Lichten Award Paper: Ground and Flight Tests of a Cable-Driven Four-Bar Linkage Robotic Landing Gear for Rotorcraft

Robotic landing gear (RLG) enhance the landing capabilities of vertical take-off and landing (VTOL) aircraft on sloped, rough, and even mobile landing surfaces. This DARPA funded research demonstrates the design, integration, and ground and flight testing of a RLG system for the commercial S-100 Camcopter, expanding the aircraft's landing capabilities to currently inaccessible terrains with slopes at and above 15°. Lagrange unconstrained and multibody dynamic simulations are elucidated and implemented to design a force feedback controller, state estimation algorithms, and drivetrain components that permit the rotorcraft fuselage to remain level on rough terrain. The system is then demonstrated using ground and flight experiments, and performance metrics are found to match design metrics. An asymmetry in left and right leg landings during flight testing is observed and analyzed as arising due to inertial cross coupling inherent to landing with three-legged rotorcraft. Finally, future work and improved RLG controllers are presented.