Cable-driven legged landing gear for unmanned helicopter: Prototype design, optimization and performance assessment

Unmanned helicopters equipped with adaptive landing gear will dramatically extend their application especially in dealing with challenging terrains. This study presents a novel cable-driven legged landing gear (CLG) with differential transmission for unmanned helicopters in complex landing environments. To obtain the preferred configuration of the legged mechanism, a multi-objective optimization framework for the CLG is constructed by concurrently considering terrain adaptability, landing stability and reasonable linkage of internal forces. The non-dominated sorting genetic algorithm II is employed to numerically acquire the optimal scale parameters that guide the mechanical design of the CLG. An unmanned helicopter prototype equipped with the devised CLG is developed with key performance assessment. Experimental results show that the devised CLG can provide energy-efficient support over uneven terrains (totally driven torque demand less than 0.1 N m) in quasi-static landing tests, and favorable terrain adaptability (posture fluctuation of the fuselage less than ±1°) in unknown slope landing tests. These exhibited merits give the proposed CLG the potential to enhance the landing performance of future aircraft in extreme environments.