ISO/PRF 20682
(Main)Autonomous underwater vehicles — Risk and reliability
Autonomous underwater vehicles — Risk and reliability
This standard is developed to link product engineering and the successful performance of an autonomous underwater vehicle, especially for “extreme missions”. An extreme mission being a relative term can be seen as any underwater expedition that is increasing in difficulty level. While these vehicles have been and are being manufactured by many companies all around the globe for several decades, their risk of failure, safety, and reliability in the sea is not commonly discussed as a standard summary of information. The scope of this standard is to define the known limitations of AUVs for successfully performing extreme missions. Excluded from this standard are any subjects related to the manufacturing and/ or operation of the following items: • Autonomous underwater gliders (AUGs) as they use a narrowly modifiable set of operational commands. • Batteries for the use of AUVs. • Electrical motors for the use of AUVs. NOTE sensors, communication devices, and any other pieces and parts directly influencing the “digital mission” of the vehicle must be held responsible for its risk of failure and are not excluded from the scope of this standard. The success of a digital mission means that a successful algorithm conducts the vehicle to achieve its sequential and final goal.
Titre manque
General Information
Standards Content (Sample)
International
Standard
ISO 20682
First edition
Autonomous underwater vehicles —
Risk and reliability
PROOF/ÉPREUVE
Reference number
ISO 20682:2025(en) © ISO 2025
ISO 20682:2025(en)
© ISO 2025
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
or ISO’s member body in the country of the requester.
ISO copyright office
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Published in Switzerland
PROOF/ÉPREUVE
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ISO 20682:2025(en)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Abbreviated terms . 4
5 Typical modules of AUVs . 4
5.1 General .4
5.2 Control .4
5.3 Sensors . .4
5.4 Structure .5
5.5 Mechanical moving elements .5
5.6 Power .5
5.7 Navigation and communication .5
5.8 Product identification and traceability .6
6 Digital mission engineering. 6
6.1 General .6
6.2 Extreme mission .6
6.3 Simulation, verification and validation .7
6.3.1 General .7
6.3.2 Virtual testing .7
6.3.3 Maximum allowable uncertainties .7
7 Fault tree analysis . 8
7.1 General .8
7.2 Markov chain: state transition .9
8 Strategy for risk assessment and risk reduction . 10
8.1 General .10
8.2 Communication for safety .11
8.3 Hardware controls .11
8.4 Judgment .11
8.5 Reasonableness check .11
8.6 Search, rescue and recovery . . 12
8.7 Signal filtering . . 12
8.8 Dependability engineering . 12
8.9 Safety case . 12
Annex A (informative) Reliability engineering mathematical background . 14
Annex B (informative) Design, verification and testing philosophy for AUVs .18
Annex C (informative) Safety of autonomous land vehicles and applications for AUVs .20
Bibliography .21
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ISO 20682:2025(en)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out through
ISO technical committees. Each member body interested in a subject for which a technical committee
has been established has the right to be represented on that committee. International organizations,
governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely
with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types
of ISO document should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 8 Ships and Marine Technology, Subcommittee
SC 13, Marine Technology.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
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ISO 20682:2025(en)
Introduction
Autonomous underwater vehicles (AUVs) are uncrewed vehicles. They rely on sensors, control units, and
mechanical parts to manoeuvre and complete mostly pre-defined tasks in the ocean environment. A growing
trend in underwater technology is to face the extreme environment, which refers to, for example, polar
environments, rapid currents, extremely high temperatures due to underwater volcanoes, underwater oil
plumes, etc. The side effect of using AUVs in extreme environments, however, is a higher risk and probability
of failure. The capacity for uncrewed underwater vehicles to perform an extreme mission, which is to
perform in an increased level of difficulty, is unknown. Usually, a team of experts employs the vehicle within
a trial-and-error process to:
a) achieve the system identification, and
b) measure (most of the time qualitatively) the reliability of the AUV for a specific mission.
This document specifies how an AUV can carry out the actions described in a) and b). This document can
therefore be used by the owners and operators of AUVs when designing missions. It should be noted that
risk and reliability by nature are probabilistic. This document serves as a linkage between the capabilities
of the vehicle and its intended mission, so as to avoid foreseeable undesired settings and circumstances.
Despite this ability to foresee problems, faults and failures of the vehicle can be due to uniquely encountered
states that have never been observed before. In such cases, dynamic risk analysis and online topic models
can be used to expand the operational proficiency of an autonomous vehicle.
