Understanding Piezo Actuators: Definition, Working Principles, Advantages and Applications

1.Definition of Piezo Actuator
2.Working Principles of Piezo Actuator
3.Advantages of Piezo Actuactors
4.Piezo Actuators Applications
5.Conclusion

Piezo actuators are now important components of many modern high precision systems. They are employed in devices that need controlled movements on a micro or nano-scale. This blog describes what the piezoelectric actuators are, how they function, what their main advantages are and what are the most common fields of their application. 
Definition of Piezo Actuator
A piezo actuator is a mechanical device which generates motion or force in response to an electric voltage. It is based upon the specific properties of piezoelectric materials and in particular, piezoelectric ceramics, where a precise and repeatable movement is achieved. These ceramics often contain materials like PZT (Piezoresistor Zirconium Titanate) which is well known to have great piezo response.
Piezoelectric materials have the ability to change their shapes when exposed to an electric field. This result is known as the inverse piezoelectric effect. A piezo actuator uses this effect to transform the electrical energy directly to mechanic displacement. This displacement produced is usually very small but it is very accurate and very fast. For this reason, piezo actuators have found widespread use in applications that demand small positioning, high stability and rapid response.
In simple terms, a piezo actuator is a small device that is constructed from layers or stacks of piezoelectric ceramics. When applied with a voltage, the actuator expands or contracts via a controlled amount. This enables engineers to accomplish micro-positioning, vibration generation, optical focusing or force control options in many different systems with high precision.
There are several common types of piezo actuators, including:
Piezo stack actuator: built from many layers of thin piezoelectric ceramic sheets to create high force and short displacement.
Piezo Bimorph actuators: made from two bonded piezoelectric ceramic layers that bend when voltage is applied, producing larger displacement with lower force.
Piezo tube actuator: cylindrical structures used in scanning systems, fiber alignment, and micro-positioning tasks.
Regardless of the type, all piezo actuators operate based on the deformation of piezoelectric ceramics when voltage is applied.

Working Principles of Piezo Actuator
The function of a piezo actuator is completely dependent on the characteristic of its piezoelectric ceramic elements. When an electric field is applied across a piezoelectric ceramic the crystal lattice within the material changes position. This change in shift causes the ceramic to change its dimensions. The magnitude of change depends on the strength of the electric field and Ceramic characteristics itself.
A stack structure is often used in piezo actuators. Many thin slices of piezo electric ceramic are combined and electrically connected. This structure increases the displacement, while maintaining a workable level of operating voltage. With voltage applied, each layer expands by some small amount. When all the layers expand together the total displacement is much greater than that which a single layer could cause.
The movement made by a piezo actuator typically is in the same direction, although multi-axis designs are possible. The response is really fast since the motion is done at the atomic level within the ceramic. There are no gears, motors or complicated mechanical parts. This direct conversion from an electrical to a mechanical motion provides piezo actuators with an excellent speed as well as accuracy.
Piezo actuators can be operated in two basic modes:
Quist static mode, in which the actuator is static for a sustained period of time.
Dynamic mode, in which it is allowed to provide a rapid vibration or oscillating motion by the actuator.
Both modes use similar elements to improve situation and use the same piezoelectric ceramic mediums, however each one uses them in a different way, depending on the application.

Advantages of Piezo Actuactors
Piezo actuators have numerous benefits that make them suitable for advanced engineering and scientific applications among many other advancements. These advantages are obtained with both mechanical design, and the unique properties of piezoelectric materials.
1. High level of Precision and Resolution
Piezo actuators come with extremely fine movement. They are capable of positioning accuracy of the order of nanometers. This precision is not possible for many other types of actuators, particularly those that rely on mechanical parts.
2. Fast Response Time
And since the movement is occurring in the ceramic crystal structure, piezo actuators are almost instant. The response times can be in the micro or milli second range. This makes them ideal for fast control loops, high speed scanner and vibration applications.
3. No Mechanical Wear
Piezo actuators are not dependent on motors, bearings or gears. The movement is created from within the piezoelectric ceramic itself. As a result, there is very little mechanical wear and the lifetime of an actuator is very long.
4. High Force in a Compact Size
In spite of their small size, piezoelectric actuators can provide a lot of force. The internal crystal structure enables them to have a strong pushing or pulling force when a voltage is applied. This high power density enables them to be used in small-sized equipment where space is a premium.
5. Low Power Consumption
The piezo actuator needs very little power to achieve a position hold. And once the ceramic is in its new shape, only a little energy is required to maintain its shape. This makes piezo actuators more energy-efficient as compared to many traditional actuators.
6. Low Noise and Smooth Engineering Movement
Because the movement is direct and there is no friction involved, piezo activates move in a quiet and smooth manner.

Piezo Actuators Applications
Piezo actuators are used in many different fields due to their precision, speed and reliability. They have been common place in systems where piezoelectric ceramics may be more efficient than electromagnetic or mechanical parts. Some of the important applications like:
1.Precision Positioning
Microscopes, semiconductor inspection tools and optical focusing systems have piezo actuators allowing nano-accuracy of change of position.
2.Consumer Electronics and Acoustics
Piezo actuators can be used to drive small speakers, haptic feedback devices, camera modules and autofocus devices.
3.Diagnostic Medical and Clinical Medical Equipment
They make fine-dosage liquid pumps, micro-pumps, surgical instruments and imaging systems possible.
4.Automotive Electronics
Piezo actuators are found in fuel injectors, valve control modules and vibration reduction system.
5.Industrial Automation
They support the applications of precision machining, robots, metrology instruments and laser alignment systems.
In all the applications mentioned above, the performance of the piezo actuator is highly dependent on the quality and stability of the internal piezoelectric ceramic material elements.

Conclusion
Piezo actuators are functional of a tool that can be used to accurately and reliably create movement to a very small scale. Their operation is based on the inverse piezoelectric effect which says that piezoelectric ceramics change shape in the presence of voltage. These materials are used to convert an electrical energy to mechanical motion with high speed and precision. Because of their unique advantages such as fast response, long life, low power consumption and high accuracy, piezo actuators remain key in areas such as electronics, medical devices, automotive systems and industrial automation.
As technology advances, there will also continue to be an increasing demand for accurate and efficient motion control. Piezo actuators, which use high performance piezoelectric materials, will continue to be an essential part of next generation devices and engineering systems.

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