DEVELOPMENT OF A SIT-TO-STAND ASSISTANCE SYSTEM

FOR PARKINSON'S DISEASE SUFFERERS

(Intellectual Handrail)

Osamu Nitta, Yasunari Fujimoto, John Surya

Tokyo Metropolitan University, 2-10-7 Higasiogu, Arakawa-ku, Tokyo, Japan

Yoshiyuki Takahashi

Toyo University, Faculty of Human Life Design, Oka 48-1, Asaka-shi Saitama 351-8510, Japan

Keywords: Parkinson's Disease, Assistance System, Stand Up, Handrail, Force Plate.

Abstract: A Sit-to-Stand Assistance System that can provide functional assistance in standing was developed. Two

650 mm stroke AC servo motor driven linear actuators were squarely combined. The handrail was installed

at the intersection of these actuators. When the user stands from a chair, the handrail leads the user’s

motion. A personal computer (PC) is used to control the handrail motion, and force plates are placed under

the feet. In this experiment the subjects were Parkinson's disease (PD) sufferers. Subjects were not able to

stand up with a fixed handrail; however, they were able to stand up using this system without help.

1 BACKGROUND

Handrails are effective welfare tools that can provide

assistance, such as walking and lifting motion, to the

elderly and disabled. In addition, handrails are

becoming widely used in many homes, and they

have become the most basic item installed in house

renovation. Previous research studies have also

shown handrails are mostly used in restrooms, stairs,

and bathrooms (Oshima et al., 2000; Takashima et

al., 2005). To be used as a welfare tool in a house, it

is necessary to fix the handrail onto the wall.

Therefore, it is not easy to reposition a handrail

once it is fixed onto a wall. Previous handrail studies

have focused primarily on finding what were the

most suitable shape and placement of a handrail.

However, a handrail that can give assistance in

standing and guiding posture has not been

investigated.

Standing-support welfare devices, such as "rising

toilet seat" "rising chair" "rising wheelchair" have

been already developed (Kamnik et al., 2005; Chugo

et al., 2005; Uplift Technologies Inc.; TOTO LTD.).

However, these devices give too much unnecessary

assistance. Moreover, each individual user’s

symptoms, standing pattern, and degree of physical

decline are varied. Naturally, these conventional

standing-support devices cannot accommodate all

these differences. It also should be pointed out that

these devices which tend to lift the entire body

“unnaturally” may unnecessarily promote physical

strength decline.

2 PURPOSE

The purpose of this research was to develop an

intelligent handrail that can give assistance in

standing to PD patients and the elderly whose

physical function has decreased. The motion of the

handrail is guided by the user’s posture, which is

calculated from the 6 axes power sensors, placed on

the handrail, and the ground reaction force sensors.

In this manner, the motion of the handrail is

synchronized with the user’s posture while standing.

In our previous studies, a handrail that could give

assistance to users in standing was developed. (Nitta

et al.; Daisuke et al., 2007).

It consists of two linear actuators which are

crossed at right angles (Fig1). The handrail was

installed at the intersection of these actuators. In this

study, the development of this handrail was

advanced further by the development of a control

program.

189

Nitta O., Fujimoto Y., Surya J. and Takahashi Y..

DEVELOPMENT OF A SIT-TO-STAND ASSISTANCE SYSTEM FOR PARKINSON’S DISEASE SUFFERERS - (Intellectual Handrail).

DOI: 10.5220/0003709701890192

In Proceedings of the International Conference on Bio-inspired Systems and Signal Processing (BIOSIGNALS-2012), pages 189-192

ISBN: 978-989-8425-89-8

 2012 SCITEPRESS (Science and Technology Publications, Lda.)

6-axis force sensor

Hand Rail

Linear Actuator

(X axis)

Frame

Linear Actuator

(Y axis)

Figure 1: A handrail that could give assistance to users in

standing.

