● Learn about the types of Piezo Actuators.
● Gain a greater understanding of how actuators function.
● Learn more about the applications that use the piezoelectric force.
Piezoelectric Buzzer and Sensor with Lead Wire
In the area of Science or Physics, there are defining points. For example, water can be cooled from 700 Fahrenheit to 330 Fahrenheit without any real noticeable changes. However, everything changes for water once we reach the defining point of 320 Fahrenheit.
As we know, at 320 F water changes state from a liquid to a solid. The piezoelectric effect functions similarly, except that the governing of its defining states is by voltage and purposeful obstruction.
The Piezo Actuator
So, what is a piezo actuator? You should first note that all actuators are device components that facilitate the conversion of signal energy into a required or necessary controlling motion. For example, when you press a button signalling an electric actuator to transfer that button press signal into a rotary motion to either close or open a valve. This type of functionality is highly desirable in applications that need precise positioning of mechanical devices.
A Piezo actuator functions on the inverse piezoelectric effect; when we apply voltage, the actuator will contract or expand. However, when we block the actuator from moving, it will generate a force. We typically use a load in the direction of travel to achieve the necessary blockage of movement.
The relationship between force and displacement in piezo materials is an inverse relationship. In summary, the more force an actuator has to generate against a load, the less movement (travel) it can produce. Conversely, a freely moving actuator that encounters no resistance to its motion will generate its maximum displacement (travel). Since they create zero force, we refer to these particular types of actuators as free stroke.
Types of Piezo Actuators
Whether the application is for mirrors on satellites or non-magnetic and miniaturized medical devices, there is a type of piezo actuator in line with the task. Piezo actuator types include pneumatic, hydraulic, electric, and mechanical. Aside from the category list of actuator types above, two other types of actuators that warrant mentioning are Stack Actuators and Stripe Actuators.
A Piezo stack actuator provides a low stroke with a high blocking force. Depending on your design requirements, a piezo stack actuator can be either co-fired or discrete. If it is indeed discrete (high-voltage stack actuators), then its composite structures are made by separately stacking finished piezoelectric ceramic rings or discs and metal electrode foil with an adhesive. Typically, operating voltages range from 500 to 1,000 volts.
Now, co-fired stack actuators (multilayer) are also called monolithic stacks, and they do not utilize adhesives. However, they do use high-temperature sintering of the complete electrode and ceramic pile, and their operating voltage can be as much as 200 volts. In either case, discrete or co-fired, it is possible to protectively insulate them from environmental extremes and mechanical stresses. Achieving this typically involves using bare stacks, coating materials, or encasing them in stainless steel.
High piezoelectric towers in the setting sun
Other Types of Piezo Actuators
The Stripe Actuator, or bending actuator, produces a reasonably large mechanical deflection in reaction to an electrical signal. In turn, this deflection provides a large stroke with a minimal blocking force in comparison to the stack actuator.
A stripe Actuator utilizes two thin layers of piezoelectric ceramic that bonds together. They are usually in the direction of the coinciding polarization with an electrically parallel connection. When we apply an electrical input, one ceramic layer contracts while the other expands, which causes the actuator to flex.
Piezoelectric Actuator Applications
Piezoelectric actuators produce minimal heat and consume minimum power while in an energized state, making them incredibly useful across a variety of industries. This includes the automotive industry, military, medical field, and aerospace, to name a few.
With their simplistic design, high-reliability, and minimal moving parts, the piezoelectric actuator warrants its widespread use. You can even find them in use in braille machines, consumer electronic devices, and precision machinery. Furthermore, with their silent drive characteristics, piezo actuators are in use in mobile phones as well as autofocusing mechanisms in microphone-equipped video cameras. Because the piezo actuator does not require any lubrication to operate, it is ideal in both vacuum environments and cryogenic applications.
Another reason for their widespread use is because stack actuators provide exceedingly fine, and virtually infinite, resolution, as well as very high voltages that translate into minute movements of expansion. In general, a typical piezo actuator will operate billions of times before deterioration or wear becomes apparent. It also provides exceptional response speed with only two limits. These limits include the inertia of the object it moves and the electronic driver's output capability.
Summary of Piezo Actuator System Advantages
- Superior force-to-weight ratio
- Vacuum compatible
- Extremely reliable (billions of cycles)
- Substantial power-to-volume ratio
- Flexure-based yields zero backlash
- Wide-bandwidth operation
- Minimum heat production
- Sub nanometer proportional displacement
- Does not require lubrication
- Minimal movement
- Solid-state design reduces component count
- Non-magnetic construction compatibility
A Well-Earned Reputation
As we have seen, the Piezo Actuator's widespread use across multiple industries speaks volumes to its functional characteristics. The variety of systems they are found in also means that there is probably an actuator type for whatever design requirements you may have. Overall, the piezo actuator's ability to produce precision motion control in a variety of environments is perhaps its most significant functional characteristic.
Voltage produced by pressure
Thankfully, with our PCB Design and Analysis overview page, you’ll be sure to have your designers and production teams working together towards implementing the use of Piezoelectric Actuators for all of your company’s applicable design and manufacturing needs. With Allegro PCB Designer, you can rest easily in any layout procedure through electronic design.
If you’re looking to learn more about how Cadence has the solution for you, talk to us and our team of experts.