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Accepted Manuscript
Enhanced Kapandji test evaluation of a soft robotic thumb rehabilitationdevice by developing a fiber-reinforced elastomer-actuator based 5-digitassist system
Kouki Shiota, Shota Kokubu, Tapio V.J. Tarvainen, Masashi Sekine,Kahori Kita, Shao Ying Huang, Wenwei Yu
PII: S0921-8890(17)30808-4DOI: https://doi.org/10.1016/j.robot.2018.09.007Reference: ROBOT 3085
To appear in: Robotics and Autonomous Systems
Please cite this article as:, Enhanced Kapandji test evaluation of a soft robotic thumb rehabilitationdevice by developing a fiber-reinforced elastomer-actuator based 5-digit assist system, Roboticsand Autonomous Systems (2018), https://doi.org/10.1016/j.robot.2018.09.007
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Title 1
Enhanced Kapandji Test Evaluation of a Soft Robotic Thumb Rehabilitation Device by 2
Developing a Fiber-reinforced Elastomer-Actuator Based 5-Digit Assist System 3
4
Author 5
Kouki Shiota1, Shota Kokubu2, Tapio V. J. Tarvainen1, Masashi Sekine3, Kahori Kita3, Shao Ying 6
Huang4, Wenwei Yu3 7 1Graduate School of Engineering, Chiba University 8
[email protected] ,[email protected] 9 2Engineering Department, Chiba University 10
[email protected] 11 3Center for Frontier Medical Engineering, Chiba University, Chiba, Japan 12
[email protected] , [email protected] , [email protected] 13 4Engineering Product Design, Singapore University of Design and Technology 14
[email protected] 15
16
Abstract 17
The main function of human hands is to grasp and manipulate objects, to which the 18
thumb contributes the most. Various robotic hand rehabilitation devices have been developed for 19
providing efficient hand function training. However, there have been few studies on thumb 20
rehabilitation devices. Previously, we proposed a soft thumb rehabilitation device which is based 21
on a parallel-link mechanism, driven by two different types of soft actuators. In this study, the 22
device was integrated into a 5-digit assist system, in which fiber-reinforced elastomer actuators 23
with improved bending angles, forces, and degrees of freedom were assembled onto a forearm 24
socket. The device was evaluated by an enhanced Kapandji-Test, which included also a pressing 25
force measurement in addition to the reachable positions of the thumb on the opposing fingers. 26
The results showed that with the proposed approach, thumb functions for hand rehabilitation 27
could be realized, which paves the way towards a full hand rehabilitation package with the 5-digit 28
soft robotic hand rehabilitation system. 29
30
Keywords: 31
Fiber-reinforced Elastomer Actuators (FEA), Enhanced Kapandji Test, Hand Rehabilitation, 32
Thumb Function, Soft Actuators, Pneumatic Artificial Rubber Muscle 33
34
1. Introduction 35
Stroke is a big social problem worldwide. In 2010, there were 17 million new stroke 36
Page 3
cases in the world, and the number of stroke patients was reported to be 33 million. These 1
figures have also been predicted to double in the next 15 years [1]. Most common impairments 2
after stroke are motor deficits, such as hemiparesis, which is experienced by approximately 80% 3
of stroke survivors [2]. These patients experience either partial or total absence of hand motor 4
function, which can considerably reduce quality of life, because of major restrictions on activities 5
of daily living (ADL) and ability to work. 6
Rehabilitation is provided under the direction and assistance of a rehabilitation staff, 7
such as an occupational therapist or a physiotherapist, in order to help the patients restore their 8
functions to improve their ability to perform ADLs adequately for their returning to normal life. 9
Especially repetitive task practice has been shown to be effective in improving motor function 10
after stroke [3, 4]. Generally, rehabilitation is labor intensive and costly due to the required long 11
hours and terms of training. 12
The main function of human hands is to grasp and manipulate objects. Recently, many 13
robotic hand rehabilitation systems have been developed to automate some of the therapy for 14
providing efficient hand function training [4, 5, 6]. However, there have been few studies on 15
thumb rehabilitation devices. This might be because thumb motions are difficult to assist: it has a 16
wide range of motion (ROM), multiple degrees of freedom are coupled with each other, and the 17
first metacarpal bone is surrounded by a thick layer of soft tissues, which makes it difficult to 18
attach a supporting device. This is not trivial because the thumb contributes to most object 19
grasping and manipulation functions. Losing the thumb causes a 40% loss of overall hand 20
function [7]. Therefore, the thumb could be considered the most important target in hand 21
rehabilitation. 22
In recent years, robotic rehabilitation devices that use soft fluidic actuators with high level of 23
elasticity have been studied [5, 8, 9]. Soft fluidic actuators are light, flexible, and ready for easy 24
maintenance. These properties make them inherently safer, and more cost-effective than many 25
other actuation systems that are based on rigid mechanics. Thus, they would be a good choice 26
for rehabilitation, which requires high level of safety, and relatively low cost, as the goal is to 27
replace or relief the intensive labor. However, thumb rehabilitation with soft robotic gloves with 28
three degrees of freedom, namely the abduction-adduction, extension-flexion, and 29
opposite-reposition, has not been investigated in detail, though it is clear that, the thumb function 30
is very important in many upper limb activities of daily living (ADL). In [8], authors presented a 31
soft robot hand that could assist hand function including a 2-DoF thumb support. In their solution, 32
one actuator for thumb function support was placed on the palm, which might cause difficulty to 33
perform some grasping functions that use whole palm. Moreover, although different grasping 34
configuration has been realized, the ROM, the force and reaching ability to oppose the other 35
fingers, have not been sufficiently tested. 36
Page 4
2
3
6
(Mck7
8
7
17
(CMC18
palma19
ROM20
illustr21
manip22
thum23
suppo24
More25
is sys26
In29
in wh30
onto 31
gene32
were 33
in wh34
thum35
furthe36
the p37
previo38
evalu39
exper40
Fig.
