This project investigates docking capabilities for autonomous underwater vehicles (AUVs) to address issues with launching and recovering AUVs from ships. The student will model the motion of AUVs, design autopilot controllers, and develop guidance strategies for docking. Motion will be modeled using 6 degree of freedom and 3 degree of freedom models. Linear parameter varying controllers will be designed for heading, depth, and longitudinal velocity. Two docking strategies, three point and N-point, will be developed using path following and evaluated for stationary and non-stationary docking scenarios. The performance of heading controllers under the two strategies will be compared.

1. Project title: Docking of Underwater Vehicle: Modeling,
Autopilot design, and guidance strategies.
Supervisors: Dr.ir. Eric Trottemant (Allseas), Prof. dr. ir. Robert Babuska (TU
Delft)
Student Name: Anand Sundaresan
Project summary:
Allseas engineering BV is an offshore company which uses underwater vehicles for conducting
subsea operations. The two primary classification of underwater vehicles are: Remote operated
vehicle (ROV) and Autonomous underwater vehicle (AUV). As the names suggests, the former
requires a human operator to control and the latter is a fully autonomous vehicle. As of now, the
company (and most of the offshore industries) customarily use ROVs. In the recent past, Allseas
was inclined to use AUVs as a measure of reducing the operational costs and conducted tests runs
with an industrial grade AUV. But the trial runs were unsuccessful and the plan of using such an
AUV was dropped. It was concluded that the major problem was in launch and recovery operations
of the AUV conducted from the ship, which was primarily affected by the disturbances from the
ship's thrusters. Therefore, this thesis aims to investigate on underwater docking capabilities of
AUVs, which not only eliminates the launch and recovery issues but improves AUV's overall
operational capabilities. In this thesis, a docking problem is formulated and the solution to the
problem covers the following aspects: modeling of AUV, motion control of AUV, and guidance
strategies addressing the docking problem.
For the motion control, an appropriate model of the vehicle is necessary. Various models used in
the literature were studied which include: 6 degree of freedom (DOF) non-linear model, 3-DOF
horizontal plane model, and 3-DOF vertical plane model. As an example, a 6 DOF non-linear
model of ARIES AUV from literature was decoupled into the respective 3-DOF models. These
models are used for controllers design and docking strategies.
A linear parameter varying (LPV) frame work based gain scheduled feedback and feed forward
controllers were developed for the vehicle heading and depth control. The controllers were
designed in the following steps: Firstly, a third order Quasi- LPV control plant for heading and
depth were derived from horizontal and vertical plane models. Then, linear controllers were
designed for fixed values of scheduling variables. Based on the dimension of the scheduling
variables, a stability preserving interpolation of gains were performed to obtain the final controller.
A PI controller was designed for controlling the longitudinal velocity of the vehicle. The
performance of the controllers were checked on 6 DOF and 3 DOF models of the ARIES AUV.
Finally, two docking strategies: three point and N-point, were developed using lookahead based
path following and investigated their performance for two scenarios: stationary dock and non-
stationary dock. The docking strategies addressed the docking problem in two aspects: geometric
path generation and path following. It was shown that the N-point docking strategy yielded better

2. convergence to the paths than the three point docking. Finally, the heading controller performance
in closed loop was compared for the two developed strategies.
Keywords: Autonomous underwater vehicle, Remote operated vehicle, Linear parameter varying,
Quasi- linear parameter varying, and Degrees of freedom.