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International Standard ISO 20682:2025(en)
Autonomous underwater vehicles — Risk and reliability
1 Scope
This document specifies the risks and reliability of an autonomous underwater vehicle (AUV) in its
underwater realm. It covers sensors, communication devices, and any other pieces and parts directly
influencing the “digital mission” of the vehicle. This document does not cover the manufacturing or operation
of the following items:
— autonomous underwater gliders (AUGs), as they use a narrowly modifiable set of operational commands;
— batteries for the use of AUVs;
— electrical motors for the use of AUVs.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
abort
to terminate, in a controlled manner, a processing activity in a computer system because it is impossible,
undesirable, or unsafe for an activity to proceed
3.2
availability
degree to which a system or resource is ready when needed
3.3
backout and recovery
activity conducted to bring the system back to a stable state, ending the accident life cycle
3.4
built-in test
test that can be designed into the system by various techniques regarding automation, software, and
firmware, and considering the life cycle of the potential accident
3.5
burn-in test
accelerated production test that is designed to detect infant mortality, that is to flush out weaknesses within
the component, device or subsystem
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3.6
characteristic value
value of a parameter (either an action or a property of a member or a material) that has a specified probability
of not being exceeded
Note 1 to entry: Action refers to external load applied to the vehicle, or an imposed deformation or acceleration.
[SOURCE: ISO 8930:2021, 3.2.2, modified — note to entry added to define the term “action” in this context.]
3.7
code calibration
determination of the reliability elements in a given code format in order to reach the reliability target
3.8
command
control signal or a request from a terminal for the performance of an operation or execution of a particular
program
3.9
design value
value to be used in the deterministic design procedure, i.e. characteristic value (3.6) multiplied by the safety
factor
3.10
deterministic method
calculation method in which the basic variables are treated as non-random
3.11
design point
most probable outcome of the basic variables when failure (3.16) occurs
Note 1 to entry: The design point is the point on the limit-state surface with the highest probability density.
3.12
digital mission engineering
modelling of things that move through space in six degrees of freedom (DoF) and time, involving sensors
and information transfer
Note 1 to entry: The term was originally coined in assisting the successful conduction of outer space missions.
3.13
error
discrepancy between a computed, observed, or measured value or condition and the true, specified, or
theoretically correct value or condition
3.14
fail-operational
design of a subsystem or device in a way that it can continue operation despite the occurrence of a discrete
malfunction
3.15
fail-safe
characteristic of a system whereby any malfunction affecting the system safety will cause the system to
revert to a state that is known to be within acceptable risk parameters
3.16
fail-soft
characteristic of a system that continues to provide partial operational capability in the event of a certain
malfunction
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ISO 20682:2025(en)
3.17
failure
inadvertent termination of a capability of a functional unit to perform its required operation
3.18
fault
inadvertent condition that causes a function to fail to perform in a required (appropriate) manner
3.19
node
point where one or more functional units interconnect, or the representation of a state or an event by means
of a point in a diagram
Note 1 to entry: In a tree structure, a node is a point at which subordinate items of data and information originate.
3.20
normal operation
conditions that arise from the intended use and application of the vehicle, including associated condition
and integrity monitoring, maintenance, and repair
Note 1 to entry: Normal operations include steady manoeuvring over the full range of design speeds, as well as possible
abrupt turns and stopping.
[SOURCE: ISO 16708:2006, 3.28, modified — “pipeline” has been changed to “vehicle” for the use of this
document.]
3.21
redundancy
existence in a system of more than one means of accomplishing a given function
3.22
reliability
ability of a system to perform its required functions under stated conditions for a specified period of time
Note 1 to entry: A reliable system is no total assurance of acceptable risk.
3.23
safety case
structured argument backed by evidence
3.24
sensor
device that converts measurable elements of a physical process into data that is meaningful to a computer
3.25
system effectiveness
function of availability, dependability, and capability:
P(E) = P(A) · P(D) · P(C)
3.26
unit
lowest level of hardware assembly for which acceptance and qualification tests are required
[SOURCE: ISO 19683:2017, 3.4]
3.27
validation
checking of data for correctness or compliance with applicable standards, rules, and conventions
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3.28
verification
act of determining whether an operation has been accomplished correctly
4 Abbreviated terms
AUV autonomous underwater vehicle
COTS commercial-off-the-shelf
GPS Global Positioning System
Dgps differential GPS
MTBF Mean Time to Failure
SaFAD Safety First for Automated Driving
SOTIF Safety of the Intended Functionality
5 Typical modules of AUVs
5.1 General
AUVs have been employed in the subsea industry for the past few decades. They have shown effective
performance in alignment with the emerging trends in science and technology. More rapid production and
versatile utilization of these vehicles is foreseen in the future because they have both a robust design and an
adaptive performance. Typical modules of a modern AUV are described in 5.2 to 5.8.
