IEC TS 62998-3:2023
(Main)Safety of machinery - Safety-related sensors used for the protection of persons - Part 3: Sensor technologies and algorithms
Safety of machinery - Safety-related sensors used for the protection of persons - Part 3: Sensor technologies and algorithms
IEC TS 62998-3:2023 gives guidance on:
- analysis of sensor technologies of different wavelength ranges, measurement methods, and the sensing unit arrangement in an SRS, respectively the arrangement of SRSs in an SRSS;
- representative physical properties of safety-related objects with due consideration of their material characteristics and the sensor technology/technologies used in an SRS/SRSS to achieve the detection capability and comparable results during verification and validation;
- analysis of the interference of objects present in the surrounding on the safety related objects and thereby the influence on the dependability of the detection capability;
- use of algorithms during design, development and maintenance to achieve appropriate detection capability and dependability of detection;
- appropriate use of algorithms during the integration of SRS or SRSS by the integrator to improve execution of measurement information or provide decision information derived from measurement information.
If an SRS/SRSS uses sensor technologies not stated in this document, then the generic approach in accordance with IEC TS 62998-1 applies.
General Information
Standards Content (Sample)
IEC TS 62998-3
®
Edition 1.0 2023-08
TECHNICAL
SPECIFICATION
Safety of machinery – Safety-related sensors used for the protection of
persons –
Part 3: Sensor technologies and algorithms
IEC TS 62998-3:2023-08(en)
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IEC TS 62998-3
®
Edition 1.0 2023-08
TECHNICAL
SPECIFICATION
Safety of machinery – Safety-related sensors used for the protection of
persons –
Part 3: Sensor technologies and algorithms
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 13.110; 21.020 ISBN 978-2-8322-7174-2
Warning! Make sure that you obtained this publication from an authorized distributor.
® Registered trademark of the International Electrotechnical Commission
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– 2 – IEC TS 62998-3:2023 © IEC 2023
CONTENTS
FOREWORD . 4
INTRODUCTION . 6
1 Scope . 7
2 Normative references . 7
3 Terms and definitions . 8
4 Sensor technologies . 11
4.1 General considerations . 11
4.2 SRS using visible light . 13
4.2.1 General . 13
4.2.2 Material considerations . 13
4.2.3 Measurement method considerations . 13
4.2.4 Sensing unit arrangement considerations . 14
4.3 SRS using near infrared radiation . 17
4.3.1 General . 17
4.3.2 Material considerations . 17
4.3.3 Measurement method considerations . 18
4.3.4 Sensing unit arrangement considerations . 18
4.4 SRS using middle infrared radiation . 19
4.4.1 General . 19
4.4.2 Material considerations . 20
4.4.3 Measurement method considerations . 20
4.4.4 Sensing unit arrangement considerations . 20
4.5 SRS using millimetre wave radiation . 21
4.5.1 General . 21
4.5.2 Material considerations . 21
4.5.3 Measurement method considerations . 21
4.5.4 Sensing unit arrangement considerations . 22
4.6 SRS using radio/millimetre wave radiation . 23
4.6.1 General . 23
4.6.2 Tag considerations . 23
4.6.3 Measurement method considerations . 23
4.6.4 Sensing unit arrangement considerations . 24
4.7 SRS using ultrasound wave radiation . 25
4.7.1 General . 25
4.7.2 Material considerations . 25
4.7.3 Measurement method considerations . 25
4.7.4 Sensing unit arrangement considerations . 26
5 Algorithm related considerations . 27
5.1 General . 27
5.2 Design and development phase . 30
5.2.1 General . 30
5.2.2 Achieve the detection of objects . 32
5.2.3 Improve the dependability of the detection capability . 33
5.2.4 Provide confidence information at the output unit . 33
5.3 Integration and installation phase . 33
5.3.1 General . 33
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IEC TS 62998-3:2023 © IEC 2023 – 3 –
5.3.2 Achieve improved detection of objects . 35
5.3.3 Improve the dependability of the detection capability . 36
5.3.4 Provide confidence information at the output unit . 36
5.4 Maintenance phase . 36
Annex A (informative) Physical property reflectivity for visible light or near infrared
radiation . 38
A.1 Process in accordance with IEC TS 62998-1 . 38
A.2 Persons or parts of a person . 39
Annex B (informative) Physical property reflectivity for millimetre wave radiation . 42
Annex C (informative) Physical property temperature for middle infrared radiation . 44
C.1 Process in accordance with IEC TS 62998-1 . 44
C.2 Exemplary determination of the temperature . 45
