KULEX: An ADL Power-Assistance Demonstration

Man Bok Hong1,†, Sin Jung Kim1, Taewoong Um1, and Keehoon Kim1

1 Interaction and Robotics Research Center, Korea Institute of Science and Technology, Seoul, 136-791, Korea

† Present address: The 5th R&D Institute – 1, Agency for Defense Development, DaeJeon, 305-152, Korea

(Tel : +82-2-978-5781; E-mail: khk@kist.re.kr)

Abstract - A new robotic system for upper-limb power

assistance for the elderly and the disabled has been

developed by our research group. It is composed of three

main modules, a 1-DOF under-actuated hand module to

assist with hand grasp motions, a 3-DOF exoskeleton-type

parallel wrist mechanism for wrist power assistance, and a

6-DOF serial chain to assist with arbitrary movements of

the operator’s forearm. The system uses a

pseudo-exoskeleton approach; accordingly, some

problems caused by the inconsistency between the joint

axes of the robot and the human operator can be

minimized. In this paper, an overview of the second

version of the robotic system is introduced. Furthermore,

the operating capability of the proposed robot is observed

in a demonstration of the robot performing several

activities-of-daily-living (ADL) tasks, such as picking up

a pen with a pinch grasp, gripping an object with a power

grasp, and the brushing of teeth.

Keywords - Exoskeleton, power assistance robot,

rehabilitation robot.

1. Introduction

The KULEX (Kist Upper-Limb EXoskeleton) robotic

system has been actively developed by our research group

for upper-limb power assistance for the elderly and

disabled in their ADL (activities-of-daily-living)

movements. The need for a power-assistant robotic system

has increased as the population has aged. Originally,

robotic systems such as MIT-MANUS [1-3] and the

Armin rehabilitation robot [4] were adopted for

upper-limb rehabilitative treatment. Recently, the

application area of this type of robotic approach has been

extended to power assistance applications for the elderly

and the disabled. In one earlier work [5], a

seven-degree-of-freedom (DOF) robotic system was

introduced to support upper-limb movement during ADL

tasks. It consists of the three modules, a 3-DOF spherical

serial chain for the support of shoulder rotational motions,

a 1-DOF elbow linkage, and another 3-DOF spherical

chain to assist with wrist movements. However, this

system has no module to assist with hand grasp motions.

This type of fully exoskeleton type of approach may be

effective to assist individual joint movements of human

upper limbs. However, for comfortable operation by the

operator, all the joint axes should be coincident with the

corresponding joint axes of human operator, which is

generally difficult to achieve.

In order to avoid this problem, a pseudo-exoskeleton

robotic system known as the KULEX robotic system was

proposed by our research group. The first version of

KULEX was introduced in [6]. This paper presents the

overall structure of the second version of the system and a

demonstration of several real ADL tasks using the

proposed upper-limb power assistance system.

2. KULEX Robotic System

2.1 Mechanism Overview

The KULEX robotic system has been under

development by our research group for several years,

intended for upper-limb power assistance for the elderly

and disabled during their ADL tasks. Figure 1 shows two

prototypes of this robotic system. The initial prototype

consists of three main modules: 1) a 1-DOF

under-actuated hand mechanism to assist with hand grasp

motions, 2) a 3-DOF parallel-type exoskeleton wrist for

wrist power assistance, and 3) a 6-DOF active serial chain.

The hand and wrist mechanisms are worn by the operator.

The end-effector of the serial chain is connected to the

bottom side of the wrist mechanism and the base of the

(a) Initial prototype

(b) Second prototype

Fig. 1. KULEX robotic system for upper-limb power

assistance.

2013 10th International Conference on Ubiquitous Robots and Ambient Intelligence (URAI)

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chain can be attached to various devices, such as a

wheelchair or the side frame of a bed. In this way, this

serial chain supports arbitrary movements of the

operator’s forearm. The overall mechanism has around

6kg of mass and the payload is about 1kg. More details of

the initial prototype were briefly introduced in [6].

