In order to realize a control system for Shape Memory Alloy (SMA) actuators, that ensure high displacement precisions, a numerical model that simulates the behaviour of a SMA wire subjected to thermo-mechanical actions, up to high number of cycles, has been set up. In particular, the constitutive model of Brinson coupled by any suitable kinetic low of transformation has been used; This model provide a simple and careful description of behavior of the shape memory alloy. Beginning from such model, some corrections has been performed, to keep into account the deviations, in term of characteristic temperatures and mechanical responds, due to a numerous thermo-mechanical cycles which the actuator has been submitted to. Furthermore, in order to complete and check the numerical model, experimental tests has been performed; initially the employed SMA wires have been characterized by several particular metallographic tests and DSC analysis in order to determine the type of phase transformations. Finally, by varying the number of work cycles of actuator, the microstructural and thermo-mechanical changes of some NiTi alloys has been detected. Such results have allowed to obtain a more correct expression of the numerical model. Starting from the experimental results, a code of numerical simulation in environment MATLAB^© has been realised; at the same time, a SIMULINK^© model has been built. This model, opportunely coupled with the experimental model, has allowed to check the actual system. An electric current has been used for the activation of the SMA actuators; the control system has subsequently been optimized taken into account the variations of electric resistivity of SMA that results related to the characteristic phase transformations for this kind of alloys.