Annex D (informative) Physical property reflectivity for ultrasound wave radiation . 47
Bibliography . 50
Figure 1 – Co-located and stationary sensing unit arrangement . 15
Figure 2 – Separated and stationary sensing unit arrangement . 15
Figure 3 – Multiple and stationary sensing unit arrangement . 16
Figure 4 – Co-located and moving sensing unit arrangement . 16
Figure 5 – Separated and moving sensing unit arrangement . 16
Figure 6 – Multiple and moving sensing unit arrangement . 16
Figure 7 – Exemplary combined stationary and moving sensing unit arrangement. 17
Figure 8 – Exemplary multiple combined and moving sensing unit arrangement . 17
Figure 9 – Algorithms exemplary applied to an SRS or an SRSS . 28
Figure 10 – Flowchart for algorithm based on requirements . 29
Figure 11 – Flowchart for algorithm based on training data . 30
Figure 12 – Exemplary use of algorithm for peak extraction . 31
Figure 13 – Exemplary use of algorithm to combine measurement information . 32
Figure 14 – Exemplary combination of two SRS in an SRSS . 34
Figure 15 – Exemplary integration of SRS measurement information in an SRSS . 35
Figure C.1 – Illustration of temperature measurement . 46
Figure D.1 – Object ultrasonic reflectivity quantified by acoustic impedance or
reflection coefficient . 47
Figure D.2 – Object ultrasonic reflectivity quantified by radar cross section . 48
Table 1 – Specific sensor types used as part of SRS . 12
Table A.1 – Range of diffuse reflectance values of human skin if detection of skin can
be derived from the intended use . 39
Table A.2 – Range of diffuse reflectance values of clothes if detection of parts of
persons can be derived from the intended use . 40
Table A.3 – Diffuse reflectance values if detection of the whole body of persons can be
derived from the intended use . 41
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INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
SAFETY OF MACHINERY – SAFETY-RELATED SENSORS
USED FOR THE PROTECTION OF PERSONS
Part 3: Sensor technologies and algorithms
FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
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rights. IEC shall not be held responsible for identifying any or all such patent rights.
IEC TS 62998-3 has been prepared by IEC technical committee TC 44: Safety of machinery –
Electrotechnical aspects. It is a Technical Specification.
The text of this Technical Specification is based on the following documents:
Draft Report on voting
44/981/DTS 44/1002/RVDTS
Full information on the voting for the approval of this Technical Specification can be found in
the report on voting indicated in the above table.
The language used for the development of this International Standard is English.
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IEC TS 62998-3:2023 © IEC 2023 – 5 –
This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available
at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are
described in greater detail at www.iec.ch/standardsdev/publications.
This document is intended to be used in conjunction with IEC TS 62998-1.
A list of all parts in the IEC 62998 series, published under the general title Safety of machinery
– safety-related sensors used for the protection of persons, can be found on the IEC website.
Future documents in this series will carry the new general title as cited above. Titles of existing
documents in this series will be updated at the time of the next edition.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under webstore.iec.ch in the data related to the
specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
IMPORTANT – The "colour inside" logo on the cover page of this document indicates
that it contains colours which are considered to be useful for the correct understanding
of its contents. Users should therefore print this document using a colour printer.
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– 6 – IEC TS 62998-3:2023 © IEC 2023
INTRODUCTION
Applications of automated guided vehicles, service robotics used in public areas or human
machine interaction in industries show an increasing demand and use of new sensor
technologies and new kinds of sensor functions with respect to hazard exposure of persons. A
rapidly increasing number of sensors, with different sensor technologies, are used in these
applications to achieve a high degree of automation up to autonomy. The systematic capabilities
of such sensors are relevant to reduce the risk of personal injury. Other aspects of functional
safety related to sensors as part of control systems are covered by e.g. IEC 61508 (all parts),
IEC 62061 or ISO 13849 (all parts).
