Sliding Mode Control of Non-Minimum Phase Autonomous Underwater Vehicles in the Dive Plane

This paper shows that the torpedo-type Autonomous Underwater Vehicle (AUV) exhibits the non-minimum phase behavior in the depth control operation for a certain range of forward velocity. Contributions in this paper are (i) Transform AUV's 6 DOF dynamic model in a diving plane to the normal form. (ii) A method to determine the range of the forward surge velocity for which zero dynamics is unstable. Understanding the non-minimum phase behavior provides insight into the controller designs in the future, specifically for the identified ranges of the forward surge velocities.