Abstract
The changes of the seabed environment caused by a natural disaster or human activities dramatically affect the life span of the subsea buried cable. It is essential to track the cable route in order to inspect the condition of the buried cable and protect its surviving seabed environment. The magnetic sensor is instrumental in guiding the remotely-operated vehicle (ROV) to track and inspect the buried cable underseas. In this paper, a novel framework integrating the underwater cable localization method with the magnetic guidance and control algorithm is proposed, in order to enable the automatic cable tracking by a three-degrees-of-freedom (3-DOF) under-actuated autonomous underwater vehicle (AUV) without human beings in the loop. The work relies on the passive magnetic sensing method to localize the subsea cable by using two tri-axial magnetometers, and a new analytic formulation is presented to compute the heading deviation, horizontal offset and buried depth of the cable. With the magnetic localization, the cable tracking and inspection mission is elaborately constructed as a straight-line path following control problem in the horizontal plane. A dedicated magnetic line-of-sight (LOS) guidance is built based on the relative geometric relationship between the vehicle and the cable, and the feedback linearizing technique is adopted to design a simplified cable tracking controller considering the side-slip effects, such that the under-actuated vehicle is able to move towards the subsea cable and then inspect its buried environment, which further guides the environmental protection of the cable by setting prohibited fishing/anchoring zones and increasing the buried depth. Finally, numerical simulation results show the effectiveness of the proposed magnetic guidance and control algorithm on the envisioned subsea cable tracking and the potential protection of the seabed environment along the cable route.
Highlights
Since the first underwater optical fiber cable came out in 1985, underwater cable systems have been extensively constructed worldwide and have played an important role in the field of cross-continental communications with the advantages of large capacity, high reliability and excellent communication quality
Based on the magnetic sensing and localization, the dedicated magnetic LOS guidance law is proposed for the cable tracking control of the under-actuated vehicle, and the simplified dynamic controller relying on the feedback linearizing technique is designed to drive the surge speed and yaw angle of the autonomous underwater vehicle (AUV) to attain the desired profiles, such that the under-actuated AUV tracks and detects along the underwater cable
A dedicated magnetic guidance and simplified control algorithm in the horizontal plane is proposed to enable the underwater cable to be precisely tracked by an inspection AUV without human beings in the loop
Summary
Since the first underwater optical fiber cable came out in 1985, underwater cable systems have been extensively constructed worldwide and have played an important role in the field of cross-continental communications with the advantages of large capacity, high reliability and excellent communication quality. In [28], a nonlinear path following controller based on the backstepping technique for an under-actuated AUV is proposed; a singularity exists in the algorithm because the orthogonal projection of the vehicle onto the path is used to build the Serret–Frenet reference frame. A simplified cable tracking controller using the feedback linearizing technique is designed to drive the AUV traveling along the cable based on the magnetic guidance law in order to enable the inspection of the buried cable environment. A comprehensive numerical simulation case is investigated to validate the effectiveness of the integrated magnetic localization, guidance and control algorithm on the envisioned underwater cable tracking and the potential protection of the seabed environment along the cable route.
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