Last Updated on May 7, 2023 by You Ling
Piezoelectric actuators and motors are widely used in various industries due to their high precision, fast response, and stable performance. Understanding their differences and applications can help in selecting the most suitable device for a specific task. In this article, we will discuss the principles behind piezoelectric actuators and motors, as well as the key distinctions between the two.
1、What is a Piezoelectric Actuator?
A piezoelectric actuator is a transducer that converts electrical energy into mechanical displacement or stress (and vice versa) based on the piezoelectric effect. They are used as high-precision positioning mechanisms due to their ability to control minute mechanical displacements at high speeds, offering advantages such as large force generation, stable displacement, and ease of use.
2、What is a Piezoelectric Motor?
A piezoelectric motor is an electric motor made using the principle of shape change in piezoelectric materials after the application of an electric field. Some piezoelectric motors utilize the inverse piezoelectric effect, where the material undergoes acoustic or ultrasonic vibrations for linear or rotational motion.
3、Differences between Piezoelectric Actuators and Motors
A piezoelectric motor is an electromechanical device that combines a piezoelectric actuator with other mechanical components.
In the context of motion control, the term “motor” generally refers to a single electromechanical device that produces rotational or linear motion to drive a system, while the term “actuator” typically refers to an integrated mechanical system driven by a motor. However, in the context of piezoelectric drives, the term “actuator” refers to a set of piezoelectric components that produce motion solely through the inverse piezoelectric effect, without any mechanical components. The term “motor” refers to a type of piezoelectric actuator that incorporates mechanical components to produce motion, usually with a longer stroke than a standalone piezoelectric actuator.
Piezoelectric actuators consist of a single layer or stack of piezoelectric components that expand and contract proportionally to the applied voltage. The arrangement of the components determines the movement mode of the actuator – parallel or perpendicular to the electric field. Piezoelectric actuators generate tiny motions – typically in the range of a few micrometers to a few millimeters – and can produce very large forces, although there is a trade-off with displacement.
Piezoelectric motors combine a piezoelectric actuator (usually a longitudinal or “stacked” actuator) with other mechanical components to produce longer strokes – up to several hundred millimeters. Common types of piezoelectric motors include ultrasonic piezoelectric motors, piezoelectric inertial motors, and piezoelectric stepper motors.
In ultrasonic piezoelectric motors, the piezoelectric actuator is electrically excited to produce high-frequency oscillations. The actuator is preloaded onto a rotor via a coupling component. As the actuator oscillates, the coupler moves along an inclined path at the same frequency, contacting the rotor and causing it to move linearly.
Piezoelectric inertial motors (also known as “stick-slip” piezoelectric motors) also use a coupling component and rotor to generate motion. However, in this design, the piezoelectric actuator expands slowly and contracts very rapidly. During expansion, the rotor can move along with the actuator, but during rapid contraction, the rotor’s inertia prevents it from following the actuator, effectively keeping the rotor in place.
Piezoelectric stepper motors employ multiple actuators that expand (or contract) and bend laterally when voltage is applied. These actuators work in pairs to grip a longitudinal rotor and move it forward. The first pair of actuators then releases the rotor, and the next pair takes over. Due to their stepping motion, the actuators in piezoelectric stepper motors are often referred to as “legs.” Although each pair of actuators moves only a few micrometers per cycle, piezoelectric stepper motors operate at very high frequencies and undergo thousands of “steps” per second, achieving very long strokes at high speeds.
Piezoelectric actuators and motors have unique characteristics and applications, offering various benefits in precision positioning and motion control. Understanding their differences and working principles can help users make informed decisions when selecting the most suitable device for their specific requirements. With continuous advancements in piezoelectric technology, it is expected that these devices will play an increasingly important role in the future of various industries, including automation, robotics, and aerospace.