kibben-type-
In [10],
C) joint, a pa
ar, ulnar and
M and force
ration. Howe
pulation func
b assistance
ort with a h
eover, the thu
stematically e
n this study, t
hich FEAs, w
a forearm s
rated force. A
measured a
hich the 5-di
b-to-opposin
er towards so
paper is orga
ous type FEA
uating the im
riment result
1: Previousl
-Artificial-Mus
an FEA (Fib
an FEA was
arallel link m
d dorsal dire
of dummy
ever, for the
ction, althoug
e. Compared
higher degre
umb function,
evaluated.
the device w
with improved
socket. The
Also, the RO
and evaluated
igit hand reh
ng-finger pos
oft robotic ha
anized as fo
As and the e
proved FEA
ts are prese
y developed
scles) for thr
ber-reinforce
s used for fl
mechanism d
ction. We te
thumb assis
proposed s
gh it is clear
d with the wo
ee of freedo
, assisted by
was integrated
d bending ang
improved F
OMs of the th
d. The device
habilitation s
sitions, but a
and rehabilita
llows. In Ma
nhanced Kap
s and thumb
nted in the R
soft robotic
ree-directiona
d Elastomer
lexion-extens
riven by 3 M
ested the thu
sted by the
soft robotic t
that the han
ork in [5,8, 9
om, without
y the thumb s
d into a wear
gles, forces,
FEAs were e
humb's radia
e was furthe
system was
also its pres
ation for hom
aterials and
pandji Test a
b assist funct
Results sect
thumb rehab
al control of t
Actuator) fo
sion motion.
Mckibben-typ
umb function
proposed m
humb, we d
nd rehabilitat
9], our work
using the p
support mech
rable 5-digit s
and degree
evaluated by
l abduction-u
r evaluated b
put on a du
ssing force w
me and in-faci
Methods sec
are introduce
tion are also
ion with furth
bilitation devi
the first meta
r flexion [10]
And for the
pe-Artificial-M
assistance
mechanism
did not evalu
tion could no
provides a
palm to cont
hanism and t
soft hand reh
s of freedom
y measuring
ulnar adducti
by an enhanc
ummy hand,
was measure
ility stroke pa
ction, the im
d. The exper
explained in
her analysis
ice with MAM
acarpal bone
]
e carpometac
Muscle (MAM
by measurin
Fig. 1 show
uate graspin
ot be done b
solution to t
tain any act
the other 4 fin
habilitation s
m, were asse
g their ROM
ion and oppo
ced Kapandj
and not on
ed. This is a
atients. The r
mprovement
rimental setu
n this section
in the Discu
Ms
e and
carpal
Ms), in
ng the
ws an
g and
y only
thumb
tuator.
ngers,
ystem,
mbled
M, and
osition
i Test,
nly the
a step
rest of
of the
ups for
n. The
ussion
Page 5
section. Finally, the paper is concluded. 1
2
2. Materials and Methods 3
In this section, we describe the requirements for the actuators developed for the hand 4
rehabilitation system and thumb function, the design for improving the FEAs, the design of a 5
forearm socket for the wearable 5-digit hand assist device, and the experiments for evaluation. 6
7
2.1 Requirements for actuators developed for hand rehabilitation systems 8
The target values for joint ROMs and torques are listed up in Tables 1 and 2. The 9
ROMs were chosen based on the normal ROMs of the joints [11]. The target torque values were 10
set based on the values reached by previously developed devices [12, 13]. Moreover, the upper 11
limit was set so that the motion would not hurt the patients, when their joints are moved [12]. 12
13
Table 1: Requirements for finger assistance 14
Range of Motion Flexion Torque
Extension [deg] Flexion [deg] Target [cNm] Upper Limit [cNm]
MP 0 90 11.0 29.3
PIP 0 100 20 28.7
DIP 0 80 10 19.7
MP: metacarpophalangeal, PIP: proximal interphalangeal, DIP: distal interphalangeal 15
16
Table 2: Requirements for thumb assistance 17
Range of Motion Flexion Torque
Extension [deg] Flexion [deg] Target [cNm] Upper Limit [cNm]
MP 0 70 11.0 26.0
IP 0 90 20.0 24.8
18
The dimensions of phalanges (finger bones) vary to some degree between individuals. 19
In this study, a collaborating hemiparetic patient’s hand was measured (Table 3), with his written 20
agreement. The length of actuators for each digit and the distance between the chambers for 21
forming air pockets, were decided based on the measurements. 22
23
Table 3: Measurement results of a hemiparetic patient’s hand 24
Digit Little [mm] Ring [mm] Middle [mm] Index [mm] Thumb [mm]
Proximal Phalanx 33 38 43 37 30
Middle Phalanx 21 25 24 20
Page 6
2
5
the o6
the su7
6
2.2 7
15
had o16
table 17
study18
actua19
cham20
was 21
variat22
16 17
18
23
frequ24
3(Lef25
(Fig. 26
mm, 27
24
25
26
27
28
29
Distal Phala
Besides
other fingers
ub-section fo
Improvem
Althoug
only a single
top, require
y, we design
ators [10], fo
mber was set
scaled for a
tion was use
Left
Moreove
ently bulge o
ft)). Also the
3(Right)). H
and the botto
L
anx 2
s the ROM a
is important.
or experimen
ment of FEA
h FEAs have
pocket [7, 8
ed in the trai
ed a new 3-
or assisting f
as 20 mm fo
all fingers ba
ed.
