Last Updated on May 8, 2023 by You Ling
The rapid development of modern technology has led to the emergence of various sensing and actuation mechanisms that play a crucial role in numerous applications. Among these mechanisms, piezoelectric sensors and actuators stand out due to their unique characteristics and capabilities. These devices harness the piezoelectric effect, which has enabled a wide array of applications in diverse fields such as aerospace, medical, consumer electronics, and nuclear instrumentation. In this article, we delve into the principles behind piezoelectric sensors and actuators, their advantages, and the key differences between them, offering a comprehensive understanding of their roles in today’s technology landscape.
1、What are Piezoelectric Sensors?
Piezoelectric sensors are a type of sensor based on the piezoelectric effect, which is a self-generating and electromechanical conversion type sensor. The sensitive elements of these sensors are made from piezoelectric materials. When these materials are subjected to force, they generate an electric charge on their surface. This charge, when amplified and transformed by a charge amplifier and measuring circuit, becomes an electrical output proportional to the external force applied. Piezoelectric sensors are commonly used for measuring flexing motion, touch, vibration, and impact. They find applications in various fields, including medical, aerospace, consumer electronics, and nuclear instrumentation.
2、What are Piezoelectric Actuators?
Piezoelectric actuators are transducers that convert electrical energy into mechanical displacement or stress based on the piezoelectric effect, and vice versa. They are widely used as high-precision positioning mechanisms due to their ability to control minute mechanical displacements at high speeds. They offer advantages such as high force generation, stable displacement, and convenient usage.
- Advantages of Piezoelectric Sensors
High-frequency response: This means that it can easily sense on a very rapid parameter.
High transient response: Because they can detect what happens in a small amount of time and generate a linear output.
High output: Refers to the ability to measure with electronic circuits.
Small size, sturdy structure: This means that they are easy to use.
4、Advantages of Piezoelectric Actuators
Displacement:
In a stacked actuator, each piezoelectric element has alternating polarity and an electric field is applied parallel to the polarization direction. When a voltage is applied, strain or displacement is induced in the polarization direction. The movement of the piezoelectric element equals the amount of voltage applied multiplied by the piezoelectric coefficient (the piezoelectric coefficient d33 is related to the efficiency of converting electrical energy into mechanical energy). Since they are connected mechanically in series, the total movement of the stacked piezoelectric actuator is the movement of a single element multiplied by the number of elements in the stack. The total displacement of a stacked actuator is typically between 0.1% and 0.15% of the actuator length.
Voltage and electric field:
Stacked piezoelectric actuators are generally classified as low voltage (below 200 V) or high voltage (up to 1000 V), referring to the maximum input voltage of the maximum stroke. The magnitude of the applicable voltage depends on the material and thickness of each element. Therefore, the electric field increases as the layer thickness decreases. Similarly, for a given electric field, the driving voltage must decrease as the layer thickness decreases.
Force and stiffness:
Actuator stiffness has a significant impact on force generation, which is determined by the elastic modulus of the piezoelectric ceramic material, the cross-sectional area of the actuator, and its length. Despite their small size, stacked piezoelectric actuators have a force density of around 30 N/mm allowing them to generate tens of thousands of Newtons of useful force. It is important to note that in steady-state operation (no motion, constant force), there is no current flow and no power supply is needed. Stacked actuators can also maintain their position when the power is off, without generating heat.
Tensile strength and preloading force:
Stacked piezoelectric actuators often withstand both compressive and tensile forces, particularly during high dynamic motion. The tensile strength of stacked actuators largely depends on the method of pressing the individual element layers together and is usually an order of magnitude lower than the compressive strength. Preloading the actuator with a force greater than the applied tensile load ensures that the actuator always remains in compression and can operate in high dynamic, bidirectional applications. Successful integration of stacked piezoelectric actuators requires any applied force to be purely axial and compressive. Manufacturers usually provide various mounting options to help prevent bending, shearing, or torsional forces.
Low power consumption
5、Differences Between Piezoelectric Sensors and Actuators
Sensors and actuators are transducers capable of responding to physical stimuli and transmitting pulses into the measured medium. Piezoelectric sensors convert physical inputs such as acceleration, pressure, or other inputs into electrical signals that serve as inputs for data processing systems. In other words, they can only convert mechanical energy into electrical energy. On the other hand, piezoelectric actuators are transducers that convert electrical energy into mechanical displacement or stress based on the piezoelectric effect.
6、Conclusion
In summary, piezoelectric sensors and actuators are both important technologies based on the piezoelectric effect, with each serving specific purposes. Piezoelectric sensors convert mechanical forces into electrical signals, while piezoelectric actuators transform electrical energy into mechanical displacement or stress. They offer various advantages and find applications in numerous fields, from medical and aerospace to consumer electronics and nuclear instrumentation.