Existing design specific sensor standards set requirements on systematic capabilities for a
selected sensor technology and how these can be assessed by analysis and test. The specific
requirements are derived from products with limited classes of safety performance and already
well-known sensor technology.
IEC TS 62998-1 sets general requirements for the development, integration and maintenance
of safety related sensors (SRS) and safety related sensor systems (SRSS) applicable to all
sensor technologies with special attention to systematic capabilities. IEC TS 62998-1 is
appropriate for the risk reduction in accordance with all classes of safety performance in an
identified application.
First assessments of SRS/SRSS in accordance with IEC TS 62998-1 identified the need for
additional guidance for the required analysis of sensor technologies and use of algorithms.
Sensor technology is defined by the wavelength range, the measurement method and the
arrangement of the sensing unit in an SRS, respectively arrangement of SRS in an SRSS. This
document gives guidance for sensor technologies without setting requirements for a specific
design or limiting the class of safety performance. If applicable to the sensor technology,
additional information is given for physical properties of the objects to be detected or relevant
objects that interfere with the detection of such objects.
Algorithms are a core element to achieve safety related functions in an SRS/SRSS, such as
signal processing to extract peaks in analogue signals, localization or classification of objects
that are important to guide an autonomous or highly automated system in a more or less known
surrounding. Platforms such as cloud services provide e.g. algorithms or measures for their
automated generation that can be implemented by different integrators of SRS into an SRSS or
by the manufacturer of such sensors. This document gives guidance on the correct
implementation of algorithms to prevent intolerable risk for persons.
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IEC TS 62998-3:2023 © IEC 2023 – 7 –
SAFETY OF MACHINERY – SAFETY-RELATED SENSORS
USED FOR THE PROTECTION OF PERSONS
Part 3: Sensor technologies and algorithms
1 Scope
This part of IEC 62998, which is a technical specification, gives guidance on:
– analysis of sensor technologies of different wavelength ranges, measurement methods, and
the sensing unit arrangement in an SRS, respectively the arrangement of SRSs in an SRSS;
– representative physical properties of safety-related objects with due consideration of their
material characteristics and the sensor technology/technologies used in an SRS/SRSS to
achieve the detection capability and comparable results during verification and validation;
– analysis of the interference of objects present in the surrounding on the safety related
objects and thereby the influence on the dependability of the detection capability;
– use of algorithms during design, development and maintenance to achieve appropriate
detection capability and dependability of detection;
– appropriate use of algorithms during the integration of SRS or SRSS by the integrator to
improve execution of measurement information or provide decision information derived from
measurement information.
If an SRS/SRSS uses sensor technologies not stated in this document, then the generic
approach in accordance with IEC TS 62998-1 applies.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies.
For undated references, the latest edition of the referenced document (including any
amendments) applies.
IEC 60079-29 (all parts), Explosive atmospheres - Part 29 - Gas detectors
IEC 61508 (all parts), Functional safety of electrical/electronic/programmable electronic safety-
related systems
IEC TS 62998-1:2019, Safety of machinery - Safety-related sensors used for the protection of
persons
EN 50402, Electrical apparatus for the detection and measurement of combustible or toxic
gases or vapours or of oxygen – Requirements on the functional safety of fixed gas detection
systems
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3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.1
acoustic impedance
at a specified surface, quotient of sound pressure by volume velocity through the surface
1
[SOURCE: IEC 60050-801:1994 [3] , 801-25-40]
3.2
algorithm
finite set of well-defined rules for the solution of a problem in a finite number of steps
Note 1 to entry: An algorithm can be implemented by software or hardware means or by a combination of both.
[SOURCE: IEC 60050-171:2019 [2], 171-05-07, modified – Note to entry has been added]
3.3
bidirectional reflectance distribution function
function describing how a wave is reflected at a surface of an object
Note 1 to entry: It is employed in the optics of real-world light, in computer graphics algorithms, and in computer
vision algorithms.
Note 2 to entry: It is usually applied in case of a mixed reflection.
