Piezoelectric MEMS Actuator with Segmented Driving Arms
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Solution Overview
Problem
Microelectromechanical mirror devices with piezoelectric actuation are sensitive to spurious out-of-plane movements and prone to shock due to the length of driving arms, leading to multiple spurious modes at low frequencies and reduced mechanical robustness.
Innovation Solution
A microelectromechanical device with a tiltable structure elastically coupled to a fixed structure via high-stiffness suspension elements and decoupling elastic elements, featuring driving arms with a trapezoidal shape and piezoelectric material, which allows for rotation with reduced spurious modes and increased mechanical robustness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the driving arms are made long to achieve wide tilting angles, then the tilting range is improved, but the mechanical robustness deteriorates and spurious out-of-plane movements increase
Solution Approach 1:
The driving arm is segmented into multiple sections (first section, second section, third section) connected by hinge joints. This segmentation allows the arm to maintain a longer effective length for wide tilting angles while reducing the moment of inertia and improving mechanical robustness. The segmented structure also helps in controlling spurious movements by allowing localized flexibility at the joints.
Solution Approach 2:
The driving arm is constructed as a composite structure combining different materials or structural configurations in different sections. This allows optimization of each section for specific functions - some sections for strength and rigidity, others for flexibility and weight reduction, thereby achieving both long length and mechanical robustness.
2Length of moving object
If the driving arms are made long to achieve wide tilting angles, then the tilting range is improved, but spurious out-of-plane movements increase
Solution Approach 1:
The driving arm is divided into multiple sections connected by hinge joints, which allows the structure to achieve wide tilting angles through coordinated rotation of segments while the joints themselves act as constraints that suppress unwanted out-of-plane movements. The segmented structure reduces the overall moment of inertia, making the system less prone to spurious vibrations.
Solution Approach 2:
The patent addresses spurious movements by designing the suspension elements and hinge joints to have specific stiffness characteristics that filter out unwanted vibrations. The elastic suspension elements are designed to provide restoring forces that counteract spurious out-of-plane movements while allowing the desired tilting motion.
3Use of energy by moving object
If piezoelectric actuation is used to reduce power consumption, then energy efficiency is improved, but sensitivity to shock increases
Solution Approach 1:
The patent incorporates damping elements and shock-absorbing features in the suspension system to protect the piezoelectric actuators from shock damage. The elastic suspension elements are designed to absorb and dissipate shock energy before it reaches the piezoelectric components, thereby maintaining reliability while using low-power piezoelectric actuation.
Solution Approach 2:
The elastic suspension elements act as intermediary components between the piezoelectric actuators and the external environment. These suspension elements isolate the piezoelectric actuators from direct shock exposure while still transmitting the controlled actuation forces, thereby protecting the sensitive piezoelectric materials from shock damage.
4Adaptability or versatility
If multiple piezoelectric bands are used on driving arms to control rotation, then the actuation capability is improved, but the device complexity increases
Solution Approach 1:
The patent combines multiple piezoelectric bands on the same driving arm that are biased with voltages of opposite polarity. By applying bipolar voltages simultaneously to adjacent bands, the system achieves bidirectional actuation and complex motion control without requiring separate actuator assemblies for each direction, thereby reducing overall device complexity while maintaining high adaptability.
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 device achieves improved mechanical and electrical characteristics by increasing the frequency ratio between spurious movements and the main rotation frequency, reducing sensitivity to shock, and enabling wide tilting angles with low biasing voltage, while maintaining low power consumption.
Implementation Method 1
Each driving arm bears a region made of piezoelectric material. The driving arms are divided into two sets driven in phase opposition to obtain rotation of the tiltable structure in opposite directions
Implementation Method 2
The tiltable structure is elastically coupled to a fixed structure via high-stiffness suspension elements and decoupling elastic elements
Data Source
Figure 1A~1B
Figure 2A~3
Figure 4A~4B
AI summary
A microelectromechanical device (20), has: a fixed structure (24) defining a cavity (23); a tiltable structure (22), elastically suspended in the cavity (23) and having a main extension in a horizontal plane (xy); a piezoelectrically driven actuation structure (30), which can be biased for causing rotation of the tiltable structure (22) about at least one first rotation axis (X) belonging to the horizontal plane (xy) and is interposed between the tiltable structure (22) and the fixed structure (24). The actuation structure (30) has at least one first pair of driving arms (32a, 32b), which carry respective regions of piezoelectric material (33) and are elastically coupled to the tiltable structure on opposite sides of the first rotation axis (X), by means of respective elastic decoupling elements (34a, 34b), which have a high stiffness in regard to movements out of the horizontal plane (xy) and are compliant in regard to torsion about the first rotation axis (X) .