Developing a controller for a spatial bending micro module actuated by shape memory alloys: Modeling and experiment

Design and fabrication of micro mechanical actuators is very useful for special robotic applications. One of the practical usages is continuum manipulators uses in medical applications such as endoscopy tool. In such applications, a maneuverable thin and flexible manipulator is highly required. In this paper, a basic module is studied for such an application. In the structure of module, three wires of shape memory alloy (SMA) are uniformly distributed and attached to the circumference of a flexible beam with an angle of 120 degrees. Stimulating wires individually or together, provide different rotation regimes. Brinson model is used for shape memory alloy wires. Afterward, a coupled model for the whole system which includes three SMA wires attached to a flexible beam is developed. The model is simulated in Matlab and provided a platform for validation of control strategy. Through the complex and nonlinear behavior of SMAs, providing a suitable controller was a challenge. In this paper, a control strategy is developed to set a desired position for the two degree of freedom module. The simulation results present a reasonable performance for the controller. Finally through the manufactured module and the provided test bed, the developed controller is experimentally verified.