Fail-safe encircling of multiple unmanned aerial vehicles with bearing only measurements

This paper presents a cooperative strategy to achieve evenly spaced circular formation of a group of unmanned aerial vehicles. The strategy is claimed to be fail-safe because the circular formation remains unaltered even if one or more unmanned aerial vehicles fail. We can also add more unmanned aerial vehicles without altering the formation. The control law uses only bearing angle information. We can pre-specify the centre of the circular formation of the unmanned aerial vehicles. The unmanned aerial vehicles will maintain the desired distance from the centre with bearing angle measurement only. We assume that the unmanned aerial vehicles are identical and can measure the bearing angle of all the other unmanned aerial vehicles. The strategy is analysed using unicycle kinematic and verified using six-degree-of-freedom model of the unmanned aerial vehicles. Extensive simulations are carried out for noisy measurement, presence of wind and moving target.