Horizontal steering control in docking the ARIES AUV

Abstract

To keep the operational cost down and increase the mission time with minimum human intervention, autonomous recovery or docking operation of an Autonomous Underwater Vehicle (AUV) is required. Central to the successful autonomous docking process of the AUV is the capability of the AUV being able to track and steer itself accurately towards the dock which is constantly perturbed by wave motion effects. In addition, for accurate acoustic homing during the final stages of the docking, the AUV requires acoustic systems with high update rates. Equipped with acoustic modem, ARIES had experimentally been tested to have an update rate of only about 0.3 Hz. These delayed data can potentially cause a false commanded reference input to the tracking system in between the updates and cause ARIES to miss the moving cage's entrance. This thesis attempts to investigate the effectiveness on the use of cross track error and line of sight error sliding mode controller coupled with dynamic waypoints allocation in horizontal steering of ARIES in docking operations. In the absence of cage heading updates, a predictive method based on angular rate and direction of motion was used to estimate the dynamics of the moving cage. Further analysis was performed in order to understand the limitations of such an implementation.