ISO/FDIS 18646-4

Robotics -- Performance criteria and related test methods for service robots

Robotique -- Critères de performance et méthodes d'essai correspondantes pour robots de service

General Information

• Status: Published
• ICS: 25.040.30 - Industrial robots. Manipulators
• Technical Committee: ISO/TC 299 - Robotics
• Drafting Committee: ISO/TC 299/WG 4 - Service robot performance
• Current Stage: 5020 - FDIS ballot initiated: 2 months. Proof sent to secretariat
• Start Date: 03-May-2021
• Completion Date: 03-May-2021

Standards Content (sample)

FINAL
INTERNATIONAL ISO/FDIS
DRAFT
STANDARD 18646-4
ISO/TC 299
Robotics — Performance criteria
Secretariat: SIS
and related test methods for service
Voting begins on:
2021-05-03 robots —
Voting terminates on:
Part 4:
2021-06-28
Lower-back support robots
Robotique — Critères de performance et méthodes d'essai
correspondantes pour robots de service
RECIPIENTS OF THIS DRAFT ARE INVITED TO
SUBMIT, WITH THEIR COMMENTS, NOTIFICATION
OF ANY RELEVANT PATENT RIGHTS OF WHICH
THEY ARE AWARE AND TO PROVIDE SUPPOR TING
DOCUMENTATION.
IN ADDITION TO THEIR EVALUATION AS
Reference number
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO-
ISO/FDIS 18646-4:2021(E)
LOGICAL, COMMERCIAL AND USER PURPOSES,
DRAFT INTERNATIONAL STANDARDS MAY ON
OCCASION HAVE TO BE CONSIDERED IN THE
LIGHT OF THEIR POTENTIAL TO BECOME STAN-
DARDS TO WHICH REFERENCE MAY BE MADE IN
NATIONAL REGULATIONS. ISO 2021
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ISO/FDIS 18646-4:2021(E)
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© ISO 2021

All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may

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ii © ISO 2021 – All rights reserved
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ISO/FDIS 18646-4:2021(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction ..................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 1

4 Test conditions ....................................................................................................................................................................................................... 3

4.1 General ........................................................................................................................................................................................................... 3

4.2 Environmental conditions ............................................................................................................................................................. 3

4.3 Operating conditions ......................................................................................................................................................................... 4

5 Test method for assistive torque index and lumbar compression reduction .......................................4

5.1 Purpose .......................................................................................................................................................................................................... 4

5.2 Relevant characteristics .................................................................................................................................................................. 4

5.2.1 General...................................................................................................................................................................................... 4

5.2.2 Assistive torque index (ATI)................................................................................................................................... 4

5.2.3 Lumbar compression reduction (LCR) ......................................................................................................... 5

5.3 Test facility .................................................................................................................................................................................................. 7

5.3.1 Test apparatus .................................................................................................................................................................... 7

5.3.2 Reference movement and target trajectory .............................................................................................. 8

5.4 Test procedure ......................................................................................................................................................................................10

5.5 Test result .................................................................................................................................................................................................11

6 Test method for rate of assistance ..................................................................................................................................................11

6.1 Purpose .......................................................................................................................................................................................................11

6.2 Relevant characteristics ...............................................................................................................................................................11

6.3 Test facility ...............................................................................................................................................................................................12

6.4 Test procedure ......................................................................................................................................................................................15

6.5 Test result .................................................................................................................................................................................................18

Annex A (informative) Time range of ATI and LCR .............................................................................................................................19

Annex B (informative) Example of lower-back support robots .............................................................................................23

Annex C (informative) Example table of test results .........................................................................................................................25

Annex D (informative) Example implementation of a test apparatus ............................................................................26

Bibliography .............................................................................................................................................................................................................................29

© ISO 2021 – All rights reserved iii
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ISO/FDIS 18646-4:2021(E)
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 documents 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).

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. 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 .html.
This document was prepared by Technical Committee ISO/TC 299, Robotics.
A list of all parts in the ISO 18646 series can be found on the ISO website.

