ISO 3691-4:2020
A Standard for AutomatedGuided Vehicles.

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Table of Contents.

03

ISO 3691-4 an adoption of ISO 13849
for driverless industrial trucks.

04

Road toward Safety.

06

Main improvements in respect to EN-1525.

07

Limitations.

08

Major Differences.
Compliance.

3

ISO 3691-4 an adoption of ISO 13849
for driverless industrial trucks.
In recent years, the optimization of time and resources has
become indispensable in the manufacturing industry.
Nowadays, the usage of the driverless industrial trucks AGV(Automated Guided Vehicles) and the smallest AGC (Automated Guided Carts) become more prominent with theimplementation of methodologies with Kanban cards (LeanManufacturing) or POLCA (Quick Response Manufacturing)and other methodologies.

Human interaction with this equipment (i.e. working islands)
poses hazards to humans with rising risks due to the increaseof interactions with the AGV / AGC.
Until now, for these systems (AGV / AGC) there was noharmonized, listed standard available, although EN
1525:1997 was used by the truck manufacturers.
This laid the basis for the definition, use and evaluation of
the basic elements of protection, referring to the superseded
EN 954, and therefore stipulating minimum Categories(B, 1, 2, 3 or 4) for some of them.

The ISO 3691-series covers the basic safety requirements
for industrial trucks. ISO 3691-4 specifies these requirements as a Type C standard for driverless industrial trucks.

TOPICS TO CONSIDER FOR A SAFET Y AGV

Hazard & Risk
Assessment

For a safe AGV / AGC the ISO 3691-4 describes
three key aspects, as shown in Figure 1:

Environment
ZoneSafety
AGV· the operating environment (i.e. defining the··different zones where the truck operates andinteracts with humans),
the hazards and risk associated, andthe correct implementation of the Safety(protection) Systems.

Safety Systems

Figure 1

4Road toward Safety.
A safety assessment is necessary for AGV / AGC. The following graphic shows
which steps should be considered in which phase.

PI L L A R S O F T H E R OA D TOWA R D SA F E T Y

Risk Assessment

Safety requirements∙ Acc. to ISO 12100:2010∙ Hazards & risk.

∙ Protective measures,acc. to Annex Belectrical, energy,
guards, interlocks,
ESPE ...

Assessment SRP / CS

∙ Safety Functions

Table 1 chapter 4.11

∙ Zones acc. toTable 1 & 2 Annex A

Verification

Documentation∙ Type testing: Test A & B ∙ Warning system∙ Stability tests∙ Instruction handbook∙ Structural tests∙ Marking∙ Functional verification∙ Commissioning
Figure 2

As usual in the safety assessments, the way starts with hazard analysis
and risk estimation.
This can be accomplished with the help of the table of ISO 3691-4,
Annex B where hazards and their possible consequences are listed.

REMARKThe standard does not cover the estimation of hazards resulting fromextreme climates, nuclear, explosive, military and specific environments.

During the design process of the protective functions, it is of main importance toput the focus on the complete system.
This contains the understanding of the relationship of the different functions andSafety Functions for the overall safety of the AGV.

5The following diagram shows the Safety protective measures stated byISO 3691-4 and their relationship.

S A F E T Y P R O T E C T I V E M E A S U R E S R E L AT I O N S H I PSteering
4.6

WarningSystem
6.2

Braking
System
4.2

Stability
4.7

Personnel
Detection
System
4.8.2

LoadHandling
4.5
SpeedControl
4.3

Truck
accessto/from theconfined zone
A.2.4.3

Emergency
Stop Function
4.8.1

Automatic,
manual andmaintenance
Modes
4.9

Automatic
Battery
Charging
4.4

Figure 3

The Control System of the AGV / AGC needs to deal with Safety and non-Safety
Functions, taking into account that some Safety Functions may affect Safety
as well as Non-Safety ones.
The AGV/AGC control system has to safely control the speed, stability, load andsteering. Some of its functions, for example, rely on the safe functioning of theBraking System and especially the Personnel Detection System.
The Performance Level (PL) for the different Safety Functions (Protection Measures) are based on Hazards listed in ISO 3691-4, Annex B, the resulting PLs
are listed in ISO 3691-4, Table 1 of the standard (see Figure 4 on the next page).

6

Main improvements
in respect to EN-1525.
P L I N S T E A D O F C AT E G O R Y

The first improvement is that the ISO 3691-4 is, as state of the art, aligned withthe ISO 13849 with the PLr (required Performance Level) requirements insteadof Categories only.
Table 1, in section 4.11 describes the Safety Function (27 in total), the associatedrisk and the minimum PLr acc. to ISO 13849-1.

E X A M P L E O F TA B L E 1 S E C T I O N 4 .11 I S O 3 6 9 1 - 4
ChapterN°

Cross-­
referencein this­d ocument

Description ofSafety Function

Main Risk

NoteMin. PL racc. toISO 13849-1

4.2 Braking
system14.2

Braking systemcontrol- C ollision with­p ersons

PL function controls thedeceleration function.

d24.2 d)Parking braking
system control- Unintended motionof the truck: Risk ofcollision.

PL function controls thatbrake is dis-engaged inorder to avoid continuous
braking when ­travelling.

b-R eduction of braking
performance if thebattery is discon­
nected (unlikely).

