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:

g2116049@fun.ac.jp). K. Chiba is with the Department of Rehabilitation, Medical Association

Hospital Hakodate, Hakodate, Hokkaido, Japan (e-mail:

k-chiba@outlook.com) Y. Ishida is with the Faculty of Human Science, Hokkaido Bunkyo

University, Eniwa, Hokkaido, Japan (e-mail: yishida@do-bunkyodai.ac.jp)

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.

REFERENCES

[1] K. Chiba, Y. Ishida, A. Kakimi, N. Ogura, Y. Furudate, K. Yamamoto,

and S. Mikami, “Effects of searching task on spinal cord excitability for

finger function recovery training with robotic device,” in 2015 8th Biomedical Engineering International Conference (BMEiCON), 2015.

[2] N. E. Saleh, B. Debs, E. Moussallem, A. R. Sarraj, and S. Saleh,

“Home-based therapy of chronic stroke survivors’ Upper limb assisted

by a finger movement finger device,” in 2015 International Conference

on Advances in Biomedical Engineering (ICABME), 2015, pp. 111-114.

[3] P. Sale, V. Lombardi, and M. Franceschini, “Hand robotics

rehabilitation: feasibility and preliminary results of a robotic treatment

in patients with hemiparesis,” Stroke Research and Treatment, vol.

2012, 2012.

[4] B. C. Tsai, W. W. Wang, L. C. Hsu, L. C. Fu, and J. S. Lai, “An

articulated rehabilitation robot for upper limb physiotherapy and

training,” in 2010 IEEE/RSJ International Conf. on Intelligent Robots and Systems, Oct. 18-22. 2010, Taiwan, 2011, pp. 1470–1475.

[5] J. Li, S. Wang, J. Wang, R. Zheng, Y. Zhang, Z. Chen, “Development

of a hand exoskeleton system for index finger rehabilitation,” Chin. J.

Mech. Eng., vol. 25, no. 2, pp. 223-233, Feb. 2012.

[6] C. L. Jones, F. Wang, R. Morrison, N. Sarkar, and D. G. Kamper,

“Design and Development of the Cable Actuated Finger Exoskeleton

for Hand Rehabilitation Following Stroke,” IEEE/ASME Transactions on Mechatronics, vol. 19, no. 1, pp. 131-140, Feb. 2014.

[7] P. Polygerinos, Z. Wang, K. C. Galloway, R. J. Wood, and C. J. Walsh,

“Soft robotic glove for combined assistance and at-home rehabilitation,” Robotics and Autonomous Systems, vol. 73, pp. 135–143, Nov. 2015.

[8] H. K. Yap, J. H. Lim, F. Nasrallah, F. Z. Low, J. C. H. Goh, and R. C. H.

Yeow, “MRC-globe: A fMRI compatible soft robotic glove for hand

rehabilitation application,” in 2015 IEEE International Conference on

Rehabilitation Robotics (ICORR), 2015, pp. 735-740.

[9] V. S. Ramachandran and E. L. Altschuler, “The use of visual feedback,

in particular mirror visual feedback, in restoring brain function,” Brain, vol. 132, no. 7, pp. 1693-1710, Jul. 2009.

[10] Y. Furudate, K. Yamamoto, K. Chiba, Y. Ishida, and S. Mikami,

“Quantification Method of Motor Function Recovery of Fingers by

Using the Device for Home Rehabilitation,” in 39th Annual

International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC’ 17), 2017.

[11] Ueda. S, Stroke rehabilitation illustrated, 3rd ed. Tokyo: University of

Tokyo Press, 2012, p. 9. (in Japanese)

[12] T. Iwasaki, K. Ogawa, N. Kobayashi, E. Hukuda, and T. Matsufusa,

Evaluation of occupational therapy: Standard occupational therapy, vol. 2, Tokyo, Japan: IGAKU-SHOIN, 2011. (in Japanese)

[13] Kapandji. A. I, Physiologie articulaire, 6th ed, 1 Vols. Paris: Malone,

2005.

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].