SMA Actuator Assembly with Gravity-Resistant Holding Mechanism
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Solution Overview
Problem
Existing actuator assemblies using shape-memory alloy (SMA) wires struggle to maintain a movable element in a stable position against gravity while allowing for three-dimensional movement when powered.
Innovation Solution
An actuator assembly comprising first and second parts connected by SMA wires, with a mechanism to hold the first part in position and orientation against gravity when the SMA wires are unpowered, using end stops and resilient elements to minimize interference with the SMA wires' ability to cause 3D movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a mechanism is added to hold the movable element against gravity, then stability against gravity is improved, but device complexity increases
Solution Approach 1:
The patent combines the holding mechanism with the existing SMA wire actuator structure. The resilient elements and end stops are integrated into the same assembly as the SMA wires, allowing the holding function to be achieved without adding a completely separate mechanism. This merging reduces overall device complexity while providing stable positioning against gravity.
Solution Approach 2:
The patent introduces resilient elements as intermediary components between the movable element and the fixed structure. These resilient elements act as mediators that provide both the holding force against gravity and allow controlled movement when SMA wires are activated. This intermediary approach enables the holding function without directly complicating the primary actuator mechanism.
2Manufacturing precision
If resilient elements and end stops are used to hold the element, then positioning accuracy is improved, but the ability of SMA wires to cause 3D movement is restricted
Solution Approach 1:
The patent applies local quality by making the resilient elements and end stops selectively engaged. The end stops are positioned to provide precision holding in specific positions while leaving other directions and positions free for SMA wire actuation. This localized application of constraints maintains positioning accuracy where needed while preserving 3D movement capability where required.
Solution Approach 2:
The patent creates a dynamic system where the interaction between resilient elements, end stops, and SMA wires allows the system to switch between held and moved states. The resilient elements can deflect to allow movement when SMA wires are activated, then return to provide holding when unpowered. This dynamic behavior reconciles the contradiction between stable positioning and versatile movement.
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 effectively maintains the movable element in a stable position against gravity without compromising the SMA wires' ability to achieve three-dimensional movement, ensuring precise control and alignment in applications like camera lenses.
Implementation Method 1
a plurality of lengths of shape-memory alloy (SMA) wire connected between the first and second parts, wherein the lengths of wire are configured, when selectively powered, to cause three-dimensional (3D) movement of the first part relative to the second part
Implementation Method 2
a set of one or more resilient elements connected between the first and second parts to bias the first part towards the at least one position and/or orientation
Data Source
AI summary
An actuator assembly comprises: first (20) and second (10) parts, wherein a primary axis (P) is defined with reference to the second part; a plurality of lengths of shape-memory alloy wire (30) connected between the first and second parts, wherein the lengths of wire are configured, when selectively powered, to cause three-dimensional movement of the first part relative to the second part; and a mechanism configured, when the lengths of wire are unpowered, to hold the first part in at least one position and/or orientation relative to the second part against the force of gravity for any orientation of the second part.