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.
iv © ISO 2021 – All rights reserved
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ISO/FDIS 18646-4:2021(E)
Introduction

This document is intended to facilitate understanding of performance of lower-back support robots

(see Annex B). This document defines the important performance characteristics and describes how to

specify them and how to test them.

The characteristics for which test methods are given in this document are those considered to affect

robot performance significantly. The user of this document selects which performance characteristics

to test, in accordance with the specific requirements.

The performance criteria specified in this document are not intended to be interpreted as the

verification or validation of safety requirements. The verification and validation of safety requirements

are specified in other standards developed by ISO TC 299.

The International Organization for Standardization (ISO) draws attention to the fact that it is claimed

that compliance with this document may involve the use of patents concerning the test apparatuses of

the performance of wearable robots for lower-back support referred to throughout the document.

ISO takes no position concerning the evidence, validity and scope of these patent rights.

The holders of these patent rights have assured ISO that they are willing to negotiate licences under

reasonable and non-discriminatory terms and conditions with applicants throughout the world. In this

respect, the statements of the holders of these patent rights are registered with ISO. Information may

be obtained from the patent database available at www .iso .org/ patents.

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights other than those in the patent database. ISO shall not be held responsible for identifying

any or all such patent rights.
© ISO 2021 – All rights reserved v
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FINAL DRAFT INTERNATIONAL STANDARD ISO/FDIS 18646-4:2021(E)
Robotics — Performance criteria and related test methods
for service robots —
Part 4:
Lower-back support robots
1 Scope

This document describes methods of specifying and evaluating the performance of lower-back support

robots.

This document applies regardless of the purpose and application of lower-back support robots and

the driving methods (e.g. electric, hydraulic and pneumatic). This document does not apply to medical

robots, although the test methods specified in this document can be utilized for medical robots.

This document is not intended for the verification or validation of safety requirements.

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.

ISO 8373, Robots and robotic devices — Vocabulary

ISO 13482, Robots and robotic devices — Safety requirements for personal care robots

3 Terms and definitions

For the purposes of this document, the terms and definitions given in ISO 8373, ISO 13482 and the

following apply.

ISO and IEC maintain terminological 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
robot

programmed actuated mechanism with a degree of autonomy, moving within its environment, to

perform intended tasks

Note 1 to entry: A robot includes the control system and interface of the control system.

Note 2 to entry: The classification of robot into industrial robot or service robot is done according to its intended

application.

[SOURCE: ISO 8373:2012, 2.6, modified — The words “actuated mechanism programmable in two or

more axes” have been replaced with “programmed actuated mechanism”.]
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ISO/FDIS 18646-4:2021(E)
3.2
wearable robot

robot that supplements or augments personal capabilities while attached to a human during use

Note 1 to entry: Wearable robots are referred to as restraint-type physical assistant robots in ISO 13482:2014.

3.3
lower-back support robot

wearable robot to reduce the load in the lower back of the user by its assistive force or torque

3.4
user

person who wears a wearable robot on his/her body and directly receives its assistive force or torque

3.5
restraint part

part of the wearable robot binding a corresponding attached body part of the user to transmit an

assistive force or torque
3.6
assistive torque
output torque of the wearable robot to assist a user to perform required tasks
3.7
attached body part

part of the user’s body on which the restraint part of the wearable robot is attached

3.8
input method

interface allowing the user to control the assistive force or torque of the wearable robot by an

appropriate input signal
3.8.1
biological input

input method where biological signals that are in correlation to the force or torque the user exerts at

his/her body part intended for assistance are used as the input

Note 1 to entry: Biological signals include bioelectrical signals such as myoelectric signals.

3.8.2
kinematic input

input method where movement and/or posture of the user’s body parts intended for assistance are

used as the input
Note 1 to entry: Biological input and kinematic input are mutually exclusive.
3.8.3
command input
any input method other than biological input or kinematic input

Note 1 to entry: Command input includes the use of commanding devices, breath switches or voice input.

Note 2 to entry: Command input includes the use of biological signals that are not in correlation to the force or

torque the user exerts at the body part intended for assistance.

