Approximate model for cycle-averaged aerodynamic forces, and its application to stability and control of bird-scale flapping-wing aircraft

We derive approximate, closed-form expressions for the cycle-averaged forces produced by flapping wings operating in a regime similar to birds and small unmanned aerial vehicles. The model is 2-D and intended mainly as an aid to performance and stability analysis, and control design. The model accounts for the nonlinear behavior of lift at high angles of attack, corrections for unsteadiness, as well as an elementary expression for drag. As an elementary application of the model, we determine the conditions under which the power consumption is minimized and those under which the range is maximized. We demonstrate how the model can be employed gainfully for stability analysis and control design.