This paper investigates the formation control problem of multiple unmanned aerial vehicles (UAVs) with limited communication in a known and realistic obstacle-laden environment. In order to deal with the limited communication constraints, the leader–follower strategy and the virtual leader strategy are integrated into an optimal control framework to formulate this formation control problem. This combination formation framework can be achieved by integrating a redefined directed graph and a proposed information vector. In more practical applications, an obstacle/collision avoidance strategy is achieved by constructing a non-quadratic cost function innovatively using a virtual flow field approach. The proposed optimal control laws, which derive from the local information rather than the global information, are proved to guarantee the stability of the close-loop system by an inverse optimal control approach. The simulation results demonstrate the effectiveness of the formation flight of multiple UAVs with limited communication in an obstacle-laden environment.
A kinematics model of planetary bevel-gear trains, which included two sun gears, four planet gears and two carriers, was established. With analyzing of the gear trains, non-oriented graph representation of the mechanism was developed. Then, the kinematic structure of the gear trains was represented. With coordinate conversion, the successive transformation matrices were derived. And then, the oriented graph representation of gear pair was obtained by analyzing rotation vectors. Lastly, the inverse kinematics equation was obtained. To given the orientation of the moving platform variables, the equations have the identify solutions.
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