Abstract
〈Vol.5 No.6(2012.12)〉
Titles
[Contributed Papers]
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■ Adaptive High Gain Feedback Control of Nonholonomic Systems with Uncertain
Control Coefficients
Kumamoto Industrial Research Institute・Ryuji Michino and
Kumamoto University・Ikuro Mizumoto
In this paper, an adaptive high gain control is investigated for nonholonomic
systems with uncertain control coefficients. By using the high gain technique,
it is possible to design a stabilizing controller for such uncertain controlled
systems. In addition, the designed adaptive controller is rather simple,
since it has only one adaptive adjusting term even though there are a lot
of uncertainties in the controlled system. The application of this controller
to a nonholonomic wheeled mobile robot is considered as an illustrative
example.
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■ Risk Presentation Aimed at Improving Older Drivers’ Understanding of
Their Problems via Simulator-Based Education Programs
University of Electro- Communications・Midori INABA and Kenji TANAKA
This study examined simulator-based methods of illustrating risks to elderly
drivers in order to improve their ability to anticipate hazards. Experiments
were performed using hypothesized driving programs, in which participants
learned the importance of considering other cars’ behaviors during lane
changes, both their own and those of other drivers. The lane change risks
that the elderly drivers were intended to learn to anticipate in their
driving were presented using the simulator. The results showed that these
presentation methods may be more effective than verbal explanations in
helping
elderly drivers with reduced metacognitive abilities understand risks.
In particular, the most effective method of exposing drivers to the experience
of risk promoted the consideration of one’s surroundings in scenarios
where another car changes lanes. Among the programs that reminded participants
of the need to consider the car behind them when changing lanes, the trailing
perspective review method was most effective. Based on our findings, we
present implications that may be useful in developing driving simulator-based
educational programs for elderly drivers.
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■ Improving Tracking Performance of Passivity Based PID-Type Teleoperation
Systems with Communication Delay
Ishikawa National College of Technology・Yasunori Kawai
and ・Keio University Toru Namerikawa
The goal of this paper is to improve tracking performance of a bilateral teleoperation
system with communication time delay. The proposed method is a passivity-based
PID-type controller. First, using feedback passivation control, we make
the master and slave robots passive with respect to the new output including
position and velocity signals. Secondly, we design the PI controller for
the new output. In the proposed method, position coordination is achieved
even with the viscous friction error situation. The stability of the proposed
PID teleoperation system and tracking performance are shown via passivity
based stability analysis. Finally, several experimental results show the
effectiveness of the proposed control methodology for teleoperation systems.
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■ Distributed function calculation in switching topology networks
Kyoto University・Mohd Ashraf AHMAD, Shun-ichi AZUMA, Toshiharu, SUGIE
This paper addresses a distributed function calculation in switching topology
networks. In particular, a linear iterative strategy is used to perform
a general function calculation of the node's initial values.
This study shows that if the union graph of the switching networks is
connected, the distributed function calculation can be performed. The distributed
algorithm allows the nodes in the switching topology network to reach consensus
in a finite number of time-steps, which is upper bounded by the size of
network and switching period. The distributed function calculation is approached
from the perspective of observability theory and treats the iterative strategy
as linear dynamic systems.
Finally, this work shows that if a jointly connected graph in the switching
topology network is structurally observable, then each node obtains enough
information to perform an arbitrary function calculation.
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■ Simultaneous Localization Assistance for Mobile Robot Navigation in
Real,Populated Environments
Peshala Jayasekara, Takeshi Sasaki, Hideki Hashimoto and Takashi Kubota
Developing autonomous mobile robots that can coexist with human in populated
environments is still considered a big challenge. To address this problem
the authors propose a novel scheme to assist mobile robots by providing
localization information externally. This scheme combines the autonomous
navigation and target tracking research fields to arrive at a structured
assistance system for autonomous mobile robots. In the proposed scheme,
the environment is sensed using a laser range finder and a camera based
sensor unit. Using the Rao-Blackwellized particle filter technique, the
robots that need assistance are continuously tracked. In contrast with
conventional laser range finder based tracking systems, the placement of
the sensor is changed to a level above average human height and the mobile
robots are modified by attaching a cylindrical pole. The experiments showed
the validity of the proposed scheme for simultaneous localization assistance
for multiple mobile robots. Two mobile robots were simultaneously navigated
in given trajectories using assistance data,
successfully.
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■ Adaptive H∞ Formation Control for a Swarm of Mobile Robots
The Institute of Statistical Mathematics・Yoshihiko Miyasato
Design methods of adaptive H∞ formation control of multi-agent systems
composed of mobile robots are presented in this paper.The proposed control
schemes are derived as solutions of certain H∞ control problems, where
estimation errors of tuning parameters and error terms in potential functions
are regarded as external disturbances to the process. It is shown that
the resulting control systems are robust to uncertain system parameters
and that the desirable formations are achieved asymptotically via adaptation
schemes.
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■ A Pragmatic Load Detecting System Based on Uncertainty Evaluation for
Construction Manipulator
Waseda University・Mitsuhiro Kamezaki, Hiroyasu Iwata, and Shigeki Sugano
A pragmatic framework for detecting (identifying the on-off state of) the
external force applied to a construction manipulator (front load) by using
a hydraulic sensor is proposed. Such a load detecting system requires high
accuracy and robustness considering the uncertainty in pressure-based force
measurement. The proposed framework first identifies the dominant error
force component, including
self-weight and driving force, using theoretical and experimental estimation
and binarizes the analog cylinder external force. It then evaluates detection
conditions to address indeterminate conditions such as stroke-end, singular
posture, and impulsive or oscillatory force and redefines three-valued
outputs such as on, off, or not determinate (ND). It finally outputs the
front load decision by combining all the cylinder decisions to improve
robustness through priority analysis. Experiments were conducted using
an instrumented hydraulic arm. Results indicate that the proposed framework
detects on, off, and ND outputs of the front load more accurately, robustly,
and stably in various detection conditions.
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■ Perceptual Equivalence of Scale and Chromatic Aspects of Environmental
Saliency Arising in Naturally Complex Scenes
Osaka Institute of Technology・Kohji Kamejima
A new framework is presented for saliency based analysis of naturally complex
scenes. In this framework, the fluctuation of local scale shift and the
diversity of subtle chromatic scattering are extracted as the environmental
saliency: viewer specific visualization of sign patterns to be ssociated
with landmark objects. Being guided by the probability distribution of
the scale shift, the scene image is partitioned into a fractal attractor
spanning the roadway area and associated distribution of boundary objects.
The chromatic diversity of the scene image is evaluated within a probabilistic
color space as the support of a saliency index. The saliency index is applied
to the estimate of the invariant measure to capture the sign patterns as
fractal attractors within the boundary distribution. Thus, the scale-chromatic
aspects of the environmental saliency are articulated into a system of
fractal attractors of perceptually equivalence to jointly identify ground-object
structure. Through experimental studies, it has been demonstrated that
the complexity of decision steps in the detection of landmark objects can
be significantly reduced by the saliency based articulation. Adding to
it, the perceptual equivalence between the scale- and chromatic-aspects
of the environmental saliency is testable via the multi-fractal articulation;
to this end, it is sufficient to match the fractal attractors
designed in 2D chromatic aspect with 3D landmarks through the projection
into 2.5D scale aspect. By this perceptual equivalence, a self-reflective
mechanism is induced in the two-aspect representation of the environmental
saliency.
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