Safety of machinery - Electro-sensitive protective equipment - Part 4-3: Particular requirements for equipment using vision based protective devices (VBPD) - Additional requirements when using stereo vision techniques (VBPDST)

IEC TS 61496-4-3:2015(E) specifies requirements for the design, construction and testing of electro-sensitive protective equipment (ESPE) designed specifically to detect persons or parts of persons as part of a safety-related system, employing vision-based protective devices (VBPDs) using stereo vision techniques (VBPDST) for the sensing function. Special attention is directed to features which ensure that an appropriate safety-related performance is achieved.
This publication is to be read in conjunction with IEC 61496-1:2012.

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Status
Published
Publication Date
18-May-2015
Current Stage
PPUB - Publication issued
Start Date
19-May-2015
Completion Date
19-May-2015
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IEC TS 61496-4-3:2015 - Safety of machinery - Electro-sensitive protective equipment - Part 4-3: Particular requirements for equipment using vision based protective devices (VBPD) - Additional requirements when using stereo vision techniques (VBPDST)
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IEC TS 61496-4-3
Edition 1.0 2015-05
TECHNICAL
SPECIFICATION
colour
inside
Safety of machinery – Electro-sensitive protective equipment –
Part 4-3: Particular requirements for equipment using vision based protective
devices (VBPD) – Additional requirements when using stereo vision techniques
(VBPDST)
IEC TS 61496-4-3:2015-05(en)
---------------------- Page: 1 ----------------------
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---------------------- Page: 2 ----------------------
IEC TS 61496-4-3
Edition 1.0 2015-05
TECHNICAL
SPECIFICATION
colour
inside
Safety of machinery – Electro-sensitive protective equipment –
Part 4-3: Particular requirements for equipment using vision based protective
devices (VBPD) – Additional requirements when using stereo vision techniques
(VBPDST)
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 13.110; 29.260.99 ISBN 978-2-8322-2611-7

Warning! Make sure that you obtained this publication from an authorized distributor.

® Registered trademark of the International Electrotechnical Commission
---------------------- Page: 3 ----------------------
– 2 – IEC TS 61496-4-3:2015 © IEC 2015
CONTENTS

FOREWORD ........................................................................................................................... 5

INTRODUCTION ..................................................................................................................... 7

1 Scope .............................................................................................................................. 8

2 Normative references ...................................................................................................... 9

3 Terms and definitions ...................................................................................................... 9

Abbreviated terms ................................................................................................................. 12

4 Functional, design and environmental requirements ...................................................... 12

4.1 Functional requirements ........................................................................................ 12

4.1.2 Sensing function ............................................................................................ 12

4.1.3 Types of ESPE .............................................................................................. 15

4.1.6 Zone with limited detection capability ............................................................. 15

4.2 Design requirements ............................................................................................. 16

4.2.2 Fault detection requirements ......................................................................... 16

4.2.12 Integrity of the VBPDST detection capability .................................................. 17

4.2.13 Test pieces for type testing ............................................................................ 19

4.2.14 Wavelength ................................................................................................... 21

4.2.15 Radiation intensity ......................................................................................... 21

4.2.16 Mechanical construction ................................................................................ 21

4.3 Environmental requirements ................................................................................. 21

4.3.1 Ambient air temperature range and humidity .................................................. 21

4.3.5 Ambient light intensity.................................................................................... 21

4.3.6 Light interference ........................................................................................... 21

4.3.7 Pollution interference ..................................................................................... 22

4.3.8 Manual interference ....................................................................................... 22

4.3.9 Optical occlusion (eclipsed by small object) ................................................... 23

4.3.10 Drift or ageing of components ........................................................................ 23

5 Testing .......................................................................................................................... 23

5.1 General ................................................................................................................. 23

5.1.2 Test conditions .............................................................................................. 23

5.1.4 Test conditions and test plan ......................................................................... 24

5.2 Functional tests .................................................................................................... 24

