Landing and Perching on Vertical Surfaces with Microspines for Small Unmanned Air Vehicles

Abstract

We present the first results of a system that allows small fixed-wing UAVs to land and cling on surfaces such as brick walls using arrays of microspines that engage asperities on the surface. The requirements of engaging and loading the spines lead to an approach in which an open-loop pitch-up motion is triggered by a range sensor as the plane nears the wall. The subsequent dynamics result in a period during which the plane stays within an envelope of acceptable orientation and velocity (pitch from 60---105 deg, vertical velocity from 0 to ??2.7 m/s and up to 3 m/s of horizontal velocity) that permit successful perching. At touchdown, a non-linear suspension absorbs the remaining kinetic energy to minimize peak forces, prevents bouncing and facilitates spine engagement. The total maneuver duration is less than 1 s. We describe the spine suspension and its analysis and present results of typical perching maneuvers (10 landings under autonomous control and 20 under manual control). Under calm conditions, the success rate for autonomous perching on building walls is approximately 80%, the failures being attributed to erroneous wall detection. We conclude with a discussion of future work to increase the robustness of the approach (e.g. with wind) and allow subsequent take-offs to resume flight.