Fig. 2: A
: CAD of FEA
er, in the p
out from betw
e bottom stra
ence, we ch
om layer ma
Fig. 3:
Left: silicone
R
20 2
nd torque of
. An enhance
nts, was prop
As
e been used
8]. Depending
ning program
-pocket FEA
flexion-exten
or MP joint,
ased on the
cross-section
A, Right: an
previous ver
ween reinfor
ain-restricting
hanged the in
terial from po
: Problems o
wall bulging
ight: delamin
21
f the thumb it
ed version o
posed to eva
for hand reh
g on the gra
m, the joints
A (Fig. 2), wh
nsion of MP,
15 mm for P
measureme
nal view of th
illustration o
rsion of FEA
rcement thre
g layer got e
nterval of rei
olypropylene
of the previou
g out from be
nated strain r
22
tself, also th
of Kapandji T
luate this as
habilitation in
sping config
s requiring a
hich is a mo
PIP, and DI
PIP joint, 10 m
ent in Table
he new FEA
f the fiber-re
As, parts of
eads when hi
easily delam
inforcement
e net to bette
us prototype
etween the re
restricting lay
18
e opposition
Test [18], whi
pect.
n several stud
urations, suc
ssist are diff
odified versio
P joints. The
mm for DIP j
3. For the t
geometry
inforced actu
f the silicon
gh pressure
inated after
cotton threa
er laminating
design
einforcement
yer
23
of the thum
ich is explain
dies, most of
ch as fist, ho
fferent [14]. I
on of our pre
e size of ea
oint. This ac
thumb, a 2-p
uator
ne wall tend
e was applied
repeated in
ad from 4 mm
rayon mesh
ts
b with
ned in
f them
ook, or
In this
evious
ach air
ctuator
pocket
ded to
d (Fig.
flation
m to 2
.
Page 7
2.3 2
6
desig7
splint8
injure9
18
9
214
15
16
17
18
19
315
417
18
18
19
21
22
22
23
Developm
A forear
gned and fab
t material (O
ed limbs. The
1) Socket fu
comforta
2) Holding
were fixe
holding m
enable th
contact w
on the ho
3) Light we
4) Alignme
actuators
ment of fore
rm socket w
bricated to m
RFIT INDUS
e following po
unction: the s
able to wear,
mechanism
ed, but also
mechanism.
he complete
with the thum
older for fixin
eight: total we
nt of the inpu
s and the for
Fig. 4: The
Fig
earm socke
ith a holding
make the syst
STRIES, Orfit
oints were co
socket shoul
and providin
for 5-digit as
the previous
As shown in
flexion of the
mb joint. Also
ng the wires
eight of the s
ut tubing: the
rearm.
forearm soc
g. 5: First me
et
g mechanism
tem wearabl
t Eco) used f
onsidered in
ld conform to
ng a stable s
ssisting actua
sly designed
n Fig. 5, a firs
e thumb, by
o, 3 screws
connected w
socket includ
e tubes shoul
cket with full s
etacarpal bon
m for the act
le (Fig. 4). It
for immobiliz
its design:
o the shape o
support for th
ators: not on
thumb assis
st metacarpa
bending up t
(denoted by
with the 3 driv
ing the actua
d be aligned
set of actuato
ne thumb hol
uators to sup
t was made o
ing, protectin
of the user’s
e actuators.
ly the 4 finge
st device wa
al bone holde
the edge of th
arrows in Fi
ving MAMs.
ators was 58
so as not to
ors attached
lder
pport 5 digit
of a thermop
ng, and supp
forearm, ma
er-assist actu
as contained
er was desig
he holder tha
ig. 5) were p
86g.
o limit the mot
d
ts was
plastic
porting
aking it
uators
in the
ned to
at is in
placed
tion of
Page 8
2.4 2
2.4.13
5
hand 6
11
meas12
patien13
joint 14
was 15
meas16
12
13
Fig14
15
20
with t21
and t22
in Ta23
flexio24
21
22 23
24
2.4.225
Experimen
1 Dummy
To evalu
structure to
The du
surements of
nt’s index fin
could only m
included un
surements. A
. 6: Dummy
The c
The dum
the enhanced
he distances
able 3. For t
on-extension
2 FEA ev
nts for eva
y fingers an
uate the perf
emulate a p
mmy index
f the FEAs.
nger (Table 3
move in flexi
der each jo
All the parts w
index finger
cross-section
mmy hand (F
d Kapandji T
s between the
he carpome
and adductio
Fig. 7: 3D-p
valuation
aluating new
nd dummy h
formance of
atient's hand
finger (Fig.
The distanc
), to match th
on-extension
int and finge
were 3D-prin
design, for tr
nal view sho
Fig. 7) was p
Test, which is
e joints were
tacarpal (CM
on-abduction
rinted dumm
Ø5
w FEAs an
hand
the prototyp
d.
6) was pre
ces between
he centers o
n direction. A
ertip to hold
ted from Pol
rajectory and
ows the inden
prepared for
s described la
e determined
MC) joint we
n. Other joint
my hand for e
37
Ø5
Ø6
Ø
1
34
nd thumb f
pe, we made
epared for u
the joints w
f the chambe
A 6 mm diam
d the force g
ylactic Acid (
d torque mea
ntation for ho
r evaluating t
ater in details
based on th
e used a pla
ts could only
evaluating thu
21 21
20
Ø5
Ø6 Ø6
1418
211
A
A
unction
dummy fing
use in joint
were determin
ers with the j
meter, 1 mm
gauge in pla
(PLA).
asurements o
olding force g
the thumb as
s. The length
he measurem
astic ball join
y move in flex
umb function
1
6
gers and a d
angle and t
ned based o
oint centers.
m deep inden
ace during t
of the new F
gauge
ssistance fu
hs of the five
ment results s
nt, which en
xion-extensio
n
ummy
torque
on the
. Each
ntation
torque
EAs
nction
digits
shown
nabled
on.
