Dynamics of sideslip perching maneuver under dynamic stall influence

Abstract

This paper presents the optimization framework and aerodynamic modeling of a sideslip perching trajectory under dynamic stall influence. Based on the optimal trajectory solutions, an impact study of dynamic stall on the spatial and state trajectories of the three-dimensional (3D) perching maneuver is also discussed. At high angles of attack, the behavioral effects of the dynamic separation point on the transient post-stall region are distinguishable with rapid changes of angles of attack and aircraft's turn rates. Introduction of three internal variables thus becomes mandatory for addressing variations in flow state influenced by the swift changes in longitudinal and lateral flight angles. These variables are then integrated into a static nonlinear aerodynamic model, developed using empirical and analytical methods, and into the simulative framework as state variables. In the absence of dynamic stall effects, there is a significant discrepancy in trajectories as opposed to counterpart trajectories inclusive of this phenomenon. The consideration of dynamic stall in longitudinal frame is found to have heightened impact on perching trajectory in response to optimized control inputs as compared to that in lateral frame. With the inclusion of dynamic stall deemed necessary, a comparative study between 2D and 3D perching models is also presented to discuss the distinct drag mechanisms involved. The 3D accommodated perch utilizes the additive combination of longitudinal and lateral drag to dispense its reliance on the gravitational force. Measured against performance parameters which include metrics of spatial cost such as perching distance, longitudinal/lateral deviations and time, the study reveals the 3D mode is an improvement over the 2D mode as the latter model's intransigent characteristic of the undershoot becomes obsolete in the 3D version.