Helical SMA Actuator Layout for Compact Translational Motion

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Solution Overview

Problem

Existing SMA actuation apparatuses face constraints in miniaturization due to the extent of SMA actuator wires projected along the movement direction, which limits the reduction in size, particularly in applications like camera lenses where translational movement is required.

Innovation Solution

The use of a helical bearing arrangement that guides helical movement, allowing the SMA actuator wire to drive rotation around a helical axis, converting it into translational movement, thereby minimizing the extent of the actuator wire along the movement direction.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Length of moving object

If SMA actuator wires extend at an acute angle to the movement direction to increase movement amount, then the movement range is improved, but the projected extent along the movement direction increases, constraining miniaturization

Engineering Contradiction:

Improvemovement rangeVSAvoidprojected extent along movement direction

Core Design Contradiction:

Length of moving objectVSVolume of moving object

Solution Approach 1:

The patent transforms the linear extension problem into a rotational dimension by using a helical bearing arrangement. The SMA actuator wire operates in a plane normal to the helical axis, converting linear contraction into rotational movement around the helical axis, which the helical bearing then converts into translational movement along the optical axis. This dimensional transformation allows the actuator to achieve the required movement range without increasing its projected extent along the movement direction.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Volume of moving object

If the SMA actuation apparatus is miniaturized along the movement direction, then the device size is reduced, but the SMA actuator wires cannot provide sufficient translational movement

Engineering Contradiction:

Improvedevice size along movement directionVSAvoidtranslational movement capability

Core Design Contradiction:

Volume of moving objectVSLength of moving object

Solution Approach 1:

The helical bearing arrangement acts as an intermediary mechanism between the SMA actuator wire and the lens element. The SMA wire provides rotational torque around the helical axis, and the helical bearing converts this rotation into translational movement along the optical axis. This intermediary mechanism decouples the actuator's physical extent from its movement capability, allowing miniaturization along the movement direction while maintaining sufficient translational movement through the rotational-to-translational conversion.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Volume of moving object

If SMA actuator wires are arranged to drive rotation around a helical axis, then the projected size is minimized, but the mechanism complexity increases due to the helical bearing arrangement

Engineering Contradiction:

Improveprojected size of actuatorVSAvoidmechanism structure

Core Design Contradiction:

Volume of moving objectVSDevice complexity

Solution Approach 1:

The helical bearing arrangement performs multiple functions simultaneously: it guides the rotational movement of the lens element around the helical axis, converts this rotation into translational movement along the optical axis, and constrains the lens element to follow a helical path. By combining these functions into a single mechanism, the patent minimizes the projected size of the actuator while managing the complexity through functional integration rather than separate components.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 approach reduces the projected size of the SMA actuation apparatus by utilizing a helical bearing arrangement to convert rotational movement into translational movement, enabling smaller device designs without compromising functionality.

Implementation Method 1

at least one shape memory alloy actuator wire connected between the support structure and the movable element in, or at an acute angle to, a plane normal to the helical axis and arranged, on contraction, to drive rotation of the movable element around the helical axis

Methodology Applied

Scientific EffectShape memory alloy contraction: Shape Memory Alloy

Implementation Method 2

a helical bearing arrangement supporting the movable element on the support structure and arranged to guide helical movement of the movable element with respect to the support structure around a helical axis

Methodology Applied

Scientific EffectHelical movement conversion: Helix

Data Source

PatentUS12554177B2Shape memory alloy actuation apparatus

Publication Date: 2026.02.17 CAMBRIDGE MECHATRONICS

AI summary

A shape memory alloy actuation apparatus comprises a support structure (2) and a movable element (10). A helical bearing arrangement (20) supporting the movable element on the support structure guides helical movement of the movable element with respect to the support structure around a helical axis (H). At least one shape memory alloy actuator wire (60) is connected between the support structure and the movable element in, or at an acute angle to, a plane normal to the helical axis, so as to drive rotation of the movable element around the helical axis which the helical bearing arrangement converts into said helical movement.