Miniature Hollow Linear Ultrasonic Motor

We propose a miniature hollow linear ultrasonic motor, which is one of the smallest linear actuators that can generate practical force. The size of the prototype stator with piezoelectric elements measures 4.5 mm in height, 4.5 mm in width, and 0.9 mm in depth (the length in the slider travel direction). There is a hole of 2.7 mm in a diameter at the stator center, and the slider inserted into the hole moves back and forth when voltages are applied to the piezoelectric elements. By optimizing the preload between the stator and slider, the motor thrust force has been improved to over 10 mN, which is a practical force for moving small objects.