Twist control of aerodynamic profiles by a reactive method (experimental results)

Active twist control of airfoils using embedded actuators has been widely studied during the last decade. To control the twist, an additional torsional moment is applied using these actuators. This active method is efficient but encounters limitations due to the amount of energy necessary to activate the system. An alternative method to this energy costly active control is proposed. Rather than applying an additional torsional moment to control the twist of the structure, the shear center of the profile is shifted using an internal mechanical system. More precisely, the activation of a clutch-like device, able to link or unlink thin internal walls, allows the redistribution of the bending and torsional shear stresses. This process leads to a possible twist control of the airfoil, significantly less energy consuming than an active one. Unlike the active twist control method, this method needs an external force to be effective, so it is called a “reactive’’ control method. Experimental investigations have been performed to verify the efficiency of this method. The results show that it is possible to obtain significant twist angle modifications. Moreover, the measurement of internal longitudinal displacements, correlated with the twist angle, enables the twist control of the structure.