Experimental Analysis of a 3-DOF Articulated Flat Empennage

This paper presents the aerodynamic analysis of a bio-inspired empennage, which mimics the way that the tail of some birds moves. To avoid a kinematic chain in the proposed design, the three axes of rotation intersect in a single point. To define the relationship between the attitude of the empennage and the aerodynamic coefficients, different tests were conducted in an open-circuit wind tunnel at low velocity, where the attitude of the empennage was changed, and the aerodynamic effects were measured by means of a force sensor and expressed with six dimensional wrenches, including forces and torques. Wrenches were transformed from the sensor’s reference frame to a frame located at the aerodynamic center of the empennage to compute the aerodynamic coefficients. A multiple regression analysis revealed a coupling effect between the aerodynamic coefficients and the attitude of the proposed empennage, as changes in any of the three Euler angles modify the aerodynamic coefficients. Besides, it is shown that both the longitudinal and the translational motion of the vehicle can be controlled by the proposed bio-inspired empennage.