A simple geometric model, which describes the changing of springs forces in relation to rotation angle will be presented, in order to outline the optimization process of the configuration of SMA and bias steel springs to achieve a rotational displacement of an arm. In according to this model the SMA and steel springs which has been designed for the application will be characterized and the results of the tailoring process of the thermo-mechanical properties will be illustrated.

The subsequently realization of a prototype, has allowed to validate the geometric model and test the thermo-mechanical properties of the springs in relation to the output torque and the required angular displacement of the blades. The thermo-mechanical characterization of the SMA and steel spring will be also presented and a preliminary standardization attempt will be described in order to demonstrated as versatile design could be exploited in the application of SMA rotative actuators in the air conditioning field but also in any further application where the thermal energy could be converted in mechanical work in relation to the temperature changing.