Development of an adaptive flap/flaperon flight control system with shape memory alloy actuation

This thesis discusses the design, manufacturing and testing of a new kind of adaptive airfoil using Shape Memory Alloy (SMA) actuation. An antagonistic arrangement of SMA wires was used in a Post-Buckled Precompressed (PBP) kind of actuator that was employed in an adaptive flap system. The thesis opens with a short survey on the history of the PBP mechanism and a literature research on different flap systems actuated by adaptive materials. The conceptual design of the SMAPBP actuator and its evolution to the actuator employed in an adaptive aerostructure is discussed in the first chapters. Experiments showed that the SMAPBP actuator could obtain tip rotations up to 65°, which nearly quadrupled the levels achieved by piezoelectric PBP actuators. In the following, former developed theory for piezoelectric PBP actuators was modified to account for the trapezoidal shape of the SMAPBP actuator. The developed theory was then compared to experimental results. A FEM model was also developed and evaluated to prove the PBP concept for this actuator numerically. In the second section of the thesis the author gives a detailed explanation of the design concept and the manufacturing of the airfoil. A NACA0012 airfoil with a chord length of 150mm and a width of 100mm was used to prove the concept of the adaptive flap system. The thesis continues with a description of the test setup, the CFD model assumptions and the results of wind tunnel tests. The developed adaptive airfoil proved its capabilities during the numerical and experimental tests and showed that the employment and actuation of the SMAPBP actuator could more than doubled the lift coefficient of the airfoil. The architecture and employment of a closed loop position feedback system to overcome the nonlinear behavior of the SMA material and the PBP mechanism is also discussed. The thesis closes with an overview over the adaptive airfoil with SMAPBP actuator and gives recommendations for future work in this field.