Abstract— In current health care system, it is difficult to have
sufficiently long period of rehabilitation in hospital. Therefore,
an automated rehabilitation support at home is needed. To this
end, we developed a simple robotic device that will support
index finger rehabilitation for patients who suffer from
aftereffects of hemiplegia. The purpose of the device is to foster
voluntary movement of index finger. It has pressure sensors for
all fingers, and a power assisted index finger lift mechanism.
The power assist lift supports to lift the patient's finger if the lift
by voluntary movement is insufficient. The pressure sensors are
used to monitor the simultaneous movement of all fingers. By
this, the system checks if undesirable movements such as
synergetic movements are found. The information is integrated
to provide a quantitative measure of recovery. Patients are able
to monitor his/her condition and continue rehabilitation as
needed. Our device is simple and compact so that it should be
placed on a desk at home. The device is used by placing the
patient's hand on keyboards. This allows the patients to see
his/her fingers during rehabilitation and is expected to enhance
the effect of rehabilitation by seeing the result of voluntary
movement at his/her real fingers. This paper shows these
concepts and the hardware design of this device in detail. This
paper also discusses the results of the measurement of
hemiplegia patients and the healthy subjects by this device. The
results show that the explicit difference was seen between the
patients and the healthy subjects, which shows the effectiveness
of this design.
I. INTRODUCTION
In Japan, the number of patients of the cerebrovascular
disease (CVD) is increasing year by year. By this, the number
of persons who suffer aftereffects of this disease is also
increasing. It is known that hemiplegia is one of the most
common aftereffects. A patient suffering from hemiplegia is
not able to perform voluntary movements by the paralysis of
one side of his/her body, which causes serious troubles in
his/her daily life.
At early stages after onset of hemiplegia, a patient will
receive sufficient rehabilitation in a hospital. However,
because of the lack of the number of medical institutions, the
patient is usually not allowed to be treated in a hospital for a
sufficiently long period. Therefore, it is expected that the
patient and his/her family, who would not have sufficient
K. Yamamoto, Y. Furudate, and S. Mikami are with the Future University
Hakodate, Kameda-Nakano-Cho, Hakodate, Hokkaido, Japan (e-mail:
[email protected]). K. Chiba is with the Department of Rehabilitation, Medical Association
Hospital Hakodate, Hakodate, Hokkaido, Japan (e-mail:
[email protected]) Y. Ishida is with the Faculty of Human Science, Hokkaido Bunkyo
University, Eniwa, Hokkaido, Japan (e-mail: [email protected])
medical knowledge, should be able to carry out proper
rehabilitation at home by themselves.
To this end, we are developing an automated home
rehabilitation support device, which is designed to be simple
and easy to use [1].
In this device, we aim at the rehabilitation of fingers. One
reason of selecting finger rehabilitation is that the device is to
be made compact. Usually, devices designed for finger are
small and are easily put on a desk at home.
Another reason is its simplicity. Finger rehabilitation is
done by hand assistance at each finger, which is just moving a
finger by applying a small amount of force. Therefore, the
device does not require large and high-powered actuators.
The last reason is the effectiveness of finger rehabilitation
over upper limb functionality recovery. In our previous report
[1], it was shown that the training for a finger to get a new
movement or skill contributes to acquire a similar skill at an
upper limb of that finger. Therefore, the rehabilitation of a
finger is also expected to contribute to the upper limb
functionality recovery.
In recent years, many types of hand rehabilitation support
devices have been proposed[2, 3]. Typical examples are the
exoskeleton type devices such as [4, 5, 6]. However, the
problem of an exoskeleton type device with joints is its
difficulty of properly aligning its joints with the finger joints
of a patient. Some globe type soft actuator devices [7, 8] do
not need to care about positioning. But the problem of
wearing complex device onto a patient’s hand still needs
some skills.
The other problem of the exoskeleton and glove devices are
that the device cover the entire hand so that the patient cannot
see his/her real hand movements.
A patient tries to voluntarily move his/her finger during
rehabilitation. If his/her finger looks different from the actual
finger, he/she could not feel the reality of trying to move
his/her own finger. The importance of seeing an actual body
during rehabilitation is known as a visual feedback. It is used
in many rehabilitations for hemiplegia patients with
hemiparesis [9].
From these points, we have designed our device as a simple
set of levers. A patient is only requested to place his/her
fingers onto the levers. The lever lifts a finger as a
rehabilitation process. It also measures pressure of each
finger applied on it during his/her trial of voluntary
movement. The time series of these measured pressures
contain many information of the patient such as the degree of
separation of finger movements and the existence of
synkinesis. In our previous research, it is expected to measure
the level of recovery from this information [10].
Home Robotic Device for Rehabilitation of Finger Movement of
Hemiplegia Patients
Kazuki Yamamoto, Yuta Furudate, Kaori Chiba, Yuji Ishida, and Sadayoshi Mikami, Member, IEEE
In this paper, we describe the detail of the mechanical
design of our finger rehabilitation device. We show that the
simple lever (keyboard) mechanism realizes a compact
hardware which gives information of the patient’s level of
recovery and performs power assistance for finger lift when it
is necessary in part of the finger rehabilitation at home.
