Composite Piezoelectric Actuator for Low-Frequency Sound
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Solution Overview
Problem
Piezoelectric materials are typically stiff and suitable only for small displacement applications, limiting their use in actuator applications that require larger mechanical movements, such as low-frequency sound production, due to their high stiffness and low strain capabilities.
Innovation Solution
A composite piezoelectric actuator unit is developed using symmetrically stacked piezoelectric bimorph beams with low stiffness, allowing for increased displacement while maintaining a small footprint, achieved by sandwiching piezoelectric layers between conductive layers and applying a voltage to induce bending moments, enabling efficient low-frequency sound output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a single plate of piezoelectric material is made thin to increase compliance for low frequency sound production, then the compliance is improved, but the x and y dimensions must be very large to output sufficient power
Solution Approach 1:
The piezoelectric actuator is segmented into multiple bimorph beams arranged in a composite structure. Each beam consists of multiple piezoelectric layers (e.g., 3-10 layers) stacked and bonded together, allowing the system to achieve high compliance through the composite arrangement rather than requiring a single thin plate. This segmentation enables sufficient power output within compact dimensions.
Solution Approach 2:
The invention uses composite piezoelectric structures where multiple piezoelectric layers are combined with conductive material layers to form bimorph beams. These composite beams are arranged in specific configurations (e.g., symmetric stacking) to achieve both high compliance and compact form factor, resolving the contradiction between compliance and area.
2Quantity of substance
If piezoelectric materials are used in bulk form, then the material volume is sufficient for power output, but the stiffness is very high resulting in only extremely small displacements
Solution Approach 1:
The bulk piezoelectric material is segmented into multiple thin layers within each bimorph beam. This allows sufficient total material volume for power output while the layered composite structure provides the flexibility needed for larger displacements, overcoming the stiffness limitation of bulk piezoelectric materials.
Solution Approach 2:
The invention changes the structural parameters by creating bimorph beams with specific layer configurations and arrangements. By controlling the number of layers, their thickness, and the overall beam geometry, the system achieves both adequate material volume for power and sufficient compliance for larger displacements suitable for low-frequency applications.
3Length of moving object
If the piezoelectric actuator is designed for low frequency applications requiring large displacement, then the displacement is improved, but the actuator dimensions would normally need to be increased
Solution Approach 1:
The invention transitions from a two-dimensional planar arrangement to a three-dimensional composite structure by stacking multiple bimorph beams vertically. This dimensional change allows the actuator to achieve large displacements through the stacked configuration rather than requiring increased horizontal dimensions, enabling compact low-frequency actuator design.
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 solution allows for equivalent sound levels across varying aspect ratios, fitting into small packages and achieving increased electric field per volt, making it suitable for low-frequency applications without increasing the actuator's dimensions.
Implementation Method 1
Piezoelectric materials are solid materials upon which large mechanical stresses can be induced by applying an electric field across the material. This conversion from electrical to mechanical energy makes them useful in electromechanical actuators.
Data Source
AI summary
A piezoelectric actuator including an upper piezoelectric bimorph beam having a first upper piezoelectric layer, a second upper piezoelectric layer and at least three upper electrode layers extending between a first end and a second end of the upper piezoelectric bimorph beam; a lower piezoelectric bimorph beam having a first lower piezoelectric layer, a second lower piezoelectric layer and at least three lower electrode layers extending between a first end and a second end of the lower piezoelectric bimorph beam, and wherein the first end of the lower piezoelectric bimorph beam is coupled to the first end of the upper piezoelectric bimorph beam by a first joint, and the second end of the lower piezoelectric bimorph beam is coupled to second end of the upper piezoelectric bimorph beam; and a base member coupled to a center region of the lower piezoelectric bimorph beam.