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Wonjong Kim - One of the best experts on this subject based on the ideXlab platform.

  • design and control of a compact lightweight planar positioner moving over a concentrated field magnet matrix
    IEEE-ASME Transactions on Mechatronics, 2013
    Co-Authors: Vu Huy Nguyen, Wonjong Kim
    Abstract:

    In this paper, a single-moving-part planar positioner with six coils is designed and implemented. A concentrated-field permanent-magnet matrix is employed as the stationary part. The moving platen has a compact size (185.4 mm × 157.9 mm), light mass (0.64 kg) and low-center-of-gravity. The moving platen carries three planar-motor armatures with two phases per motor. Force calculation is based on the Lorentz force law and conducted by volume integration. In order to deal with the nonlinearity due to trigonometric dependencies in the force-Current Relation, modified proportional-integral-derivative (PID) and lead-and-PI compensators are designed with computed Currents to close the control loop and obtain the desired performances. Experimental results verified the commutation law and the force calculation. The new design with only six coils allows for simplification of the control algorithm and reduced power consumption of the positioner. The maximum travel ranges in x, y, and the rotation about the vertical axis are 15.24 cm, 20.32 cm, and 12.03°, respectively. The positioning resolution in x and y is 8 μm with the rms position noise of 6 μm. The positioning resolution in rotations about the vertical axis is 100 μrad.

  • novel electromagnetic design for a precision planar positioner moving over a superimposed concentrated field magnet matrix
    IEEE Transactions on Energy Conversion, 2012
    Co-Authors: Vu Huy Nguyen, Wonjong Kim
    Abstract:

    This paper presents the electromagnetic design and force calculation of a compact multiaxis precision positioner. A six-coil single-moving-part platen moves over a superimposed concentrated-field permanent-magnet matrix. With a rectangular coil placed in the magnetic field generated by the superimposed concentrated-field magnet matrix, the force acting on the coil is calculated by volume integration based on the Lorentz force law. The distance between the long sides and that between the short sides of a rectangular coil are designed to be a half pitch and one pitch of the magnet matrix, respectively. This allows for the simplification of force generation and calculation, compact size, and light mass (0.64 kg) of the moving platen. Six coils are divided into three two-phase linear-motor armatures with 270° or 450° phase differences. The complete force-Current Relation for the entire platen with the six coils is derived. Experimental results are presented to verify the working principle of the positioner designed in this paper. The positioner can be employed for the stepping and scanning applications that require 3-DOF planar motions with long travel ranges in two horizontal directions and small rotational motions about the vertical axis.

Vu Huy Nguyen - One of the best experts on this subject based on the ideXlab platform.

  • design and control of a compact lightweight planar positioner moving over a concentrated field magnet matrix
    IEEE-ASME Transactions on Mechatronics, 2013
    Co-Authors: Vu Huy Nguyen, Wonjong Kim
    Abstract:

    In this paper, a single-moving-part planar positioner with six coils is designed and implemented. A concentrated-field permanent-magnet matrix is employed as the stationary part. The moving platen has a compact size (185.4 mm × 157.9 mm), light mass (0.64 kg) and low-center-of-gravity. The moving platen carries three planar-motor armatures with two phases per motor. Force calculation is based on the Lorentz force law and conducted by volume integration. In order to deal with the nonlinearity due to trigonometric dependencies in the force-Current Relation, modified proportional-integral-derivative (PID) and lead-and-PI compensators are designed with computed Currents to close the control loop and obtain the desired performances. Experimental results verified the commutation law and the force calculation. The new design with only six coils allows for simplification of the control algorithm and reduced power consumption of the positioner. The maximum travel ranges in x, y, and the rotation about the vertical axis are 15.24 cm, 20.32 cm, and 12.03°, respectively. The positioning resolution in x and y is 8 μm with the rms position noise of 6 μm. The positioning resolution in rotations about the vertical axis is 100 μrad.

