Fault-Tolerant Control for ROVs Using Control Reallocation and Power Isolation

Abstract

This paper describes a novel thruster fault-tolerant control system (FTC) for open-frame remotely operated vehicles (ROVs). The proposed FTC consists of two subsystems: a model-free thruster fault detection and isolation subsystem (FDI) and a fault accommodation subsystem (FA). The FDI subsystem employs fault detection units (FDUs), associated with each thruster, to monitor their state. The robust, reliable and adaptive FDUs use a model-free pattern recognition neural network (PRNN) to detect internal and external faulty states of the thrusters in real time. The FA subsystem combines information provided by the FDI subsystem with predefined, user-configurable actions to accommodate partial and total faults and to perform an appropriate control reallocation. Software-level actions include penalisation of faulty thrusters in solution of control allocation problem and reallocation of control energy among the operable thrusters. Hardware-level actions include power isolation of faulty thrusters (total faults only) such that the entire ROV power system is not compromised. The proposed FTC system is implemented as a LabVIEW virtual instrument (VI) and evaluated in virtual (simulated) and real-world environments. The proposed FTC module can be used for open frame ROVs with up to 12 thrusters: eight horizontal thrusters configured in two horizontal layers of four thrusters each, and four vertical thrusters configured in one vertical layer. Results from both environments show that the ROV control system, enhanced with the FDI and FA subsystems, is capable of maintaining full 6 DOF control of ROV in the presence of up to 6 simultaneous total faults in the thrusters. With the FDI and FA subsystems in place the control energy distribution of the healthy thrusters is optimised so that the ROV can still operate in difficult conditions under fault scenarios.

An electrical power control system for explorer-class remotely operated underwater vehicle (ROV)

“…This table also has shown that DC motors/thrusters draw most of power. Various magnet volume and torque usually give different results [17,18]. For Tech_SAS ROV, 12V/1.3A 1100 GPH bilge pump is chosen and modified into water-proofed DC motor as a thruster [19,20].…”

Robust Control of Underwater Vehicle-Manipulator System Using Grey Wolf Optimizer-Based Nonlinear Disturbance Observer and H-Infinity Controller

“…In [8][9][10][11][12][13], the schemes based on the improved chattering-free sliding mode control (SMC) are used to control the underwater robot system with the unmodeled uncertainties and external disturbances. In [14][15][16][17][18][19][20][21][22][23], the adaptive control schemes designed on the particular structure of the underwater robot are used to realize the trajectory tracking control with system disturbances. In [24,25], the adaptive backstepping control schemes are designed by an inverse procedure of making system robust stable which is used to make the UVMS track the desired trajectory.…”

Collision Detection for Underwater ROV Manipulator Systems

“…Often called telemanipulators, these devices are usually deployed to worksites onboard support base vehicles which are also remotely operated—therefore referred to as Remotely Operated Vehicles (ROVs). Work-class ROV technology has served subsea Intervention, Repair, and Maintenance (IRM) operations in various offshore industries, including oil and gas, marine construction, marine science, naval defence, and Marine Renewable Energy (MRE) [ 1 , 2 , 3 ]. Submarine work-class ROVs are generally equipped with two manipulators; one dexterous seven function manipulator that is used to perform the actual intervention task, and one simple, powerful grabber that is used to hold the ROV stationary relative to the structure on which the operation is taking place.…”