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Optimised Layout of Shape Memory Actuators by a Numerical Modelling Approach

Horst Meier 1Sascha Dilthey 

1. Ruhr-University (RUB), Universitatsatrasse 150, Bochum D-44780, Germany


Shape-Memory-Alloy (SMA) actuators used in technical applications are still mainly parameterised by trial-and-error methods, because of a lack of computer-aided design tools for this active material. This paper describes a numerical modelling approach to design and optimise the geometry of SMA actuators and the load and heating conditions of the technical system. The Shape-Memory Effect used in most technical Systems is the extrinsic two way effect (2WE).

A numerical model was developed to simulate this effect. It was implemented in MATLAB/SIMULINK©. The focus of the model lays on the activation behaviour of the SMA actuator, which defines its rate of heating and cooling. These parameters describe the dynamical characteristics of the actuator and the complete SMA powered system. Various load conditions and actuator geometries and shapes, e.g. wire or spring actuator are simulated by a calculation of the energetic balance of the whole system. The numerical model can be used to simulate time variant heating currents in order to obtain an optimal system performance or match a defined time response of the actuator. It can also be used to calculate the activation behaviour of a SMA actuator with given heating and mechanical loading conditions.

The numerical model is validated by using a testing rig, which is capable of generating all the included parameters and boundary conditions of the numerical model that can be simulated for SMA-wire or SMA-spring actuators. Finally the archived knowledge is use to design the prototype of a SMA-powered Stepping Drive base on the moving principle of a Wave Drive Gear Set. In this concept the external engine is substituted by SMA-Wire-Actuators to combine the advantages of this Drive Set with the huge energy loading capabilities of Shape Memory Materials.


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Presentation: Poster at E-MRS Fall Meeting 2007, Symposium E, by Sascha Dilthey
See On-line Journal of E-MRS Fall Meeting 2007

Submitted: 2007-05-14 13:52
Revised:   2009-06-07 00:44