Design and characterization of a thin linear ultrasonic motor for miniature focus systems

• Published in: Sensors and actuators. A. Physical. Vol. 329; p. 112797
• Main Authors: Izuhara, Shunsuke, Mashimo, Tomoaki
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 01.10.2021; Elsevier BV
• Subjects: Autofocus; Design optimization; Feedback control; Feedback control systems; Lenses; Micromotors; Motors; Piezoelectric actuators; Piezoelectricity; Sensors; Stators; Thrust; Ultrasonic motor; Ultrasonic technology; Visual feedback; Ultrasonic motor; Visual feedback; Micromotors; Autofocus; Piezoelectric actuators
• ISSN: 0924-4247; 1873-3069
• DOI: 10.1016/j.sna.2021.112797

[Display omitted] •We propose a miniature linear piezoelectric ultrasonic motor with a thin and hollow design.•The size of the stator measures 4.5 mm in height and width and 0.9 mm in thickness.•A thrust force 12.9 mN and linear velocity of 92.8 mm/s are obtained at 100 Vp−p.•The motor drive system is used to demonstrate the positioning of a lens group. We present a miniature linear piezoelectric ultrasonic motor with a thin and hollow design, which can serve as an essential component of autofocusing features in next-generation camera modules. It consists of a thin square stator with a hole and an elastic cylindrical slider with a slit. The motor design, in which the slider inserted into the stator hole expands outward, enables a hollow structure for centering a lens and an optimal preload for enhancing the motor thrust force. In this study, we model the relationship between the dimensions and the preload statically to quantify the preload value and clarify the design methodology of the motor. After optimizing the preload empirically, we evaluate the fundamental characteristics experimentally. The stator with a side length of 4.5 mm and a thickness of less than 1 mm provides a thrust force of 12.9 mN that leads to a quick response, which is a requirement of autofocusing. Finally, the motor drive system with visual feedback control is used to demonstrate the positioning of an actual lens group in front of an image sensor to obtain clearer images.