor under the exciting voltage of 200 Vrms. The proposed motor showed great potential for linear driving of large thrust force and high power density.
Highlights
Piezoelectric ultrasonic motors (PUMs) have developed rapidly in the recent 40 years with the increasing demands of the actuators in engineering applications [1,2]
They drive the runners or rotors with the frictional forces that are generated by the specific movements of the driving feet, which are excited via the vibrations of the piezoelectric elements. They show the merits of small size, simple structure, high power weight ratio, high accuracy and resolution, quick response, self-locking when power off, and a lack of electromagnetic radiation [3,4,5,6]. They have been successfully used in the field of high-tech and civilian use, such as robot driving, high precision machine, micro electro mechanical system (MEMS), and digital camera autofocus system [7,8]
PUMs can be divided into three types: traveling wave ultrasonic motors [10,11,12,13,14,15,16,17], standing wave ultrasonic motors [18,19,20], and composite vibrations ultrasonic motors [21,22], according to the ways to generate the elliptical-trajectory movements
Summary
Piezoelectric ultrasonic motors (PUMs) have developed rapidly in the recent 40 years with the increasing demands of the actuators in engineering applications [1,2]. The PUMs using composite vibrations have simple structures, large thrust force, and high output speed, so they have become more popular in recent years. This type of PUMs usually uses the modes of longitudinal and bending hybrid vibrations [23,24], longitudinal and torsional hybrid vibrations [25,26,27], two orthogonal longitudinal hybrid vibrations [28,29,30,31,32], and two orthogonal bending hybrid vibrations [33,34,35,36] to form the elliptical-trajectory movements.
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