Shape Memory Alloy Actuator for Aerodynamic Surface Control
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Solution Overview
Problem
Existing shape memory alloy (SMA) actuators for air vehicles face challenges in controlling aerodynamic surfaces due to structural stiffness and require excessive power and complexity, with known SMA twist tube actuators needing continuous electrical power to maintain position.
Innovation Solution
A method and system that applies a force couple to shape memory alloy workpieces to impart a generally planar transformational behavior, using thermal cycles and strain cycles to create a trained SMA actuator with edge-wise racking loads, integrated into a structural spar to influence the shape of aerodynamic surfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If known SMA twist tube actuators are used to control aerodynamic surfaces, then the ability to twist and deform surfaces is improved, but continuous electrical power is required to maintain position, increasing system weight and complexity
Solution Approach 1:
The patent applies periodic thermal cycling to train the SMA actuator, creating a racking motion that transforms the material's phase between martensite and austenite. This periodic thermal action allows the actuator to achieve position control without continuous power, as the thermal cycles create discrete transformation points rather than requiring sustained heating
Solution Approach 2:
The SMA actuator utilizes the inherent shape memory effect of the material to maintain trained positions passively. Once trained through thermal cycling, the actuator self-maintains its configuration through phase transformation memory, eliminating the need for continuous electrical power to hold position
2Force
If mechanical actuators are used to overcome structural stiffness of aerodynamic surfaces, then the ability to twist and bend surfaces is improved, but excessive power and complexity are required
Solution Approach 1:
The patent changes the material parameter of the actuator from conventional mechanical materials to shape memory alloy, which exhibits temperature-dependent phase transformations. By controlling temperature parameters during training and operation, the SMA material can generate sufficient force to overcome structural stiffness while consuming less power than traditional mechanical actuators
Solution Approach 2:
The patent exploits the phase transition between martensite and austenite in the SMA material to generate actuation force. During training, thermal cycling induces phase transformations that create racking motion, and during operation, phase transitions provide the necessary force to deform aerodynamic surfaces without requiring excessive continuous power
3Ease of manufacture
If SMA actuators are trained by conventional methods (pulling wires, bending plates, twisting tubes), then the actuators can be integrated into existing systems, but control precision and transformational behavior are limited
Solution Approach 1:
The patent segments the transformational behavior into discrete racking motions through controlled thermal cycling during training. By applying thermal cycles with force couples, the SMA material develops a segmented transformation pattern that provides precise, controllable motion stages rather than continuous deformation, improving control precision while maintaining manufacturability
Solution Approach 2:
The patent creates a composite training process that combines thermal cycling with mechanical force couples during the training phase. This composite approach to training the SMA material produces a trained structure with enhanced transformational behavior and control precision, while the final actuator can be integrated using conventional manufacturing methods
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 allows for efficient control of aerodynamic surfaces with reduced weight and complexity, enabling improved performance and fuel efficiency by using thermally controlled SMA actuators that can warp or twist surfaces without continuous power requirements.
Implementation Method 1
Shape memory alloys can exist in one of several distinct temperature-dependent phases. The most commonly utilized of these phases are the so-called martensite and austenite phases. Upon heating a shape memory alloy through a transformation temperature, the shape memory alloy changes from the martensite phase into the austenite phase.
Implementation Method 2
If a component made of a shape memory alloy material, for example, NiTinol, is deformed while in a martensitic state (low yield strength condition) and then heated to its transition temperature to reach an austenitic state, the shape memory alloy material of the component will resume its original (undeformed) shape.
Implementation Method 3
A method and system that applies a force couple to shape memory alloy workpieces to impart a generally planar transformational behavior, using thermal cycles and strain cycles to create a trained SMA actuator with edge-wise racking loads
Data Source
AI summary
There is provided a training system capable of performing work. The system has a shape memory alloy (SMA) actuator exhibiting a generally planar transformational behavior. The system further has one or more heating elements for transforming the SMA actuator from an original shape to a trained shape, thereby performing work.