Design and dynamic modeling of a module included a compressive spring and actuated by shape memory alloy wire

In recent years many investigations have been performed on design and fabrication of micro mechanical manipulators. These manipulators have a wide application in industry specifically medical applications. A practical usage of this manipulator is endoscopy system. In the endoscopy system, we need a small manipulator with high maneuverability and flexible body to make the probe’s movement into a colon easier than classic manipulators. In this paper a basic flexible module is developed for use in this structure. Connecting three wires of shape memory alloy uniformly distributed in circumference of a compressive spring with angle of 120 degrees, it is possible to make an almost large displacement in the end planes with small strain of wires. In this paper, a model is developed to define the spring deformation which in the following is coupled with the model of SMA wire presented by Brinson to describe the module behavior definitely. Dynamic modeling and simulation is implemented in MATLAB-Simulink and module performance in addition to proper geometry for the considered application is extracted. Through the results of simulation verified by experiment, proper parameters of module for providing more deflection and rotation when activated by SMA are extracted.