Page 9
4
rehab5
desig6
5
Comp6
9
were 10
and w11
15
Ltd.) 16
a ver17
8). Th18
20 kP19
the a20
20
finger21
The a22
in pla23
of the24
21
22
23
24
The FE
bilitation. Firs
gn was evalu
parison betw
First, the
verified. The
wall thicknes
To estim
was used to
rtical position
he pressure
Pa. The mea
ngle at 0 kPa
The torq
r with a ball j
actuators we
ace. A steel w
e distal bone
Fig. 8: Mo
EAs were tes
st, a compa
ated.
ween previou
e effects of c
e thumb actu
s of 3 mm w
mate the bend
record the m
n, and two m
inside the FE
asurements w
a as a refere
que was mea
joint (Fig. 9)
ere strapped
wire connecte
. The measu
otion capture
sted to confi
rison was m
s and improv
changes to th
uator with two
ere used for
ding angle, a
motion from t
arkers were
EA was gradu
were repeate
ence.
asured by co
, which was
to the dumm
ed to a force
urements we
e setup for co
irm whether
made with the
ved FEAs
he reinforcem
o 30-mm-lon
r this purpose
a motion cap
he side. The
placed on th
ually increas
ed 3 times. T
oupling the a
described in
my joint, whic
e gauge (UDP
re repeated
omparing the
they satisfie
e previous d
ment thread
ng pockets, 1
e.
pture system
e FEA was cla
he tip of the
sed from 0 kP
The tip bendi
actuators to a
n detail in on
ch was attac
P 50N, IMAD
three times.
e old and new
ed the requi
design. Then
interval, and
16 mm x 16 m
(Himawari G
amped from
FEA to form
Pa to 280 kPa
ng angle wa
a 3D-printed
e of our prev
hed to a clam
DA Co.) was
w FEAs for th
irements for
n, a new 3-p
d the bottom
mm cross-se
GE 60, Librar
its proximal
its tip vecto
a, in increme
as measured
two-bone d
vious studies
mp that held
attached to t
he thumb.
hand
pocket
layer,
ection,
ry Co.,
end in
r (Fig.
ents of
using
ummy
s [13].
d them
the tip
Page 10
2
3
3-poc4
9
using10
joint, 11
increa12
angle13
10
11 12
13
14
20
place21
meas22
meas23
unde24
at a s25
21
22
Fig. 124
25
Fig. 9: Torqu
cket FEAs
A 3-poc
g the motion
DIP joint, an
ased from 0
e between th
For mea
ed as shown
surement po
sured in the w
r measureme
step of 20 kP
11: Joint torq
ue measurem
ket FEA was
tracking sys
nd tip of the d
kPa to 280
e three mark
Fig. 10: M
asuring the
in Fig. 11.
int and poin
way slightly d
ent was then
Pa. The meas
ue measurem
ment setup fo
s fixed to a du
stem. The tra
dummy finge
kPa, in incre
kers above, o
Motion trackin
torque of the
Each joint's
ts of suppor
different with
n inflated, inc
surement wa
ment setup, w
inflated
or comparing
ummy index
acking marke
er (Fig.10). T
ements of 20
on, and below
ng measurem
e actuators,
torque was
rt accordingl
h that in Fig.
creasing the
as repeated t
with the cham
d to target pr
g the old and
finger, whos
ers were pla
The pressure
kPa. Each j
w the joint.
ment of a 3-p
the force ga
measured in
y. That is th
9. The cham
pressure gra
three times.
mber on the
ressure
new FEAs fo
se joint trajec
ced on the r
e inside the F
oint angle w
pocket FEA
auge and du
ndependently
e reason wh
mber corresp
adually from
dummy finge
or the thumb
ctory was rec
root, MP join
FEA was gra
was acquired
ummy finger
y by changin
hy the torqu
ponding to th
0 kPa to 280
er’s PIP joint
b.
corded
nt, PIP
dually
as an
r were
ng the
e was
e joint
0 kPa,
being
Page 11
2
2.4.33
7
abdu8
[15]. 9
abdu10
11
meas12
and o13
chang14
16
can b17
the fi18
press19
as sh20
17
18 19
20
21
22
Table24
to25
State
1
2
3
4
3 ROM o
The wid
ction-adduct
Based on t
ction-adduct
The ang
sured using f
on the wrist
ged as show
Moreove
be measured
rst metacarp
sure of each
hown in Table
e 4: Sequenc
o measure th
e ID Dorsal
20
18
16
14
of the thumb
de range of
tion motions.
the research
tion and radia
gle of thumb
four markers
t (Fig. 12 (L
wn in Table 4.
er, the angle
d through fou
pal bone, on
MAM (Dorsa
e 4. The mea
Fig. 12
L
Righ
ce of pressur
e palmar abd
Palmar abdu
[kPa] Ulna
00
80
60
40
b
f motion of
Many activit
h reported i
al abduction-
b palmar-ab
placed on th
Left)). The p
. The measu
e of thumb r
r markers sh
ne on the ind
al , Ulnar an
asurement w
measureme
Left: palmar
ht: radial abd
re changes fo
duction-addu
uction-adduc
ar [kPa] Pa
20
20
20
20
the CMC j
ties of everyd
n [16] and
-ulnar adduc
duction (
he thumb tip,
pressure of e
rement was
radial-abduct
hown in Fig.
