Buckled Sheet Undulatory Structure With Neutral-Stability Actuation
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Solution Overview
Problem
Undulatory propulsion systems and mechanical transformers face challenges such as high complexity, cost, and inefficiency due to the need for multiple actuators and sophisticated control systems, as well as issues with elastic restoring forces that reduce output capability and cause distortion.
Innovation Solution
A buckled sheet with a sinuously-shaped profile is used, which is deformed in an undulating manner by work input elements, allowing each point on the sheet to travel a figure eight-shaped path, dynamically counterbalancing elastic forces and maintaining neutral stability, thus enhancing efficiency and reducing noise and vibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple actuators and sophisticated control systems are used in undulatory propulsion systems, then the propulsive performance and control precision are improved, but the device complexity and cost increase significantly
Solution Approach 1:
The propulsion system is divided into multiple discrete actuator elements distributed along the fin structure. Each actuator independently controls a specific segment of the fin, enabling complex undulatory motions through coordinated activation of individual segments rather than requiring a single complex control system
Solution Approach 2:
The system transitions from static or rigid fin structures to dynamically adaptable flexible fins that can change their deformation characteristics in real-time. The flexible material allows the fin to naturally form undulatory waves when actuated, reducing the need for complex control mechanisms while maintaining high propulsive performance
2Strength
If rigid segments with sliding joints are used to construct fins, then the structural strength is improved, but the device complexity increases due to the need for sliding joints to accommodate varying distances
Solution Approach 1:
The fin is constructed from flexible material that can bend and deform continuously without requiring rigid segments or sliding joints. This flexible structure naturally accommodates varying distances between actuation elements through its inherent compliance, eliminating the complexity of mechanical joints while maintaining structural integrity
Solution Approach 2:
Instead of using continuous rigid segments, the fin is divided into multiple flexible segments or zones that can independently deform. This segmentation allows each zone to accommodate local distance variations without requiring mechanical joints between segments
3Device complexity
If flexible material is used to construct fins to allow slack between actuation elements, then the device complexity is reduced, but the propulsive efficiency and power handling capability deteriorate
Solution Approach 1:
The system optimizes the physical parameters of the flexible material, including its stiffness, density, and damping characteristics, to achieve the desired balance between flexibility and propulsive efficiency. By carefully selecting and tuning these parameters, the fin maintains sufficient rigidity for effective power transmission while retaining enough flexibility to form undulatory waves
4Device complexity
If the general shape of the rubber strip is unconstrained in simple undulatory propulsion systems, then the device complexity is reduced, but the power delivery becomes suboptimal and difficult to control due to damping and wave reflection
Solution Approach 1:
The fin is pre-formed with a specific optimal geometry and pre-tensioned to the desired shape before operation. This preliminary configuration ensures that when actuation begins, the fin is already in the optimal state for efficient power delivery and controlled wave propagation, eliminating the need for complex real-time shape adjustment mechanisms
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 enables improved force, displacement, and distortion characteristics, along with high efficiency and wideband performance, reducing the need for complex control systems and minimizing elastic restoring forces, leading to more effective and efficient operation of undulatory propulsion systems and mechanical transformers.
Implementation Method 1
the sheet is in a post-buckled state in which said sheet has bent, warped or wrinkled as a result of an elastic instability
Data Source
Figure 1A~2
Figure 3~5B
Figure 6A~6B
AI summary
An undulatory structure and methods for the fabrication and use thereof. The undulatory structure includes a buckled sheet and one or more work input elements for deforming the buckled sheet in an undulating manner wherein each point in a series of points on a sinuously-shaped profile of the buckled sheet travels at least partially along a figure eight-shaped path. The undulatory structure can be adapted for use as a solid-state transducer wherein the buckled sheet provides mechanical advantage without appreciable opposition from elastic restoring forces, thereby achieving improved force, displacement and efficiency characteristics.