UAV circumnavigating an unknown target under a GPS-denied environment with range-only measurements

One typical application of unmanned aerial vehicles (UAVs) is the intelligence, surveillance, and reconnaissance mission, where the objective is to improve situation awareness through information acquisition. For example, an efficient way to gather information regarding a target is to deploy UAV in such a way that it orbits around this target at a desired distance. Such a UAV motion is called circumnavigation. The objective of this paper is to design a control algorithm such that this circumnavigation mission is achieved under a GPS-denied environment when only range measurement is used. The control algorithm is constructed in two steps. The first step is to design a control algorithm by assuming the availability of both range and range rate measurements, where the associated control input is always bounded. The second step is to further eliminate the use of range rate measurement by using an estimated range rate, obtained via a sliding-mode estimator based on range measurement, to replace actual range rate measurement. Such a controller design technique is applicable in other UAV navigation and control missions when a GPS-denied environment is considered.