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 SICE Jounal of Control,Measument,and System Integration

  

Abstract

〈Vol.2 No.1(2009.1)〉


Titles


■ Computing the PageRank Variation for FragileWeb Data

Tokyo Institute of Technology・Hideaki ISHII,Politecnico di Torino・Roberto TEMPO

Search engines utilize numerous measures to rank the webpages in the search results. At Google, the so-called PageRank algorithm provides crucial information by quantifying the importance of webpages. The PageRank values are considered to be objective since the algorithm requires only the data of the web link structure. In this paper, we first introduce the original PageRank algorithm and give a brief overview of the distributed randomized approach recently proposed by the authors. Then, we consider the problem of computing the variation in the PageRank values that can be caused by erroneous data in the web structure when some links are fragile. An efficient (centralized) algorithm in the form of linear programming is proposed. This approach employs results from the field of interval matrices. Numerical examples are given to verify the effectiveness of the approach.


■ A Realization-based Method for Identification of Closed-loop Systems using Measurable Disturbance

JFE Systems・Hajime Ase,Doshisha University・Tohru Katayama

We derive a closed-loop subspace identification method based on a realization theory without using probing inputs, but we assume that there is a measurable disturbance that can be used as a test input for closed-loop identification. The orthogonal decomposition (ORT) technique is applied to obtain deterministic and stochastic components of the joint input-output process.An ORT-based closed-loop subspace identification method is then developed by combining realizations of the deterministic and stochastic components, followed by a model reduction procedure to obtain lower dimensional models. Some numerical results are included to show the applicability of the present method.


■ Scheduling Capacitated One-Way Vehicles on Paths with Deadlines

Kyoto Institute of Technology・Jun UCHIDA,Kyoto University・Yoshiyuki KARUNO,
and Kyoto University・Hiroshi NAGAMOCHI

In this paper, we deal with a scheduling problem of minimizing the number of employed vehicles on paths. Let G=(V,E) be a path with a set V=\{v_{i} \mid i=1,2,...,n} of vertices and a set E=\{\{v_{i},v_{i+1}\} \mid i=1,2,\ldots,n-1\}$ of edges. Vehicles with capacity $b$ are initially
situated at v_1. There is a job $i$ at each vertex $v_{i} \in V$, which has its own handling time $h_{i}$ and deadline $d_{i}$. With each edge $\{v_{i},v_{i+1}\} \in E$, a travel time $w_{i,i+1}$ is associated. Each job is processed by exactly one vehicle, and the number of jobs processed by a vehicle does not exceed the capacity $b$. A routing of a vehicle is called {\em one-way} if the vehicle visits every edge $\{v_{i},v_{i+1}\}$ exactly once~(i.e., it simply moves from $v_{1}$ to $v_{n}$ on $G$). Any vehicle is assumed to follow the one-way routing constraint. The problem asks to find a schedule that minimizes the number of one-way vehicles, meeting the deadline and capacity
constraints. A greedy heuristic is proposed, which repeats a dynamic programming procedure for a single one-way vehicle problem of maximizing the number of non-tardy jobs. We show that the greedy heuristic runs in $O(n^{3})$ time, and the approximation ratio is at most $\ln b + 1$.


■ Precise Speed Tracking Control of Ultrasonic Motors via Sampled-Data H∞ Control

Nagaoka University ofTechnology・Tharathip VONGSAROJ, Yasuhide KOBAYASHI, Hisaya FUJIOKA, and Shigeo YANABE

In this paper, we consider a synthesis problem of digital controllerfor speed tracking control systems of ultrasonic motors. In the previous work, continuous-time H∞ control based synthesis involving Tustin transformation has been utilized to solve the problem, where it has been empirically known that over-estimation of modeling error is needed to avoid speed fluctuation in high frequency range. In this paper, it is shown that desirable performance can be obtained by sampled-data H∞ control synthesis without such conservativeness in modelings.


