FAQ - Piezoelectric Motors

A piezoelectric motor is an actuator or motor using ultrasonic vibrations of piezo element to create rotary or linear motion.

They use the inverse piezoelectric effect meaning that when an alternating electric field is applied to a piezoelectric element it causes a mechanical deformation and vibration of the piezoelectic element itself. 

A travelling wave ultrasonic motor, like our Wavelling Motor range, is using a transducer (mechanical element coupled to a piezoelectic material) as a vibrating Stator, while a rotor is applied on it. 

Differences is that an ultrasonic motor is not using directly the deformation of the piezoelement but uses its vibration at certain frequencies (30-60 kHz) in order to create a deformation of the stator in a “travelling wave” form.

This wave drives the rotor by friction, i.e., the rotor is constrained on the stator and is forced to follow the progressive wave.
All this is based on the concept of resonance, allowing the piezoelectric element to deliver a lot of force.

These motors therefore differ from other piezoelectric motors in that their assembly and operation go beyond the simple deformation of a piezoelectric element. This allows them to deliver a lot of torque and achieve control more similar to that of a “conventional” motor: the motor can rotate in any direction and be controlled to the desired position.

In addition, this technology offers specific characteristics: high torque density, static torque allowing the motor to hold its position when not powered (without a brake or gearbox), and excellent response time (500 µs).

Ultrasonic motors can be controlled as Electromagnetic Motor (EM Motor) but with characteristics of piezoelectric motor. It allows for use where an EM motor cannot be used either practically (not enough space) or due to the environemnt restraints (vacuum, stronc magnetic field, etc.).

As a result, Ultrasonic Motors are used in Camera lens, Optics mechanisms, space and lab equipment due to their ability to give torque while remaining very precise and compact. They are also used in MRI environment and space, due to their ability to not be harmed by strong magnetic fields. They can also be implemented in very restrictive space, such as guided ammunition or surgical robots, where they can still deliver torque and precision. 

Yes, our ultrasonic motors are non-magnetic and already used in MRI-guided surgery and medical imaging, making them safe and ideal for such environments. They do not contain any ferro-magnetic materials and their principle of operation does not use any electromagnetic field or any magnetic property. As a result our motors can operate smoothly even in very strong magnetic fields. 

Their magnetic signature is also very low : < 5 nT in operation.

[See our MRI case studies].

Yes, they can operate in vacuum and space conditions where traditional motors fail. The fact that our motor uses a friction based motion and does not contain any materials subject to degassing makes it great to use, even in high vacuum.

Regarding the use of Wavelling motor in Space environment you can [Check our Space Heritage].

Unlike stepper or DC motors, piezo motors are non-magnetic, compact, lightweight, and silent. They deliver ultra-precise motion and torque without gears and can operate in extreme environments such as vacuum, MRI, or space.

In terms of technology, ultrasonic motors use the inverse piezoelectric effect and friction mechanism, while electromagnetic motors use magnets and electromagnetic fields to operate. Electromagnetic motors offer a very good power-to-size ratio, but with a predilection on speed for small size. To deliver torque they require reduction gear, creation issues in terms of backlash and footprint.