dex DIP joint
d Palmar as
was repeated
ent of ROM o
abduction-ad
uction - ulna
for the three
uction and ra
ction
almar [kPa]
20
40
60
80
joint enable
day life requ
[17], the ta
ction angles w
) and pa
side of the b
each MAM
repeated for
tion ( )
12 (Right). T
t, and anoth
s shown in Fi
for three tim
of thumb mec
dduction ang
ar adduction a
MAMs drivin
adial abductio
Radial a
Dorsal [kPa
20
20
20
20
s the thum
ire these two
rget values
were both se
almar-adduct
ball joint, on t
for contracti
r three times
and ulnar-a
Two were pla
er on the ind
g. 1) was g
mes.
chanism
gle
angle
g the paralle
on-ulnar add
abduction-Ul
a] Ulnar [kP
20
40
60
80
b opposition
o complex m
of thumb p
et as 60 degr
tion ( )
the index DI
ion was gra
.
adduction (
aced on the s
dex MP join
gradually cha
el link mecha
duction motio
lnar adductio
Pa] Palmar
20
18
16
14
n and
otions
palmar
rees.
were
P joint,
adually
)
side of
t. The
anged
anism,
ons
on
r [kPa]
0
0
0
0
Page 12
5 120 20 100 20 100 120
6 100 20 120 20 120 100
7 80 20 140 20 140 80
8 60 20 160 20 160 60
9 40 20 180 20 180 40
10 20 20 200 20 200 20
11 20 40 200 20 180 40
12 20 60 200 20 160 60
13 20 80 200 20 140 80
14 20 100 200 20 120 100
15 20 120 200 20 100 120
16 20 140 200 20 80 140
17 20 160 200 20 60 160
18 20 180 200 20 40 180
19 20 200 200 20 20 200
20 40 180 180
21 60 160 160
22 80 140 140
23 100 120 120
24 120 100 100
25 140 80 80
26 160 60 60
27 180 40 40
28 200 20 20
1
2.4.4 The Kapandji test and its enhanced version 2
The Kapandji Test is one of the methods for evaluating thumb opposition. It gives a 3
score based on how many predefined positions the thumb can reach on the opposing fingers 4
(Fig. 13(Left)) [18]. By mounting the full hand assist system on the dummy hand, it is possible to 5
perform the Kapandji Test to evaluate position control of the assisted thumb. However, the 6
pressing force, which is important for hand function in daily living, could not be made clear 7
through the basic test. 8
In this study, we propose an enhanced Kapandji Test, in which not only the thumb to 9
opposing-finger position, but also the pressing force between the thumb and the opposing finger 10
for some of the scoring positions is measured. Here, the positions selected for pressing force 11
measurement were scoring positions 1-4, which are most frequently used opposing positions in 12
Page 13
daily 3
scorin4
7
press8
mm, 9
meas10
For e11
for a12
press13
oppo14
12
13
14
15
16
Right17
18
3. 19
3.1 20
R31
the s32
mean33
the m34
[deg] 35
press36
becau37
the m38
type. 39
an ad40
their 41
object mani
ng position 3
A press
sing force. Ru
height: 3 mm
surement.
each position
ll the releva
sures for all
sition.
t: The sensor
Results
Compariso
Results of to
tandard dev
n maximum b
mean maximu
at 200 [kPa
sure (50 kPa
use of the st
modified one
This allowed
dditional exp
resting state
ipulation [19
3.
sure sensor
ubber pads w
m) were plac
, the pressin
ant actuators
the actuato
F
Left: S
Middle
r for pressing
on betwee
orque and be
viations. In p
bending ang
um torque w
a]. Fig. 15 sh
, 100 kPa), th
trong constra
could be infl
d the modifie
periment, we
es within 0.39
9]. Figure 13
(Flexi Force
with a trunca
ced on both
ng force was
s. The mean
ors were cho
Fig. 13: Enha
coring positio
e: Pressing fo
g force meas
en previous
ending angle
revious type
le was 137 [d
was 36.1 [cN
hows the act
he modified a
aint from den
ated to highe
ed prototype t
e confirmed t
9�0.05s ( av
3 (Middle) sh
e A201-100,
ated cone sha
sides of the
measured fo
n and stand
osen empiric
anced Kapan
ons of the or
orce measure
surement
s and impro
e measureme
e, the mean
deg] at 150
m] and the m
tuators’ resp
actuators sh
nser reinforc
er pressures
to bend over
that, the mo
verage stan
hows the pre
Tekscan, In
ape (upper ra
e sensor to i
or 30 second
dard deviatio
cally to plac
ndji Test setu
riginal Kapan
ement for loc
oved FEAs
ent are show
maximum to
[kPa]. On the
mean maxim
onses at diff
owed a lowe
cement cotto
s, which was
r 170 [deg] at
odified protot
ndard deviati
essing force
c.) was use
adius: 9 mm,
ncrease the
ds to let the p
on were then
e the finger
up
ndji Test
cation 3
s
wn in Fig. 14
orque was 20
e other hand
mum bending
ferent pressu
r angle than
n threads. O
not possible
t a faster res
type actuato
on for 10 rep
measureme
ed to measu
, bottom radi
steadiness
pressures sta
n calculated
rs and thum
4. Error bars
0.5 [cNm] an
d, in modified
g angle was
ures. To the
the previous
On the other
e with the pre
ponse (Fig. 1
ors could ret
petitions), aft
ent for
re the
us: 11
of the
abilize
d. The
b into
show
nd the
d type,
169.7
same
s type,
hand,
evious
15). In
urn to
ter the
Page 14
air pressure is released. Considering the fact that the rehabilitation for stroke patients does not 1
