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FRAMEWORK OF AN ESTIMATION ALGORITHM OF TIME
VARYING MULTIJOINT HUMAN ARM VISCOELASTICITY
Mingcong Deng, Ni Bu and Akira Yanou
Graduate School of Natural Science and Technology
Okayama University 3-1-1 Tsushima-Naka, Okayama 700-8530, Japan
Keywords:
Multijoint human arm viscoelasticity, Non-Gaussian system, Robust estimation.
Abstract:
The paper concerns a framework of an estimation of multijoint human arm viscoelasticity in a small sufficient
time period. The uncertainties have to be considered in estimating the viscoelasticity of the multijoint human
arm. In general, the uncertainties existing in the structure of the human arm and the motor command from
the central nervous system are subject to the non-Gaussian noises. A generalized Gaussian ratio function is
brought in to deal with the non-Gaussian noises. The momotonicity of the generalized Gaussian ratio function
is studied based on the approximation formula of Gamma functions, then a robust condition is proposed for
the computation of even moments using shape parameters. That is, we can guarantee the accuracy of the
simulation results and experimental results by the robust condition. The effectiveness of the proposed method
is confirmed by the experimental results.
1 INTRODUCTION
One of the key characteristics that human beings sur-
pass the animals is the human arm. According to the
central nervous system (CNS), human can do many
things by making full use of human arm. Simply,
when human beings want to do something by arm,
(e.g. taking something in front of him) the arms move
forward following the guide of the CNS, adjust the di-
rection and gradually reduce the distance between the
hand and the object, finally the object can be taken.
Actually, the human arm is derived by the multijoint
muscle generated torque, which is assumed to be a
function of angular position, velocity and motor com-
mand of CNS (Gomi and Kawato, 1996; Gomi and
Kawato, 1997). The change of the torque is caused by
multijoint arm viscoelasticity which consists of joint
stiffness. Joint stiffness is regulated by muscle inher-
ent spring-like properties, neural feedbacks, and vis-
cosity. In the fields of industrial robots and medical
service, the study of the human arm viscoelasticity
plays an important part. For example, if the knowl-
edge of how the arm moves according to the CNS is
known, some artificial limbs can be designed to help
the disabled. So in order to get some corresponding
knowledge about the moving human arms, the esti-
mation of the human arm viscoelasticity is discussed
in this paper.
The estimation of the viscoelasticity of the hu-
man arm has been studied by many researchers
(Deng, Inoue, Gomi and Hirashima, 2006; Gomi and
Kawato, 1996; Gomi and Kawato, 1997; Deng, Saijo,
Gomi and Inoue, 2006; Kim, Kang, Kim and Park,
2009). A high-performance manipulandum was de-
veloped to measure human arm stiffness based on
the equilibrium-point control hypothesis (Gomi and
Kawato, 1996). The authors discussed the manipu-
landum in details in (Gomi and Kawato, 1997): by
using the manipulandum and a new estimation al-
gorithm, human multi-joint arm stiffness parameters
during multi-joint point-to-point movements on a hor-
izontal plane were measured. Later, online estima-
tion algorithm of the human arm viscoelasticity was
proposed in (Deng et al, 2006), (Deng, Inoue and
Zhu) and (Iseki, Deng, Inoue and Bu, 2009). An in-
tegrated procedure to study on real time estimation
of time varying multijoint human arm viscoelastic-
ity was proposed in (Deng et al.) concerning the
uncertainty factor consisting of time-varying motor
command from central nervous system, measurement
noises and modeling error of the rigid body dynam-
ics. However, there exist some problems, for ex-
ample, in (Gomi and Kawato, 1996) and (Gomi and
Kawato, 1997), the stiffness, viscosity, and inertia pa-
258
Deng M., Bu N. and Yanou A. (2010).
FRAMEWORK OF AN ESTIMATION ALGORITHM OF TIME VARYING MULTIJOINT HUMAN ARM VISCOELASTICITY.
In Proceedings of the Third International Conference on Bio-inspired Systems and Signal Processing, pages 258-263
DOI: 10.5220/0002727202580263
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