Segmented SMA Actuator with Self-Regulating PTC Heaters

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Solution Overview

Problem

Conventional shape memory alloy systems require complex and costly sensors, feedback loops, and controllers to manage standard heaters, introducing points of failure and inefficiency.

Innovation Solution

A shape memory alloy actuator system with segmented SMA bodies and self-regulating PTC heaters, where each heater maintains a predetermined temperature based on resistance, allowing for discrete and predictable actuation without the need for extensive sensing and control systems.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If standard heaters are used to transform shape memory alloy, then the shape memory alloy can be actuated, but complex sensors, feedback loops, and controllers are required which increase device complexity and cost

Engineering Contradiction:

Improveactuation reliabilityVSAvoidcontrol system complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The PTC heater elements inherently self-regulate their temperature through their positive temperature coefficient characteristics, automatically limiting their own temperature without requiring external temperature sensors or feedback control systems. This self-service property eliminates the need for complex control infrastructure while maintaining reliable actuation.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The patent utilizes the temperature-resistance parameter relationship of PTC materials, where resistance increases with temperature. This parameter change automatically regulates power dissipation and temperature, transforming a potential control challenge into a self-regulating mechanism that simplifies the overall system.

Inventive Principle:

Principle #35Parameter changes

2Temperature

If standard heaters with external control are used, then temperature can be managed, but additional failure points are introduced into the system

Engineering Contradiction:

Improvetemperature controlVSAvoidsystem failure points

Core Design Contradiction:

TemperatureVSReliability

Solution Approach 1:

Inventive Principle:

Principle #25Self-service

3Ease of operation

If thermal isolation portions are added to the SMA body, then discrete segment actuation is achieved, but manufacturing complexity increases

Engineering Contradiction:

Improvediscrete actuation controlVSAvoidSMA body manufacturing

Core Design Contradiction:

Ease of operationVSEase of manufacture

Solution Approach 1:

The SMA body is divided into discrete segments separated by thermal isolation portions, allowing independent thermal and mechanical control of each segment. This segmentation enables precise discrete actuation control while the thermal isolation portions serve as both structural and thermal boundaries.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The thermal isolation portions utilize materials with different thermal conductivity properties than the SMA segments, creating a composite structure that provides both mechanical continuity and thermal discontinuity. This composite approach achieves discrete actuation control through material property differentiation rather than complex geometric features.

Inventive Principle:

Principle #40Composite materials

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 system enables efficient and reliable actuation of shape memory alloy components by eliminating the need for complex control systems, reducing weight and failure points, and allowing for incremental control of angular twists in vehicles and machinery.

Implementation Method 1

Each heater of the plurality of heaters is configured to maintain a predetermined temperature based on a predetermined resistance of the heater when a voltage is applied to the heater

Methodology Applied

Scientific EffectJoule Heating: Joule Heating

Implementation Method 2

Each heater of the plurality of heaters is configured to maintain a predetermined temperature based on a predetermined resistance of the heater when a voltage is applied to the heater

Methodology Applied

Scientific EffectPositive Temperature Coefficient (PTC):

Implementation Method 3

A segment of the plurality of segments is configured to be effectuated in response to increasing a temperature of the heater associated with the segment

Methodology Applied

Scientific EffectShape Memory Effect: Shape Memory Alloy

Implementation Method 4

The thermal isolation portions include portions of the unitary piece of SMA that have lower thermal conductivity than the thermal conductivity of each of the plurality of segments

Methodology Applied

Scientific EffectThermal Insulation: Thermal Insulation

Data Source

PatentUS10288048B2Deforming shape memory alloy using self-regulating thermal elements

Publication Date: 2019.05.14 THE BOEING CO

AI summary

Disclosed herein is an actuator for effectuating a shape memory alloy (SMA). The actuator includes a body including shape memory alloy. The body includes a plurality of segments. The actuator also includes a plurality of heaters that are each configured to maintain a predetermined temperature based on a predetermined resistance of the heater when a voltage is applied to the heater. Each heater of the plurality of heaters is associated with a different segment of the plurality of segments. A segment of the plurality of segments is effectuated in response to increasing a temperature of the heater associated with the segment.