require fast movement, the time response characteristics of these actuators is enough for the 2
application. 3
4
(a) Bending angle (b) Torque
Fig. 14: Comparison between previous FEAs and the modified type 5
6
(a) Previous type (b) Modified type
Fig. 15: Response time of previous and modified type FEAs 7
8
3.2 Evaluation of the 3-pocket FEAs 9
Fig. 16 shows the results of the bending angle and torque of each joint of the 3-pocket 10
FEA. The mean maximum bending angle was 68.9 [deg] for DIP joint, 73.2 [deg] for PIP joint, 11
and 109.1 [deg] for MP joint. For the DIP joint and PIP joint, the values were about 10 [deg] and 12
30 [deg] lower than the target angle values, respectively. Whereas, the angle of MP joint was 20 13
[deg] bigger than the target value. Regarding the torque of each joint, as shown in Fig. 16 14
0
50
100
150
200
0 25
50
75
100
125
150
175
200
Bending Angle [deg]
Pressure [kPa]
ModifiedPrevious
0
5
10
15
20
25
30
35
40
0 25
50
75
100
125
150
175
200
Torque [cN
m]
Pressure [kPa]
Modified
Previous
0
50
100
150
200
0 1 2 3 4 5
Bending Angle [deg]
Time [s]
0
50
100
150
200
0 1 2 3 4 5
Ben
din
g A
ng
le [
deg
]
Time [s]
50 [kPa]
100 [kPa]
150 [kPa]
200 [kPa]
100 [kPa]
125 [kPa]
50 [kPa]
Page 15
(Lower), the mean maximum torques were 9.8 [cNm], 13.5 [cNm], and 28.9 [cNm] for DIP, PIP, 1
and MP joint respectively. The torque of the PIP was even lower than the lower target value, 2
while that of the MP reached upper limit of the target value. The durability for long-term use will 3
be tested in the near future. 4
5
Fig. 16: Bending angle and torque results of the 3-pocket FEAs 6
7
DIP PIP MP
Bending Angle [deg]
DIP PIP MP
Torque [cNm]
‐10
0
10
20
30
40
50
60
70
80
90
0 60 120180240
Bending Angle [deg]
Pressure [kPa]
Target
‐20
0
20
40
60
80
100
120
0 60 120 180 240
Bending an
gle [deg]
Pressure [kPa]
Target
0
20
40
60
80
100
120
0 60 120180240
Bending an
gle [deg]
Pressure [kPa]
Target
0
5
10
15
20
25
0 60 120180240
Torque [cN
m]
Pressure [kPa]
limit
target
0
5
10
15
20
25
30
35
0 60 120180240
Torque [cN
m]
Pressure [kPa]
limit
target
0
5
10
15
20
25
30
35
0 60 120180240
Torque [cN
m]
Pressure [kPa]
limit
target
Page 16
3.3 Thumb palmar abduction-adduction and radial abduction-ulnar adduction 1
The results are shown in Fig. 17. As the state number increases, the pressure of the 2
palmar side increases (refer to Table 4), and the thumb moves to palmar abduction. The mean 3
maximum angle was 55.3 [deg] at state 20, and the mean minimum angle was 6.7 [deg] at state 4
1. Their difference was 48.6 degrees, which is lower than the target value. Similarly, the mean 5
maximum palmar abduction angle was 55.3 [deg] at state 20, and the mean minimum angle was 6
16.2 [deg] at state 28. Their difference was 39.1 [deg] 7
8
9
10
Fig. 17: measurement of thumb assist actuators 11
Upper: palmar abduction-adduction, Lower: radial abduction-adduction 12
13
On the other hand, as shown in Fig. 17 (Lower), the mean maximum radial adduction 14
angle was 47.3 [deg] at state 10, and the mean minimum angle was 10.7 [deg] at state 1. Their 15
difference was 36.6 [deg]. Similarly, the mean maximum ulnar abduction angle was 47.3 [deg] at 16
0
10
20
30
40
50
60
70
1 3 5 7 9 11 13 15 17 19 21 23 25 27
Angle [deg]
State Number
0
10
20
30
40
50
60
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19
Angle [deg]
state number
Page 17
state 9
[deg]10
recor11
three12
dorsa13
avera14
stroke15
mech16
10
3.4 11
17
scorin18
possi19
palm 20
given21
positi22
18
19
10, and the
. Regarding
rd the time n
e-direction ac
al, palmar
age�standar
e patients d
hanism is eno
Enhanced
The res
ng positions
ible to reach
of the curre
n under the
ion, but it wa
Locatio
Mean: 525
SD: 22
Locatio
Mean: 118
SD: 9.8
F
e mean minim
the time res
needed. The
ctuation of t
direction,
rd deviation
does not re
ough for the
d Kapandji
sults of the
1~5 but not
h, because it
nt dummy ha
figures for
as difficult to
n 1
5.5 [gf]
.4 [gf]
n 4
8.8 [gf]
[gf]
Fig. 18 The m
mum angle w
sponse of thu
results are
the mechani
respectively
for 10 repet
quire fast m
application.
Test
Kapandji Te
t positions 6~
t would have
and is rigid. T
positions 1-4
measure the
M
measurement
was 16.2 [de
umb mechan
similar to th
ism is 0.87
y. Note, th
titions. Cons
movement, t
est are show
~10. The sco
e required m
The mean pr
4. For posit
e pressing fo
Location 2
Mean: 504.7 [
SD: 1.2 [gf]
Location 5
t results of th
eg] at state
nism, we ha
at of the FE
0.20s, 0.58
he time r
sidering the
the time res
wn in Fig. 18
oring positio
motion of the
ressing force
ion 5, the th
rce effective
[gf]
he enhanced
19. Their dif
ve designed
EAs. The time
80.27s, 1.43
esponse is
fact that the
sponse char
8. The thum
ns on the litt
fifth metaca
es and stand
humb could
ly.
