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Fault Tolerant Control of the Electric Propulsion 21
for Autonomous Surface Vehicles

because of autonomously. If Δx is negative, it means there could be some problems at a control
unit or motor controller or GPS. It leads to increase of boat speed.

• The third class faults are regards to energy consumption which is performed by a current
sensor or amperemeter.

ΔI = Iref – I (amps)

Reasons of the energy consumption faults may be very different. These faults could be derived
from batteries, current sensors, motor controller, telemetry system or thruster faults. If problem is
derived from current sensors or telemetry system, correct values of current couldn’t be known.
On the other hand, if problem doesn’t take it’s source from the measuring parts, measurement
could be right and some solutions may be found.

6. Fault Detection and Isolation Methodology

The basic assumption used in developing the FDI (Fault Detection and Isolation) scheme, is that
the faults can occur independently and just when the reference signals nref, xref, and Iref are
constants and the system has reached the steady state.

7. Conclusion

As an emerging and active area of research in automatic control, fault-tolerant control has
recently attracted more and more attention. A brief technical review and bibliography listing on
the historical and new development in active faulttolerant control systems (AFTCS) have been
presented in this paper.

In this paper, a simple design of a fault tolerant control system applied to a Autonomous Surface
Vehicle’s electric propulsion system has been described. After a brief description of the system
a fault and risk analysis has been carried out and a set of possible remedial actions has been
found. In order to prevent faults on fully autonomous surface vehicles during operation, there is
not so much alternative solution. Especially faults derived from electronic equipments such as
GPS, sensors and other connection equipments, even action could be changed, generally
operation is canceled depending on the severity of fault. In order to faults for mechanical
systems and water proofing, several preventive solutions may be found. However, if faults on
mechanical systems occur on the operation time, vessel should send emergency signal to land
and protect its position. On the other hand, in order to decrease the risk priority number, control
system algorithm should be tempered to all fault probabilities. Since there is not casualty on the
ASVs, most important risk on the autonomous boats is economical. As a result, control system
algorithm of the autonomous vehicle should be tempered to described fault probabilities. To
prevent other faults derived from electroic equipments, economical situation should be
considered.

Sayı 5, 2016 GiDB|DERGi