Decentralized control design approaches for formation control of unmanned aerial vehicles

Abstract

The leader follower type formation of Unmanned Aerial Vehicles usually demands decentralized yet co-operative control among the vehicles. The decentralized control approach is superior to centralized control in view of lesser involvement of delay, minimal information sharing requirement, reduced computational effort for controller design etc. The dynamic model of leader follower formation with an information structure constraint, in which each vehicle except the leader have the information of all the states of vehicle in front of it. The formation is treated as an interconnected system with overlapping control gains in the sense an UAV share information only with its neighbouring ones.In this thesis, two approaches are used: (i) Inclusion principle (ii) Graph theory based approach for designing control gains. In the inclusion principle approach, control gain is designed separately for each disjoint subsystem in the expanded space. The static state feedback control law and linear matrix inequalities tool boxes are used for designing the controllers for each subsystem. Finally decentralized controllers are contracted back so as to be applied to the original system. In the graph theory approach, an overlapping information flow structure is constructed that determines the outputs of the system available in constructing any input signal of the system. The Graph theory is used to transform the overlapping interconnected system to decentralized one. The static state feedback type controller is used and a DK iterative algorithm is used to find out control gain. Then, a comparison between these two decentralized approaches is reported in the thesis so as to obtain the relative merits and demerits. There is delay in information flow form leader to follower in the formation so frequency domain stability analysis is done for time delay system. Frequency sweeping test is conducted for getting maximum tolerable communication delay between any two UAVs.