NOTE The major subsystems of an AUV include the propulsion system, navigation system, communication system,
[1]
power system, security detection system and sensor system.
5.2 Control
The control unit has the most direct involvement in the fault incident. Although it is not physically engaged
with the AUV mission, the control module of the vehicle shall correctly receive inputs from and send
commands to other units.
5.3 Sensors
For this document, the sensors gather every input that must be known for either data acquisition or control
purposes of the vehicle. For data acquisition, where data are gathered for subsequent analysis and processing
of the mission conditions, a fault incident is not critically detrimental to the mission. At a later time, the
operator decides to either replicate or interpolate and extrapolate the missing part of the data. Where data
are used as input to the control module, a sensor fault means one or both of the following.
a) Data input is completely interrupted in a way that one or many of the input parameters are completely
missing. Depending on the input-output relations, that is the parametric response, the vehicle is
susceptible to either incremental or immediate malfunction. Based on such a response, the autonomous
vehicle decides on how to abort the mission. In other words, mission abort is a definite result, while the
vehicle can hinder abort if this helps to avoid a more severe failure (i.e. fail-soft).
b) Data input is a parasitic intermittent signal. Two scenarios can be imagined:
— signal disturbance sustains at a level that does not invoke an emergency action (i.e. fail-operational);
— signal disturbance excites an increasing level of errors that interfere with mission integrity (i.e. fail-
safe).
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5.4 Structure
The vehicle structure carries all the static and dynamic loads that are present in the sea. These include
contact and non-contact forces and moments. A fault in a structural module falls under a wide range of
exceedance criteria for stress, strain, leakage, breakage, rupture, etc. The present technology is incapable
of the online recognition and cure of a structural fault. Biomimetics can progress the technology of future
uncrewed vehicles to have “living” tissues that sense “pain” as a fault. At present, a fault in the structure
is indirectly detected through the sensor module as an exceeded level of elements such as pressure or
moisture.
NOTE The structure of the vehicle is the boundary that encapsulates and therefore protects all parts of the
vehicle from outside harm. Any part that protrudes the structural boundary can itself have a shield or shroud to act as
a safety guard.
5.5 Mechanical moving elements
These include every actuator, manipulator and machine that works for one or both of the following purposes:
a) to move and manoeuvre the AUV either on the surface of the sea or subsea;
b) to trigger a change of mode of motion between different mission phases.
A fault in mechanical moving elements respective to the above types is categorized as:
c) having an immediate effect on the vehicle motion;
d) being hidden until a trigger is commanded.
5.6 Power
The power module of the vehicle has the most obvious fault symptom as compared to the other modules:
depleted or malfunctioning power immobilizes the vehicle.
NOTE Electric motors and batteries are not covered in this document. It is assumed that electric motors and
batteries work within their prescribed range of safe operation.
5.7 Navigation and communication
[2]
AUV navigation and localization tools and techniques can be categorized as follows.
a) Inertial or dead reckoning, which may function in the form of one or several of the following technologies:
1) compass
2) doppler velocity logger (DVL)
3) inertial measuring unit (IMU)
4) pressure sensor
b) Acoustic transponders, which are commonly chosen among the following technologies:
1) single fixed beacon
2) short baseline
3) ultra-short baseline (USBL)
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4) long baseline (LBL) or GPS intelligent buoys (GIBs)
c) Geophysical, which can use any of the following technologies:
1) optical, which uses cameras, and they are varied by their capability in recognizing scales and
dimensions as follows:
i) monocular
ii) stereo
2) acoustic, which is used in the geophysical sense, that is to use a sound navigation and ranging device
(SONAR) for building an acoustic image of the surroundings by either of the following technologies:
i) imaging sonar
ii) ranging sonar
3) magnetic, which uses the magnetic field maps for localization by the following technology:
i) magnetometer
A safe-navigation capability specified in International Regulations for Preventing Collisions at Sea (COLREG)
[3]
can be implemented when deploying autonomous marine vehicles.
