UAV Circumnavigating an Unknown Target Under a GPS-denied Environment   with Range-only Measurements
  One typical application of unmanned aerial vehicles is the intelligence, surveillance, and reconnaissance mission, where the objective is to improve situation awareness through information acquisition. For examples, 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 the paper is to design a UAV control algorithm such that this circumnavigation mission is achieved under a GPS-denied environment using range-only measurement. The control algorithm is constructed in two steps. The first step is to design a UAV 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 using range measurement, to replace actual range rate measurement. Such a controller design technique is applicable in the control design of other UAV navigation and control missions under a GPS-denied environment. 
Yongcan Cao
cs.SY cs.RO math.OC