5.2.1 Sensing function ............................................................................................ 24

5.2.9 Verification of optical performance ................................................................. 28

5.2.10 Wavelength ................................................................................................... 28

5.2.11 Radiation intensity ......................................................................................... 28

5.3 Performance testing under fault conditions ........................................................... 28

5.3.2 Type 1 ESPE ................................................................................................. 28

5.3.3 Type 2 ESPE ................................................................................................. 28

5.3.4 Type 3 ESPE ................................................................................................. 29

5.3.5 Type 4 ESPE ................................................................................................. 29

5.4 Environmental tests .............................................................................................. 29

5.4.2 Ambient temperature variation and humidity .................................................. 29

5.4.4 Mechanical influences ................................................................................... 29

5.4.6 Light interference ........................................................................................... 30

5.4.7 Pollution interference ..................................................................................... 36

5.4.8 Manual interference ....................................................................................... 37

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IEC TS 61496-4-3:2015 © IEC 2015 – 3 –

5.4.9 Optical occlusion ........................................................................................... 37

6 Marking for identification and for safe use ..................................................................... 38

6.1 General ................................................................................................................. 38

7 Accompanying documents ............................................................................................. 38

Annex A (normative) Optional functions of the ESPE ........................................................... 40

A.9 Setting the detection zone and/or other safety-related parameters ........................ 40

A.9.1 Functional requirements ................................................................................ 40

A.9.2 Verification .................................................................................................... 40

A.10 Selection of multiple detection zones .................................................................... 41

A.10.1 Functional requirements ................................................................................ 41

A.10.2 Verification .................................................................................................... 41

Annex B (normative) Catalogue of single faults affecting the electrical equipment of

the ESPE, to be applied as specified in 5.3 ................................................................... 42

B.7 Imaging sensor ..................................................................................................... 42

Annex AA (informative) The positioning of VBPDST employing a volume as a

detection zone in respect of parts of the human body ........................................................... 43

AA.1 Calculation of distances for electro-sensitive protective equipment employing

vision based protective devices (VBPDST) ............................................................ 43

AA.1.1 General ......................................................................................................... 43

AA.1.2 Calculation of the overall minimum distance S .............................................. 43

AA.1.3 Vision based protective devices with a detection capability > 40 mm and

≤ 55 mm ........................................................................................................ 44

AA.1.4 Vision based protective devices with a detection capability > 55 mm and

≤ 200 mm ...................................................................................................... 45

AA.1.5 Examples of detection zone and tolerance zone ............................................ 45

AA.2 Application examples for body detection of a VBPDST employing a volume

as a detection zone ............................................................................................... 49

Annex BB (informative) Relationship between position accuracy and tolerance zones

for VBPDST .......................................................................................................................... 51

BB.1 Probability of detection ......................................................................................... 51

BB.2 Tolerance zone related to probability .................................................................... 52

BB.3 Determination of tolerance zone for systems not providing object distance

information ............................................................................................................ 52

BB.4 Determination of tolerance zone for systems providing distance information ......... 53

BB.5 Tolerance zone related to systematic interferences ............................................... 54

BB.6 Adding the tolerance zone on the outer border of the detection zone .................... 54

Annex CC (informative) Basic principles of physics for contrast of convex

homogeneous bodies ............................................................................................................ 56

CC.1 Illumination on a surface element .......................................................................... 56

CC.2 Brightness of a surface element ............................................................................ 58

Bibliography .......................................................................................................................... 63

Figure 1 – Image planes in imaging device of a VBPDST ...................................................... 10

Figure 2 – 3D view of a vision based protective device using stereo vision techniques

(VBPDST) ............................................................................................................................. 13

Figure 3 – 2D view of a vision based protective device using stereo vision techniques

(VBPDST) ............................................................................................................................. 14

Figure 4 – Examples for periodic surface structures on the background ................................ 28

Figure 5 – Test setup for indirect light interference on the background.................................. 34

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– 4 – IEC TS 61496-4-3:2015 © IEC 2015

Figure 6 – Test setup for VBPDST of identical design with PAPT .......................................... 35

Figure 7 – Test setup for direct light interference on the sensing device ............................... 36

