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ABSTRACT: Since communication time delay is a serious problem for bilateral control systems, a great number of researches about delay compensation in bilateral teleoperation with time delay have been studied so far. Some of delay compensators are designed to eliminate phase lag of feedback control and applicable to 4ch-controllers. However, the desired results are not always obtained, even though those compensators are applied to the conventional bilateral 4ch-controller with time delay. This is because these compensators do not take force controllers into account. This paper presents a bilateral 4ch-controller that delay compensators are applied to by considering the force controllers. The proposed controller is designed to control both position and force of a master robot and a slave robot by using only 2 degrees of freedom (DOF). One DOF is utilized for position control, and the other is utilized for force control. Therefore, the position controller and the force controller are shared by the master and slave robots. If delay compensators are applied to the proposed bilateral controller, position and force responses of the master robot correspond with those values of the slave robot, respectively. The validity of the proposed method is verified by simulation and experimental results.
Industrial Technology, 2006. ICIT 2006. IEEE International Conference on; 01/2007
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ABSTRACT: Perpendicular recording media noise is investigated with a microstructure model based upon magnetic clustering for irregular magnetization transitions. This model uses cylinders to account for the distribution of cluster diameters. Quantitative comparisons between experiments and calculations indicate that the cluster-size distribution of media can be estimated from the read/write properties. Estimates show that the cluster-size deviation of perpendicular recording media is somewhat larger than that of longitudinal recording media. Because calculations show that transition jitter depends strongly on the cluster-size distribution, reduction of the cluster-size deviation, as well as reducing the average cluster size, can significantly improve the signal-to-noise ratio of perpendicular recording media.
IEEE Transactions on Magnetics 08/2004; · 1.36 Impact Factor
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ABSTRACT: In perpendicular magnetic recording, the transition position jitter σ<sub>j</sub> is a dominant source of medium noise. The transition width πa influences isolated pulsewidth. The influence of these parameters on error rate performance at an areal density of 200 Gb/in<sup>2</sup> is studied using a software channel for the perpendicular response. The dependence of the calculated bit-error rate (BER) on the parameters is explicitly shown. The results indicate that the transition jitter strongly restricts the BER, unless the pulsewidth is small enough. However, for larger pulsewidth, it remarkably deteriorates BER. Under typical conditions, the pulsewidth T<sub>50</sub> and the transition jitter σ<sub>j</sub>, should be less than 26 and 1.6 nm, respectively for 200 Gb/in<sup>2</sup>.
IEEE Transactions on Magnetics 08/2004; · 1.36 Impact Factor
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ABSTRACT: Iron sulfide (FeS) particles produced by sulfate-reducing bacteria are an excellent adsorbent for heavy metal ions. To select the bacteria which produce a magnetic FeS as an adsorbent for the high gradient magnetic separation, an open gradient magnetic separator operating at a 10 Tesla magnetic field was used. Magnetization study showed that the magnetic FeS particles consist of paramagnetic like and ferro-magnetic component.
IEEE Transactions on Appiled Superconductivity 07/2004; · 1.04 Impact Factor
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ABSTRACT: We successfully fabricated channel waveguides utilizing photonic crystal (PhC) dispersion having a very low loss of ∼0.1 dB/mm by the autocloning method. We achieved the loss reduction by improving the fabrication condition and adjusting the core width. The result of propagation loss can be regarded as a "milestone," and it enables us to realize practical PhC circuits that contain functional components such as chromatic dispersion equalizers and high Q wavelength filters.
IEEE Photonics Technology Letters 05/2004; · 2.19 Impact Factor
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ABSTRACT: A review of the current status of ultralow-loss channel waveguides, guided-wave functional elements, and surface-normal type free-space optical components, all of which consisting of heterostructured photonic crystals, are discussed.
Lasers and Electro-Optics, 2003. CLEO/Pacific Rim 2003. The 5th Pacific Rim Conference on; 01/2004
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ABSTRACT: A heterostructured photonic-crystal functional chip consisting of a resonator and waveguides is fabricated by a simple "autocloning" process. First, we prepare a substrate with different corrugation patterns by electron beam lithography and dry etching, and Ta/sub 2/O/sub 5/-SiO/sub 2/ multilayers are successively formed upon the substrate. An in-line resonator is fabricated and characterized by fiber-in-fiber-out measurement, and a resonance peak with Q=270 is demonstrated. The future outlook for the technology is also discussed.
