Shape optimization of a compliant mechanism for an actively conformable rotor airfoil

In the present study, the optimal shape of a limited amount of passive material in a compliant mechanism of predetermined topology was determined. The simple compliant mechanism with a small number of actuators can be packaged in the long, narrow space of the rotor airfoil cross-section. The compliant mechanism is designed for maximum rotation angle under actuation loads, and minimum deflection under aerodynamic loads. Rotation angle (RA) and Strain Energy (SE), are used as measures of the deflections created by the actuation and aerodynamic loads, respectively. The design objectives are achieved by maximizing a multi-criteria objective function that represents a ratio of the RA to SE. Shape optimization of the compliant mechanism is conducted and the results indicate that the optimal compliant mechanism consists of a passive substructure with uniform cross section. The optimal geometry of the compliant mechanism is also determined in a parametric study (optimal ratio of the length to height of 0.3), and this structure can produce rotation angle of 13 Deg/m. when the actuators provide 1% actuation strain. The deflection due to aerodynamic loads is extremely small. The performance of the mechanism is examined further with variations in material and actuator properties. Additional results include an analysis of a compliant mechanism structure based on a modified topology, which is introduced to reduce numbers of actuators.