Abstract
〈Vol.2 No.4(2009.7)〉
Titles
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■ Accessibilities of Wheelchair Users to Cross the Gaps and Steps between Platforms and Trains
Hyogo Assistive Technology Research and Design Institute・Tsutomu HASHIZUME, Toyo University・Ikuo YONEDA, Hyogo Assistive Technology Research and Design Institute・Hiroshi KITAGAWA, The University of Tokushima・Shoichiro FUJISAWA, and Osamu SUEDA
Gaps and steps between platforms and trains reduce the accessibility and mobility of people with wheelchairs in railway transportations. Using an experimental platform, the observations are performed how gaps and steps influence their capabilities for manual wheelchair or electric powered wheelchair users with spinal cord injury. A quantity of Normalized Driving Force (NDF) is introduced to evaluate the manual wheelchair user's abilities in the case of getting on or off the trains. The three types of electric powered wheelchairs are also tested under the same experimental conditions as the manual wheelchair. The dynamic wheelchair driving force is measured by using a torque meter equipped on a wheelchair to analyze the required force when getting on the trains. To improve practical accessibility of such people, an assistive device for boarding the trains is designed and its effect is verified.
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■ GPS Positioning Method under Condition of Only Three Acquired Satellites
Keio University・Masashi NOMURA, and Toshiyuki TANAKA
To measure a position by GPS (Global Positioning System), observing more than three satellites is usually needed. If there are not obstacles near a receiver, more than three satellites are generally observed and the position is located. However, in an urban area or a forest, more than three satellites can not be frequently acquired because of buildings and trees. Then we suggest a new algorithm for positioning using only three satellites. When only three satellites are observed, the data for positioning is not enough. To solve the problem, we use consecutive data and measure the position. Other methods using only three satellites usually need past data of the receiver such as the position or external data by the reference station or devices other than the receiver. However our method does not need other data and has only to fix a receiver for a few seconds. Therefore our method is useful for pedestrians. When consecutive data is used, noise of pseudo range influences the positioning acc uracy. Then we use carrier phase in the L2 signal and make the noise less. In this paper, we show the effectiveness of our method using a dual frequency receiver and received data from three satellites whose elevation angles are high.
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■ Dynamic Programming on Reduced Models and Its Evaluation Goodbreak through Its Application to Elevator Operation Problems
Kobe University・Tsutomu INAMOTO, Hisashi TAMAKI, and Hajime MURAO
In this paper, we display a modified dynamic programming (DP) method. The method is basically same to the value iteration method (VI), a representative DP method, except the preprocess of a system's state transition model for reducing its complexity, and called the dynamic programming on reduced models (DPRM). That reduction is achieved by imaginarily considering causes of the probabilistic behavior of a system, then cutting off some causes with low occurring probabilities. In computational illustrations, VI, DPRM, and the real-time Q-learning method (RTQ) are applied to elevator operation problems, which can be modeled by using Markov decision processes. The results show that DPRM can compute quasi-optimal value functions which bring more effective allocations of elevators than value functions by RTQ in less computational times than VI, and this characteristic is notable when the traffic pattern is complicated.
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■ Evolution of Active Sensing for Wall-Following Navigation of Snake-like
Robot
Doshisha University・Ivan TANEV, and Katsunori SHIMOHARA
We propose an approach of automated co-evolution of the optimal values of attributes of active sensing (orientation, range and timing of activation of sensors) and the control of locomotion gaits of a simulated snake-like robot (Snakebot) that result in a fast speed of locomotion in a confined environment. The experimental results illustrate the emergence of a contactless wall-following navigation of fast sidewinding Snakebots. The wall-following is accomplished by means of differential steering, facilitated by the evolutionary defined control sequences incorporating the readings of evolutionary optimized sensors.
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■ Multirate-Sampling Dynamic Quantizers for Non-Minimum Phase Linear Control
Systems
Maizuru National College of Technology・Yuki MINAMI,
Kyoto University・Shun-ichi AZUMA, and Toshiharu SUGIE
This paper addresses a problem of finding an optimal dynamic quantizer
for systems including discrete-valued signal constraints. In our previous
works, an optimal dynamic quantizer has been derived, and its effectiveness
has been illustrated. However, since our former results have been derived
under a strong assumption, the quantizer can be applied to limited cases.
To overcome this drawback, we provide a dynamic quantizer based on a multirate
sampling technique. First, we formulate an optimization problem for a class
of multirate sampling type dynamic quantizers, and then we give a closed
form solution as an extension of our former single-rate sampling case.
Finally, the validity of the proposed dynamic quantizer is demonstrated
by an experiment with a cart system.
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■ A Fixed-Point Theoretic Solution of the Hamilton-Jacobi Equation and Its Application to Nonlinear H∞ Control
Shinshu University・Hidenori MATSUZAKI, Masayoshi EGUCHI, and Yasunari
SHIDAMA
This paper proposes a novel approach to the Hamilton-Jacobi equation (HJE).
Through a functional analytic formulation, a stabilizing solution of the
HJE is derived from a fixed-point of a nonlinear mapping on a function
space. A sufficient condition for the existence of such a fixed-point is
derived quantitatively. For computing the fixed-point, a numerical method
based on optimization techniques is introduced. Based on these results,
the nonlinear H∞ control problem is reconsidered. Simple numerical examples
show that the resulting controllers have enough performance and computed
solutions can approximate their analytical counterparts almost uniformly
in the entire region under consideration.
▲ ■ A Statistical Process Control Method for Semiconductor Manufacturing
Shibaura Institute of Technology・Tomoaki KUBO, Toshiba Corporation・Tomomi INO, Kazuhiro MINAMI, Shibaura Institute of Technology・Masateru MINAMI, and Tetsuya HOMMA
To maintain stable operation of semiconductor fabrication lines, statistical
process control (SPC) methods are recognized to be effective. However,
in semiconductor fabrication lines, there exist a huge number of process
state signals to be monitored, and these signals contain both normally
and non-normally distributed data. Therefore, if we try to apply SPC methods
to those signals, we need one which satisfies three requirements: 1) It
can deal with both normally distributed data, and non-normally distributed
data, 2) It can be set up automatically, 3) It can be easily understood
by engineers and technicians. In this paper, we propose a new SPC method
which satisfies these three requirements at the same time. This method
uses similar rules to the Shewhart chart, but can deal with non-normally
distributed data by introducing "effective standard deviations".
Usefulness of this method is demonstrated by comparing false alarm ratios
to that of the Shewhart chart method. In the demonstration, we use various
kinds of artificially generated data, and real data observed in a chemical
vapor deposition (CVD) process tool in a semiconductor fabrication line.
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■ A Recognition Method for Sweet Pepper Fruits Using LED Light Reflections
Kochi University of Technology・Shinsuke KITAMURA, and Koichi OKA
This paper describes a method for sweet pepper picking robots working in greenhouses to distinguish the pepper fruits from the leaves. The fruits of the sweet pepper plant are recognized by image processing techniques, using a parallel stereovision system installed in the robot. However, as fruits and leaves of the sweet pepper have almost the same color, it is very difficult to recognize fruits using only color information. In this paper, we propose a new method using reflections of LED lights. The fruits of the sweet pepper are more reflective than the leaves; therefore, we can identify fruits by assuming that the more reflective parts are the fruits. We perform experiments using the improved image processing algorithm in a greenhouse, and the algorithm indeed improves the recognition ability of the robots.
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