Passivity-based output synchronization of networked Euler-Lagrange systems subject to nonholonomic constraints

In this paper, we study the output synchronization problem of networked Euler-Lagrange(EL) systems subject to nonholonomic constraints. An EL system subject to nonholonomic constraints can be input-output linearized if a proper decoupling matrix can be found, and the linearized form is equivalent to a double integrator. Although a double integrator is not a passive system, with proper design of the control law and some coordinate transformation, we are able to obtain a new state-space representation of the EL system which is a linear passive system. The underlying assumption is that the communication graph is bidirectional and strongly connected. To deal with time-varying communication delays among the interconnected agents, we embed the scattering transformation into our proposed setup and show that output synchronization can be achieved in this case as well.