ISO/FDIS 18646-6

ISO /TC 299
Secretariat: SIS
Date: 2025-11-112026-01-14
Robotics — Performance criteria and related test methods for
service robots — —
Part 6:
Lower-limb wearable robots
Robotique - ExigencesRobots et composants robotiques — Critères de sécurité pour les performance et
méthodes d'essai correspondantes pour robots de service —
Partie 6: Robot portable pour les membres inférieurs
FDIS stage
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Contents
Foreword . v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Test conditions . 2
4.1 General. 2
4.2 Wearable robot conditions . 2
4.3 Environmental conditions . 3
4.4 Operating conditions . 3
5 Test device . 3
5.1 ATDR configuration requirements . 3
5.2 ATDR size . 6
5.3 ATDR signal measurement conditions . 9
5.4 Safety considerations for the test setup . 9
6 Preparation for the test . 10
6.1 Reference trajectory for ATDR walking . 10
6.2 ATDR half squat reference trajectory . 14
6.3 ATDR control performance requirements. 17
6.4 Wearable robot performance evaluation index . 18
6.5 Ground reaction conditions . 21
7 Test methods for walking test . 21
7.1 General. 21
7.2 Test device . 21
7.3 Test procedure . 22
8 Test methods for half squat test . 29
8.1 General. 29
8.2 Test device . 29
8.3 Test procedure . 31
9 Test report . 33
Bibliography . 36

Foreword . iv

1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Test conditions . 2
4.1 General. 2
4.2 Wearable robot conditions . 2
4.3 Environmental conditions . 3
4.4 Operating conditions . 3
5 Test device . 3
5.1 ATDR configuration requirements . 3
iii
5.2 ATDR size . 5
5.3 ATDR signal measurement conditions . 7
5.4 Emergency stop function . 7
6 Preparation for the test . 7
6.1 Reference trajectory for ATDR walking . 7
6.1.1 Configuration of the ATDR reference trajectory . 7
6.1.2 Design of ATDR walking reference trajectory . 8
6.2 ATDR half squat reference trajectory . 9
6.2.1 Configuration of the ATDR reference trajectory . 9
6.2.2 Design of ATDR half squat reference trajectory . 10
6.3 ATDR control performance requirements. 11
6.4 Wearable robot performance evaluation index . 11
6.5 Ground reaction conditions . 13
7 Test methods for walking test . 13
7.1 General. 13
7.2 Test device . 14
7.3 Test procedure . 14
7.3.1 Test principle . 14
7.3.2 No-load walking test . 16
7.3.3 Loaded walking test . 17
8 Test methods for half squat test . 18
8.1 General. 18
8.2 Test device . 18
8.3 Test procedure . 19
8.3.1 Test principle . 19
8.3.2 No-load half squat test . 19
8.3.3 Loaded half squat test . 20
9 Test report . 21
9.1 General. 21
Bibliography . 25
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Foreword
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This document was prepared by Technical Committee ISO/TC 299, Robotics.
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Field Code Changed
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DRAFT International Standard ISO/DIS 18646-6:2025(en)

