Modeling and Experiment of a Flexible Module Actuated by Shape Memory Alloy Wire

In recent years many investigations have been performed on design and fabrication of micro mechanical manipulators. One of the practical usages of this manipulator is endoscopy. In an endoscopy system, a small manipulator with high maneuverability and flexibility is required to support the probe’s movement into a colon easier than classic manipulators. In this paper a basic flexible module is presented for use in such an application. The structure of presented module is simple and includes a compressive spring which could be bent to the sides. This tends to more simplicity in addition to proper flexibility. Connecting three wires of shape memory alloy (SMA) uniformly distributed in circumference of spring with an angle of 120 degrees, it is possible to provide an almost large displacement and orientation change between the end planes of module. By using three wires and stimulating them individually or together, different rotation regimes are provided. The flexible module deformation is modeled in this paper thoroughly. Deflection and orientation of spring as the basic structure of the module is studied under the loads. Also, Brinson model is used for modeling the shape memory alloy wire. Afterward, the spring model is coupled with SMA model to describe the dynamic behavior of module under a defined activation. The simulation is implemented in MATLAB-Simulink Though the developed simulation platform, the trajectory of module may be extracted and used for developing a modular manipulator. An experimental setup is prepared to verify the simulation results. Through the simulations, module performance in addition to proper geometrical parameters for the considered application is calculated through the simulations. It is shown that a proper relation between geometrical parameters of spring (like outer diameter, spring wire diameter and number of coils) in combination with a suitable SMA wire in diameter, affect the maximum deformation of SMA-actuated module.