Distributed tracking for networked Euler-Lagrange systems using only relative position measurements

In this paper, the problem of distributed coordinated tracking control for networked Euler-Lagrange systems using only relative position measurements is studied. Under the condition that only a subset of followers have access to the leader, sliding mode estimators are developed to estimate the states of the dynamic leader accurately in finite time. A set of distributed observers which only uses relative position information is designed to deal with the unavailability of the followers´ velocities. Using the observer outputs, distributed control laws are proposed such that the objective of tracking a dynamic leader under a spanning tree is achieved. The asymptotic stability of the proposed distributed observer-controller is proved through Lyapunov method. Numerical simulation results are also provided to show the effectiveness of the control laws.