Nitinol Wire Pivot Assembly for Inertial Stability

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Solution Overview

Problem

Conventional electromechanically driven pivot mechanisms are inadequate for applications requiring limited physical space, minimized weight, and inertial stability during operation.

Innovation Solution

An electrically driven pivot assembly using Nitinol wires, where each end of the wire is coupled to arms that rotate about a circular collar, contracting when heated to apply simultaneous counter-rotational forces, maintaining angular inertia stability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional electromechanically driven pivot mechanisms are used, then reliable mechanical motion is achieved, but weight and device complexity increase

Engineering Contradiction:

Improvemechanical motion reliabilityVSAvoidpivot mechanism weight

Core Design Contradiction:

ReliabilityVSWeight of moving object

Solution Approach 1:

The patent replaces conventional electromechanical actuators with a shape memory alloy (SMA) wire system. The SMA wires undergo phase transformation when heated by electrical current, generating mechanical force to rotate the arms. This substitution eliminates complex mechanical components like motors, gears, and bearings, significantly reducing weight while maintaining actuation functionality.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The invention utilizes the temperature-dependent phase transformation properties of shape memory alloy wires. By controlling the temperature of the SMA wires through electrical heating, the material transitions between austenite and martensite phases, causing reversible length changes that drive the mechanical motion. This parameter-based actuation method replaces traditional force-based mechanical systems.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If conventional electromechanically driven pivot mechanisms are used, then reliable mechanical motion is achieved, but device complexity and volume increase

Engineering Contradiction:

Improvemechanical motion reliabilityVSAvoidpivot mechanism complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The invention merges the actuation function into a single integrated SMA wire system rather than using separate actuators for each arm. The wires are coupled to both arms simultaneously, and their contraction/extension directly produces the required counter-rotational motion, simplifying the overall mechanism structure.

Inventive Principle:

Principle #5Merging (Combining)

3Force

If arms are deployed using conventional actuators, then deployment force is achieved, but angular inertia changes substantially

Engineering Contradiction:

Improvedeployment forceVSAvoidangular inertia stability

Core Design Contradiction:

ForceVSStability of the object's composition

Solution Approach 1:

The patent employs an asymmetric wire routing configuration where the SMA wires are arranged to produce equal and opposite torques on the two arms. The wires are coupled to both arms in a manner that ensures when they contract, they generate counter-rotational forces that are symmetric in magnitude but opposite in direction, thereby maintaining angular inertia stability at the base.

Inventive Principle:

Principle #4Asymmetry

Solution Approach 2:

The invention uses the second arm as a counterweight to the first arm. As one arm rotates in one direction, the other arm rotates in the opposite direction, creating counterbalancing moments that cancel out changes in angular inertia at the base. This counter-rotational mechanism ensures the base remains stable during deployment.

Inventive Principle:

Principle #8Anti-weight (Counterweight)

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

Enables efficient deployment of arms without substantial change in angular inertia, reducing the need for heavy actuators and minimizing weight and volume, suitable for applications like unmanned aeronautical vehicles.

Implementation Method 1

Each end of a Nitinol wire is coupled to the first and second arms and contracts in length when heated by the flow of electrical current

Methodology Applied

Scientific EffectJoule heating: Joule Heating

Implementation Method 2

Nitinol wire... at least portions of the Nitinol wire have been conditioned to contract in length when heated

Methodology Applied

Scientific EffectShape memory alloy effect: Shape Memory Alloy

Data Source

PatentUS10280904B2Electrically activated pivot assembly

Publication Date: 2019.05.07 NORTHROP GRUMMAN SYSTEMS CORP

AI summary

An exemplary rotational assembly includes a base having a circular collar and first and second arms that rotate about the circular collar in opposite angular directions. In a stored state the arms have substantially the same angle relative to the circular collar; in a deployed state the arms have rotated into opposing positions. Each end of a Nitinol wire is coupled to the first and second arms and contracts when heated by the flow of electrical current. This contraction causes the simultaneously application of a rotational force to the first and second arms causing the first and second arms to rotate about the circular collar in opposite angular directions. The simultaneous counter rotating angular forces during rotation of the arms causes no substantial change in angular inertia at the base.