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Laboratory of Intelligent Machine Control
Okayama University
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| Location |
Okayama, Japan |
| Responsible Leader: |
Prof. Toshiro Noritsugu
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| Address |
Division of Industrial Innovation Sciences of the Graduate School of Natural Science and Technology,
Okayama University, 3-1-1, Tsushimanaka, Okayama,
700-8530, Japan
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| Telephone number |
+81(86)251 8061
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| Fax number |
+81(86)251 8061
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| Email |
toshiro@sys.okayama-u.ac.jp
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| Internet Site |
http://mcrlab.sys.okayama-u.ac.jp
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From Editor
International Journal of Fluid Power would like to introduce the fluid
power research and education centres with their expertise and
particular interests in this column. Jumping from continent to
continent we like to offer every research centre the opportunity to
present itself.
FLUID POWER RESEARCH CENTRES WORLD-WIDE
1 Background
The Laboratory
The
laboratory belongs to the Department of Intelligent Mechanical Systems
in the Division of Industrial Innovation Sciences of the Graduate
School of Natural Science and Technology, Okayama University,
Japan. The Laboratory is supervised by Prof. Toshiro Noritsugu.
The staff include Associate Prof. Masahiro Takaiwa, Assistant Prof.
Daisuke Sasaki and Technical staff Yoshinori Tawara. 3 doctor course
students, 13 master course students and 12 undergraduate students are
studying in our laboratory.
The major research topics are control engineering, pneumatics, robotics
and mechatronics. The pneumatic power control technology has been
the foundation of the laboratory. Recently, its application to a
welfare robotic technology has been one of the most interesting
research subjects. The development of a wearable power assist device
driven with pneumatic rubber artificial muscle and a rehabilitation
device driven with pneumatic cylinders and so on are executed.
Mechanical Engineering Department
Throughout its 42 years of existence, the Mechanical
Engineering Department has been recognized as a
centre of excellence providing highly qualified professionals,
and it has consistently been awarded the maximum
evaluation level by the Ministry of Education for
its undergraduate and postgraduate courses.
Its activities are integrated with several industrial
sectors, such as: metallurgical, electro-electronics,
semi-conductor, textile, and automotive industries,
along with institutions from several countries, bringing
together modernity and tradition in an academic environment
with technological infrastructure and highly
qualified human resources.
The Mechanical Engineering Department occupies
an area of 15,000 m2 where its 26 research groups are
distributed. With 69 academic staff, its postgraduate program (POSMEC) has graduated 772 Master’s and
220 Doctors since 1967.
The Department
Our laboratory is
a part of the Department of Intelligent Mechanical Systems. The
Department is composed of eight laboratories including our laboratory.
8 professors, 5 associate professor, 2 senior assistant professors, 6
assistant professors and 4 technical staffs are working for the
department. The main teaching and research subjects are system safety,
control engineering, production engineering, robotics and mechatronics.
The fluid power technology is studied in two laboratories besides
us. One is in the same department, which applies pneumatics. The
other is in the Department of Mechanical Engineering, which researches
on hydraulics.
The University
The Okayama University has been established in 1949.
It consists of 11 faculties and graduate schools. There are over 14000
students including about 500 overseas students. It is in Okayama City
located in the west in Japan. It takes about 3.5 hours from Tokyo by
Shinkansen train, about 1.5 hours by airplane. Figure 1 shows the
Library of Okayama University.
Fig. 1: The Library of Okayama University
2 Research
The major research
subjects of the laboratory are described below. In the future advanced
age and few-birth rate society, especially, the increase of elderly and
the lack of care giver will become a serious problem. To overcome the
problem it is expected to introduce a machine or robot to assist the
elderly, disabled people, care giver, nurse, and so on. Such a human
assist technology has become of major interest recently.
Since these kinds of machines or robots have to work near humans
or directly act on the human body, both safety and friendliness are
essentially important. To satisfy these requirements, an actuator, safe
and friendly for humans is desired. It should be small, lightweight and
has to provide a proper softness. An ideal candidate for such an
actuator would be the pneumatic rubber artificial muscle. We have
developed and manufactured some types of pneumatic rubber artificial
muscles. Using these muscles, some wearable power assist devices are
constructed. Further, a wrist rehabilitation device is being studied.
Pneumatic rubber artificial muscle
A McKibben type pneumatic rubber artificial muscle
is well known. We have developed some new types of pneumatic
rubber artificial muscle besides the McKibben type [1].