■ Mean Square Optimal Hedging with Non-Uniform Rebalancing Intervals

Kyoto University・Kenji Sato,Yuji Yamada,Hisaya Fujioka

This paper proposes a method of discrete hedging by extending the MSOH (mean square optimal hedging) problem. In the proposed method, the risk of option sellers is minimized in terms of the mean square hedging error as in the MSOH problem,while it is allowed to rebalance with non-uniform intervals as opposed to the uniform assumption in the MSOH problem. The benefit of the extra freedom is demonstrated via numerical simulations.


■ An iterative method for the output-feedback mixed H_2/H∞ control problem

Akashi National College of Technology・Yasushi Kami,
Kyushu Institute of Technology・Eitaku Nobuyama

This paper is concerned with the mixed H_2/H∞ control problem with output-feedback. To propose a new iterative method for the problem we firstly construct a controller sequence which converges to the unconstrained globally optimal $H_2$ controller. After then, using this sequence, we propose an iterative method for the mixed $H_2/H∞ control problem. The advantage of our method is to guarantee that the obtained solution is either the globally optimal solution or a feasible solution in the neighborhood of the boundary of the H∞ norm constraint. A numerical example shows the efficiency of our method.


■ Global Asymptotical Stabilization of Morse-Smale Systems using Weak Control-Lyapunov Functions

RIKEN・Gou Nishida,Takayuki Tsuzuki,Hisakazu Nakamura,Yuh Yamashita

This paper proposes a method of constructing weak control-Lyapunov functions for nonlinear systems by introducing a topological geometric assumption called a Morse-Smale system.A Lyapunov function is one of the most important tools to study stability and stabilization in nonlinear systems.
However, a general way of finding Lyapunov functions has not been found yet.First, we confirm there is a weak Lyapunov function in Morse-Smale systems.Next, we define the escapability for singular structures of the weak Lyapunov function.If all singular structures are escapable, then the Morse-Smale system is a global asymptotical stabilizable one.Finally, we present the method of constructing a set of weak control-Lyapunov functions to achieve global stabilization.The method is described in terms of a recursive sequence of singular structures.We call the sequence a weak Lyapunov filtration.


■ Motion Control of Inverted Pendulum Robots Using a Kalman Filter Based Disturbance Observer}

Polytechnic University・Akira Shimada,Chaisamorn Yongyai

A high-speed motion control technique for inverted pendulum robots, utilizing instability and a disturbance observer, based on the Kalman filtering technique, is introduced. Inverted pendulums are basically controlled as they do not topple. Shimada et al. developed a contrary idea and presented a controller that deliberately off balanced the robot when it moved. To implement the idea, a controller was designed using zero dynamics, which was derived by partial feedback linearization. However, the control system was not robust or sufficiently reliable. Although they presented a revised method using H∞ control law, it was complex. Shimada et al. also presented a design method for a disturbance observer using Kalman filtering. This paper presents the latest control technique, combining both control laws to solve the problem, and introduces an application with respect to inverted pendulum robots. It further shows experimental results to confirm its validity.


■ Improved Particle Filter for Service Robot Self-Localization

Tokyo Institute of Technology・Guanghui Cen,Nobuto Matsuhira,Junko Hirokawa,Hideki Ogawa,Ichiro Hagiwara,Yasumasa Fujisaki

Mobile robot localization is the problem of determining a robot'spose in an environment, which is also the most basic problem in mobile robotics application. Recently, particle filter becomes the most popular approach in mobile robot localization and has been applied with great success to a variety of state estimation problems. In this paper, the particle filter is applied in our service robot position tracking and global localization. Moreover, the posterior distribution of robot pose in global localization is usually multi-model due to the symmetry of the environment and ambiguous detected features. Considering these characteristics, we proposed an improved cluster particle filter to increase the global localization robustness and accuracy. On-line experiments based detailed analysis of coordinate error and algorithm efficiency are given. On-line experiment results also show the efficiency and robustness of our approach in our service robot ApriAlpha$ ^{\textrm{TM}}$ Platform.


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