Lo
Mean
SD:
Kapandji Te
fference was
d an experim
e response
30.43s, in
s expresse
e rehabilitati
racteristics o
mb tip could
tle finger we
arpal, wherea
dard deviation
nearly reac
ocation 3
n: 165.4 [gf]
: 35.7 [gf]
est
s 31.1
ment to
of the
ulnar,
d as
on for
of the
reach
re not
as the
ns are
ch the
Page 18
2
4. 3
4.1 4
10
actua11
Thus12
highe13
The r14
usele15
4.2 11
19
while20
air po21
the m22
consi23
the p24
mode25
speci26
25
config26
contr27
FEAs28
using29
is to s30
26
27
28
4.3 29
31
type s32
Discussio
Compariso
Bulging
ators. Howev
, the modifie
er pressures,
response to
ess inflation.
Evaluation
The ben
e the MP joint
ockets. Since
material prope
idering those
ocket size. I
els will be es
ific hand disa
The adv
gurations do
ribute to the
s played a ro
g two of the t
say, it is impo
Straight
F
ROM of th
A comp
system [10]
on
on betwee
of the silicon
ver, it can be
ed type cou
, while the pr
the pressur
n of 3-pock
nding angles
t angle went
e the actuatio
erties, and re
e factors. In
n our next s
stablished to
ability.
vantage of th
o not relate
hand rehab
ole also in th
hree pockets
ortant to sele
Fig. 19 The 3
humb assis
parison betwe
is shown in T
en previous
ne between
e controlled b
ld achieve h
revious type
e was also f
ket FEAs
achieved fo
easily over t
on is the res
elative dimen
[20], [21] sim
tep towards
synthetically
e 3-pocket F
directly to
bilitation by e
he enhanced
s, for DIP and
ectively activ
Fist
3-pocket FEA
st device
een the wea
Table 5. The
s and modi
the reinforce
by decreasin
higher torque
could not be
faster than t
or DIP and PI
the requirem
sult of interac
nsions of the
mple models
individualize
y design the
FEAs is show
the thumb f
enabling sep
d Kapandji Te
d PIP, was b
vate some of
As for differe
arable type sy
e radial abdu
ified FEAs
ements is de
ng the interva
e and bendi
e used at a p
the previous
IP joints were
ments. Appar
ction betwee
e three pocke
s were estab
ed soft hand
actuators to
wn in Fig. 19.
function, the
parate contr
est. In test fo
better than us
the three po
Hook
ent bending c
ystem of this
ction and uln
trimental to t
al of the rein
ng angle va
pressure hig
type, due to
e lower than
ently, this rel
n overall size
ets, the issue
blished to ana
rehabilitatio
o meet each
Although the
e 3-pocket F
ol of the join
or scoring po
sing all the th
ockets.
configuration
s study and o
nar adduction
the function
nforcement th
alues by tole
her than 150
o the reduct
n the target v
lates to the s
e of the actu
e should be s
alyze the eff
n system, re
user’s need
e different be
FEAs could
nts. The 3-p
osition 3 (Fig
hree pockets
Table top
s
our previous
n angles ach
of the
hread.
erating
0 kPa.
tion of
alues,
size of
uators,
solved
fect of
ealistic
ds and
ending
really
pocket
g. 18),
s. That
s fixed
hieved
Page 19
by the wearable type system are smaller than those of the fixed type system. This is because in 1
the fixed type, the MAMs could be aligned to achieve the biggest moment arm (Fig. 1). On the 2
other hand, in the wearable version the MAMs and wires had to be arranged taking into 3
consideration the mobility of the device. Thus, the moment arm was not as big as that of the fixed 4
type. This could be improved by changing the shape of the ring-type first metacarpal bone thumb 5
holder shown in Fig. 5, and the attachment points of the wires. Nevertheless, the thumb assist 6
device could reach the most essential scoring positions of the Kapandji Test. 7
The soft actuators used to drive the thumb assist device inevitably result in the 8
hysteresis characteristics, which could be identified from the results in both [10] for the fixed type 9
and Fig. 17 for the wearable type. The hysteresis characteristics made clear through the 10
measurement experiment could be used to adjust the control input: air pressure, to improve the 11
accuracy of position control. 12
13
Table 5: Comparing the radial abduction and ulnar adduction angles achieved by previous type 14
[10] and wearable type (this work) 15
Radial abduction [deg] Ulnar adduction [deg]
Target value 60 60
Fixed type [10] 54.0 59.3
Wearable type 36.6 31.1
16
4.4 Enhanced Kapandji Test 17
The Kapandji Test results showed that our system could reach all the scoring positions 18
except the ones on the little finger. As our dummy hand had the fifth metacarpal bone fixed in 19
place, and the little finger could not move in abduction-adduction, it could not be positioned to 20
oppose the thumb. On the other hand, we have shown in our previous study that it is possible to 21
enable finger abduction-adduction with soft fiber-reinforced actuators [13]. Thus, we believe that 22
our device would be able to reach at least some of the scoring positions on the little finger on a 23
real human hand. 24
In [20], the Kapandji Test was used to evaluate the thumb function of a soft robotic 25
hand made of FEAs. The study showed the potential of the FEAs to perform hand-like motions, 26
and the robotic hand's ability to hold everyday objects. However, the actuators were not 27
connected to an assisted hand structure. In our study, we showed that the actuators can be used 28
also in this manner to reach the Kapandji Test’s scoring positions. Moreover, we provided 29
quantitative pressing forces for the four first test positions that are important for the daily living 30
hand function, and therefore essential for hand rehabilitation. 31
Moreover, in the other studies on soft robotic gloves that aim to also support the thumb 32
Page 20
function [7][8], the radial-abduction and ulnar-adduction were not considered. Therefore, though 1
the scoring position 1 and 2 might be reached by the thumb, no pressing force could be exerted. 2
3
4.5 Future direction 4
In this study, the FEAs that assist the flexion of the fingers and the thumb were 5
improved and integrated to a 5-digit hand rehabilitation device. However, it is impossible to 6
realize finger extension, which is important for hand rehabilitation, by just adjusting the current 7
geometry and reinforcement mechanisms. Thus, a new type of FEA that can support both flexion 8
and extension needs to be developed. 9
The material to make the soft robot hand: silicon rubber is weak to tear stress. On the 10
other hand, since the soft robot hand will be worn on the subject’s hand, the tearing force, usually 11
generated during grasping and/or holding heavy objects, might not work directly on it. Moreover, 12
the FEAs (Fiber-reinforced Elastomer Actuators), as it is named, is reinforced with fibers. 13
Although the main aim of the fiber reinforcement is to provide certain biases to silicon structures 14
to enable the actuation, the fiber reinforcement could help to resist part of the tearing force, too. 15
Nevertheless, to realize long-term use of the soft robot hand in a home environment, its 16
robustness to tearing stress needs to be further improved. 17
