Yusoff, Mohd Akmal Mohd
(2013)
Fault-Tolerant Control For A Remotely Operated Vehicle (Rov) Propulsion System.
Masters thesis, Universiti Sains Malaysia.
Abstract
Remotely Operated Vehicle (ROV) propulsions system is frequently exposed to harsh operating and underwater environments. Faults and undesired working conditions contribute to performance degradation thus repair actions are required. Stop of operation causes operational cost to increase. Therefore, a Fault-Tolerant Control System (FTCS) is introduced to deal with this situation. This method aims to ensure reliability, sustainability and safety of a dynamical system. This thesis presents a fault-tolerant control specifically designed for ROV electric propulsion system with brushed DC motor thrusters. There are two components in FTCS which are the Fault Detection and Diagnosis (FDD) and Controller Re-Design (CRD). The FDD is done by monitoring two thruster parameters i.e. armature voltage and current load and compare between actual and reference process parameters. Via statistical design of experiment techniques, an offline experiment is performed to simulate possible event of faults. Analysis of variance (ANOVA) methods such as two-factor factorial design and Tukey’s Kramer rule are used to analyze the faults and provides the reference model to implement the controller re-design i.e. fault accommodation. A Takagi-Sugeno (T-S) fuzzy system is used to design the fault accommodation and ROV motion controller. The FTCS method has been tested in fresh water pool and proved to be fast in handling the thruster faults. It takes about 500 ms for a fault in a single thruster to be detected, isolated and new thruster command to be initiated. The FTCS method causes the ROV degree of freedom (DOF) to be reduced to a minimum but the ROV still able to continue the operation.
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