Note 3 to entry: Command input includes movement and/or posture of the user’s body parts not intended for

assistance.
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ISO/FDIS 18646-4:2021(E)
3.9
assistive torque index
ATI

measure of how much the output torque of the user is reduced when the user performs a specific

movement during a specific time range using the lower-back support robot

Note 1 to entry: ATI is an absolute quantity with respect to the average torque during the specific time period of

a specific test motion profile. It can be helpful for the relative comparison between robots.

3.10
lumbar compression reduction
LCR

measure of how much the compressive force on the user’s lumbar disks is reduced when the user

performs a specific movement during a specific time range using the lower-back support robot

3.11
normal operating conditions

range of environmental conditions and other parameters which can influence robot performance (such

as electrical supply instability, electromagnetic fields) within which the performance of the robot

specified by the manufacturer is valid

Note 1 to entry: Environmental conditions include, for example, temperature and humidity.

[SOURCE: ISO 8373:2012, 6.1]
3.12
rate of assistance

measure of the reduced torque by a lower-back support robot integrated over the time period of a

specific test motion profile

Note 1 to entry: Rate of assistance is a normalized quantity with respect to the integrated torque over the time

period of a specific test motion profile. It can be helpful for the relative comparison for different test motion

profiles within the robot.
4 Test conditions
4.1 General

The lower-back support robot shall be completely assembled, sufficiently charged and operational. All

self-diagnostic tests shall be satisfactorily completed. It should also be ensured that the robot operates

in a safe manner throughout the test.

The tests shall be preceded by the preparations for operation as specified by the manufacturer,

including calibration of any relevant sensors that effect on the test results.

All conditions specified in Clause 4 should be satisfied for the tests described in this document, unless it

is stated otherwise in the specific clauses.

Each test described in Clause 5 and Clause 6 of this document have different test configurations which

require separate test apparatuses and test procedures.
4.2 Environmental conditions
The following environmental conditions shall be maintained during all tests.
— Ambient temperature: 10 °C to 30 °C
— Relative humidity: 0 % to 80 %
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ISO/FDIS 18646-4:2021(E)

If the environmental conditions specified by the manufacturer are outside the given conditions, then

this shall be declared in the test results.
4.3 Operating conditions

All performance shall be measured under normal operating conditions. When the performance is

measured under conditions outside the normal operating conditions, these conditions shall be specified

along with the test results.
5 Test method for assistive torque index and lumbar compression reduction
5.1 Purpose

This clause describes the method of specifying and evaluating the performance of lower-back support

robots.

NOTE Theoretical backgrounds and validation experiments are provided in Reference [6] which provides a

rationale of focusing only on bending torques and compression forces. At the current stage of the market, there

are only the products that are intended to assist sagittal movement. To keep the test apparatus and test method

simple, the limitation of the test method is considered acceptable to measure a representative performance of

the robots.
5.2 Relevant characteristics
5.2.1 General

Two performance indices are introduced for this test method: Assistive torque index (ATI) and Lumbar

compression reduction (LCR).

By the assistive torque of the robot, the user’s extension force of hip joints and that of the trunk will

be reduced, and then the compressive force on lumbar disks will be reduced. Ideally, the lumbar

compression can be derived from the extension torque of hip joints and the posture of the trunk.

The extension torque can be reduced by the assistive torque of the robot. For the robot with such

characteristics, the lumbar compression does not need to be measured because it can be inferred from

the assistive torque and the posture of trunk.

For some robots for which lumbar compression could be increased because of the robot’s mechanical

structure, mass and mass distribution above the lumbar joint and/or actuation method (e.g. artificial

muscles on user’s back skin), lumbar compression should be measured together with assistive torque.

