Observer design for euler lagrange systems: application to path following control of an underactuated surface vessel

This paper presents a practical method to design an output feedback controller for a general mechanical system described by Euler Lagrange equations. An application of such an observer is formulated to path following controller for an underactuated surface vessel moving in a horizontal plan. The surface vessel is underactuated in the sway direction and has only position and orientation measurement available. The control development is based on Lyapunov direct method and backstepping technique.