II. HEMIPLEGIA CAUSED BY CVD
A. Recovery Process of Patients
Recovery of finger movements of a hemiplegic patient
consists of three stages. First, a patient suffers flaccid
paralysis. At this stage, patients cannot move their fingers at
all. Second, the patient exhibits synkinesis and associative
reaction. At this stage, when he/she tries to move a finger,
other parts of body such as different fingers or hand will
move involuntarily. Finally, the patient will be able to
perform synergic movement at his/her fingers. This is the
stage where voluntary movement at finger is established,
and the patient should be regarded as mostly approaching to
the normal state [11].
The target of our rehabilitation device is the second
stage of the recovery, and the purpose of the device is to
help recovery from synergic movement by fostering his/her
voluntary movement of a finger. A widely used medical
scale for a patient suffering from hemiplegia at a hand is the
Brunnstrom stage (Brs) [12]. In terms of Brs, we are
targeting the stage III to VI. A patient of these stages is
usually treated at home and goes to the hospital for periodic
treatment. This is the reason for our home use design.
Also, we focus on index finger rehabilitation since it is
most frequently used part in fingers in daily life.
B. Detection of Synergic Movement (Positive Sign)
Synergic movement (a positive sign) of fingers is a sign
that a patient unintendedly moves fingers other than the
finger he/she tries to move. The degree of this positive sign
indicates the separation of voluntary movement of their
finger, which is usually monitored by a therapist. Therefore,
the device we developed has pressure sensors that monitor
pressures of every finger to detect synergetic movement and
measure its degree.
C. Effect of Visual Feedback
Visual feedback, where a patient looks at his/her fingers
during voluntary movements, is known to enhance the
effect of rehabilitation [9]. For this, we made our device
constructed by simple keyboards where a patient puts
his/her fingers onto plates. Fig. 1 shows an overview of the
keyboard by CAD drawing. Fig. 2 shows the actual use by a
patient. As seen from this figure, the patient easily
recognizes his/her fingers.
III. DESIGN OF THE DEVICE
A. Rehabilitation Process by Using the Device
We mount four keyboards (Fig.1) on the rehabilitation
device to place a patient’s fingers. The device has a motor to
lift the keyboard for an index finger (Fig. 3). By this, we
design the rehabilitation process of the device as follows
(Fig. 4):
i. The device instructs the patient to raise an index
finger.
ii. If the patient can raise the index finger, the device
instructs him/her to keep raising the finger for 5
seconds. If not, the keyboard of the index finger assists
to raise the patient’s finger by a motor.
iii. After 5 seconds, the device instructs the patient to put
back the finger onto keyboard and judges the degree of
the recovery. The measured degree of recovery is
presented to the patient or his/her family, so that they
are expected to keep motivation to continue
rehabilitation at home.
Figure 1. Keyboards on which the patient put his/her fingers.
Figure 2. A typical usage of the rehabilitation support device.
Figure 3. An index finger lift assistance mechanism.
B. Hand and Finger Positions
Fig. 2 and 5 show the hand position. Fig. 6 and 7 show a
thumb pressure sensor unit. A thumb has a different
movement from other four fingers because it has opposition
movement [13]. Therefore, the position of thumb largely
differs to each person. To fit to the position of the thumb for
each patient, we made a thumb sensor unit being affixed by
a Velcro tape (Fig.7).
C. Finger Lift Assistance
The finger lift mechanism can move the keyboard by a
geared motor. Fig. 7 shows the lift mechanism. This
mechanism uses the 1/128 geared motor operated by DC
6V (HS-GM21-DLW, Fig. 8).
D. Finger Pressure Sensing
The rehabilitation device developed in this study
senses finger pressure to judge positive sign and the
patient’s recovery. To make the device compact, we use
the flexible flat pressure sensors (FSR-402, Fig.9). As in
Fig. 10, we place these sensors on the back of each
keyboard. When a patient’s finger presses a keyboard, a
small bump pushes the flat pressure sensor (Fig. 11). A
thumb pressure sensing unit contains a pressure sensor
which is directly pushed by the patient’s thumb (Fig. 12).
Additionally, we also place a pressure sensor on a position
of a patient’s thenar eminence (Fig. 13).
Figure 4. Rehabilitation flow.
Figure 5. Side view of the device.
Figure 6. The thumb sensor unit.
Figure 7. Attach the unit with Velcro.
Figure 8. Geared moto for finger lift (HS-GM21-DLW).
E. Finger Pressure Sensing During Lift Assistance
In the rehabilitation by this device, a patient is asked to
raise his/her index finger. During this period, the index
finger pressure is monitored by the flat pressure sensor. If
some pressure value is observed, it is regarded that the lift
was insufficient, and the index finger lift is assisted by the
motor. Monitoring the force to lift the finger is important
to measure the level of the voluntary movement for the
index finger. However, the keyboard does not touch on
the pressure sensor during raising (Fig. 14). To this end,
the device has a load cell (strain gauges on an aluminum
block) on the finger lift mechanism to sense the finger lift
pressure (Fig. 15). Fig. 16 shows an image of sensing the
finger pressure during lift assistance.