Contracted linear type (MxKibben type)
Figure 2 shows a
McKibben type rubber muscle, manufactured by covering the
surrounding of a rubber tube with fiber net. By pressurizing the rubber
tube, the muscle generates an axial contraction force. We can
manufacture the rubber muscle with an arbitrary size using commercially
available rubber tube and polyester fiber net. The manufactured rubber
muscle comprises a rubber tube with an outer diameter of 11.6 mm, an
inner one of 8.0 mm, and a length of 793 mm when not pressurized. The
maximum contraction is about 25%. When pressurizing the rubber tube to
600 kPa, the contraction force reaches about 340 N. The large generated
force is valuable for various applications.
Contracted curved type
Figure 3 shows a contracted curved type pneumatic rubber muscle, which
is constructed by reinforcing one side of a McKibben type rubber muscle
with an elastic acrylic sheet. When the rubber tube is pressurized,
only the top side is contracted by the effect of reinforcement of the
bottom side. As a result, the upward curved motion can be realized as
shown. By increasing the stiffness of the elastic sheet, the recovery
force increases but the generated curved force decreases.
Fig. 2: McKibben type rubber muscle
The muscle composed of parallel two rubber tubes with outer and
inner diameters of 11.6 mm and 8.0 mm, respectively, can generate the
curved angle of 126 degree and the maximum curved force of 78 N when it
is pressurized to 500 kPa.
Fig. 3: Contracted curved type muscle
Extended curved type
Figure 4 shows an extended curved type rubber
muscle consisting of a rubber tube with outer and inner diameters of
8.4 and 6 mm respectively, and a polyester bellows with the outer and
inner diameters of 16 and 13 mm respectively. To inhibit the extension
of the bottom axial direction, the polyester fiber bellows are
reinforced with a fiber tape. Three muscles of lengths 140, 120 and 80
mm are manufactured. By the reinforcement, when compressed air is
supplied into the rubber muscle, the rubber muscle can curve to the
reinforced side as shown in Fig. 4(b). Figure 5 shows the measured
fundamental characteristics of three rubber muscles. The generated
force is almost independent of the length of muscle. The
generated force for the supply pressure of 500 kPa is about 23 N, and
the relation between force and pressure is almost linear for inner
pressures above 150 kPa.
Fig. 4: Extended curved type muscle
Fig. 5: Fundamental characteristics of extended curved type muscle
Wearable power assist devices
It must be an earnest hope for the old aged or disable people to
perform daily living activities, as much as possible, by themselves
without the support of others. Further, their positive participation in
the society is desired. These devices also ease the physical burden of
the care giver. We have developed a wearable power assist device to
cope with the above situation. A human wears the device. It supports
various motions of the human by assisting the muscle power. This device
has to be a human friendly mechanism, which can be constructed with a
pneumatic rubber artificial muscle. We have developed some types of
wearable power assist devices driven with a different type of pneumatic
rubber artificial muscle.
Fundamental concept
Our fundamental concept in the development of a
wearable power assist device is to use the most suitable type actuator
for each part of human in order to make the structure as simple as
possible.
Figure 6(a) shows a power assist device for elbow driven with a
contracted curved type pneumatic rubber muscle shown in Fig.3. The
rubber muscle is attached to the elbow through a supporter. The assist
force can be controlled by adjusting the inner pressure of rubber
muscle. The subject can bend the elbow without their own muscle power
due to the power assist. Fig.6(b) shows another example of a
power assist device for shoulder part consisting of three McKibben type
pneumatic rubber muscles. It assists a flexion of upper arm using two
rubber muscles of lengths 562 mm and 793 mm. The adduction is assisted
using the muscle with 408 mm length.
The power assist devices shown in Fig. 6 are plot types of our research
aimed as simple, lightweight and human friendly as possible wearable
power assist device. Two examples are still primitive, they are
available as a simple and easy power assist device.
(a) Elbow
assisit
(b) Shoulder assist
Fig. 6: Fundamental power assist devices
Power assist glove
We have developed a power assist glove for
supporting activities of daily living, rehabilitation and various heavy
tasks [2]. Figure 7 shows the structure and the outlook of developed
power assist glove. It consists of the extended curved type pneumatic
rubber artificial muscles put on the backside of fingers, and the
extended linear type muscles put on a root of thumb.
A proposed wearable power assist glove can be easily manufactured
by attaching the pneumatic rubber muscles to an usual glove. The
manufactured power assist glove is available to support the finger
works required in daily living. Rehabilitation and various training may
be additional effective applications of this glove.
Power assist splint for upper arm
In the
design of a wearable power assist device, a mechanical interface to
transmit the generated force by actuator to the human body is
important. Ideally, the interface made of soft material such as
supporter, band and glove are desired for comfort. However, where a
large assist force is required, the combination with a suitable
orthosis may be considered.
