Marine Vehicle Path Following Using Inner-Outer Loop Control

This paper addresses the problem of marine vehicle path following using innerouter loop control, with due account for the vehicle dynamics. We propose an inner-outer control structure that lends itself to a simple intuitive interpretation and exhibits three key advantages: i) it allows for decoupling in the design of the inner and outer control loops, ii) the design of the outer loop controller does not require in depth knowledge of the internal vehicle dynamics, and iii) it affords practitioners a very convenient method to effectively implement path following controllers on a wide range of vehicles. The mathematical tools used for systems characterization and stability analysis borrow from Input to Output Stability (IOS) theory and small gain theorems. In this paper, formal system analysis is done only for the case where the paths to be followed are straight lines. However, the technical machinery developed and the results obtained shed light into the process of designing path following controllers with an inner-outer loop structure for arbitrary paths. The efficacy of the path following control structure developed has been proven during tests with an AUV and an ASV at sea.