  • novel electromagnetic design for a precision planar positioner moving over a superimposed concentrated field magnet matrix
    IEEE Transactions on Energy Conversion, 2012
    Co-Authors: Vu Huy Nguyen, Wonjong Kim
    Abstract:

    This paper presents the electromagnetic design and force calculation of a compact multiaxis precision positioner. A six-coil single-moving-part platen moves over a superimposed concentrated-field permanent-magnet matrix. With a rectangular coil placed in the magnetic field generated by the superimposed concentrated-field magnet matrix, the force acting on the coil is calculated by volume integration based on the Lorentz force law. The distance between the long sides and that between the short sides of a rectangular coil are designed to be a half pitch and one pitch of the magnet matrix, respectively. This allows for the simplification of force generation and calculation, compact size, and light mass (0.64 kg) of the moving platen. Six coils are divided into three two-phase linear-motor armatures with 270° or 450° phase differences. The complete force-Current Relation for the entire platen with the six coils is derived. Experimental results are presented to verify the working principle of the positioner designed in this paper. The positioner can be employed for the stepping and scanning applications that require 3-DOF planar motions with long travel ranges in two horizontal directions and small rotational motions about the vertical axis.

M Sugano - One of the best experts on this subject based on the ideXlab platform.

  • change of the v i curve and critical Current with applied tensile strain due to cracking of filaments in bi2223 composite tape
    Superconductor Science and Technology, 2008
    Co-Authors: J K Shin, S Ochiai, Hiroshi Okuda, M Sugano
    Abstract:

    The critical Current at 77 K of multifilamentary Bi2223 composite tape was studied under applied tensile strain experimentally and analytically. Beyond the irreversible strain, the critical Currents (IC) decreased significantly with increasing applied tensile strain (ec), due to the enhanced cracking of the Bi2223 filaments. The voltage generation in the voltage–Current Relation was calculated by the Current share model in which the transport Current is shared by the Bi2223 filament and Ag near the cracked portion. Then the critical Current was estimated with a 1 µV cm−1 criterion. By the application of the Current share model to the experimental result, the effective crack length responsible for the reduction in critical Current was estimated, with which the change of critical Current could be described satisfactorily as a function of applied strain.

  • tensile damage and its influence on the critical Current of bi2223 ag superconducting composite tape
    Superconductor Science and Technology, 2003
    Co-Authors: S Ochiai, Hiroshi Okuda, M Sugano, T Nagai, Masaki Hojo, Mototsugu Tanaka, Kozo Osamura
    Abstract:

    We have studied the tensile behaviour of Bi2223 superconducting composite tapes at room temperature, and the influence of the tensile damages introduced at room temperature on the critical Current Ic and the n values at 77 K. In the measurement of the Ic and n values, the overall composite with a gauge length 60 mm was divided into six elements with a gauge length of 10 mm in order to find the corRelation of the Ic and n values of the overall composite to those of the local elements which constitute the composite. From the measured stress–strain curve of the composite and the calculated residual strain of the Bi2223 filaments, the intrinsic fracture strain of Bi2223 filaments was estimated to be 0.09–0.12%. When the applied strain was lower than the onset strain of the filament damage, the original Ic and n values were retained both in the overall composite and the elements. In this situation, while the overall voltage at the transition from superconductivity to normal conductivity of the composite was the sum of the voltages of the constituent elements, among all elements the overall voltage was affected more by the element with the lower Ic (higher voltage). The damage of the filaments arose first locally, resulting in a reduction of the Ic and n values in the corresponding local element, even though the other elements retained the original Ic and n values. In this situation, the voltage of the overall composite stemmed dominantly from that of the firstly damaged weakest element, and the overall Ic and n values were almost determined by the values of such an element. After the local element was fully damaged, the damage arose also in other elements, resulting in segmentation of the filaments. Thus, the Ic and n values were reduced in all elements. The corRelation of Ic between the overall composite and the elements could be described comprehensively for non-damaged and damaged states from the voltage–Current Relation.

