Shape Memory Alloy Actuators for Compact High-Stroke Autofocus
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Solution Overview
Problem
Existing shape memory alloy (SMA) systems for camera lens elements suffer from complexity, resulting in bulky systems with large footprints and limited Z-stroke range, failing to provide a compact, low-profile solution for auto-focusing drives.
Innovation Solution
The development of SMA actuators with a compact footprint and high Z-stroke range, utilizing buckle and bimorph actuators that include a base, buckle arms, and shape memory alloy wires or ribbons, which are actuated by electrical signals to achieve precise movement in the Z-direction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional SMA systems with multiple components (bearing, flexure element, balls) are used, then the system provides reliable actuation, but the system becomes bulky with large footprint and height clearance
Solution Approach 1:
The patent combines multiple traditional components (support assembly, moving assembly, flexure elements, and bearing balls) into an integrated SMA actuator structure. The buckle arms and bimorph actuators directly couple the moving element to the base, eliminating the need for separate support assemblies and reducing overall footprint while maintaining actuation reliability.
Solution Approach 2:
The patent extracts and eliminates unnecessary intermediate components from the traditional SMA system. By removing the complex support assembly with multiple balls and flexure elements, the design achieves compact dimensions (height ≤2.2mm, footprint ≤3mm) while preserving the essential actuation function through simplified SMA wire or bimorph actuator mechanisms.
2Stability of the object's composition
If traditional SMA systems with multiple components are used, then the system provides stable movement, but the height clearance becomes large
Solution Approach 1:
The patent transitions from a traditional three-dimensional multi-component structure to a planar two-dimensional configuration. The buckle arms and bimorph actuators operate within a compressed height profile (≤2.2mm) while achieving stable Z-stroke movement through in-plane mechanical leverage and out-of-plane actuation, effectively trading vertical space for lateral stability.
3Area of stationary object
If compact SMA actuator design is implemented, then the footprint is reduced, but the Z-stroke range becomes limited
Solution Approach 1:
The patent employs dynamic mechanical advantage through the buckle arm mechanism, where the geometry of the buckle arms changes during actuation to amplify the Z-stroke displacement from the SMA wire contraction. This dynamic leverage system enables a Z-stroke greater than 0.4mm from a compact actuator with footprint ≤3mm, effectively decoupling stroke range from footprint size.
Solution Approach 2:
The patent utilizes bimorph actuators composed of layered materials with different thermal or electrical expansion properties. These composite structures provide both the actuation force and the mechanical amplification needed to achieve extended Z-stroke range from a compact footprint, combining material properties to overcome the size-stroke trade-off.
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 SMA actuators provide a compact design with a Z-stroke greater than 0.4 millimeters and a height of 2.2 millimeters or less, suitable for applications such as autofocus, micro-fluidic pumps, optical image stabilization, and haptic feedback, offering improved actuation performance and reduced size.
Implementation Method 1
The SMA actuator includes an SMA wire configured to receive an electrical signal and transform the electrical signal to a length change of the SMA wire
Implementation Method 2
Each of the SMA wires has one end attached to the support assembly, and an opposite end attached to the moving assembly. The suspension is actuated by applying electrical drive signals to the SMA wires
Implementation Method 3
at least one bimorph actuator including a shape memory alloy material
Implementation Method 4
The bimorph actuator attached to the base
Data Source
AI summary
SMA actuators and related methods are described. One embodiment of an actuator includes a base; a plurality of buckle arms; and at least a first shape memory alloy wire coupled with a pair of buckle arms of the plurality of buckle arms. Another embodiment of an actuator includes a base and at least one bimorph actuator including a shape memory alloy material. The bimorph actuator attached to the base.