Abstract
We propose miniature ultrasonic motors using stators made of a single bulk piezoelectric element. The bulk piezoelectric stator has the potential to increase output by reducing the dissipation that occurs in the adhesion layer between the PZTs and a metallic component in the stator. In this paper, we build two kinds of bulk piezoelectric stators: a cubic bulk stator with a side length of 4.2 mm and a hole of 3 mm in diameter, and a cylindrical bulk stator with an outer diameter of 4.2 mm and the same hole diameter. We evaluate their electrical and mechanical characteristics, such as impedance and vibration velocity. The experiments clarify the advantages of the bulk piezoelectric stators, such as low dissipation. The cubic bulk stator, which shows higher performance than the cylindrical one, is compared with a similar-shaped stator using a bronze cube and thin piezoelectric plates. The performance measures of the cubic bulk ultrasonic motor are optimized by the preload between the stator and rotor.
Highlights
Millimeter-scale electric motors with a high torque density are one of the essential components in realizing future mechatronic devices in mobiles, medicine, and rescue
Electrostatic actuators have excellent scalability and enable their miniaturization by MEMS process [7, 8], but their weak driving force limits their deployment as millimeter-scale motors
We propose miniature ultrasonic motors using stators made of a single bulk piezoelectric element
Summary
Millimeter-scale electric motors with a high torque density are one of the essential components in realizing future mechatronic devices in mobiles, medicine, and rescue. Many micromotors have been proposed in the past 30 years [1–4]. Electromagnetic motors are the most available actuators but have several problems for further miniaturization. They require tiny components, but they induce serious torque reduction due to the scaling law, in which the torque scales down with the fourth power of a characteristic length [5, 6]. Very small actuators less than sub-millimeters use electrostatic forces. Electrostatic actuators have excellent scalability and enable their miniaturization by MEMS process [7, 8], but their weak driving force limits their deployment as millimeter-scale motors
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