SMA Actuator with Elastic Biasing and Locking Mechanism
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Solution Overview
Problem
Actuator devices employing shape memory alloy (SMA) elements face challenges in temperature stability and energy efficiency, particularly in automotive applications where full functionality is required across a wide temperature range, and often require costly and bulky SMA elements to overcome biasing forces.
Innovation Solution
The actuator device incorporates an SMA element that transitions between expanded and contracted states, coupled with an elastic element for biasing and a locking mechanism to selectively lock the actuation member, allowing for on-demand biasing force and reduced power consumption by using a further SMA element to provide strain relief and temperature stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by stationary object
If SMA elements are used to provide biasing force, then the actuator can operate without continuous heating, but the device requires costly and bulky SMA elements to overcome biasing forces
Solution Approach 1:
The biasing function is segmented from the SMA element to a separate elastic element. This allows the SMA element to be smaller and less bulky, as it only needs to provide actuation force rather than overcome biasing force. The elastic element independently provides the biasing force, resolving the contradiction between energy efficiency and device weight.
Solution Approach 2:
An elastic element is introduced as an intermediary component to provide the biasing force. This mediator allows the SMA element to operate more efficiently without needing to be oversized to counteract biasing forces, thus reducing both the bulkiness and weight of the device while maintaining energy efficiency.
2Reliability
If continuous heating is applied to maintain SMA element functionality, then the actuator operates reliably across temperature ranges, but power consumption increases significantly
Solution Approach 1:
Instead of continuous heating, the SMA element is heated periodically only when actuation is required. The elastic element maintains the biasing force during non-heating periods, allowing the system to achieve operational reliability through periodic activation rather than continuous energy input, thus significantly reducing power consumption.
Solution Approach 2:
The elastic element serves itself by automatically maintaining the biasing force without requiring external energy input. This self-service capability allows the SMA element to remain functional across temperature ranges without continuous heating, improving reliability while reducing power consumption.
3Ease of operation
If the elastic element is designed with high headroom to overcome biasing forces, then the SMA element can transition smoothly, but the device complexity and size increase
Solution Approach 1:
The forces required for actuation are segmented between the SMA element (providing actuation force) and the elastic element (providing biasing force). This segmentation allows each component to be optimized independently, enabling smooth transitions without requiring excessive headroom in the elastic element, thus reducing device complexity.
4Stability of the object's composition
If the SMA element operates across a wide temperature range without biasing assistance, then temperature stability is maintained, but the SMA element becomes bulky and expensive
Solution Approach 1:
The elastic element acts as an intermediary that provides biasing force assistance, allowing the SMA element to maintain temperature stability across wide temperature ranges without needing to be oversized. This mediator enables the SMA element to remain compact and cost-effective while achieving the required temperature stability.
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
This configuration enhances temperature stability and energy efficiency by reducing the need for significant headroom in the elastic element, allowing the SMA element to operate effectively across a wide temperature range without continuous heating, thus improving power efficiency and load capacity.
Implementation Method 1
the SMA element transitions between an expanded state and a contracted state
Implementation Method 2
upon thermal activation and deactivation, the SMA element transitions between an expanded state and a contracted state
Implementation Method 3
The elastic element is configured to bias the SMA element towards the expanded state
Implementation Method 4
The locking element is configured to selectively lock the actuation member in the first position when the SMA element is in the expanded state
Implementation Method 5
the SMA element is arranged to release the locking of the locking element upon a transition of the SMA element from the expanded state towards the contracted state
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
An actuator device (100) comprising a shape memory alloy, SMA, element (101) configured to transition between an expanded state (201) and a contracted state (202); an actuation member (103) coupled to the SMA element (101) to displace between a first position (251) and a second position (252) when the SMA element (101) transitions between the expanded state (201) and the contracted state (202); an elastic element (105) configured to bias the SMA element (101) towards the expanded state (201); and a locking element (104) configured to selectively lock the actuation member (103) in the first position (251) when the SMA element (101) is in the expanded state (201).