Cooperative Control of UAVs Over an Unreliable Communication Network

This article proposes a method for the cooperative control of two unmanned aerial vehicles (UAVs) to guarantee collision avoidance. The UAVs are locally controlled and are able to change their trajectories at any time. They are connected over an unreliable communication network that may induce packet losses and transmission delays. The network has no coordinator and necessary information for collision avoidance can solely be communicated. In order to reduce the communication effort, information are only transmitted at discrete time instants when they are necessary. Depending on the current situation, one UAV is responsible for avoiding the collision by adjusting its trajectory. To this aim, a control unit is introduced for the UAVs that uses the idea of event-based control and combines methods from communication technology and control theory. The control unit has to execute four tasks: estimation of the current network properties, prediction of the movement of the neighboring object, invocation of communication in an event-based fashion, and planning of the collision avoiding trajectory. It is proved that the control aims are satisfied even in the presence of time delays and packet losses induced by the communication network. A simulation study with two quadrotors shows the suitability of the method.