(Wear and release of thebrake to be checked withperiodic maintenance).
Figure 4

Figure 4 shows the abstract Table 1, presenting two Safety Functions related to
the Braking System. Derived from the nature of the associated risks, a specific
PL acc. to ISO 13849-1 is required, PLr d for Safety Function number 1 (BrakingSystem) and PLr b for Safety Function number 2 (Parking Braking System).

THE ISO 3691-4 SPECIFIES THE NORMAL CLIMATIC CONDITIONS· Avg. ambient temperature continuous duty:· Max. ambient temperature, short term (up to 1h):
· Lowest ambient temperature, normal use indoor:· Lowest ambient temperature, normal use outdoor:· Altitude:+ 25 º C+ 40 º C+5 º C- 20 º C
2,000 mLike EN 1525, the ISO 3691-4 states that for severe conditions (e. g. extremeclimates, freezer applications, strong magnetic fields,…) the designer needs toevaluate the risks. This means that there is no clear limit for the outdoor use of
AGV / AGC, but if the conditions are outside, for the normal climatic conditions
an additional assessment has to be performed.

7
B E T T E R D E F I N I T I O N A N D C L A S S I F I C AT I O N
OF THE ZONES

EN 1525 in Annex A defines only two zones for the equipment as Restricted Zone and Hazard Zone – now with theISO 3691-4 additionally the Confined Zone is defined.
Furthermore, the requirements for every zone are better
defined than in EN 1525 (e.g. truck speed).

In addition to Annex A Table1 of ISO 3691-4, the classi­
fication of zones are also distinguished between active orinactive Personnel Detection means.

E X T R A C T O F TA B L E A .1

In addition to Table A.1 of ISO 3691-4, the classificationof zones are also distinguished between active or inactive
Personnel Detection means.
Clearance between truck
and continuous fixedclosed structure
Clearance
on one side,C1 (mm)Clearanceon the otherside, C2 (mm)Clearance fromcurrent position
to the fixedclosed structure/object in the­d irection of travel,
C3mm

Personnel
Detectionmeansin travel
direction
active (PL D)

1a> 500> 500

Max
speed 5Requiredzone
classi­fication

Reachable
stopfunctionrequired
within
600 mmFloor/
groundmarking or
extra
warnings
RequiredAutomatic
restartpermitted

Active

Rated
speed

Operating

NONONO

Muted

0,3 m/sOperatinghazardNOYES-b> 500

1bb - In these specific cases, automatic restart is permitted without personnel detection means if side clearance is > 500 mm on at least one side or clearanceis >  5 00 mm from the current position to the fixed closed structure/object in the direction of travel if determined to be acceptable by a risk assessment.

Figure 5C O N D I T I O N S T O M U T E , O V E R R I D E O R D E A C T I VAT E

B R A K I N G S Y S T E M C O N T R O L D E F I N E D A S A N S R P/ C S

THE PERSONNEL DETECTION MEANS ARE GIVEN

The Braking System acc. to EN 1525 needs to fulfill somefunctional requirements but has no dedicated Category
requirement. The ISO 3691-4 maintains these requirementsand adds the Control of the Braking System to the list ofSRP / CS with respective PL requirements (see Table 1).

Following the requirements of section 4.8.2.3 if suchfunction is possible. The EN 1525 only specifies that theBypass of Safety Functions has to fulfill Category 2.
T H E I N T E R AC T I O N W I T H C O N V E YO R S F I T T E D TO
A TRUCK IS DESCRIBEDUnderstanding that AGV / AGC interact with conveyors,
the ISO 3691-4 includes this topic and defines requirements accordingly (see section 4.13.).

Limitations.
T H E I S O 3 6 9 1 - 4 A L S O H A S S O M E L I M I TAT I O N S , A S D E S C R I B E D B E L O W· Humans approaching the truck or stepping sideways
into the path of the truck or out of scope(see section 1 ‘Scope’)· There is no PL or even Category (as in the formerrEN 1525) specified for the steering (see table 1 inISO 3691-4), although the PL and tolerable speed
depends on the direction of travel (see Safety
Functions for Personal Detection System in table 1).

8Major Differences.
Although the adoption of the new ISO 3691-4 instead ofEN 1525 represents a change of the general approach forthe assessment of AGV / AGC, the requirements where it
has a more direct impact on is related to the Detection ofPersons and the Braking System.

The other key difference is the definition of the Safety
Function “Detection of persons in the guide path” as“They shall be so designed that trucks shall stop before
contact between the rigid parts of the truck or load anda stationary person…”.

In EN 1525, the Safety Function “Detection of persons
on the travelling path” is defined in section 5.9.5.1 point b)
as “They shall generate a signal enabling the truck to bestopped by the braking system…” but without further
requirements concerning Category or Performance Level.

The difference lies in “generate a signal” (EN 1525) and“stop” (ISO 3691-4). This makes mandatory to assess theoverall system including the Braking System.

According to Annex A Table 1 of ISO 3691-4, there aresafety requirements for the Safety-Related Parts of aControl Systems (SRP / CS) for the Personnel Detection
System and the Braking System (Control) in reference toISO 13849-1. This is one major difference to EN 1525.

Compliance.
ISO 3691-4:2020 is a new Type C standard, well alignedwith ISO 13849 and will be a good guide to carry out safetyassessments of the entire AGV/AGC. Complying with thisstandard will lead to safer self-driving vehicle environments
like factories or logistics centres.

The standard clarifies that the SRP / CS of the Detectionof Personnel and the Braking System have to comply
with a level of PLr d.

DE21_I07_FSCS_2100831_en

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