Download development of gait training system using bi

Proceedings of the 7th JFPS International
Symposium on Fluid Power, TOYAMA 2008
September 15-18, 2008
P1-47
DEVELOPMENT OF GAIT TRAINING SYSTEM
USING BI-ARTICULAR MUSCLE MODEL
Yoshiyuki SHIBATA*, Motoki TAKAGI*, Tasuku MIYOSHI*, Ryota AOYAMA*
Shin-ichiroh YAMAMOTO* and Yukio KAWAKAMI*
* Graduate School of Engineering, Functional Control Systems
Shibaura Institute of Technology
307 Fukasaku, Minuma-ku, Saitama-City, Saitama, 337-8570 Japan
(E-mail: [email protected])
ABSTRACT
The purpose of this study was to develop a pneumatic gait training system which was consisted by Mckibben type
actuators to achieve the normal gait patterns of lower limb joint angular displacements. These actuators were arranged
as human musculoskeletal system; mono- and bi-articular muscles. The system provided a proportional directional
control valve which controlled antagonistic actuators, and this system had PID controller and joint angular displacement
feedback circuit. In the results, the output of the knee joint movement pattern had well validation for the input signal
which was recorded from natural treadmill walking in healthy subjects. This system made the orthosis reproduce like
the human natural walking. In conclusion, we structured a fundamental bi-articular muscle type of the gait training
system using Mckibben type actuators.
KEY WORDS
Bi-articular muscle, Mckibben Actuator, Gait training system
INTRODUCTION
The value of partial body weight support treadmill
training (BWSTT) for disabled individuals has been well
established, especially when initiated soon after an injury.
Wernig et al. [1] had demonstrated that 25 out of 33
incomplete spinal cord injured persons learned to walk
independently at the end of 3-20 weeks (median 10.5)
with partial BWSTT. However, this treatment presents
special challenges for the therapist. The passive moving
of a disabled person's legs is ergonomically difficult
since the individual being treated cannot support and/or
move his legs by himself. In order to improve this
therapy, Colombo et al. [2] developed a driven gait
orthosis (DGO) that can be used on patients with varying
degrees of paresis or spasticity for up to one-half hour.
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Dietz et al. [3] using this gait training system for
paraplegic patients, and they suggested the afferent input
from hip joints is important for the leg muscle activation
during locomotion.
In the previous studies, we had constructed the two types
of gait training systems using the Mckibben type of
pneumatic actuators to achieve the repetitive
physiological gait patterns [4-5]; one was mono-articular
muscle model [4], the other was bi-articular muscle
model [5]. The Mckibben type actuator had similar
mechanism to human muscle contraction for a force
generating, and it has high degree of freedom of design
and contributes to orthosis lightening. In addition, both
of our system has some advantages over the partial
BWSTT on land; the system is electrically and
mechanically safe since it consists of pneumatic
Copyright © 2008 by JFPS, ISBN 4-931070-07-X
actuators to prevent short circuits and a burn, and the
main frame is an exoskeleton type of the hip-knee-ankle
orthosis which is used in general gait training. According
to Miyoshi et al. [4], they had developed a robotic gait
trainer in water (RGTW) and had demonstrated its
efficacy which could reduce the enhanced hip extensor
muscle activities, since the water walking needs
propulsive forces against the water resistance [6]. In this
respect, the bi-articular muscle model could reduce the
hip extensor muscle activities [5], since the bi-articular
muscles had unique function in force-directing because
of their ability to simultaneously regulate or tune
adjacent joint torques [7]. The bi-articular muscles are
through the two joint, and are arranged in a pair of
antagonists; e.g. biceps brachii and triceps brachii, rectus
femoris and biceps femoris. The synergistic activities of
one antagonistic pair of the bi-articular muscles and two
antagonistic pair of the mono-articular muscles might be
able to reproduce by single command signal informing
force direction via a simple spinal level neural network
proposed [8]. To our knowledge, however, there is no
gait training system using bi-articular muscle model,
because the bi-articular muscle model is redundant and
torque shearing problem for two joints is infinite
combination.
