Principle and Features of Ultrasonic Motors

Differences between ultrasonic motors and general motors

Typical motors rely on electromagnetic force for rotation, making them unsuitable for high-voltage or magnetic field environments. Additionally, they lose posture control when power is cut. Ultrasonic motors offer a solution by operating without electromagnetic force, using ultrasonic vibrations instead for rotation. This makes them suitable for challenging environments and allows them to maintain position even without power.

Technology & Development

　Principle and Features of Ultrasonic Motors

　PSM Development Story

　PSM Applied Products

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ultrasonic motor

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DC motor

Stepping motor

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Illustration of a robot with a dead battery

General motors

Power OFF

I can't hold my posture

High voltage, magnetic field environments

Cannot operate properly

I can hold my posture

Power OFF

Ultrasonic motor

High voltage, magnetic field environments

Can operate normally

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Piezo Sonic ultrasonic motors

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Piezo Sonic is developing applications that integrate motors and robotics.

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Introduction of Robot Development Business

Piezoelectric ceramics, which deform under applied voltage, are used instead of coils or magnets for rotational energy. The deformation is amplified by a metal stator, generating rotational motion on its surface. This motion is transmitted to the rotor via frictional force, causing rotation. The shaft, fixed to the rotor, transmits motor torque and rotation. Constantly generated frictional force allows the motor to maintain position even when de-energized and uncontrolled (high holding force), enabling backlash-free direct drive.

Piezo Sonic's ultrasonic motors offer significantly longer lifespan and increased torque compared to conventional ultrasonic motors. Through structural and material improvements, their service life exceeds twice that of conventional models, rivaling that of stepping motors. These advancements have been recognized with patents and prestigious awards such as the "Monozukuri Award" from the Japan Society for Precision Engineering in 2018 and the "Good Design Award" in 2019.

Features of ultrasonic motors

DC Motor

This area diagram focuses on the relationship between torque and speed for ultrasonic motors, DC motors, and stepping motors of the same size.

Compared to other motors, ultrasonic motors are characterized by low speed and high torque.

They can maintain high holding force even when uncontrolled by frictional force and have no backlash, making it possible to build direct-drive actuator systems without using gears.

Stepping motor

Ultrasonic motors

This area diagram focuses on the relationship between position controllability and weight (lightweight) of ultrasonic motors, DC motors, and stepping motors of the same size.

Compared to other motors, ultrasonic motors are characterized by their light weight and high position controllability.

The light weight of the rotating part results in low inertia, and when the drive signal stops, the motor instantly comes to rest due to frictional force, enabling precise positioning. (Final positioning accuracy depends on the external sensor: encoder or potentiometer and the control controller.)

Ultrasonic motors

Stepping motor

DC Motor