Figure 8 shows the outlook and structure of the developed power assist
splint, constructed with an orthosis made by forming a plastic used as
a mechanical interface between rubber muscles and human body. It
assists the bending motions of wrist and elbow. Mechanical joints are
equipped on both sides to restrict its movable range to the smaller
than average maximum bending angles of Japanese male [3].
(a) Structure
(b) Manufactured assist glove
Fig. 7: Power assist glove
(a) Outlook
(b) Structure
Fig. 8: Power assist splint
Fig. 9: Wearable master-slave device
An extended curved
type rubber muscle shown in Fig.4 is used. A pair of the rubber muscles
is attached to the wrist and elbow, respectively. The rubber muscle
manufactured for the elbow consists of a rubber tube and polyester
bellows. The outer and inner diameters are 20 and 14 mm and the length
is 290 mm. The outer diameter of polyester bellows is 40 mm. The
bellows are reinforced with a fiber along the axial direction. Owing to
the reinforcement, when the compressed air is supplied into the
actuator, only the non-reinforced side extends in the axial direction
and produces a bending motion.
Figure 9 shows an application to the wearable
master-slave device which may be effectively used for a rehabilitation
system. A physical trainer wears the master device, a patient
wears the slave one. By constructing the bilateral type master-slave
system, the physical trainer can train the patient with a feel for the
patient’s conditions.
Standing assist device
Figure 10 shows a
standing assist device manufactured in our laboratory, which is
composed of leg orthosis and McKibben type pneumatic rubber artificial
muscles. Knee and ankle joints are driven with rubber muscles. The knee
joint lifts up the human body to stand up. The ankle joint controls the
gravity center position of human. Figure 11 illustrates the assist
effect. The human stands up by means of only upper arm force. The upper
arm force measured thorough the rings. In the figure, a top line
is for no assist, a center line for a case with only knee joint
is assisted, a bottom one for the case where both joints are assisted .
When both joints are assisted, the required force for the human can be
decreased to about 10% compared with the no assist case.
Application of pneumatic servo cylinder
A pneumatic servo control is a fundamental
technology in our laboratory. We have already published many papers on
position or force servo control of pneumatic cylinder, its application
to active suspension and active vibration control and so on.
Recently, we are studying an application
of pneumatic parallel manipulator for a wrist rehabilitation
exercise. Six pneumatic cylinders are used as driving actuators to
construct Stewart type platform as shown in Fig.12. The controller is
constituted with an impedance control scheme using a disturbance
observer[4].
Fig.10: Assist device for standing up motion
Fig.11: Assist effect for standing up motion
Fig.12 Pneumatic parallel manipulator3 Conclusion
A human assist technology is essential in an aged
society. A pneumatic power is effective to develop the human assist
technology due to its inherent flexibility and human friendliness. A
pneumatic rubber artificial muscle is applicable to construct various
human assist devices. In this paper, some types of rubber muscles
developed and manufactured in our laboratory are introduced. These
muscles are available to constitute a human friendly wearable power
assist device. The power assist device with a simple structure can be
designed by using the suitable type of rubber muscle according to the
property of assisted part of human body.
We have continued to establish a human assist
technology based on soft mechanism and wearable power assist device
with effective application of pneumatic power.
The academic research activities are funded by
Grant-in Aid for Scientific Research, Scientific Research (B) 16360124
and Scientific Research in Priority Areas 16078210, Japan. We have
cooperated with researchers in medical and welfare fields. In addition,
we have promoted an industrial collaborations to put the above research
accomplishment to practical use.
The collaboration among related technologies is expected for the innovation of fluid power technology.
4 References
1. Noritsugu, T., Takaiwa, M. and Sasaki, D, Development of Pneumatic Rubber Artificial
Muscle for Human Support
Applications, Proceedings of the Ninth Scandinavian International
Conference on Fluid Power, 2005.
2. Noritsugu, T., Yamamoto, H., Sasaki, D. and
Takaiwa, M., Wearable Power Assist Device for Human hand
Grasping Using
Pneumatic Artificial Rubber Muscle, Proceedings of SICE Annual
Conference in Sapporo,
2004, pp.420-425.
3. Sasaki, D., Noritsugu, T. and Takaiwa, M.,
Development of Pneumatic Power Assist Splint “ASSIST”
Operated by Human Intention,
Journal of Robotics and Mechatronics, 2005, 17-5.
4. Takaiwa, M. and Noritsugu, T., Development of
Wrist Rehabilitation Equipment using Pneumatic Parallel
Manipulator, Proceedings of the 2005 IEEE International Conference on
Robotics and Automation,
2005, pp.2313-2318.
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