B. A. Larsen - One of the best experts on this subject based on the ideXlab platform.

  • overlap of the plasmasphere and ring Current Relation to subauroral ionospheric heating
    Journal of Geophysical Research, 2005
    Co-Authors: C Gurgiolo, Bill R. Sandel, D G Mitchell, J.d. Perez, B. A. Larsen
    Abstract:

    [1] The overlap of the ring Current with the outer plasmasphere is thought to play a major role in storm-time related increases in the subauroral ambient topside electron temperature. Instabilities generated within the overlap region, Coulomb collisions of plasmaspheric electrons with the ring Current ions, and charge exchange are all thought to work either individually or together to generate a downward heat flux into the ionosphere to produce the increase in temperature. Analysis of IMAGE two-dimensional ring Current and plasmasphere density maps together with in situ DMSP ambient electron temperature data shows that the heating generally occurs over a small radial extent within the plasmasphere/ring Current overlap region and may be significantly earthward of the plasmapause. This argues against collisional heat conduction as the source of the heat flux and for an instability-based process. The finding that the heating occurs within well-defined ratios of the cold plasmasphere to hot ring Current density strengthens this supposition.

S Ochiai - One of the best experts on this subject based on the ideXlab platform.

  • change of the v i curve and critical Current with applied tensile strain due to cracking of filaments in bi2223 composite tape
    Superconductor Science and Technology, 2008
    Co-Authors: J K Shin, S Ochiai, Hiroshi Okuda, M Sugano
    Abstract:

    The critical Current at 77 K of multifilamentary Bi2223 composite tape was studied under applied tensile strain experimentally and analytically. Beyond the irreversible strain, the critical Currents (IC) decreased significantly with increasing applied tensile strain (ec), due to the enhanced cracking of the Bi2223 filaments. The voltage generation in the voltage–Current Relation was calculated by the Current share model in which the transport Current is shared by the Bi2223 filament and Ag near the cracked portion. Then the critical Current was estimated with a 1 µV cm−1 criterion. By the application of the Current share model to the experimental result, the effective crack length responsible for the reduction in critical Current was estimated, with which the change of critical Current could be described satisfactorily as a function of applied strain.

  • tensile damage and its influence on the critical Current of bi2223 ag superconducting composite tape
    Superconductor Science and Technology, 2003
    Co-Authors: S Ochiai, Hiroshi Okuda, M Sugano, T Nagai, Masaki Hojo, Mototsugu Tanaka, Kozo Osamura
    Abstract:

    We have studied the tensile behaviour of Bi2223 superconducting composite tapes at room temperature, and the influence of the tensile damages introduced at room temperature on the critical Current Ic and the n values at 77 K. In the measurement of the Ic and n values, the overall composite with a gauge length 60 mm was divided into six elements with a gauge length of 10 mm in order to find the corRelation of the Ic and n values of the overall composite to those of the local elements which constitute the composite. From the measured stress–strain curve of the composite and the calculated residual strain of the Bi2223 filaments, the intrinsic fracture strain of Bi2223 filaments was estimated to be 0.09–0.12%. When the applied strain was lower than the onset strain of the filament damage, the original Ic and n values were retained both in the overall composite and the elements. In this situation, while the overall voltage at the transition from superconductivity to normal conductivity of the composite was the sum of the voltages of the constituent elements, among all elements the overall voltage was affected more by the element with the lower Ic (higher voltage). The damage of the filaments arose first locally, resulting in a reduction of the Ic and n values in the corresponding local element, even though the other elements retained the original Ic and n values. In this situation, the voltage of the overall composite stemmed dominantly from that of the firstly damaged weakest element, and the overall Ic and n values were almost determined by the values of such an element. After the local element was fully damaged, the damage arose also in other elements, resulting in segmentation of the filaments. Thus, the Ic and n values were reduced in all elements. The corRelation of Ic between the overall composite and the elements could be described comprehensively for non-damaged and damaged states from the voltage–Current Relation.