Abstract: The path following of incomplete symmetric unmanned amphibious platform in shallow water is discussed in order to improve its reliability and maneuverability. The influence of water depth on hydrodynamic derivatives is analyzed, the hydrodynamic derivatives is corrected, and a more accurate model is established. The path following errors are described in Serret-Frenet coordinate after the transformation of model and reference path, and then two cascade subsystems are obtained, namely the position following subsystem and the course and surge velocity following subsystem. The velocity following subsystem is proved to be equivalent to the whole system based on cascade theory. A global stable controller of the velocity following subsystem is designed based on backstepping method. The mathematic simulations and lake trial were carried out, which illustrate that the global stable controller is available for the incomplete symmetric unmanned amphibious platform to track a straight-line and a circle paths.

Key words: ordnance science and technology, incomplete symmetry, unmanned amphibious platform, path following, Serret-Frenet frame, cascade theory