Flight forces and altitude regulation of 12 gram I-Bird

Ornithopter flight forces are typically measured with the body fixed to a force sensor. Here, we demonstrate the identification of free flight aerodynamic forces at a stable equilibrium point of an ornithopter and compare them with the tethered flight aerodynamic forces. For this demonstration, we have developed a closed-loop altitude regulation for the ornithopter using an external camera and custom made onboard electronics. The results show that the tethered aerodynamic force measurement of a 12 gram ornithopter with zero induced velocity underestimates the total flight force by 24.8 mN.