5.8 Product identification and traceability
The establishment of a common set of data and well-defined definitions and formats for product identification
and traceability provides the base on which to build specific requirements for the exchange of product life
cycle information.
ISO/IEC 15434 defines a syntax that is used in many applications.
6 Digital mission engineering
6.1 General
In digital mission engineering, the moving objects that are traced also communicate together, thus enabling
[4]
the engineer to analyse and plan a mission.
Digital mission engineering can increase the reliability of AUVs by analysing of elements and components of
their missions. It analyses the engineering trade-offs at different levels of the system stack and their impact
on the mission, such as the virtual what-if possibilities when the AUV is deployed in the real world and
[4]
becomes operational.
For a successful mission, it is a subject of increasing importance to accurately plan, predict, estimate, and
follow detailed pieces of information in time and space. The successful completion of a mission (failure-free
[5]
mission) increases vehicle reliability.
The success of a digital mission means that a successful algorithm guides the vehicle to achieve its sequential
and final goal.
6.2 Extreme mission
Underwater explorations, considering that the place is unoccupied by humans, belong to extreme
environments. As a result, every underwater journey is originally aidless when viewed from the human
civilization point of view. Elements of hazard control such as backout and recovery, built-in test, burn-in test,
and redundancy, can save the system in such conditions.
When a mission has new features concerning either geographical location or speed, or both, as well as the
dynamic and interactive circumstances that occur, then the journey is even more aidless than before. The
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best chance that the AUV does not fail in such conditions is described by aspects such as characteristic
value, code calibration, design value, deterministic method, design point, normal operation and system
effectiveness.
In summary, the probability of failure in an extreme mission is higher than in a typical mission if they are
both tried for a sufficiently large number of repetitions. It means that when the system goes by its design
value, assuming a deterministic method is run and code calibration performed, then during adverse
conditions, hazard control is run, the vehicle is more likely to survive if the mission is not extreme.
An example of an extreme mission is the sea trials of the AUV named Explorer in response to an underwater
[6] [7]
oil spill. Azarsina analysed this case by calculating the performance margins of the control planes.
The following three states are defined for each of the components.
— U is the up state (i.e. actuation of the correct hydrodynamic force from one node to the next within a
given actuating time), P(U) = 0,979 probability of the up state.
— D is the down state (i.e. no actuation of the planes due to failure of the component, e.g. gears stuck,
electric lines broke, or exceedance of actuating time), and
— P(D) = 0,02 is the probability of the down state.
According to Reference [7], it is known that there have been not many instances of a down state. There
have been instances when fish (squid) or large kelp have obstructed or constrained plane movement. A
probability of down state of 2 % is likely a reasonable estimate. The fault state, F, is the running of a fault
actuation, e.g. wrong order of actuation, coupling of motions, or corruption of signal. The probability of the
fault state is P(F) = 0,001.
In the future, climate change and an increased use of underwater space by humans could push subsea
technology further into extreme missions. The virtual what-if scenarios defined in digital mission
engineering can help decrease uncertainty in every condition.
NOTE Human operators of an uncrewed vehicle, which is designed to work in hazardous environments, such as a
[8]
mine sweeper, can stay in an “assist vehicle” during the procedure and are never exposed to a minefield, etc.
