Robust consensus tracking control of second-order nonlinear systems without using velocity information

In this work, we propose a new method for distributed consensus tracking control of second-order nonlinear systems under a directed communication graph, where the leader node is the root. In each follower agent, only the relative positions and filtered inputs from its neighbors are available. To facilitate cooperative controller design, in each follower of the network, a group of K-filters which do not require estimation of the velocity signals is introduced. Then the consensus tracking error dynamics of the follower is expressed as a second-order system with mismatched uncertainties. Therefore, we can design a robust consensus tracking controller for each follower agent by using backstepping design procedure, where an finite-time disturbance observer is adopted to estimate the uncertainties. The control performance is theoretically analyzed. And simulation examples confirm the efficacy of the performance of the proposed method.