An investigation into the use of springs and wing motions to minimize the power expended by a pigeon-sized mechanical bird for steady flight

In this paper we investigate the effect of using springs and wing motions to minimize the power required by a mechanical bird to fly. Inertia forces as well as aerodynamic forces on the wing are included. The design takes into account different flight speeds in the range from 0 to 20 m/s. Four ways in which springs can be attached, are considered. The frequency of wing beat is kept fixed and both flapping and feathering are assumed to be simple harmonic. Constraints are imposed on the maximum power expended by the two actuators of a wing. The results show that introduction of springs increases the power required at lower speeds, marginally reducing the power at higher speeds. In the manner in which they are used here, springs do not appear to be useful to reduce power. However the optimal solutions obtained without springs indicate that it is possible to develop pigeon-like mechanical birds which can hover and fly steadily up to 20 m/s.