3.4
cloud service
one or more capabilities offered via cloud computing invoked using a defined interface
[SOURCE: ISO/IEC 20924:2021 [12], 3.1.8]
3.5
concentration
amount of the gas or vapour of interest in a specified amount of the background gas or air
Note 1 to entry: Typical units include volume fraction (V/V); molar (moles per mole – m/m); percentage of the LFL
of a particular substance; parts per million by volume (ppm); and parts per billion by volume (ppb).
3.6
depth from focus/defocus
changing of focal setting parameters to estimate distances in a scene
Note 1 to entry: Usually the distances are related to an observed surface of that scene.
Note 2 to entry: The distances are reconstructed from a set of two or more images related to the changed focal
parameters of the observing sensor (e.g. light field cameras)
___________
1
Numbers in square brackets refer to the bibliography.
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IEC TS 62998-3:2023 © IEC 2023 – 9 –
3.7
diffuse reflectance value
ratio of the diffusely reflected part of a wave and the incoming wave
Note 1 to entry: An ideal diffuse reflecting surface is said to exhibit Lambertian characteristic, meaning that there
is equal luminance when viewed from all directions lying in the half-space adjacent to the surface.
3.8
diffuse reflection
scattering by reflection in which, on the macroscopic scale, there is no regular reflection
[SOURCE: IEC 60050-845:2020 [4], 845-24-054, modified – Note to entry has been removed]
3.9
direct time-of-flight
when a pulse is emitted, time difference between outgoing and incoming signals measured as
an equivalent of time-of-flight
Note 1 to entry: For the use in an SRS/SRSS, the wavelength range for near infrared radiation is defined between
50 µm and 1 mm.
3.10
illuminated portion
effective echoing area of an object in terms of radar cross section
3.11
indirect time-of-flight
when a continuous amplitude modulated signal is emitted, phase difference between outgoing
and incoming signals measured as an equivalent of time-of-flight
3.12
level switching
comparison of a detected signal related to a predefined threshold
3.13
machine learning model
mathematical construct that generates an inference, or prediction, based on input data
EXAMPLE If a univariate linear function (y = θ0 + θ1x) has been trained using linear regression, the resulting model
can be y = 3 + 7x.
[SOURCE ISO/IEC 22989:2022 [13], 3.2.11, modified –Note to entry has been removed]
3.14
measurement method
generic description of a logical organization of operations used in a measurement
Note 1 to entry: Measurement methods may be qualified in various ways such as: substitution measurement
method, differential measurement method, and null measurement method; or direct measurement method and indirect
measurement method. See IEC 60050-300 [6].
[SOURCE: ISO/IEC GUIDE 99:2007 [18], 2.5]
3.15
middle infrared radiation
part of the infrared spectrum of optical radiation in which the wavelengths are longer than those
of near infrared radiation and shorter than those of long infrared radiation
Note 1 to entry: For the use in an SRS/SRSS, the wavelength range for middle infrared radiation is defined between
3 µm and 50 µm.
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3.16
mixed reflection
partly regular and partly diffuse reflection
[SOURCE: IEC 60050-845:2020 [4], 845-24-056]
3.17
near infrared radiation
part of the infrared spectrum of optical radiation in which the wavelengths are longer than those
of visible radiation and shorter than those of middle infrared radiation
Note 1 to entry: For the use in an SRS/SRSS, the wavelength range for near infrared radiation is defined between
780 nm and 3 µm.
3.18
passive infrared sensor
sensor that is used to detect temperature changes
Note 1 to entry: Unlike other temperature sensors (e.g. thermography cameras), passive infrared sensors do not
respond to a specific temperature level that is constant over time, but only to the change in temperature.
Note 2 to entry: Passive infrared sensors are based on pyroelectricity, a property of some piezoelectric
semiconductor crystals.
3.19
practical use
use that involves real situations and events, rather than just ideas, theories or generally
understood patterns of usage
EXAMPLE Derivation of real situations, events and scenarios from the application of the SRS/SRSS in the end user
environment.
Note 1 to entry: The practical use can be a subset or an expansion of the intended use.
3.20
radar cross section
RCS
equivalent echoing area which is 4 π times the ratio of the power per unit solid angle scattered
in a specified direction to the power per unit area in a plane wave incident on the scatterer
...
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