6.3 Simulation, verification and validation
6.3.1 General
The autonomous system involves multiple failure modes. Simulation is increasingly important in enabling
many cases and specific combinations of circumstances to be seen. Rou
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Date: 2025-07-0112-11
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Autonomous Underwater Vehicles underwater vehicles — Risk and
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Reliabilityreliability
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St l D fi iti
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ISO copyright office
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ISO/DISPRF 20682:2025(en)
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Contents
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Foreword . v
Introduction . vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Abbreviated terms . 4
5 General requirements . 4
5.1 General. 4
5.2 Control . 5
5.3 Sensors . 5
5.4 Structure . 5
5.5 Mechanical moving elements . 5
5.6 Power . 6
5.7 Navigation and communication . 6
5.8 Product identification and traceability . 7
6 Digital mission engineering . 7
6.1 General. 7
6.2 Extreme mission . 7
6.3 Simulation, verification and validation . 8
6.3.1 General. 8
6.3.2 Virtual testing. 8
6.3.3 Maximum allowable uncertainties . 8
7 Fault tree analysis. 9
7.1 General. 9
7.2 Markov chain: state transition . 10
8 Strategy for risk assessment and risk reduction . 10
8.1 General. 10
8.2 Communication for safety . 11
8.3 Hardware controls. 11
8.4 Judgment . 11
8.5 Reasonableness check . 12
8.6 Search, rescue and recovery . 12
8.7 Signal filtering . 12
8.8 Dependability engineering . 12
8.9 Safety case . 12
Annex A (informative) Reliability engineering mathematical background . 14
A.1 Hazard function . 14
A.2 Performance function . 15
A.3 Reliability index . 15
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A.4 Design (or failure) point . 16
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A.5 Importance sampling method . 16
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Annex B (informative) Design, verification and testing philosophy for AUVs . 18
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B.1 COTS . 18
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v
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B.2 Design . 18
B.3 Verification . 18
B.4 Testing . 19
Annex C (informative) Safety of autonomous land vehicles and applications for AUVs . 20
Bibliography . 21
Foreword . vii
Introduction . viii
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Abbreviated terms . 4
5 Typical modules of AUVs . 4
5.1 General. 4
5.2 Control . 5
5.3 Sensors . 5
5.4 Structure . 5
5.5 Mechanical moving elements . 5
5.6 Power . 6
5.7 Navigation and communication . 6
5.8 Product identification and traceability . 7
6 Digital mission engineering . 7
6.1 General. 7
6.2 Extreme mission . 7
6.3 Simulation, verification and validation . 8
7 Fault tree analysis. 9
7.1 General. 9
7.2 Markov chain: state transition . 12
8 Strategy for risk assessment and risk reduction . 13
8.1 General. 13
8.2 Communication for safety . 14
8.3 Hardware controls. 14
8.4 Judgment . 14
8.5 Reasonableness check . 14
8.6 Search, rescue and recovery . 15
8.7 Signal filtering . 15
8.8 Dependability engineering . 15
8.9 Safety case . 15
Annex A (informative) Reliability engineering mathematical background . 17
Annex B (informative) Design, verification and testing philosophy for AUVs . 22
Annex C (informative) Safety of autonomous land vehicles and applications for AUVs . 24
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Bibliography . 25
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Foreword
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ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out through
ISO technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types of
ISO documentsdocument should be noted. This document was drafted in accordance with the editorial rules
of the ISO/IEC Directives, Part 2 (see www.iso.org/directiveswww.iso.org/directives).
Attention is drawnISO draws attention to the possibility that some of the elementsimplementation of this
document may beinvolve the subjectuse of (a) patent(s). ISO takes no position concerning the evidence,
validity or applicability of any claimed patent rights. in respect thereof. As of the date of publication of this
document, ISO had not received notice of (a) patent(s) which may be required to implement this document.
However, implementers are cautioned that this may not represent the latest information, which may be
obtained from the patent database available at www.iso.org/patents. ISO shall not be held responsible for
identifying any or all such patent rights. Details of any patent rights identified during the development of the
document will be in the Introduction and/or on the ISO list of patent declarations received (see
www.iso.org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see
www.iso.org/iso/foreword.htmlwww.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 8 Ships and Marine Technology, Subcommittee
SC 13, Marine Technology.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.htmlwww.iso.org/members.html.
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vii
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Introduction
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Autonomous underwater vehicles (AUVs) are unmanneduncrewed vehicles. They rely on sensors, control
units, and mechanical parts to manoeuvre and complete mostly pre-defined tasks in the ocean environment.
A growing trend in underwater technology is to face the extreme environment, which refers to, for example,
polar environments, rapid currents, extremely high temperatures due to underwater volcanoes, underwater
oil plumes, etc. The side- effect of using AUVs in extreme environments, however, would beis a higher risk and
probability of failure. The capacity for unmanneduncrewed underwater vehicles to perform an extreme
mission, which is to perform in an increased level of difficulty, is unknown. Usually, a team of experts employs
the vehicle within a trial-and-error process to:
a) a) achieve the system identification, and
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b) b) measure (most of the time qualitatively) the reliability of the AUV for a specific mission.
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This document specifies how an AUV can carry out the actions described in a) and b). This document can Asian text and numbers
therefore be used by the owners and operators of AUVs when designing missions. It should be noted that risk
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and reliability by nature are probabilistic. This document serves as a linkage between the capabilities of the
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vehicle and its intended mission, so as to avoid foreseeable undesired settings and circumstances. Despite
this ability to foresee problems, faults and failures of the vehicle can be due to uniquely encountered states
that have never been observed before. In such cases, dynamic risk analysis and online topic models can be
used to expand the operational proficiency of an autonomous vehicle.
