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Mathematical Problems in Engineering
Volume 2014 (2014), Article ID 324813, 12 pages
Research Article

Modifications of Control Loop to Improve the Depth Response of Autonomous Underwater Vehicles

1Department of Mechanical Engineering, National Chiao Tung University, Hsinchu 30010, Taiwan
2Information and Communication Research Division, Chung Shan Institute of Science and Technology, Taoyuan 32546, Taiwan

Received 9 April 2014; Revised 12 July 2014; Accepted 13 July 2014; Published 12 August 2014

Academic Editor: Oded Gottlieb

Copyright © 2014 Sheng-Ping Hsu and Tzong-Shi Liu. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


During a constant depth maneuver of an autonomous underwater vehicle (AUV), its pitch attitude and stern plane deflections create forces and moments to achieve equilibrium in the vertical plane. If an AUV has a proportional controller only in its depth control loop, then different weights or centers of gravity will cause different steady-state depth errors at trimmed conditions. In general, a steady-state depth error can be eliminated by adding an integral controller in the depth control loop. However, an improper integrator may lead to a bad transient response, even though the steady-state depth error can finally be eliminated. To remove the steady-state depth error, this study proposes methods that adjust the depth command and add a switching integral controller in the depth control loop. Simulation results demonstrate that the steady-state depth error can be eliminated and the transient response can be improved.