NOTE According to Reference [1], compressive force on lumbar disks can be the major cause of back injury

and, therefore, often used as an index to estimate the risk of back injury. Based on this background, LCR is

introduced as a performance indication of the robot.
5.2.2 Assistive torque index (ATI)
Lower Lower Hold

The Assistive Torque Index (ATI) consists of 5 representative values, ATI , ATI , ATI ,

1 000 200 1 000
Raise Raise

ATI and ATI , which are calculated by the following formulae with t and t specified in

1 000 200 1 2
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ISO/FDIS 18646-4:2021(E)

Table 1. The superscript and the subscript of ATI indicate a phase of reference movement and a time

duration in milliseconds, respectively.
ref
ATI = ψτ ()tt, τ () dt
tt−
tt−
where
αβ−≥if α 0
ψ αβ, = ,
−−αβ if α < 0
ref

is the actual output torque of the hip joints of the test apparatus (see 5.3.1) during the

τ t
reference movements (without robot);

τ ()t is the actual output torque of the hip joints of the test apparatus (see 5.3.1) during the

reference movements (with robot).

NOTE 1 In general, assistive torque of the robot interferes with the duration of the movement and the

necessary force or torque of the user. This is a source of instability of the test results. Therefore, this document

adopts a time average within a specific time range during the reference movements.

ref

NOTE 2 As the reference movements defined in 5.3.2 are antigravity movements, τ ()t is expected to be

always negative and the relationship ψ ()αβ, =−()αβ− always applies. However, this document defines ψ in

a more general form to make ψ positive when the necessary torque for the reference movement and the torque

of the robot are in the same direction. See Annex A.

NOTE 3 When ψ is positive, the torque of the robot in the antigravity direction (extension) can reduce the

necessary torque of the user to achieve the reference movements. Or, in some cases, the user has to output the

torque in the gravity direction (flexion) to resist the torque of the robot. Whenψ is negative, the torque of the

robot in the gravity direction (flexion) can increase the necessary torque of the user to achieve the reference

movements. See Annex A.
5.2.3 Lumbar compression reduction (LCR)
Lower Lower

The Lumbar Compression Reduction (LCR) consists of 5 representative values LCR , LCR ,

1 000 200
Hold Raise Raise
LCR , LCR and LCR , which are calculated by the following equations with t and t
1 000 1 000 200 1 2

specified in Table 1. The superscript and the subscript of LCR indicate a phase of reference movement

and a time duration in milliseconds, respectively.
ref
LCR = ψ Ft() , Ft() dt
tt−
21 ∫
tt−
where
αβ−≥if α 0
ψ ()αβ, = ,
−−()αβ if α < 0
refref ref
Ft()=φ Mt() +Ft() ,
Ft()=φ Mt() +Ft() ,
γγ/,0050if ≥
φγ = ,
−<γγ/,01 if 0
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ISO/FDIS 18646-4:2021(E)
ref

is the actual lumbar compressive force of the test apparatus in z-axis direction during

the reference movements (without robot);
Ft()

is the actual lumbar compressive force of the test apparatus in z-axis direction during

the reference movements (with robot);
ref

is the actual lumbar bending moment of the test apparatus around y-axis during the

Mt()
reference movements (without robot);

() is the actual lumbar bending moment of the test apparatus around y-axis during the

reference movements (with robot).
The axes of the coordinate system are shown in Figure 1.

NOTE 1 In general, assistive torque of a robot interferes the duration of the movement and the compressive

force on the lumbar disks of the user. This is a source of instability of the test results. Therefore, this document

adopts a time average within a specific time range during the reference movements.

NOTE 2 A human would stiffen his/her muscles to resist the change of posture by the lumbar bending moment

around the y-axis. This tension of the muscles is known as a source of compressive force on lumbar disks. On the

other hand, the trunk of the test apparatus does not have muscles and its mechanical structure does not allow

any change of posture unlike the spine. To compensate for this difference, the equation for LCR uses the corrected

ref ref

lumbar compressive force Ft() and Ft() under the assumption that Mt() and Mt() are all supported

y y

by virtual erector spinae muscles and virtual abdominal rectus muscles. This document adopts a 0,05 m moment

arm from the L5/S1 lumbar disk to the virtual erector spinae muscles and a 0,1 m moment arm to the virtual

[4][5]
abdominal rectus muscles .

