A Self-Rotary Aerial Robot With Passive Compliant Variable-Pitch Wings

Inspired by maple seeds, the self-rotary winged aerial robots reflect the advantages of both multi-rotor aircraft and fixed-wing robots. However, their self-rotating speed is related to the takeoff weight, which may affect their application and flight stabilization. To provide a practical and feasible solution, this work proposes a passive compliant variable-pitch mechanism on the self-rotary winged aircraft without requiring extra actuators. Depending on the weight of the payload, the pitching angle of the wings can be passively varied to minimize the increase in the rotating speed and enhance attitude stabilization ability. Besides, an adaptive attitude controller is also designed to address the challenges in attitude stabilization, which are caused by parameter uncertainties and the variable pitching angle. To elaborate on the design and fabrication of the prototype, necessary identification experiments are arranged to find the relationship of pitching angle, thrust generation, power draw, and rotating speed. The experimental findings indicate the proposed robot with optimal pitch angles achieves around 56.8% more power loading than using propellers directly, from 4.4 to 6.9 g/w. The combination of the passive compliant mechanism and adaptive controller improves flight performance from 0.16 to 0.08 meters (mean of absolute translational error).