Robotics — Performance criteria and related test methods for service
robots —
—
Part 6:
Lower-limb wearable robots
1 Scope
This document specifies performance index and related test methods to evaluate the assistance and
enhancement performance of lower-limb wearable robots by using an anthropomorphic test dummy robot
(ATDR).
This document applies to wearable robots that are operated by being attached to lower limbs regardless of
the purpose of use or the driving method (powered/non-powered, electric/hydraulic).
This document does not apply to lower-limb wearable robots that operate based on biosignals such as
electromyography.
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/obphttps://www.iso.org/obp
— — IEC Electropedia: available at https://www.electropedia.org/https://www.electropedia.org/
3.1 3.1
wearable robot
robot that supplements or augments physical capabilities by driving human body while attached to a human
Note 1 to entry: Wearable robots are referred to as restraint-type physical assistant robots in ISO 13482.
[SOURCE: ISO 18646-4:2021, 3.2, modified — The words “while attached to a human during use” have been
replaced with “by driving human body while attached to a human”.]
3.2 3.2
lower-limb wearable robot
wearable robot attached to (part of) human lower-limbs
3.3 3.3
anthropomorphic test dummy robot
ATDR
robot that has a similar configuration to the lower-limb skeleton of a human and actively performs movements
such as walking and half squats while wearing a lower-limb wearable robot
3.4 3.4
tester
person who manages and conducts performance evaluation tests, performs ATDR management and writes up
the test result during the test process
3.5 3.5
stance phase
period of time in which the foot is in contact with the ground, the state in which weight is exerted to the ground
Note 1 to entry: Stance phase is divided into heel strike, single-limb support and double-limb support.
3.6 3.6
swing phase
period of time in which the foot is not in contact with the ground
3.7 3.7
single-limb support
state in which one leg supports the weight and the other leg performs the swing motion
3.8 3.8
double-limb support
state in which both legs are in contact with the ground and support the body weight
4 Test conditions
4.1 General
The lower-limb wearable robot (hereinafter referred to as the wearable robot) shall be completely assembled.
And theThe battery shall be charged to a level sufficient for testing. All self-diagnostic tests, if applicable, shall
be satisfactorily completed. It should also be ensured that the robot operates in a safe manner throughout the
test so that no one will beis injured during the test.
The tests shall be preceded by the preparations for operation as specified by the manufacturer, including
calibration of any relevant sensors that can affect the test results.
All conditions specified in Clause 4Clause 4 should be satisfied for the tests described in this document, unless
stated otherwise in the specific clauses.
4.2 Wearable robot conditions
The wearable robot shall satisfy the following conditions for the test:
a) a) The wearable robot used in the test shall be stored at room temperature and tested with
sufficient power required for each test.
b) b) All accessories required for the use of the wearable robot shall be available during the test.
c) c) The movable part of the wearable robot shall be warmed up to a state where it can perform the
test operation without difficulty.
2 © ISO #### 2026 – All rights reserved
d) d) Tests shall be performed only for:

1) 1) the weight below the payload of the wearable robot;
2) 2) the speeds below the maximum walking speed of the wearable robot;
3) 3) the angles within the maximum range of joint motion of the wearable robot.
e) e) Before the test, the length of the link of the wearable robot shall be adjusted to ensure proper
alignment with the ATDR joint.
f) f) When fastening with the ATDR, apply the specified clamping pressure (or tension) of the cuff.
If there is no specified value, fasten it to the extent that two fingers (index and middle finger) can be
inserted.
4.3 Environmental conditions
The following environmental conditions shall be maintained during all tests:
— — ambient temperature: 10 °C to 30 °C;
— — relative humidity: 0 % to 80 %%.
If the environmental conditions specified by the manufacturer are outside the given conditions, then this shall
be declared in the test results.
4.4 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 device
5.1 ATDR configuration requirements
The ATDR shall satisfy the following requirements:
a) a) To connect the wearable robot, it shall consist of an upper body and two legs.
b) b) It shall be able to perform walking and a half-squat motion on a treadmill. These are the main
test motions.
c) c) A minimum of two degree of freedom (DOF) active rotational joints (one DOF knee joint, one
DOF hip joint) are required for each leg.
d) d) The ankle shall be made of rotational joint with one or more degrees of freedom. If the wearable
robot actively assists the ankle joint and its performance evaluation is required, the ankle joint shall be
manufactured as an active rotation joint.
e) e) To measure and control the joint angle, the rotation angle of the joint shall be measured with
an incremental or absolute encoder.
f) f) When the ATDR is supported by a harness or structure, the upper body (or neck joint) shall be
able to move up and down and forward and backward so that the upper body can move naturally while
walking. A rotational joint about an axis perpendicular to the sagittal plane for the point of support shall
be provided.
g) g) To determine the walking state or walking cycle and the suitability of the walking trajectory, it
shall be possible to measure the ground reaction force.
NOTE 1 The ground reaction force can be measured by installing two force sensors on the front and back of the
sole.
h) h) It shall be possible to measure the angle of the upper body to confirm the control stability of
the ATDR and the repeatability of the posture during the test.
NOTE 2 The posture can be measured with a tilt sensor or an inertial measurement sensor.
i) i) The ATDR shall be controlled to generate joint motion and a ground reaction force similar to
those generated by humans during walking.
j) j) The torque and angular velocity of the joint drive motor or the joint shall be measurable.
k) k) In all tests, a harness (or a device equivalent to the harness) shall be applied to secure the
accuracy and safety of the test and protect the ATDR and the wearable robot from damage. The harness
shall be firmly fixed by a support device. In addition, the harness support device shall be able to maintain
enough rigidity to prevent the ATDR from falling over.
Figure 1Figure 1 is an example of an ATDR design implemented for testing.
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Key
1 passive rotating joint
2 optional (active/passive) prismatic joint
3 active rotational joint
4 active rotational joint
5 optional (active/passive) rotational joint
1 passive rotating joint
2 optional (active/passive) prismatic joint
3 active rotational joint
4 active rotational joint
5 optional (active/passive) rotational joint
Figure 1 — ATDR design example
5.2 ATDR size
The wearable robot user’s weight and body size are distributed over a wide range. In general, the wearable
robot can variably adjust the link length according to the body length. It is therefore not necessary to specify
the size of the ATDR by a representative value. In addition, since the ATDR walks while supporting its own
weight or operates with its own power, the weight does not have a significant effect on the test results.
However, in order to maximize the objectivity and universality of the test results, the dimension ratio of each
body part should be similar to IEC 60601-1:2005, Figure A.19. Each body part of the ATDR and its
corresponding height is shown in Figure 2. Table 1Figure 2. Table 1 shows example dimensions of body parts
. Depending on the geographical location, the size of the ATDR can vary to better represent the morphology of
the users.
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Key
1 shoulder height 8 knee joint
2 waist height 9 ankle joint
3 hip height 10 waist circumference
4 knee height 11 hip circumference
5 shoulder 12 thigh circumference
6 waist 13 calf circumference
7 hip
1 shoulder height
2 waist height
3 hip height
4 knee height
5 shoulder
6 waist
7 hip
8 knee joint
9 ankle joint
10 waist circumference
11 hip circumference
12 thigh circumference
13 calf circumference
Figure 2 — Size of each body part of the ATDR

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Table 1 — Example of ATDR size
Weight 75 ± 32 kg
Thigh circumference 496 ± 119 mm
Calf circumference 365 ± 83 mm
Hip circumference 948 ± 150 mm
Waist circumference 783 ± 200 mm
Shoulder height 1 336 ± 174 mm
Knee high 430 ± 60 mm
Hip height 807 ± 100 mm
Waist height 1 088 ± 108 mm
When measuring the ATDR, the height of the hip of the ATDR is considered to be equal to the height of the hip
joint. The waist of the ATDR is 100 mm to 200 mm above the hip axis of rotation. The circumferences of the
thigh and calf are measured at the midpoint of the ATDR thigh and calf lengths. The weight of the ATDR is
measured using a scale or plantar ground reaction force. The size of the ATDR can be adjusted to a range
outside the values given in Table 1Table 1 if there is difficulty in wearing the wearable robot.
5.3 ATDR signal measurement conditions
a) a) The accuracy of the joint angle measurement shall be 0,1 degrees or better.
b) b) The ground reaction force shall be measured to verify the similarity to human reference ground