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viii © ISO #### 2025 – All rights reserved
viii
DRAFT International Standard ISO/DIS 20682:2025(en)
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Autonomous Underwater Vehiclesunderwater vehicles — Risk and
Reliabilityreliability
1 Scope
This document has been developed to link product engineering with the successful performance of an
autonomous underwater vehicle in an underwater expedition at an increased level of difficulty. The
objective of this standard is to guide the reliability and risk of AUVs during normal as well as extreme
missions.
This document specifies the risks and reliability considerations of an autonomous underwater vehicle
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(AUV) in its underwater realm. It includescovers sensors, communication devices, and any other pieces
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and parts directly influencing the “digital mission” of the vehicle. This document does not cover the
manufacturing or operation of the following items:
— — autonomous underwater gliders (AUGs), as they use a narrowly modifiable set of operational
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commands;
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— — batteries for the use of AUVs; 3.5 cm + 4.2 cm + 4.9 cm + 5.6 cm + 6.3 cm + 7 cm
— — electrical motors for the use of AUVs.
2 Normative references Formatted: Adjust space between Latin and Asian text,
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There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
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— — ISO Online browsing platform: available at https://www.iso.org/obphttps://www.iso.org/obp
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— — IEC Electropedia: available at https://www.electropedia.org/https://www.electropedia.org/
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3.1 3.1
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abort
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to terminate, in a controlled manner, a processing activity in a computer system because it is impossible,
numbers
or undesirable, or unsafe for an activity to proceed
3.2 3.2
availability
degree to which a system or resource is ready when needed
3.3 3.3
backout and recovery
activity conducted to bring the system back to a stable state, ending the accident life cycle
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3.4 3.4
built-in test
test that can be designed into the system by various techniques regarding automation, software, and
firmware, and considering the life cycle of the potential accident
3.5
3.5
burn-in test
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usually an accelerated production test that is designed to detect infant mortality, that is to flush out Asian text, Adjust space between Asian text and
weaknesses within the component, device or subsystem numbers
3.6 3.6
characteristic value
value of a parameter (either an action or a property of a member or a material) that has a specified
probability of not being exceeded
Note 1 to entry: Action refers to external load applied to the vehicle, or an imposed deformation or acceleration.
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[SOURCE: ISO 8930:2021, 3.2.2, modified — note to entry added for definingto define the term "“action"”
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in this context.]
3.5 cm + 4.2 cm + 4.9 cm + 5.6 cm + 6.3 cm + 7 cm
3.7 3.7
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code calibration
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determination of the reliability elements in a given code format in order to reach the reliability target
numbers
3.8 3.8
command
control signal or a request from a terminal for the performance of an operation or execution of a
particular program
3.9 3.9
design value
value to be used in the deterministic design procedure, i.e. characteristic value (3.6)(3.6) multiplied by
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the safety factor
3.10 3.10
deterministic method
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calculation method in which the basic variables are treated as non-random
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3.11 3.11
3.5 cm + 4.2 cm + 4.9 cm + 5.6 cm + 6.3 cm + 7 cm
design point
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most probable outcome of the basic variables when failure (3.16)(3.16) occurs
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numbers
Note 1 to entry: The design point is the point on the limit-state surface with the highest probability density.
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3.12 3.12
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digital mission engineering
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modelling of things that move through space in six degrees of freedom (DoF) and time. It involves,
involving sensors and information transfer. Formatted: TermNum2, Adjust space between Latin and
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Note 1 to entry: The term was originally coined in assisting the successful conduction of outer space missions. numbers
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3.13 3.13
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error
discrepancy between a computed, observed, or measured value or condition and the true, specified, or
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theoretically correct value or condition
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2 © ISO #### 2025 – All rights reserved
ISO/DISPRF 20682:2025(en)
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3.14 3.14
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fail-operational
design of a subsystem or device in a way that it can continue operation in spite ofdespite the occurrence
of a discrete malfunction
3.15 3.15
fail-safe
characteristic of a system whereby any malfunction affecting the system safety will cause the system to
revert to a state that is known to be within acceptable risk parameters.