Figure AA.1 – Minimum distance S – Example 1 .................................................................... 45

Figure AA.2 – Overall minimum distance S without tolerance zone – Example 1 .................. 46

Figure AA.3 – Overall minimum distance S including tolerance zone – Example 1 ............... 46

Figure AA.4 – Minimum distance S – Example 2 .................................................................... 47

Figure AA.5 – Overall minimum distance S without tolerance zone – Example 2 .................. 48

Figure AA.6 – Overall minimum distance S including tolerance zone – Example 2 ............... 48

Figure AA.7 – Application example for body detection of a VBPDST employing a

volume as a detection zone .................................................................................................. 50

Figure BB.1 – Relationship between test piece position and the probability of detection ....... 51

Figure BB.2 – Example for measurement of the probability of detection ................................ 52

Figure BB.3 – Relationship between detection zone and tolerance zone ............................... 54

Figure BB.4 – Overall minimum distance S including tolerance zone ................................... 55

Figure CC.1 – Illumination model – Sphere illuminated by a point source .............................. 57

Figure CC.2 – Illumination model – Sphere illuminated by a half-Ulbricht sphere .................. 57

Figure CC.3 – Brightness of a surface element of a sphere in spherical coordinates ............. 58

Figure CC.4 – Brightness distribution in an image of a sphere .............................................. 58

Figure CC.5 – Grey value profile over a sphere with low contrast for a typical imaging

contrast (Modulation Transfer Function) ................................................................................ 59

Figure CC.6 – Grey value profile over a sphere with the same colour as the

background ........................................................................................................................... 59

Figure CC.7 – Grey value profile over a sphere in front of a background that is half as

bright .................................................................................................................................... 60

Figure CC.8 – Grey value profile over a sphere in front of a background that is twice as

bright .................................................................................................................................... 60

Figure CC.9 – Grey value profile over a sphere by low contrast ............................................ 61

Figure CC.10 – Grey value profile over the sphere from Figure CC.9 but with the

direction to the imaging device changed by 10° .................................................................... 61

Figure CC.11 – Grey value profile over a small sphere that results in an image that is 5

pixels in diameter .................................................................................................................. 62

Table 1 – Verification of detection capability requirements (see also 4.2.12) ......................... 25

Table 2 – Overview of light interference tests........................................................................ 30

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IEC TS 61496-4-3:2015 © IEC 2015 – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
SAFETY OF MACHINERY –
ELECTRO-SENSITIVE PROTECTIVE EQUIPMENT –
Part 4-3: Particular requirements for equipment using
vision based protective devices (VBPD) –
Additional requirements when using stereo
vision techniques (VBPDST)
FOREWORD

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whether they can be transformed into International Standards.
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– 6 – IEC TS 61496-4-3:2015 © IEC 2015

IEC TS 61496-4-3, which is a technical specification, has been prepared by IEC technical

committee 44: Safety of machinery – Electrotechnical aspects.
The text of this technical specification is based on the following documents:
Enquiry draft Report on voting
44/711/DTS 44/722/RVC

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.

This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.

This part is to be used in conjunction with IEC 61496-1:2012.

This part supplements or modifies the corresponding clauses in IEC 61496-1:2012 to specify

particular requirements for the design, construction and testing of electro-sensitive protective

equipment (ESPE) for the safeguarding of machinery, employing vision based protective

devices (VBPD) using stereo vision techniques (VBPDST) for the sensing function.

Where a particular clause or subclause of Part 1 is not mentioned in this Part 4-3, that clause

or subclause applies as far as is reasonable. Where this part states "addition", "modification"

or "replacement", the relevant text of Part 1 shall be adapted accordingly.

Clauses and subclauses which are additional to those of Part 1 are numbered sequentially,

following on the last available number in Part 1.Terminological entries (in Clause 3) which are

additional to those in Part 1 are numbered starting from 3.4301. Additional annexes are

lettered from AA onwards.

A list of all parts in the IEC 61496 series, published under the general title Safety of

machinery – Electro-sensitive protective equipment, can be found on the IEC website.

