Bistable SMA Actuator Structure for Zero-Power Position Holding
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Solution Overview
Problem
Existing actuators using shape memory alloys (SMA) struggle to maintain a moving member in an open or closed position without continuous external force, limiting their efficiency and functionality in applications like micro valves and fluid control systems.
Innovation Solution
A bistable SMA actuator design that utilizes two opposite SMA actuators to move a structure between two positions, leveraging spring forces to hold the position without external power, and includes features like directional control valves and diaphragms for fluid management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a shape memory alloy (SMA) element is used to actuate a moving member between multiple positions, then the actuator can achieve position control, but continuous external force is required to maintain the position
Solution Approach 1:
The patent implements a bistable mechanism that dynamically transitions between two stable positions. The moving member is designed with elastic elements that create two potential energy wells, allowing the system to naturally maintain positions without continuous actuation. The SMA element only provides transient force during position transitions, while the elastic restoring forces maintain the positions statically.
Solution Approach 2:
The bistable mechanism uses its own elastic elements to automatically maintain positions and return to stable states. When the SMA element releases, the elastic elements self-generate the restoring force needed to hold the moving member in either position, eliminating the need for continuous external power or control systems.
2Stability of the object's composition
If continuous external force is applied to maintain the moving member in a position, then position stability is achieved, but energy consumption increases
Solution Approach 1:
The system transitions from static force application to dynamic bistable positioning. The elastic elements are designed to create two stable equilibrium positions where the moving member naturally resides. The system exploits the dynamic characteristics of elastic deformation and energy minimization to achieve stable positioning without continuous energy input.
Solution Approach 2:
The SMA element operates in periodic cycles of actuation and relaxation. During actuation, it provides force to transition the moving member between positions. During relaxation, the elastic elements maintain the positions passively. This periodic operation pattern eliminates continuous energy consumption while maintaining position stability throughout the cycle.
3Use of energy by moving object
If a bistable structure with springs is used to hold positions without external force, then energy efficiency improves, but device complexity increases
Solution Approach 1:
The patent merges the positioning function and the spring elements into a single integrated bistable structure. The elastic elements are not separate components but are incorporated directly into the moving member geometry, creating a unified structure that provides both mechanical support and bistable positioning functionality, thereby reducing overall device complexity.
Solution Approach 2:
The elastic elements serve multiple functions simultaneously: they provide structural support for the moving member, create the bistable positioning mechanism, and generate the restoring forces for position maintenance. This multi-functionality reduces the number of separate components needed, offsetting the added complexity of the bistable design with functional consolidation.
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
Enables efficient, power-efficient operation of actuators in micro valves, electrical relays, and fluid control systems by maintaining stable positions without continuous power input, enhancing reliability and reducing energy consumption.
Implementation Method 1
an actuator can include a static member and a moving member, with a SMA element connecting the static member and moving member. Further, a current can be applied to a SMA element to cause the SMA element to actuate to an actuated position
Implementation Method 2
a current can be applied to a SMA element to cause the SMA element to actuate
Implementation Method 3
The bistable structure can include multiple springs that use force(s) from the springs to hold the bistable structure at a position with zero external force provided by the SMA actuators
Implementation Method 4
The bistable structure can include multiple springs that use force(s) from the springs to hold the bistable structure
Data Source
AI summary
The present embodiments relate to a bistable SMA actuator. The bistable SMA actuator as described herein can include a two-position actuator to move a bistable structure between two positions. Multiple SMA actuators can be disposed opposite one another to move the bistable structure between the two positions. For example, a first SMA actuator can actuate to move the bistable structure from a first position to a second position. After actuation by the first SMA actuator, the actuator can de-actuate, and the bistable structure can use spring force to hold the bistable structure in the second position. The bistable structure can include multiple springs that use force(s) from the springs to hold the bistable structure at a position with zero external force provided by the SMA actuators.