All issues
Volume 47, Issue 2
Displaying 1-7 of 7 articles from this issue
- |<
- <
- 1
- >
- >|
Paper
Measurement
-
Yukinori NAKAMURA, Kensuke NAGAI, Kenji SUGIMOTO2011 Volume 47 Issue 2 Pages 81-89
Published: 2011
Released on J-STAGE: December 19, 2011
JOURNAL FREE ACCESSThis paper proposes a method for robust state estimation for systems with irregular sensing failure. It is often experienced that non-contact sensors give abnormal signals (outliers) due to sensing failure. To compensate their effect, the proposed estimator switches observer gains to select normal signals based on the current estimation of the sensor signals. Stability of the error system is guaranteed in terms of switched Lyapunov functions. Both numerical and experimental results show the effectiveness of the proposed method.View full abstractDownload PDF (1743K)
Control
-
Yoshiro FUKUI, Hisakazu NAKAMURA, Hirokazu NISHITANI2011 Volume 47 Issue 2 Pages 90-99
Published: 2011
Released on J-STAGE: December 19, 2011
JOURNAL FREE ACCESSThis paper considers a real-time obstacle avoidance control problem of a two-wheeled nonholonomic mobile robot. In this research, we propose a discontinuous asymptotic stabilizing state feedback control law for the problem via the minimum projection method. The proposed method does not need path planning. Hence, the computational cost is reduced. Moreover, the method theoretically guarantees the asymptotic stability of the system. Owing to these advantages, we can redesign the control law in real-time depending on the location and the size of the obstacle. Therefore, the method can be used as a control law for searching unknown space. The effectiveness of the method is confirmed by experiments using a two-wheeled mobile robot, Khepera 2.View full abstractDownload PDF (1600K) -
Kazunori SAKURAMA, Kazushi NAKANO2011 Volume 47 Issue 2 Pages 100-109
Published: 2011
Released on J-STAGE: December 19, 2011
JOURNAL FREE ACCESSThis paper deals with consensus problems of networked multi-agent systems with non-uniform and asymmetric time-delays. It has been known that multi-agent systems without time-delays achieve average-consensus, which means that all the states of agents converge to the average of their initial states. However, our target systems do not necessarily achieve average-consensus because of the non-uniform and asymmetric time-delays on the networks. The goal of this paper is to derive the necessary and sufficient condition of the network structures under which these systems achieve average-consensus. First, we derive a conservative quantity and calculate a consensus value, which all the agents converge to. We show that the consensus value depends not only on the structures of the time-delay networks and the initial states of the agents, but also on the initial functions, which define the initial conditions for the time-delay systems. Then, the necessary and sufficient condition for average-consensus is derived, which is represented by the eigenvectors of the delay-transition and the delay-weight Laplacians. These Laplacians are newly introduced in this paper to express the structures of the time-delay networks. Finally, the validity of the analysis results are demonstrated by simulations with six-agent systems.View full abstractDownload PDF (609K) -
Mitsunori UEMURA, Sadao KAWAMURA2011 Volume 47 Issue 2 Pages 110-118
Published: 2011
Released on J-STAGE: December 19, 2011
JOURNAL FREE ACCESSThis paper investigates a new motion control method of multi-joint robots utilizing stiffness adjustment of mechanical elastic elements for the purpose of energy saving. This control method is designed to realize a condition similar to resonance of linear systems by the stiffness adjustment, even though the controlled systems have nonlinear dynamics and multi degree-of-freedom. The control method has two control objectives. One is to realize trajectory tracking control. The other is to reduce actuator torque as much as possible by the stiffness adjustment. This controller does not require exact parameter values of the controlled systems. Some fundamental parts of stability analysis and an energy saving effect are discussed mathematically. Some simulation results demonstrate the effectiveness of the proposed control method.View full abstractDownload PDF (716K)
System and Information
-
Mitsuru TERAWAKI, Zu SOH, Akira HIRANO, Toshio TSUJI2011 Volume 47 Issue 2 Pages 119-125
Published: 2011
Released on J-STAGE: December 19, 2011
JOURNAL FREE ACCESSAlthough the quality of tap water is generally examined using chemical assay, this method cannot be used for examination in real time. Against such a background, the technique of fish bioassay has attracted attention as an approach that enables constant monitoring of aquatic contamination. The respiratory rhythms of fish are considered an efficient indicator for the ongoing assessment of water quality, since they are sensitive to chemicals and can be indirectly measured from bioelectric signals generated by breathing. In order to judge aquatic contamination accurately, it is necessary to measure bioelectric signals from fish swimming freely as well as to stably discriminate measured signals, which vary between individuals. However, no bioassay system meeting the above requirements has yet been established. This paper proposes a bioassay system using bioelectric signals generated from small fish in free-swimming conditions. The system records signals using multiple electrodes to cover the extensive measurement range required in a free-swimming environment, and automatically discriminates changes in water quality from signal frequency components. This discrimination is achieved through an ensemble classification method using probability neural networks to solve the problem of differences between individual fish. The paper also reports on the results of related validation experiments, which showed that the proposed system was able to stably discriminate between water conditions before and after bleach exposure.View full abstractDownload PDF (1746K) -
Hiroshi OKAJIMA, Kenji SAWADA, Nobutomo MATSUNAGA2011 Volume 47 Issue 2 Pages 126-133
Published: 2011
Released on J-STAGE: December 19, 2011
JOURNAL FREE ACCESSThis paper proposes a design method of the dynamic quantizer for the networked control systems. In the networked control systems, the data size of the signals is limited because of the transmission rate of the communication channel. It is well known that feedback type dynamic quantizers such as Delta/Sigma modulator are effective for quantization of data series. The dynamic quantizer includes a set of the dynamic filter and the static quantizer. Many methods have been proposed to design the dynamic filter. However, the static quantizer part has not been designed although the quantization level number of the static quantizer has an effect on the data size. The simultaneous design of dynamic filter and the quantization level will be important issue to satisfy the given communication rate. In this paper, the integrated design method of the filter and the static quantizer is proposed based on the communication rate constraints. The proposed method is derived based on the invariant set analysis with LMIs. The effectiveness is shown by numerical examples.View full abstractDownload PDF (674K)
System Integration
-
Hitoshi YAMAUCHI, Atsuhiro KOJIMA, Masanao KOEDA2011 Volume 47 Issue 2 Pages 134-139
Published: 2011
Released on J-STAGE: December 19, 2011
JOURNAL FREE ACCESSThe Rescue Robot Contest is one of the robot contests concerning lifesaving in urban disasters. In this contest, loads of rescue dummies simulating disaster victims, and contest progression status are presented to audiences, and team members operating robots. This presentation is important for both robot activity evaluation and production effect. For these purposes, a game management system for Rescue Robot Contest is originally constructed and operated. In this system, a database system is employed as base system. And this system's role is for both recording all data and events, and real-time processing for the presentation. In this paper, design and implementation of the tables and built-in functions of the database which is foundation of this system are presented. For real-time processing, embedded functions and trigger functions are implemented. These functions generate unique latest records into specific tables which stores only latest data for quick access.View full abstractDownload PDF (1705K)
- |<
- <
- 1
- >
- >|