NOTE 3 During the reference movement, the weight of the upper body of the test apparatus is expected to

always compress the fixed lumbar joint and ψ ()αβ, =−αβ always applies. However, this document defines

ψ in a more general form to be applicable to tensile forces and to be consistent with the formula for ATI.

NOTE 4 When ψ is positive, the lumbar stress of the user is expected to be reduced during the reference

movement. When ψ is negative, the lumbar stress of the user is expected to be increased during the reference

movement.
Table 1 — Time range to calculate ATI and LCR
Reference move-
b b a a
ATI LCR t t
1 2
ments
Lower Lower
c c
Lowering t −1 [s] t [s]
ATI LCR
d d
1 000 1 000
Lower Lower c c
Lowering t −02, [s] t [s]
ATI LCR
d d
200 200
t t
Hold Hold d d
Holding
ATI LCR −05, +05,
1 000 1 000 [s] [s]
2 2

t and t define a time range when the necessary torque of the user and the lumbar stress are the largest assuming

1 2

the beginning time of each reference movement is 0 (see Annex A). Because the angle trajectories of the reference movement

are increasing or decreasing monotonically, ATI and LCR can be considered as an average within a specific angle range.

However, because 1) assistive torque can generate varying angle trajectories; 2) it is difficult to define the relevant angle

ranges of the trunk, the hip joint and the knee joint simultaneously; and 3) the amount of data points for calculating the

average can vary, this document adopts a time average to define ATI and LCR.
Lower Hold Raise Lower Hold Raise

ATI and LCR with a 1 s average ( ATI , ATI , ATI , LCR , LCR and LCR ) can also be

1 000 1 000 1 000 1 000 1 000 1 000

considered as an indication whether the robot can output assistive torque and reduce the lumbar stress continuously. On

Lower Raise Lower Raise

the other hand, ATI and LCR with a 0,2 s average (ATI , ATI , LCR and LCR ) can be an indication of

200 200 200 200

how much the robot can reduce the peak of necessary torque and the compressive force on the lumbar disks responsively

(see Annex A). This is due to the fact that they only focus on a short time range. This document adopts a 0,2 s response time

[3][9]
for humans to reflect the reaction to sudden load on lumbar spinal cord .
t is the actual duration of the reference movement.
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ISO/FDIS 18646-4:2021(E)
Table 1 (continued)
Reference move-
b b a a
t t
ATI LCR
1 2
ments
Raise Raise
Raising 0 s 1 s
ATI LCR
1 000 1 000
Raise Raise
Raising 0 s 0,2 s
ATI LCR
200 200

t and t define a time range when the necessary torque of the user and the lumbar stress are the largest assuming

1 2

the beginning time of each reference movement is 0 (see Annex A). Because the angle trajectories of the reference movement

are increasing or decreasing monotonically, ATI and LCR can be considered as an average within a specific angle range.

However, because 1) assistive torque can generate varying angle trajectories; 2) it is difficult to define the relevant angle

ranges of the trunk, the hip joint and the knee joint simultaneously; and 3) the amount of data points for calculating the

average can vary, this document adopts a time average to define ATI and LCR.
Lower Hold Raise Lower Hold Raise

ATI and LCR with a 1 s average ( ATI , ATI , ATI , LCR , LCR and LCR ) can also be

1 000 1 000 1 000 1 000 1 000 1 000

considered as an indication whether the robot can output assistive torque and reduce the lumbar stress continuously. On

Lower Raise Lower Raise

the other hand, ATI and LCR with a 0,2 s average (ATI , ATI , LCR and LCR ) can be an indication of

200 200 200 200

how much the robot can reduce the peak of necessary torque and the compressive force on the lumbar disks responsively

(see Annex A). This is due to the fact that they only focus on a short time range. This document adopts a 0,2 s response time

[3][9]
for humans to reflect the reaction to sudden load on lumbar spinal cord .
t is the actual duration of the reference movement.
5.3 Test facility
5.3.1 Test apparatus
A test facility shall include a test apparatus which has a linked and actuated
...