Composite Piezoelectric Actuator Design for High Power Density
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Solution Overview
Problem
Existing piezoelectric actuators face challenges in achieving high compactness and design flexibility, particularly in applications where size and weight are critical, and there is a need for actuators that can deliver high torque and power density without the complexity of electromagnetic motors.
Innovation Solution
A method of fabricating composite piezoelectric actuators by bonding planar outer layers of piezoelectric material to a reinforcement layer, with an electrically conductive coating and etching to define tongue portions, allowing for complex shapes and independent control of multiple actuators connected to a support element, enabling high precision and high power density in compact forms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If traditional electromagnetic motors are used, then power and torque can be delivered, but size and weight increase, and manufacturing complexity increases for small sizes
Solution Approach 1:
The patent changes the fundamental operating principle from electromagnetic to piezoelectric, utilizing the direct piezoelectric effect where mechanical stress generates electrical charge, and the converse piezoelectric effect where electrical fields generate mechanical strain. This parameter change enables compact actuator design with high power density, as piezoelectric materials can deliver significant force in extremely small volumes compared to electromagnetic motors
Solution Approach 2:
The patent employs composite structures combining piezoelectric ceramic layers with metal electrodes and flexible substrates. The piezoelectric layers (e.g., PZT - lead zirconate titanate) are bonded to metal electrodes to form sandwich structures that can be integrated onto flexible circuits. This composite approach enables high power density while maintaining compact size and allowing for flexible form factors
2Power
If piezoelectric actuators are miniaturized, then power density increases, but manufacturing difficulty increases
Solution Approach 1:
The patent segments the piezoelectric actuator into discrete functional layers: piezoelectric ceramic layers, metal electrode layers, and flexible substrate layers. Each layer can be manufactured separately using optimized processes (e.g., screen printing for electrodes, ceramic firing for piezoelectric layers) and then assembled through lamination. This segmentation enables precise control of each component's properties while simplifying the overall manufacturing process
Solution Approach 2:
The patent designs universal electrode patterns and flexible circuit boards that can accommodate multiple piezoelectric actuators of different sizes and configurations. The same basic manufacturing process and material stack-up can produce actuators ranging from sub-millimeter to centimeter scales, allowing high power density actuators to be manufactured using the same techniques as larger actuators
3Manufacturing precision
If complex shapes are required for high precision control, then actuator performance improves, but manufacturing complexity increases
Solution Approach 1:
The patent uses flexible printed circuit boards and thin flexible substrates as the base for piezoelectric actuators. These flexible films can be easily shaped, bent, and conform to complex geometries without compromising structural integrity. The flexibility allows creation of complex actuator shapes (e.g., curved surfaces, irregular geometries) while maintaining simple manufacturing processes through standard flexible PCB techniques
Solution Approach 2:
The patent transitions from rigid three-dimensional actuator structures to two-dimensional flexible planar structures that can be folded or bent into complex three-dimensional shapes. This dimensional reduction simplifies manufacturing (using flat laminar processes) while the ability to fold or bend the flexible substrate enables complex final geometries for high precision control applications
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method allows for the creation of compact, highly controllable piezoelectric actuators with increased force and power density, suitable for applications in microsurgery, robotics, and other fields requiring precise mechanical control, while reducing the component count and size.
Implementation Method 1
In a converse piezoelectric effect mechanical strain in the material is generated as the result of the application of an electric field.
Implementation Method 2
Some materials are known to generate an electrical charge in response to the applied mechanical stress. When piezoelectric materials are deformed by application of an external force they generate a surface electrical charge. This is known as the direct piezoelectric effect
Implementation Method 3
assembling and bonding at least one planar outer layer of piezoelectric material to a planar reinforcement layer to form a laminar assembly while the reinforcement layer is in an expanded condition relative to the piezoelectric layer such that a lateral compressive stress develops in the at least one outer layer when the at least one outer layer and the reinforcement layer in the laminar assembly is at the same temperature
Data Source
Figure 1
Figure 1a~1e
Figure 2a
AI summary
A piezoelectric bending actuator (1) is disclosed comprising a plurality of actors (2) with a composite structure wherein each actor (2) has at least a first planar outer layer (10) of piezoelectric material bonded to a planar reinforcement layer (14), an electrically conductive outer coating on an external surface of the first planar outer layer (10) defining a tongue portion in the plane of the coating and wherein each of the actors (2) are connected to and extend from a support element (6). The actors can be individually controlled. In addition composite actuators comprising five to one hundred of the disclosed actuators. In some embodiments actors on respective actuators are connected to a linkage arranged to transfer a force or displacement. The disclosed actuators may be used in micro motors and in valve arrays.