The purpose of this study was to develop the bi-articular
muscle model type of the pneumatic gait training system
for achieving the repetitive physiological normal gait
patterns of lower limb joint angular displacements, and
to design the specific controller for bi-articular muscle
model based on PID.
SYSTEM DESIGN
Pneumatic Control
Figure 1 represents the gait training system. The orthosis
drives by contraction of the Mckibben type actuators,
and we applied antagonistic arrangement of the
Mckibben type actuators like human muscles. So, we
used proportional directional control valve(servo valve).
This valve has 1 input port and 2 output ports which
attached to the Mckibben type actuators posterior and
anterior. Therefore it’s very suitable for control by
antagonistic actuators.
Mckibben type actuator
Figure 2 shows the Mckibben type actuator. This actuator
generated force by contraction. The outer-tube of mesh
texture transformed a radial force into an axial force
when inner rubber-tube generated force by expansion.
Contraction ratio was 30% on natural length.
750 mm
Joined
Natural length
Shortening
Figure 2 The mechanism of Mckibben type actuator
Figure 1 Gait training system schematic diagram
Copyright © 2008 by JFPS, ISBN 4-931070-07-X
Joined
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parameter sets P:1.0, I:0, D:0, to all actuators. The hip
joint angle output value was twice as value than the
target value, and there were phase shifting(figure 5). The
mono-articular muscle model had time-delay, and
couldn't reach the maximum target angle.
Walking program and control interface
We used a Digital Signal Processor(DSP) for input and
output of signals. This equipment has A/D and D/A
converter, and control program run the Simulink of
Matlab(The MathWorks). Figure 3 shows the block
diagram of servo system. Input data was joint angle of
gait cycle by healthy people. Hip and knee joint angle of
orthosis got feedback which detected by the
potentiometer. The PID controller value decided
voluntarily from the experiment.
The DSP provides interface function which called Virtual
Console. It function is very useful which is able to create
one's own GUI, and load parameter from Simulink of
Matlab. The user is able to change the parameters
without Simulink of Matlab.
C (s)
kI s
T in (s)
+
-
kp
+ +
+
G (s )
T out (s )
kD s
Figure 4 Left leg of orthosis
㻢㻜
㼐㼑㼓㼞㼑㼑㻌㻌㻌㼒㼘㼑㼤㼠㼕㼛㼚
Figure 3 Block diagram of servo system. T in (s ) : Target
angle, T out (s ) : Controlled angle, C (s ) : PID controller,
G (s ) : Servo valve control voltage gain.
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㼔㼕㼜㻌㼕㼚㼜㼡㼠
㻠㻡
㻟㻜
㻝㻡
㻜
The following show equipment list.
a) Mckibben type actuator: Hitachi Medical Corp.
b) Servo valve: MPYE-5-1/8-HF-010-B, FESTO Corp.
c) DSP: ADX5430, A&D Co. Ltd.
Orthosis overview
Figure 4 shows the orthosis overview. The left leg of
orthosis fixed to the frame, and suspended. At first, we
build up this system only unilateral leg of orthosis on a
trial basis. The Mckibben type actuator attached to the
anterior and posterior of each joint. The orthosis drove
because these actuators contract alternately.
