GPALM—Multifunctional Underactuated Mechanism With Grasping, Perching, and Adaptive Landing Skills for Drone Applications

Abstract Autonomous drones deployed on missions for inspection, surveillance, search, or rescue often need the ability to interact with the environment or land on unknown terrains. Existing developments for grasping objects with drones, landing on uneven terrain, and perching on various support structures to conserve battery exhibit one or two functions with dedicated mechanisms, making them bulky or use-case specific for a drone. This article proposes a novel underactuated multifunctional mechanism (GPALM) capable of active grasping, passive perching, and acting as adaptive landing gear. GPALM comprises two linkage-driven underactuated fingers or legs, which can be driven actively (using a linear actuator) or passively (using two closed-loop linkages). Introducing an elastic element in series with the active mechanism decouples the active power while perching and allows passive motion. The experimental demonstrations show that GPALM can actively grasp a wide range of objects of different shapes and sizes, and it can passively perch on cylindrical support structures with its own weight. Thanks to the underactuation, the mechanism can adapt to the landing surface’s inclination to keep the drone leveled with respect to the ground. The developed laboratory prototype can carry a payload of up to 3 kg and land on inclined surfaces of up to 10 deg.