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Volume 50, Issue 10
Displaying 1-7 of 7 articles from this issue
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Paper
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Takao NISHI, Ryuichi TAKASE, Takashi YOSHIMI, Yoshihiro KAWAI, Fumiaki ...2014 Volume 50 Issue 10 Pages 693-702
Published: 2014
Released on J-STAGE: October 18, 2014
JOURNAL FREE ACCESSOne of the most significant and classic problems on area-based stereo vision is mismatching caused by photometric variations in the stereo images. Some approaches to the problem have applied spatial filters to images to decrease the variations in success to some extent with special scenes. These methods, however, could not solve an issue where local photometric variations are on objects with various directed surfaces (e.g., a fish scale). Accordingly, we propose the area-based stereo correspondence method with the spatial filter named “Standardized Coefficient Filter” (SC Filter) for that issue, and analyze the filter qualitatively. SC Filter is a kind of high-emphasis filter based on statistical analysis. This filter has two characteristics in amplifying high frequency components; 1) in direct proportional to mean curvature of low frequency components in a window, 2) in inversely proportional to absolute value of mean gradient of low frequency components in a window. In this paper, we show that SC Filter keeps stable output in the case of wave length of low frequency components varied, notwithstanding that LoG and zero-mean filter outputs varied. And we describe that the area-based stereo correspondence method with SC Filter is able to solve the issue where local photometric variations are on objects with various directed surfaces, too.View full abstractDownload PDF (3876K) -
Hidenobu ICHIKAWA, Takahiro TSUKAHARA, Kaoru IWAMOTO, Yasuo KAWAGUCHI2014 Volume 50 Issue 10 Pages 703-711
Published: 2014
Released on J-STAGE: October 18, 2014
JOURNAL FREE ACCESSIn the context of the practical significance of flow-rate control as required in semiconductor manufacturing, the ultrasonic vortex flowmeter has been increasingly used in processing equipment. However, there still remains an issue related to the measurement of gas-liquid two-phase flows which are associated with chemical and biomedical engineering using ultrasonic vortex flowmeters. In this research, a visualization study using a high-speed camera was performed to examine the bubble behaviors behind a vortex shedder. Based on the visualization and the signal analysis, we determined the measurement limit of the liquid velocity for flows accompanied by bubbles, as a function of the void fraction. The high-speed tracking of bubbles revealed that most bubbles were gathered in the shedding Kármán vortices and formed into clusters, which should affect the ultrasonic wave transmitted across the pipe flow. We draw the following three major conclusions: (i), a low-frequency noise in the obtained signal was due to the interception of the ultrasonic wave by large bubble clusters deviating from the Kármán vortex; (ii), a high-frequency noise was induced by small bubbles; and (iii), the doubled frequency of the Kármán vortex array was caused by amplitude modulation by bubbles gathered into the Kármán vortex.View full abstractDownload PDF (1790K) -
Kenji KASHIMA, Daisuke INOUE2014 Volume 50 Issue 10 Pages 712-720
Published: 2014
Released on J-STAGE: October 18, 2014
JOURNAL FREE ACCESSIn natural world, there are many systems that utilize stochasticity to improve its robustness and performance. The aim of this paper is to show that such stochasticity can be utilized for multiple purposes simultaneously in networked control systems. To this end, we investigate the double role of randomizing effect and non-reproducibility that can enhance signal precision and control system security, respectively. In addition to numerical demonstration, we propose a method to evaluate the effectiveness based on invariant probability measure analysis.View full abstractDownload PDF (832K) -
Kenji NAGASE, Norio KIKUCHI2014 Volume 50 Issue 10 Pages 721-730
Published: 2014
Released on J-STAGE: October 18, 2014
JOURNAL FREE ACCESSThis paper proposes a new feedback control design methodology for multi-fingered robot hands applicable to multiple contact situations. We derive a general expression of the system motion valid for both the contact and non-contact situations, and design a linearizing compensator based on this expression. The compensator has inputs to control relative motion and constrained force. We show that we can control either of these variables if we set the input for the other variable zero, according to the current contact situation. The method can be applied to redundant manipulation systems, which we will call partially constrained systems, where the number of control inputs is greater than the number of constraints in the contact situation. As a design example for such systems, a catching/releasing task by a hand-arm robot system is provided.View full abstractDownload PDF (2207K) -
—Center-stable Manifold Approach—Kazuo ISHIKAWA, Noboru SAKAMOTO2014 Volume 50 Issue 10 Pages 731-738
Published: 2014
Released on J-STAGE: October 18, 2014
JOURNAL FREE ACCESSThis paper proposes a framework for optimal control of mechanical systems possessing conserved quantities such as control moment gyros (CMGs). It will be shown that output regulation theory is appropriate to handle such constraints and that the center-stable manifold method for solving the associated Hamilton-Jacobi equation is effective for computing the optimal feedback control. With this framework, it is possible to design robust and high performance controller for CMGs. Simulations show the effectiveness of the proposed method.View full abstractDownload PDF (819K) -
Yuichi TAKAKU, Takashi KIDA2014 Volume 50 Issue 10 Pages 739-745
Published: 2014
Released on J-STAGE: October 18, 2014
JOURNAL FREE ACCESSThe stability of linear time invariant mechanical systems described with second-order matrix differential equations has been well studied and design methods for static output feedback control have been proposed based only on sign-definiteness of closed-loop coefficient matrices. This paper extends the approach to more general class of time varying mechanical systems. For the purpose, we first derive the closed-loop stability and optimality conditions. We then propose a design method of scheduled optimal static output feedback gain matrices by solving a finite number of linear matrix inequalities. In order to verify the efficiency, some numerical studies are performed. Finally, by specifying the results to linear time invariant systems, we discuss their effectiveness compared with existing approaches.View full abstractDownload PDF (934K) -
—Applying to Model Predictive Parking Control—Kentaro OYAMA, Kazuma SEKIGUCHI, Kenichiro NONAKA2014 Volume 50 Issue 10 Pages 746-754
Published: 2014
Released on J-STAGE: October 18, 2014
JOURNAL FREE ACCESSIn this paper, we propose a path-following control for front-steering vehicles based on time-state control form (TSCF) using travel distance as a virtual time-axis. The technique of TSCF can transform the nonlinear dynamics of front-steering vehicles into two linear subsystems. The proposed method uses a travel distance as a virtual time-axis based on geometric relationship between controlled vehicle and reference path. This method can realize path-following control independent of vehicle heading angle. In addition, we utilize the proposed method in model predictive parking control considering the constraints of vehicle steering angle, travel range and singular point. This method can realize parking control in the area larger than the conventional method. The performance of proposed method is verified through numerical simulations and experiments with a one-tenth scale model car.View full abstractDownload PDF (1380K)
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