In order to simplify the overall mechanical structure,

however, in the second prototype shown in Fig. 1(b), the

active serial chain has been replaced with a fully

passive-type gravity compensation mechanism.

Furthermore, the hand mechanism has been redesigned as

shown in Fig. 2 for compactness and lightweight. The

revised version of the hand mechanism is composed of a

passive thumb link with a flexure hinge structure, an active

linkage for motion generation of the operator’s index

finger, and one rotary actuator. When the operator intends

to grasp an object, the small movement of the thumb’s

distal phalange induces the deflection of the flexure hinge

at the thumb link. The bending strain of the hinge is then

measured by means of a pair of strain gauges, and this

signal is used for the actuation of the motion generation

linkage. The planar linkage was synthesized on the basis

of the natural closing motion of the human index finger.

For compactness, the rotary actuator is located along the

longitudinal direction of the hand. In this case, however,

power transmission between two perpendicular rotation

axes (i.e., the axis of the actuator and the rotation axis of

actuating joint of the planar linkage) is required. For this

purpose, a spherical four-bar linkage was implemented,

and it was synthesized to have efficient torque amplifying

performance. Thus, the proposed hand mechanism is able

to generate up to 40N of normal force at the center of the

proximal phalange using a BLDC motor with power of

4.5W.

2.2 Demonstration of Several Selected ADL Tasks

In order to evaluate the operating performance of the

proposed KULEX robotic system, an experiment was

conducted. For the operation, the base link of the robotic

system is attached to the back frame of a wheelchair, and

the forearm of an operator sitting in the wheelchair was

strapped to the base of the exoskeleton wrist. The

operator’s hand is inserted into the hand mechanism, and

each phalange of the user’s index finger is also strapped to

the corresponding link of the motion generation linkage of

the hand mechanism. The operator’s thumb is tied to the

passive thumb link with a strap only at the distal phalange

so that a small tip movement of the user’s thumb induces

the deflection of the flexure hinge at the thumb link. The

signal obtained from strain gauges attached to the flexure

hinge is then used to operate the closing and opening

motions of the hand mechanism.

A demonstration of the ADL functionality of the

KULEX-robotic system was done, as illustrated in Fig. 3.

In this experiment, two ADL tasks, picking up a pen with a

pinch grasp and gripping an object with a power grasp,

were tested to check the operating performance of the

proposed hand mechanism (see Figs. 3(a) and (b)).

Furthermore, the functionality of the overall robotic

system was tested by performing several ADL tasks, in

this case eating with fork and spoon, drinking water, and

brushing one’s teeth. Among these tasks, an illustration of

the ADL task, the brushing of one’s teeth, is shown in Fig.

3(c).

After an operator learned and became accustomed to

operating this robotic system, most of the tasks were

performed without any significant difficulty. However, it

was confirmed that the functionality of the lateral pinching

motion is very important, especially for the ADL tasks of

eating with a fork or spoon, and brushing one’s teeth.

Currently, due to the fixed posture of the thumb link of the

hand mechanism, only a tip or pulp pinch is possible by the

operator, which results in some difficulty when attempting

to use the system to brush one’s teeth.

(a) pinch grasp motion

(b) power grasp motion

(c) brushing teeth task

Fig. 3. Demonstration of the KULEX robotic system for

several selected ADL tasks.

Fig. 2. KULEX-hand mechanism of the second

prototype.

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Acknowledgement

This work was supported by the R&D Program of

MKE/KEIT (10035201), ADL Support System for The

Elderly and Disabled and the Global Frontier R&D

Program on <Human-centered Interaction for

Coexistence> funded by the National Research

Foundation of Korea grant funded by the Korean

Government(MSIP) (NRF-M1AXA003-2010-0029748).

Acknowledgments may be made to individuals or

institutions not mentioned elsewhere in the work who have

made an important contribution.

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