Distributed Leaderless and Leader-Following Consensus Control of Multiple Euler-Lagrange Systems with Unknown Control Directions

This paper investigates leaderless and leader-following consensus control problems for a group of Euler-Lagrange systems with unknown identical control directions under an undirected connected and time-invariant graph in the presence of parametric uncertainties. For both leaderless and leader-following consensus cases, distributed adaptive controllers are presented using the backstepping technique and a Nussbaum-type function. Moreover, these controllers are distributed in the sense that the controller design for each system only requires relative information between itself and its neighbors. The projection algorithm is applied to guarantee that the estimated parameters remain in some known bounded sets. Lyapunov stability analysis shows that the consensus errors converge to zero asymptotically. Simulation results on multiple two-link planar elbow manipulators are provided to illustrate the performance of the proposed algorithms.