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Geometric Insight into the Control Allocation Problem for Open-Frame ROVs and Visualisation of Solution

Department of Electronics and Computer Engineering, Centre for Robotics and Intelligent Systems, University of Limerick, V94 T9PX, Limerick, Ireland
Author to whom correspondence should be addressed.
Robotics 2020, 9(1), 7;
Received: 8 November 2019 / Revised: 22 December 2019 / Accepted: 21 January 2020 / Published: 29 January 2020
(This article belongs to the Special Issue Advances in Underwater Robotics)
The overall control system for an open-frame Remotely Operated Vehicle (ROV) is typically built from three subsystems: guidance, navigation and control (GNC). The control allocation plays a vital role in the control subsystem. Typically, open-frame underwater vehicles have p actuators (thrusters) for the motion in the horizontal plane, and the control allocation problem, in this case, is very complex and hard to visualise, because the normalised constrained control subset is a p-dimensional unit cube. The aim of this paper is to give a clear picture and a geometric interpretation of the problem and to introduce a hybrid method, based on the integration of a weighted pseudoinverse and the fixed-point method. The main idea of the hybrid method is visualised, and the deep geometric insight is provided using a “virtual” ROV in low-dimensional control spaces, including visualisation of the attainable command set, solution lines, control energy spheres and the role of pseudoinverse and fixed-point iterations. The same concepts are then extended to higher-dimensional cases, for open-frame ROV with four X-shaped (vectored) horizontal thrusters, which is one of the most common thruster configurations for commercial ROVs. The proposed hybrid method has been developed, integrated into a generic fault-tolerant ROV control system and evaluated in virtual and real-world environments off the west coast of Ireland using observation-class ROV Latis and work-class ROV Étaín.
Keywords: fault-tolerant control; control allocation; ROV fault-tolerant control; control allocation; ROV
MDPI and ACS Style

Omerdic, E.; Trslic, P.; Kaknjo, A.; Weir, A.; Rao, M.; Dooly, G.; Toal, D. Geometric Insight into the Control Allocation Problem for Open-Frame ROVs and Visualisation of Solution. Robotics 2020, 9, 7.

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