3 METHOD

The effect of this control program, a trajectory

generator device placed on the handrail, on standing

movement of PD patients was investigated. In

measuring the force that will be exerted on the

handrail, the center of gravity trajectory, angle of the

body, knee joint torque, load on the body at the time

of standing, and the stability of the center of gravity

were evaluated. In this manner, what would be an

effective trajectory was investigated. In addition, the

research aimed to compare the standing movement

of two healthy adults with two PD subjects.

The average height of the two PD subjects is

1.60 (sd0.03)[m], and their average weight is 48.5

(sd5.5)[kg].The severity of their Parkinson's disease

was stage 4 on Hoehn Yahr scale. Using a

conventional handrail, it was not possible for the two

PD subjects to stand.

Figure 2: 14 optical markers.

As for the healthy adults, their average height is 1.73

(sd0.01)[m], and average weight is 70.5 (sd1.5)[kg].

The subjects were positioned on a height-adjustable

stool. The initial lower limb posture was as follows:

hip flexed 90 degrees and knee flexed 80 degrees.

The trajectory generator of the handrail was

based on the ground reaction force data. The value

of the vertical reaction force, derived from the right

and left feet force plates, changes the trajectory of

the handrail at a certain threshold. For this

experiment, the following values 50[%], 70[%],

80[%] of the subjects’ weight were assumed to be

the thresholds. All subjects were subjected to the 3

thresholds. Healthy subjects did not use this

intelligent handrail; however, they were told to stand

slowly and statically

Each subject executed the experiment 2 times.

As shown in Figure 2, a total of 14 optical markers

were placed on the subjects (the head of the 5th

metatarsal bone, lateral malleoluses, knee joints, hip

joints, shoulders, top of the head, elbow, and wrist)

and the handrail (the edge). Vicon motion analysis

system (Oxford Metrics Company) was used for the

measurement of the location of these body markers.

6 axes power sensors (Nitta Company) were placed

on the handrail and measured the power exerted on

the X-axis and Y-axis of the handrail.

Each set of vertical reaction force was

established from the left and right feet force plates

and the sampling frequency was set to 30Hz. Then,

the angle of the hip joint, the location of the center

of gravity, and the knee joints torque were

calculated. For the PD subjects, measurement was

conducted from the beginning to the end of the

handrail movement. While the healthy adults were

measured from the start of standing until the

acromion marker stopped. Each segment of standing

time, from start to finish, was divided, and the

standing ratio time was established. When it is

established that the power of the Y-axis of the

ground reaction force, under the chair became 0[N],

this indicates the point when hip is off the seat

4 RESULTS

Figure 3 shows an example of the handrail trajectory

of the PD subjects. The starting point (0) is the

initial position of the handrail. Among the 3

thresholds, the 80[%] threshold has the furthest

trajectory. Figure 4 shows the center of gravity

trajectory at the time of standing. The starting

position (0) is when standing movement starts.

In addition, the distance from the starting point is

normalized by the height of the subjects. In healthy

adults, the center of gravity, initially, advances

obliquely downward. Thereafter, it advances upward

curvilinearly. In the PD subjects, when the threshold

was set at 50[%], standing was not possible because

BIOSIGNALS 2012 - International Conference on Bio-inspired Systems and Signal Processing

190

Figure 3: Examples of the handrail trajectory.

the center of gravity did not advance sufficiently to

the supporting feet. When the PD subjects were

made to move at 70% threshold trajectory, it was

possible for them to stand; however, the trajectory of

the center of gravity became linear. When the PD

subjects’ center of gravity was compared with the

healthy adults’ center of gravity, the former center of

gravity advanced very little. On the average, the

furthest center of gravity of the PD subjects was

37[%] of their body height. When the threshold is

set at 80[%], the PD subjects could stand by

themselves, and the handrail continued moving

forward.

Figure 4: The center of gravity trajectory at the time of

standing.

The furthest center of gravity location of this time

was about the same with the healthy adults’ value at

the time of standing, which was 54[%] on the

average. Figure 5 shows the knee joint torque of the

PD and healthy subjects in standing.