3.16 3.16
fail-Softsoft
characteristic of a system that continues to provide partial operational capability in the event of a certain
malfunction
3.17 3.17
failure
inadvertent termination of a capability of a functional unit to perform its required operation
3.18 3.18
fault
inadvertent condition that causes a function to fail to perform in a required (appropriate) manner
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3.19 3.19
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point where one or more functional units interconnect, or the representation of a state or an event by 3.5 cm + 4.2 cm + 4.9 cm + 5.6 cm + 6.3 cm + 7 cm
means of a point in a diagram
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Note 1 to entry: In a tree structure, a node is a point at which subordinate items of data and information originate.
numbers
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3.20 3.20
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normal operation
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conditions that arise from the intended use and application of the vehicle, including associated condition
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and integrity monitoring, maintenance, and repair
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Note 1 to entry: Normal operations include steady manoeuvring over the full range of design speeds, as well as
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possible abrupt turns and stopping.
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[SOURCE: ISO 16708:2006, 3.28, modified — "“pipeline"” has been changed to "“vehicle"” for the use of
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this document.]
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3.21 3.21
numbers
redundancy
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existence in a system of more than one means of accomplishing a given function.
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3.22 3.22
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reliability
ability of a system to perform its required functions under stated conditions for a specified period of time
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Note 1 to entry: A reliable system is no total assurance of acceptable risk.
numbers
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3.23 3.23
safety case Formatted: FooterCentered, Left, Space Before: 0 pt,
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structured argument backed by evidence
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3.24 3.24
sensor
device that converts measurable elements of a physical process into data that is meaningful to a computer
3.25 3.25
system effectiveness
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SE
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function of availability, dependability, and capability:
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P(SEE) = P(A) · P(D) · P(C)
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3.26 3.26
unit
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lowest level of hardware assembly for which acceptance and qualification tests are required
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[SOURCE: ISO 19683:2017, 3.4] 3.5 cm + 4.2 cm + 4.9 cm + 5.6 cm + 6.3 cm + 7 cm
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3.27 3.27
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validation
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checking of data for correctness or compliance with applicable standards, rules, and conventions
numbers
3.28 3.28 Formatted: English (United Kingdom)
verification
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act of determining whether an operation has been accomplished correctly
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4 Abbreviated terms
numbers
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AUV Autonomousautonomous underwater vehicle
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COTS Commercialcommercial-off-the-shelf
numbers
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GPS Global Positioning System
and Asian text, Adjust space between Asian text and
Dgps Differentialdifferential GPS
numbers
MTBF Mean Time to Failure
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SaFAD Safety First for Automated Driving
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SOTIF Safety of the Intended Functionality
numbers
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5 General requirements
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numbers
5 Typical modules of AUVs
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5.1 General
numbers
AUVs have been employed in the subsea industry duringfor the past few decades. They have shown Formatted: Adjust space between Latin and Asian text,
effective performance in alignment with the emerging trends in science and technology. More rapid Adjust space between Asian text and numbers
production and versatile utilization of these vehicles is foreseen in the future because they have both a
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robust design and an adaptive performance. Typical modules of a modern AUV are described in 5.2 to
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5.8.5.2 to 5.8.
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NOTE The major subsystems of an AUV include the propulsion system, navigation system, communication
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[1] [1]
system, power system, security detection system and sensor system. .
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4 © ISO #### 2025 – All rights reserved
ISO/DISPRF 20682:2025(en)
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5.2 Control
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The control unit has the most direct involvement in the fault incident. Although it is not physically
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engaged with the AUV mission, the control module of the vehicle shall correctly receive inputs from and
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send commands to other units.
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5.3 Sensors
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For this document, the sensors gather every input that must be known for either data acquisition or
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control purposes of the vehicle. For data acquisition, where data are gathered for subsequent analysis
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and processing of the mission conditions, a fault incident is not critically detrimental to the mission. At a
later time, the operator decides to either replicate or interpolate and extrapolate the missing part of the Formatted: Adjust space between Latin and Asian text,
data. Where data are used as input to the control module, a sensor fault means one or both of the Adjust space between Asian text and numbers
following.
a) a) Data input is completely interrupted in a way that one or many of the input parameters
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are completely missing. Depending on the input-output relations, that is the parametric response, b, c, … + Start at: 1 + Alignment: Left + Aligned at: 0 cm
the vehicle is susceptible to either incremental or immediate malfunction. Based on such a response, + Indent at: 0 cm, Adjust space between Latin and
the autonomous vehicle decides on how to abort the mission. In other words, mission abort is a Asian text, Adjust space between Asian text and
numbers, Tab stops: Not at 0.7 cm + 1.4 cm + 2.1 cm
definite result, while the vehicle can hinder abort if this helps to avoid a more severe failure (i.e. fail-
+ 2.8 cm + 3.5 cm + 4.2 cm + 4.9 cm + 5.6 cm + 6.3
soft).
cm + 7 cm
b) b) Data input is a parasitic intermittent signal. Two scenarios can be imagined:
— — signal disturbance sustains at a level that does not invoke an emergency action (i.e. fail- Formatted: Adjust space between Latin and Asian text,
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operational);
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— — signal disturbance excites an increasing level of errors that interfere with mission
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integrity (i.e. fail-safe).
