SMA-Actuated Propeller Blades for Variable Pitch Control

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Solution Overview

Problem

Variable pitch propellers are complex and add weight, with existing mechanical actuators requiring constant operation for engine speed control, and fixed propellers compromise performance as their design point is fixed at a specific engine speed and power level, limiting adaptability to different flight conditions.

Innovation Solution

A propeller assembly utilizing a shape memory alloy actuator that applies torque to adjust blade pitch by transforming between martensite and austenite phases in response to heat, allowing for optimized performance across various flight conditions without the need for complex mechanical linkages or constant power consumption.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If variable pitch mechanisms are used to adjust blade pitch, then propeller performance is optimized across different flight conditions, but device complexity and weight increase

Engineering Contradiction:

Improvepropeller performance optimizationVSAvoidmechanical actuator complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent replaces complex mechanical actuators and linkages with a shape memory alloy (SMA) actuator that uses thermal energy to change blade pitch. The SMA actuator transforms between martensite and austenite phases in response to heat application, directly adjusting the blade pitch angle without requiring mechanical transmission components, thereby reducing device complexity while maintaining adaptability.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The invention changes the physical state parameter of the shape memory alloy actuator (temperature-induced phase transformation between martensite and austenite) to achieve blade pitch adjustment. By controlling the temperature of the SMA actuator, the blade pitch can be varied to optimize performance across different flight conditions without complex mechanical systems.

Inventive Principle:

Principle #35Parameter changes

2Ease of operation

If mechanical actuators are used for engine speed control, then blade pitch can be adjusted, but constant power consumption is required

Engineering Contradiction:

Improveblade pitch controlVSAvoidpower consumption

Core Design Contradiction:

Ease of operationVSUse of energy by moving object

Solution Approach 1:

The shape memory alloy actuator operates through periodic heating and cooling cycles to adjust blade pitch. The SMA material transforms from martensite to austenite phase when heated, achieving the desired pitch change, and returns to martensite phase when cooled, enabling the system to achieve control without continuous power consumption, only during phase transition moments.

Inventive Principle:

Principle #19Periodic action

3Device complexity

If fixed pitch propellers are used, then device complexity is reduced, but performance is compromised due to fixed design point

Engineering Contradiction:

Improvepropeller system simplicityVSAvoidpropeller efficiency

Core Design Contradiction:

Device complexityVSProductivity

Solution Approach 1:

The patent introduces dynamic adaptability to the propeller system through the shape memory alloy actuator. While the overall structure remains simple like fixed-pitch propellers, the blade pitch can be dynamically adjusted in response to changing flight conditions by controlling the temperature of the SMA actuator, thereby maintaining high productivity across various operating regimes without sacrificing system simplicity.

Inventive Principle:

Principle #15Dynamics

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 adjustment of blade pitch to optimize propeller performance across different flight conditions, reducing weight and complexity while maintaining control over engine speed, thereby enhancing overall aircraft efficiency and adaptability.

Implementation Method 1

a shape memory alloy actuator that applies torque to adjust blade pitch by transforming between martensite and austenite phases in response to heat

Methodology Applied

Scientific EffectShape memory alloy phase transformation: Shape Memory Alloy

Data Source

PatentEP3127804B1Shape memory alloy-actuated propeller blades and shape memory alloy-actuated propeller assemblies

Publication Date: 2019.05.15 THE BOEING CO

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AI summary

Shape memory alloy-actuated propeller blades and shape memory alloy-actuated propeller assemblies are disclosed. An example propeller blade includes a propeller body (212), a plate (222) coupled to the propeller body (212), a torque transfer member (220), and a shape memory alloy (SMA) actuator (218). The torque transfer member (220) has a distal end attached to the plate (222) such that the torque transfer member (220) applies to the plate (222) at least a portion of a torque applied to the torque transfer member (220) at a proximal end ofthe torque transfer member (220). The SMA actuator (218) has a distal end and a proximal end. The distal end of the SMA actuator (218) is attached to the torque transfer member. (220) The proximal end ofthe SMA actuator (218) is coupled to the propeller body (212) such that the distal end is mated to the propeller body. (212) The SMA actuator (218)is configured to apply the torque to the proximal end of the torque transfer member (220) in response to an application of heat to the SMA actuator (218).