On the Development of a Robotic Hummingbird
This paper describes the design, development and flight testing of a 62 gram hummingbird inspired flapping wing micro air vehicle with hovering capability. There were several design challenges encountered and innovative techniques were implemented to overcome them. To achieve the required large flap stroke amplitudes necessary to generate lift for hover at moderate flap frequencies ~25Hz) a novel "5 bar" mechanical linkage system was developed which amplifies the output of a standard 4 bar crank rocker mechanism. Utilizing aeroelastic tailoring techniques, lightweight ~0.8 grams) flexible wings were designed which produce the required lift for hover and their performance was optimized for a specific operational frequency range. Insect based wing kinematic modulation mechanisms were developed for control and stabilization by varying two parameters: the tilt of the flapping planes relative to the vehicle, and the flapping amplitude, both of which alter the magnitude and direction of the lift vector of each wing to achieve motion or trim in a particular direction. These mechanisms are controlled via a kinematic autopilot, which senses the vehicle attitude and, using an on board closed loop proportionalderivative controller, transmits corrective signals to the modulation mechanism actuators which stabilize the vehicle. A systematic approach to tuning the vehicle trim and controller gain values has been implemented, leading to several stable controlled flight experiments. One such flight test lasted ~5.0 seconds in which the vehicle ascended and sustained an altitude of ~1 meter with minimal drift. The final vehicle weighs 62 grams and flaps at about 22Hz during hover.