The committee has decided that the contents of this publication will remain unchanged until

the stability date indicated on the IEC web site under "http://webstore.iec.ch" in the data

related to the specific publication. At this date, the publication will be
• transformed into an International standard,
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
A bilingual version of this publication may be issued at a later date.

IMPORTANT – The 'colour inside' logo on the cover page of this publication 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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IEC TS 61496-4-3:2015 © IEC 2015 – 7 –
INTRODUCTION

An electro-sensitive protective equipment (ESPE) is applied to machinery presenting a risk of

personal injury. It provides protection by causing the machine to revert to a safe condition

before a person can be placed in a hazardous situation.

The working group responsible for drafting this technical specification was concerned that,

due to the complexity of the technology, there are many issues that are highly dependent on

analysis and expertise in specific test and measurement techniques. In order to provide a high

level of confidence, independent review by relevant expertise is required. They considered

that if this high level of confidence could not be established these devices would not be

suitable for use in safety related applications.
---------------------- Page: 9 ----------------------
– 8 – IEC TS 61496-4-3:2015 © IEC 2015
SAFETY OF MACHINERY –
ELECTRO-SENSITIVE PROTECTIVE EQUIPMENT –
Part 4-3: Particular requirements for equipment using
vision based protective devices (VBPD) –
Additional requirements when using stereo
vision techniques (VBPDST)
1 Scope
Replacement:

This part of IEC 61496 specifies requirements for the design, construction and testing of

electro-sensitive protective equipment (ESPE) designed specifically to detect persons or parts

of persons as part of a safety-related system, employing vision-based protective devices

(VBPDs) using stereo vision techniques (VBPDST) for the sensing function. Special attention

is directed to features which ensure that an appropriate safety-related performance is

achieved. An ESPE may include optional safety-related functions, the requirements for which

are given in Annex A of IEC 61496-1:2012 and this Technical Specification.

This part of IEC 61496 does not specify the dimensions or configurations of the detection

zone and its disposition in relation to hazardous parts for any particular application, nor what

constitutes a hazardous state of any machine. It is restricted to the functioning of the ESPE

and how it interfaces with the machine.

The detection principle is based on the evaluation of images from different viewing points

(stereoscopic view) for the determination of distance information. This distance information is

used to determine the location of an object(s).

– This part of IEC 61496 is limited to vision based ESPEs with distances (stereo base) and

directions between the different imaging devices fixed during manufacture.

– It is limited to vision based ESPEs, with a minimum distance from the sensing device to

the detection zone of 4 times of the stereo base.

– It is limited to vision based ESPEs that can detect objects with at least 5 pixel diameter in

the image plane.

– It is limited to vision based ESPEs that do not require human intervention for detection.

– It is limited to vision based ESPEs that detect objects entering into or being present in a

detection zone(s).

– It is limited to VBPDSTs employing radiation at wavelengths within the range 400 nm to

1 500 nm.

– This part of IEC 61496 does not address those aspects required for complex classification

or differentiation of the object detected.

– This part of IEC 61496 does not consider the aspects of a moving ESPE installation.

Additional requirements and tests can apply in the following cases:
– Use of multi-spectral (colour) techniques;

– Setups other than as shown in Figures of 4.1.2 (e.g. changing backgrounds, horizontal

orientation of the optical axis with respect to the floor);
– Intended for outdoor applications.
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IEC TS 61496-4-3:2015 © IEC 2015 – 9 –

This technical specification is relevant for VBPDSTs having a stated detection capability up to

200 mm.

This technical specification may be relevant to applications other than those for the protection

of persons or parts of persons like arm or fingers (in the range 14 mm to 200 mm), for

example the protection of machinery or products from mechanical damage. In those

applications, additional requirements can be necessary, for example when the materials that

are to be recognized by the sensing function have different properties from those of persons.

This technical specification does not deal with EMC emission requirements.
2 Normative references
Addition:

IEC 60825-1:2014, Safety of laser products – Part 1 – Equipment classification and

requirements
IEC 61496-1:2012, Safety of machinery – Electro-sensiti
...

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