Another challenge is that our current prototype is not equipped with any feedback 18
system such as sensing elements. A feedback control system is required for more accurate 19
control. In order to make the device more robust in terms of autonomy and feedback response to 20
external stimuli, different types of sensors such as pressure sensor, soft elastic joint angle sensor, 21
and force sensor [15] are required. For example, Flexiforce sensor described in Section III could 22
be used in a feedback loop to control the fingertip force. 23
As the next step, the detection of the subject’s intention needs to be considered. 24
The reason is that active training is much more preferable than passive training in terms of 25
rehabilitation effects. The signal source for intention detection could be bio-signals, such as 26
electromyogram. The position and force control will be implemented to support the active 27
training, to realize reliable, repeatable, and accurate control according to subjects’ intention. 28
Moreover, in this study, we evaluated the function of our soft hand rehabilitation system 29
by attaching the actuators and the full system to dummy fingers and the dummy hand for 30
practical and safety reasons. Because the stiffness of the stoke patients’ joints needs to be taken 31
into special consideration, it is very important to develop a dummy hand with sensing ability of 32
internal stress of joints. The measurement of internal stress of joints will be used to guide the 33
optimization and mathematical modelling of the soft robot hand. 34
After this step, we will be testing it in the future on healthy and disabled subjects for 35
evaluating the system’s usability and performance in rehabilitation. 36
Page 21
1
5. Conclusions 2
In this study, we integrated a soft thumb rehabilitation device proposed in our previous 3
work into a 5-digit robotic hand assist system, in which Fiber-Reinforced Elastomer-Actuators 4
with improved bending angles, forces, and degrees of freedom were assembled onto a forearm 5
socket. An enhanced Kapandji Test was proposed to evaluate it. The results showed that part of 6
thumb functions for hand rehabilitation could be realized, which paves the way towards a full 7
package hand rehabilitation with the 5-digit soft robotic hand assist system. 8
9
6. Acknowledgments 10
This work was supported by JSPS Grant-in-Aid for Scientific Research (B) 17H02129. 11
12
13
Page 22
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26
Page 24
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degree in
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currently a
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al basis of
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the Unive
ternationa
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movemen
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course stu
and medic
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on science
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ersity of To
l and Nat
ant Profess
iba, Japan
t disorders
ngineering
udent of C
cal devices
ans.
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Page 25
Mas
tech
Engi
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Univ
Univ
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ashi Sekin
nical staff
ineering, C
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ude mecha
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putational
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Chiba Univ
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Page 26
trans
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didate at
earch intere
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ity since 20
rvainen rec
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Chiba Un
ests includ
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e design a
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gineering,
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and prototy
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Finland. H
School of
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habilitation
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Engineerin
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elastomer
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T).
em enginee
robotics.
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ently a Doc
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prosthetics
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letop
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ersity
Aalto
ctoral
. His
, soft
s for
Page 27
Wen
1989
engi
depa
profe
inter
biom
of Ja
nwei Yu rec
9 and 199
neering, H
artment of
essor of C
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apan), JSM
ceived his
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Hokkaido U
medical sy
Center for
in neurop
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ctively. His
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ystem eng
Frontier M
prosthetics
ssing. He is
nese Socie
MEng from
s PhD wa
Japan in
gineering, C
Medical En
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s a membe
ety for Med
m Shangh
as receive
1997. He
Chiba Univ
ngineering
ation robo
er of IEEE
dical and B
ai Jiao Ton
d in syste
has been
versity sinc
g, since 20
otics, moto
and RSJ
iological E
ng Univers
em inform
a profess
ce 2009, th
013. His m
or control
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Engineering
sity in
ation
sor of
hen a
major
and
ociety
g).
Page 28
Highlights
Our final goal is to develop a full 5-digit soft robotic hand rehabilitation system. Previously, we
have studied a soft thumb rehabilitation device which is based on a parallel-link mechanism,
and driven by two different types of soft actuators, McKibben type pneumatic artificial muscles
and fiber-enforced elastomer actuators (Shiota et al., Proceedings of IAS-14, 2016). The current
manuscript continues to build on our previous work.
In this manuscript, we present a 5-digit hand assist system that consists of the previously
mentioned parallel-link mechanism for thumb, improved fiber-reinforced elastomer actuators
for each finger, and a wearable forearm socket that acts as a support for the actuators.
We evaluated the developed prototype system with an enhanced Kapandji Test, in which not
only the thumb to finger opposition positions, but also its pressing force was measured. Finally,
we show that the required thumb functions for hand rehabilitation and separate control of the
finger joints could be realized with the system. This paves the way towards comprehensive soft
robotic hand rehabilitation.
Our manuscript contributes to the field by providing experimental insight on thumb motion
assist by soft robotics, as well as data on the function of multi-pocket fiber-reinforced elastomer
actuators.