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5.4 Structure
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The vehicle structure carries all the static and dynamic loads that are present in the sea. These include
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contact and non-contact forces and moments. A fault in a structural module falls under a wide range of
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exceedance criteria for stress, strain, leakage, breakage, rupture, etc. The present technology is incapable
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of the online recognition and cure of a structural fault. Biomimetics can progress the technology of future
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unmanneduncrewed vehicles to have “living” tissues that sense “pain” as a fault. At present, a fault in the
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structure is indirectly detected through the sensor module as an exceeded level of elements such as
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pressure or moisture.
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NOTE The structure of the vehicle is the boundary that encapsulates and therefore protects all parts of the
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vehicle from outside harm. Any part that protrudes the structural boundary can itself have a shield or shroud to act
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as a safety guard.
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5.5 Mechanical moving elements
+ 2.8 cm + 3.5 cm + 4.2 cm + 4.9 cm + 5.6 cm + 6.3
cm + 7 cm
These include every actuator, manipulator and machine that works for one or both of the following
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purposes:
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a) a) to move and manoeuvre the AUV either on the surface of the sea or subsea; Formatted
...
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b) b) to trigger a change of mode of motion between different mission phases.
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A fault in mechanical moving elements respective to the above types is categorized as:
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c) c) having an immediate effect on the vehicle motion;
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d) d) being hidden until a trigger is commanded.
5.6 Power
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The power module of the vehicle has the most obvious fault symptom as compared to the other modules:
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depleted or malfunctioning power immobilizes the vehicle.
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NOTE Electric motors and batteries are not covered in this document. It is assumed that Electricelectric motors
and batteries work within their prescribed range of safe operation. Formatted: Adjust space between Latin and Asian text,
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stops: Not at 0.7 cm + 1.4 cm + 2.1 cm + 2.8 cm +
5.7 Navigation and communication
3.5 cm + 4.2 cm + 4.9 cm + 5.6 cm + 6.3 cm + 7 cm
[2] [2]
AUV navigation and localization tools and techniques can be categorized as follows .
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a) a) Inertial or dead reckoning, which may function in the form of one or several of the
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following technologies:
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1) Compass
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Numbering Style: a, b, c, … + Start at: 1 + Alignment:
1) Dopplercompass
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between Latin and Asian text, Adjust space between
2) doppler velocity logger (DVL)
Asian text and numbers
3) Inertialinertial measuring unit (IMU) Formatted: List Number 2, Indent: Left: 0 cm, First line:
0 cm, Numbered + Level: 1 + Numbering Style: 1, 2, 3,
4) Pressurepressure sensor … + Start at: 1 + Alignment: Left + Aligned at: 0 cm +
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text, Adjust space between Asian text and numbers, Tab
b) b) Acoustic transponders, which are commonly chosen among the following technologies:
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3.5 cm + 4.2 cm + 4.9 cm + 5.6 cm + 6.3 cm + 7 cm
1) Singlesingle fixed beacon
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2) Shortshort baseline
Numbering Style: a, b, c, … + Start at: 2 + Alignment:
Left + Aligned at: 0 cm + Indent at: 0 cm, Adjust space
3) Ultraultra-short baseline (USBL) between Latin and Asian text, Adjust space between
Asian text and numbers
4) Longlong baseline (LBL) or GPS intelligent buoys (GIBs)
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0 cm, Numbered + Level: 1 + Numbering Style: 1, 2, 3,
c) c) Geophysical, which can use any of the following technologies:
… + Start at: 1 + Alignment: Left + Aligned at: 0 cm +
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1) Optical;optical, which uses cameras, and they are varied by their capability in recognizing scales
text, Adjust space between Asian text and numbers, Tab
and dimensions as follows:
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3.5 cm + 4.2 cm + 4.9 cm + 5.6 cm + 6.3 cm + 7 cm
i) Monocular
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...
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