**4.7. Applications**

The relevance of piezoelectric actuators for active blade systems comes from the large specific work they can output [41] while being small and easily integrable. Moreover their reliability makes them suitable for safely powering mechanisms in smart blade concepts.

Many actuation systems for the active trailing-egde rotorblade are actuated using amplified stack actuators [33, 44, 56]. Other designs use piezoelectric patch actuators bonded onto a beam [28] or piezoelectric shear actuators built as a torsional actuator as shown in Figure 15 [12].

Some studies on the design of airfoils with controllable camber involve stack actuators inside a structure that convert and amplify the motion into a change of curvature of the airfoil [19, 20].

For the deployment of the Gurney flap at the trailing edge, bimorph piezoelectric actuation mechanisms are being studied [59], as well as more complex structures to amplify the displacement of piezoelectric patch actuators and MFCs [42]. AFC and MFC actuators have also been tested successfully for the active-twist application [65]. They provide distributed strain over all the rotorblade surface to successfully twist the blade under operating conditions [46, 50].

Research on flow control systems has considered piezoelectric diaphragms to deliver enough airflow speed for synthetic jets and achieve proper flow control [31, 67].
