Tunable Mechanism Enables Robust Surface Perching Under Different Landing Impacts and Orientation Misalignment

Perching significantly enhances the energy efficiency and operational versatility of aerial robots. This article introduces a passive and tunable perching mechanism designed for smooth surfaces. The design features a bistable mechanism (BM) with a soft suction cup, augmented by two sets of shape memory alloy (SMA) actuators for active tuning. The BM enables rapid attachment upon surface contact. A set of SMA wires can increase the BM's triggering force to handle high contact speeds, while a set of SMA springs attached to the suction cup's edges can pull the cup to handle orientation misalignment. Experiments are conducted to characterize how the SMA actuators influence the BM's triggering force and the suction cup's displacement under continuous steady-state low-voltage heating. Additional experiments demonstrate fast tuning using momentary high-voltage heating of the SMA actuators to enhance energy efficiency. The mechanism enables successful perching on smooth surfaces and adapt to varying contact speeds and misalignments when properly tuned for three scenarios: pendulum-based perching, ground perching, and ceiling perching. With its tuning capability, the perching mechanism can alleviate the need for precise motion control for an aerial robot during perching, expanding the applications of aerial robots in areas like environmental monitoring or infrastructure inspection.