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Fault Tolerant Control of the Electric Propulsion 15
for Autonomous Surface Vehicles

FAULT TOLERANT CONTROL OF THE ELECTRIC
PROPULSION FOR AUTONOMOUS SURFACE VEHICLES

Hakan Akyıldız, Erhan Türkmen
Department of Ship Building and Ocean Engineering, Istanbul Technical University

ABSTRACT

The application of a simple design of fault tolerant control (FTC) methodology to the electric propulsion
of autonomous surface vehicle is presented. The existing approaches to fault detection and isolation and
fault tolerant control in a general framework of a active fault tolerant control are considered according to
design methodologies and applications. FMEA (Failure Mode and Effects Analysis) is carried out as a fault
analysis, precarious parts of propulsion system are found and offered a solutions to risky applications.

Keywords: Fault Tolerant, Autonomous Surface Vessel, FMEA, Electric Boat, FTC, Risk Analysis

1. Introduction

A customary risk analysis methods for a modern autonomous vessel systems may cause an overall
system instability and safety deficiency. To reach increased performance and safety requirements,
new approaches to control system design have been developed. For safety-critical systems, the
consequences of a minor fault in a system part can be disaster. For the purpose of improve the
reliability, safety, economically and fault tolerance, it is necessary to design control systems
which are capable of tolerating potential faults, namely, fault tolerant control.

Fault detection and diagnosis are systems of great importance for modern electric vehicles. Fault
is an unpermitted deviation of a parameters of the system from the acceptable condition.

Defects in sensors or in controllers can cause undesired reactions and consequences. When a fault
occur in a system, the main problem to be addressed is to raise an alarm, ideally diagnose what
fault has occured, and then decide how to deal with it. The problem of detecting a fault, finding
the source/location and then taking appropriate action is the basis of fault tolerant control in safety
critical systems such as aircraft, robots, space systems and underwater autonomous vehicles. In
other wards, by designing a dynamical system, an approach of the fault detection and isolation is
processing input/output data, which is able to detect the presence of an incipent fault and
eventually to precisely isolate it. Then, the design of a reconfiguration unit, namely a fault tolerant
control, performs control reconfiguration for the faulty system.

The paper presents first a brief description of the overall benchmark, then the analysis of the
possible faults acting on the systemon the basis of the failure mode and effects analysis (FMEA).
Afterwords, a simple FDI strategy is described, which allows perfect isolation of the three possible
faults proposed in the benchmark. Finally, the information provided by the FDI unit are used to
develop a control reconfiguration structure in order to achive a fault tolerant system.

2. Fault Diagnosis and Fault Tolerant Control

All real systems in nature (physical, biological and engineering systems) can malfunction and fail
due to faults in their components. The chances for failures are increasing with the system’s

Sayı 5, 2016 GiDB|DERGi