IEEE Photonics Technology Letters 07/2003; · 2.19 Impact Factor
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ABSTRACT: We describe the fabrication and evaluation of a low-loss, high-delta optical waveguide consisting of heterostructured photonic crystals. The waveguide is composed of a multilayer stack of Ta2O5/SiO2 and is prepared by use of the autocloning technique. Light is guided in the waveguide by the difference in the effective refractive indices of the constituent photonic crystals. By improving the design of the core region so that is has a flat multilayer structure, we achieve delta = 3.09% for the in-plane direction and net propagation loss of 0.56 dB/mm at lambda = 1.6 microm. Experiments also suggest that the bending loss of the waveguide can be reduced to less than 0.1 dB if the curvature radius is larger than 700 microm.
Optics Letters 06/2003; 28(9):734-6. · 3.40 Impact Factor
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ABSTRACT: We investigate the characteristics of in-plane light propagation
in 2-D photonic crystals fabricated by the autocloning method, by which
multiple layers are stacked while preserving periodic surface
corrugation. A numerical analysis shows that
Ta<sub>2</sub>O<sub>5</sub>/SiO<sub>2</sub> autocloned photonic crystals
are applicable to waveguides and lenses since a sufficient amount of
change of the effective refractive index is obtained by adjusting the
aspect ratio of the unit structure. It is also shown that the crystals
have a wide bandgap applicable to Bragg reflectors and resonators.
Experimental results reveal that in-plane propagation losses for the two
directions are less than 1.4 dB/mm at λ=1.55 μm, showing the
crystals are useful for low loss in-plane devices
IEEE Journal of Quantum Electronics 08/2002; · 1.88 Impact Factor
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ABSTRACT: We present novel optical circuits consisting of low-loss photonic crystal butt-jointable to/from fibers (Fiber-to-fiber loss of 4.6 dB over a waveguide 3 mm long). To show its versatility, we demonstrate an in-line resonator with Q = 270
Optical Communication, 2002. ECOC 2002. 28th European Conference on; 02/2002
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ABSTRACT: Summary form only given The realization of perpendicular magnetic recording critically depends on the reduction of medium noise. The CGC media structure with a continuous layer and a granular layer is a candidate for attaining high SNR. The noise characterization of the CGC double-layered media is described by focusing on the transition jitter and magnetization transition analysis using an MFM. CGC media with three different thickness (1.2, 3.6, 6 nm) of the Co/Pt continuous layer were used in this study. All of them had the same 15 nm granular layer. The plain granular medium was chosen as a reference. A single-pole head was used for writing.
Magnetics Conference, 2002. INTERMAG Europe 2002. Digest of Technical Papers. 2002 IEEE International; 02/2002
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ABSTRACT: We fabricate photonic crystals for the visible range by the autocloning technique, in which multilayers are stacked by an appropriate combination of sputter deposition and sputter etching. TiO2/SiO2 and Ta2O5/SiO2 are chosen as materials since they are transparent in the range and give a high contrast of refractive indices. The fabrication technique has flexibility regarding materials and size and is very reliable and reproducible even if the pitch is less than 0.2 m. We also study the application of photonic crystals to birefringent elements such as waveplates and polarization selective gratings and experimentally verify that they are useful for optical pick-up systems.
Optical and Quantum Electronics 12/2001; 34(1):63-70. · 0.82 Impact Factor
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ABSTRACT: Summary form only given. A photonic crystal is an artificial multidimensional periodic structure composed of two kinds of material. It is characterized by the following optical properties: bandgaps, high dispersion in pass bands, and anisotropy in the band structure. The paper reports on the fabrication of photonic crystals for the visible range and their applications for optical pick ups by utilizing their anisotropy.
Quantum Electronics and Laser Science Conference, 2000. (QELS 2000). Technical Digest; 06/2000
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ABSTRACT: The digitization of audio signals for video tape recorder has been studied, and a prototype VTR providing digital audio sounds has been developed. Depth recording technique has been adopted for digital audio recording to avoid interference between audio and video signals. Using Offset-QPSK modulation, a symbol error rate of less than 10<sup>-6</sup>is attained at a transmission rate of 2.6 Mbps. A newly developed digital signal processing circuit has also been employed to record audio signals having asynchronous sampling frequency with video signals. With this VTR, digital dubbing from various audio sources such as the DBS system and CD player can be performed.
Acoustics, Speech, and Signal Processing, IEEE International Conference on ICASSP '86.; 05/1986