Figure 9. A flat pressure sensor (FSR-402).
Figure 10. Positions of pressure sensors (from back of the keyboard).
Figure 11. The mechanism of pressure sensor.
Figure 12. Pressure sensor on position of patient’s thumb.
Figure 13. Pressure sensor on position of patient’s thenar eminence.
Figure 14. The keyboard cannot touch on a pressure sensor.
Figure 15. Index finger pressure sensing by a load cell (strain gauge).
Figure 16. An image of finger pressure sensing by strain gauge.
F. Finger Angle Sensing
Another important value of determining a degree of
recovery is to measure the height of the index finger when the
patient is asked to voluntarily lift the finger. This is measured
by lifting the keyboard for index finger with a weak power
and holding it when it touches on the finger. The motor for
lifting the keyboard is associated with a rotary encoder. The
encoder measures the angle (the height) of the index finger
(POLOLU-2590, Fig. 17, 18). Fig. 19 shows an image of the
finger angle sensing by the rotary encoder.
IV. EXPERIMENTAL RESULTS
Fig. 20 shows the entire view of the finger rehabilitation
device. The system is fabricated by a 3D printer with ABS
resin, and is controlled by a Raspberry Pi 3 with an Arduino
microcontroller. Hence the system is inexpensive so that the
patients would be able to afford to use at home. The user
interface is simple. The user only needs to follow the
instructions displayed on LCD and push some buttons. The
degree of recovery will also be displayed on the LCD, but this
functionality is under construction.
Fig. 21 and 22 show the profiles of sensory signals
measured by the pressure sensors of this device during
performing the rehabilitation procedures in Fig.4. These
signals are normalized as having the maximum amplitude to 1.
Fig. 21 is by healthy subject and Fig. 22 is by a patient with
light hemiplegia. As seen in these figures, there is an explicit
difference between two profiles. In Fig. 22, it is shown that
the patient is able to lift the index finger since the index finger
pressure signal drops down at the time when the instruction to
lift was given. However, in Fig. 22, the pressure signals of the
thumb (both at the fingertip and thenar) largely changed after
the patient tried to raise the index finger. This is a typical
synergetic movement which represents that the patient still
suffers from hemiplegia aftereffect. The device is able to
detect this diagnostic information.
Figure 17. A rotary encoder (POLOLU-2590).
Figure 19. Finger angle sensing by rotary encoder.
Figure 20. The prototype.
Figure 21. Pressure values of healthy subject measured by this
device. Image of finger pressure sensing by strain gauge.
Figure 18. Its position.
To provide quantitative information of the degree of
recovery, it is necessary to integrate these pressure signals
and the lift angles information. In our recent paper [10], we
have shown an integration method which is based on DP
matching between sensory time series of standard healthy
subject and those of the targeting patient. Fig. 23 shows the
result described in [10] with 50 healthy subjects and 20
patients. It is shown that the quantitative recovery measure
(dissimilarity with healthy subject) is consistent with the
medical scale (Brunnstrom stages). Therefore, the sensory
information by our device is expected to give a quantitative
measure of recovery.
V. CONCLUSION
In this paper, we introduced a home-use simple robotic
device for patients suffering from aftereffects of hemiplegia.
The device measures the degree of recovery and helps to
improve finger functionality by giving finger lift assistance if
necessary. Our simple keyboard design, where patients put
their fingers on, gives visual feedback effect during trying to
lift an index finger voluntarily. The finger pressure sensors
give information to determine the level of recovery. By these,
the device would be useful for home use where medical staff
support is not available.
At this moment, the algorithm to derive recovery measure
[10] uses only part of the sensors of this device. Currently, we
are investigating the algorithm to integrate more sensors such
as the height of the index finger lift.
There are also some hardware problems to be improved.
One is the support of lifting fingers other than an index finger.
Although index finger is the most used part than the other
fingers, there are some cases where severe paralysis is found
on other fingers. In that case, the device should be able to
change the power assisted keyboard to a different finger
position. At this moment, this is only realized at the time of
assembling. Another point is the support for patients with
severe contracture at finger. The keyboard is designed to fit
for a natural posture of hand. But for the patients with highly
contracting finger, it is not easy to measure the pressure. To
this end, we are considering another type of keyboard that has
a fixed joint in the middle.
In future, we would like to carry out long term
experiments for evaluation of this rehabilitation device.
ACKNOWLEDGMENT
Authors would like to thank the staffs in Takikawa
Neurosurgical Hospital for their advices and help with the
development and the experiments of this device.
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Figure 22. Pressure values of light hemiplegia patient measured by
this device.
Figure 23. Quantitative recovery values (dissimilarity with healthy
subject) calculated by DP matching of pressure signals [10].