Knee joint torque extension is indicated by

negative value. A knee joint torque was normalized

by the weight of the subject. The maximum knee

joint extension torque of the healthy adults was

greater in comparison with the PD subjects. When

the threshold was set at 50[%], the knee joint torque

of the PD subjects was smaller than knee joint

torque at other thresholds because the center of

gravity did not shift. In addition, at 70[%], and

80[%], there was a little difference in the knee joint

Figure 5: Knee joint torque of the PD and healthy subjects

in standing.

torque of the PD subjects. Figure 6 shows the power

exerted on the X-axis of the handrail by the PD

subjects. In the case of 50[%], 70[%], 80[%]: At

50[%], power exerted on the handrail was the

greatest.

Figure 6: The power exerted on the X-axis of the handrail

by the PD subjects.

However, at 70[%], 80[%], it was barely discernible.

Figure 7 also shows the power exerted on the Y-axis

of the handrail by the PD subjects. Positive value

indicates subjects are pushing down on the handrail.

At 80[%], the maximum power exerted on the

handrail is almost half the power exerted at other

thresholds. As mentioned above, the handrail

trajectory was calculated from the ground reaction

force. The finding shows that the 2 PD subjects, who

could not stand with conventional handrail, were

able to stand without help by using this intelligent

handrail. Finally, we concluded that the center of

gravity trajectory at 80 [%] threshold is the most

effective because it is similar to a healthy adult’s

trajectory.

5 DISCUSSION

In healthy adults, the center of gravity trajectory

plots a curve after hip is off the seat. Moreover, at

this moment, the body inclines forward and moves

vertically after hip off the seat. In addition, the

DEVELOPMENT OF A SIT-TO-STAND ASSISTANCE SYSTEM FOR PARKINSON'S DISEASE SUFFERERS -

(Intellectual Handrail)

191

Figure 7: The power exerted on the Y-axis of the handrail

by the PD subjects.

maximum location of the center of gravity was

54[%] on the X-axis, on the average. At this

trajectory, a person is able to stand stably because

posture stability is met. In addition, from this

experiment, it was determined that the maximum

extension torque of the knee joint was

1.19[N*m/kg]. When the PD subjects tried to stand

using the intelligent handrail, standing was not

possible when the vertical reaction force trajectory

was set at 50[%]. This is so because the center of

gravity did not advance sufficiently to the supporting

feet. At 70[%], PD subjects were able to stand.

However, the trajectory of the center of gravity

became linear. It was thought that the timing when

the subject’s body began to move vertically was too

soon. As a result, the handrail began to move

vertically before the subject’s hip was lifted from the

seat. The body’s movement observed here is

different from the standing up movement of a

healthy adult. When the handrail moved vertically,

the center of gravity of the subject is still left behind

the handrail. Therefore, it is thought that the weight

of the subject was exerted on the handrail. Thus, the

power exerted on the handrail was greater than in

other conditions. When the threshold is set at 70

[%], subjects could stand but unstably because too

much load is placed on the upper limbs and the

center of gravity is left behind the supporting feet.

When the threshold was set at 80[%], the PD

subjects’ center of gravity trajectory was similar to

healthy adults’, and thus, standing was possible. The

physical movement resembled a healthy adult’s

movement, in which the body moved vertically after

hip was lifted from the seat. The center of gravity

position of the X-axis trajectory at the time the hip

was lifted from the seat moved to the supporting

feet. In addition, the knee joint torque of the

extension direction became 0.94[N*m/sec] and was

smaller than knee joint extension torque

1.02[N*m/sec], which is typically shown among the

elderly who need assistance, including PD patients.

From this study, it could be suggested that 80[%]

threshold enabled the elderly and disabled

individuals to stand stably. Finally, the application

of this finding is the experimental production of a

small intelligent handrail, shown in Figure 8.

Figure 8: The experimental production of a small

intelligent handrail.

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