Hybrid Flapping and Gliding Flight for Robot Bird Using Closed-Loop Nonlinear Optimal Control: Indoors Experimentation

Hybrid flight of flapping-wing flying robots (FWFRs) is one of the advantages of flapping-wing mechanisms for thrust and lift generation of aerial platforms. Hybrid flight refers to the capacity of switching between flapping and gliding modes. The source of thrust and lift generation is the flapping state; however, in the condition of favorable wind and sufficient height from the ground, gliding flight can be achieved. The gliding phase, flight without a main flapping motor offers several important features: requiring less energy per covered horizontal distance, and flight without oscillation. The focus of this work is to investigate the reduction of oscillation in indoor flights where the flight zone is a closed limited space. In point-to-point control of the robot bird, the last meter approach to the final desired point, ideally demands less oscillations. The implementation of the closed-loop nonlinear control on the FWFR is studied; the controller is so-called the state-dependent Riccati equation (SDRE). The experiments showed successful switching between flapping and gliding controllers in the indoor tests. The lack of wind in an indoor environment increases the difficulty of gliding and the results showed a significant decrease in height with an increase in the gliding distance.