reaction force (GRF) profile (see Reference [5]) . [5]).
NOTE GRF can be measured either with two force sensors installed per sole or with instrumented treadmill.
c) c) The sensor for measuring the angle of the upper body shall be measurable in units of
0,5 degrees or less.
d) d) All sensor signals shall be measured at least 1 000 cycles per second for real-time control.
5.4 Safety considerations for the test setup
For the safety of the tester and to prevent damage to the test system, the test setup shall incorporate
appropriate safety measures. Such measures shall ensure that hazardous situations (e.g. excessive control
error, foot drag, falling of the ATDR, or other abnormal operation) can be promptly detected and mitigated.
Examples of possible safety measures include, but are not limited to:
— — provision of an emergency stop function that can immediately halt the ATDR and treadmill;
— — protective structures or harness systems to prevent the ATDR from falling or causing injury;
— — monitoring systems capable of detecting abnormal operation and initiating protective actions.
The specific implementation of safety measures is left to the test facility, as long as the measures provide
adequate protection for the tester and equipment during the tests.
6 Preparation for the test
6.1 Reference trajectory for ATDR walking
6.1.1 Configuration of the ATDR reference trajectory
The reference trajectory for the ATDR walking shall satisfy the following conditions:
a) a) The ATDR walking reference trajectory shall be divided into a stance phase and a swing phase
in the same way as human walking.
b) b) In the stance phase, the weight of the ATDR shall be supported by the leg. In the swing phase,
the leg of the ATDR should be moved in the direction of the ATDR walking without ground (or treadmill)
contact.
c) c) The stance phase shall be divided into heel strike, single-limb support and double-limb
support.
d) d) In the heel contact, the heel of the ATDR shall contact the ground (or treadmill) immediately
after swing.
e) e) In the double-limb support, both legs shall be in contact with the ground (or treadmill),
supporting the ATDR weight with both legs. The double-limb support shall appear repeatedly
immediately after the heel strike and single-limb support
f) f) In the single-limb support, the weight of the ATDR shall be supported by one leg. The leg not
supporting the weight of the ATDR shall perform the swing motion.
NOTE More information on the biomechanics of human walking can be found in Reference [4]. [4].
Figure 3Figure 3 is an example of the configuration of the ATDR walking reference trajectory.
10 © ISO #### 2026 – All rights reserved
(a) Heel strike      (b) Single support   (c) Double support

a) Heel strike b) Single support c) Double support
Figure 3 — Example of ATDR walking reference trajectory configuration
6.1.2 Design of ATDR walking reference trajectory
The ATDR walking reference trajectory shall be composed of time trajectories of hip and knee joint angles. It
should be designed based on the trajectories obtained through the measurement of human walking motion.
However, human walking trajectories are diverse, and the structure of the human skeleton and the
characteristics of the ATDR mechanism (degree of freedom, joint position and structure, etc.) are different.
This means it can be difficult to implement the human walking trajectory on the ATDR operating on a
treadmill. Therefore, a reference trajectory suitable for the ATDR can be designed and applied through
analysing dynamics and kinematics, and by optimizing the gait trajectory to match ATDR’s treadmill walking
conditions.
The trajectories applicable for the ATDR shall be designed to prevent slip between the treadmill moving at a
constant speed and the feet of the ATDR. They shall also be designed to minimize damage to the ATDR from
the impulsive force at heel strike while following the characteristics of the human walking trajectory (stride
length, period, upper body height, sole angle, ground reaction force, etc.) as closely as possible. Such
trajectories can be designed through inverse kinematic analysis, dynamic analysis of the mass centres of the
ATDR parts and optimization to minimize the ground reaction force. The validity of the designed trajectories
can be verified by checking whether the requirements of 6.1.16.1.1 are met and the patterns of the joint angle
movement are reasonable for a gait. If the wearable robot to be tested has an active ankle, the ATDR walking
reference trajectory shall include the ankle angle trajectory also.
Figure 4Figure 4 is an example of reference trajectory generation for the ATDR walking. Figure 4(b)Figure 4
b) shows the generated reference trajectories based on the trajectory generation algorithm in
Figure 4(a).Figure 4 a).
(a) Reference trajectory generation algorithm (b) Reference trajectory generation result
Key
X time(sec)
Y1 hip joint angle (deg)
Y2 knee joint angle (deg)
1 left hip joint angle
2 right hip joint angle
3 left knee joint angle
4 right knee joint angle
Figure 4 — Example of the reference trajectory generation for ATDR walking
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The reference trajectory applied to the test shall be specified in the test result report.

6.2 ATDR half squat reference trajectory
6.2.1 Configuration of the ATDR reference trajectory
The ATDR half squat reference trajectory shall satisfy the following conditions:
a) a) The soles of the feet shall remain in contact with the ground.
b) b) With the feet in contact with the ground, the ATDR shall support its weight with the legs and
move the upper body upward and downward.
c) c) As the upper body moves downward,
...