This paper presents the results of theoretical modeling and experimental characterization of PiezoSystems Jena P-177-00 large stroke piezoelectric actuator and of Etrema AA-140J025-ES1 large stroke/large power magnetostrictive actuator. An improved smart-material actuators measurement method suited for static and low frequency actuation was devised. Analytical and finite element modeling (ANSYS) of the experimental setup to determine stiffness component characteristics was performed. The output displacements of the active material actuators were recorded in quasi-static and dynamic regimes, under varied pre-stress level, voltage and frequency values. The measurements indicated a strong dependence of the actuator stiffness and piezoelectric properties on the electromechanical loading conditions. The study also identified and calculated the parameters of the induced strain actuators electro-mechanical model. These parameters are necessary for performing design optimization to achieve maximum energy transfer and minimum power requirements. Experimentally verified data characterizing piezoelectric and magnetostrictive actuators in the full stroke/full power regime is provided.