Consensus disturbance rejection with disturbance observers

This paper deals with consensus disturbance rejection of network-connected dynamic systems using disturbance observers. The control objective of consensus disturbance rejection is to achieve a common state trajectory for the network-connected subsystems that are under deterministic disturbances. The difference from the existing disturbance rejection methods is that only the relative state information is used for disturbance rejection, and as a consequence of using the relative state information, only the part of the disturbances that affect the common trajectories will be rejected. The conditions for designing disturbance observers for consensus control are identified for networked-connect multi-agent systems. Certain features of the individual subsystems are analysed for possible implementation of disturbance-observer based rejection, and the disturbance observers are designed based on the relative state information obtained from the neighbouring subsystems under different network connections. When the network connectivity is available for the disturbance observer design, consensus disturbance rejection is achieved for a directed network with a spanning tree. A fully distributed consensus disturbance rejection design is presented for an undirected network with the use of adaptive parameters for the estimation of the unknown network connectivity. Disturbance observers are also proposed for disturbance rejection in the leader-follower consensus control.