Research
We propose a micro linear ultrasonic motor, which is one of the smallest linear actuators that can generate practical force. Such a small actuation mechanism can be used for a wide range of applications, such as auto-focus systems used in thinner cell phones and smaller endoscopes. The size of the prototype stator with piezoelectric elements measures 2.6 mm in height, 2.6 mm in width, and 2.2 mm in depth (the length in slider travel direction). There is a hole of 1.4 mm in diameter at the stator center, and the slider inserted into the hole moves back and forth when voltages are applied to the piezoelectric elements. A maximum thrust force of 20 mN which is a practical force for moving small objects has been obtained at applied voltages with an amplitude of 150 Vp−p.
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. 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.