㻙㻝㻡
㻙㻟㻜
㻙㻠㻡
㻙㻢㻜
㼐㼑㼓㼞㼑㼑㻌㻌㼒㼘㼑㼤㼠㼕㼛㼚
㻢㻜
㼗㼚㼑㼑㻌㼛㼡㼠㼜㼡㼠
㼗㼚㼑㼑㻌㼕㼚㼜㼡㼠
㻡㻜
㻠㻜
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RESULTS
㻜
It is possible for proportional directional control valve to
control the both agonistic/antagonistic Mckibben type
actuators. Thus, it can be decreased the number of
control valves to the number of actuators. We achieved
simplification of the pneumatic pipe arrangement in this
system. This experiment was performed the same
parameter between bi-articular muscle model and hip
mono-articular muscle model. The PID controller
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㻜
㻞
㻠
㻢
㻤
㻝㻜
㻝㻞
㻝㻠
㼟㼑㼏
Figure 5 Joint angle variation during orthosis walking.
Knee joint angle data(bottom), and hip joint angle
data(upper). Target values were hip and knee joint angle
for healthy people(one gait cycle:0.5Hz, solid line: target
joint angle, break line: controlled angle value).
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Copyright © 2008 by JFPS, ISBN 4-931070-07-X
6. T. Miyoshi, T. Shirota, S. Yamamoto, K. Nakazawa
and M. Akai, Effect of the walking speed to the lower
limb jointangular displacements, joint moments and
ground reaction forces during walking in water,
Disability and Rehabilitation, 2004;VOL.26, NO.12,
724–732.
7. G. J. Van Ingen Schenau, From rotation to translation:
Constraints on multi-joint movements and the unique
action of bi-articular muscles, Human Movement
Science, Volume 8, Issue 4, August 1989, Pages
301-337.
8. M. Kumamoto, T. Oshima, and T. Fujikawa,
Bi-articular muscle as a principle keyword for
Biomimetric motor link system, Microtechnologies in
Medicine & Biology 2nd Annual International
IEEE-EMB Special Topic Conference on, 346-351,
2002.
DISCUSSION
The hip joint angle response was larger than target
angle value, it was not appropriate parameter of servo
valve control voltage gain. The reason of phase shifts
might be overlarge proportional value of PID controller.
The bi-articular muscle model was through the two joint,
but the angle feedback was performed only hip joint
angle. It wasn’t optimal follow-up control. The human
walking had coinstantaneous rotation knee and hip joint.
Hence, we have to determine the PID controller value
and feedback parameter for each muscle models.
CONCLUSION
We developed a fundamental gait training system
with position feedback and PID controller functions,
drove by pneumatic Mckibben type actuator. This system
might be possible which reproduce the movement like
the human natural walking.
FUTURE WORK
In this study, it was difficult for the bi-articular
muscle model to control by hip joint angle feedback. We
will determine about the optimal PID controller value of
mono-articular muscle model and the appropriate control
parameter for the bi-articular muscle model. We have to
superstruct control system which mono and bi-articular
muscle models will be possible to produce their
coordination.
REFERENCES
1. Wernig A, Muller S, Nanassy A, Cagol E. Laufband
therapy based on 'rules of spinal locomotion' is
effective in spinal cord injured persons. Eur J
Neurosci 1995;7:823-9.
2. G. Colombo, M. Joerg, R. Schreier, and V. Dietz,
Treadmill training of paraplegic patients using a
robotic orthosis, Journal of Rehabilitation Research
and Development Vol. 37 No. 6, pp.693-700, 2000.
3. V. Dietz, R. MuÈller and G. Colombo, Locomotor
activity in spinal man: significance of afferent input
from joint and load receptors, Brain, 125, 2626-2634,
2002.
4. T. Miyoshi, K. Hiramatsu, S. Yamamoto, K.
Nakazawa and M. Akai, Robotic gait trainer in water:
Development of an underwater gait-training orthosis,
Disability and Rehabilitation, 2008; 00(0): 1–7.
5. S. Yamamoto, T. Miyoshi, T. Komeda, K. Hiramatsu,
K. Nakazawa, and M. Akai, Development of
pneumatic gait assist system, Complex Medical
Engineering, 2007. CME 2007. IEEE/ICME
International Conference on, 1337 – 1340.
Copyright © 2008 by JFPS, ISBN 4-931070-07-X
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