The purpose of this study is to develop a prosthetic ankle joint intelligently controlled by specially designed linear MR (Magneto-Rheological) brake. MR fluid changes its rheology depending on the intension of an applied magnetic field. The brake using MR fluid (we call it MR brake) has a simple structure and can control its braking force with a low voltage. Prosthesis users often tumble because they don't have dorsiflexor , so that we propose putting MR brake taking the place of dorsiflexion. We hope that prosthesis users can walk more naturally and smoothly by use of developed intelligent prosthetic ankle joint with MR brake. We developed a prototype of it and evaluated it with walking experiments before. But there were some problems with the prototype in terms of hardware and experimental environments. Therefore we have developed a 2nd prototype of the intelligent prosthetic ankle joint with the MR brake, which was improved considering previous problems, and then we have carried out the walking experimental evaluation of it.

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Force display systems are important in virtual reality and other applications. While conventional force displays are active systems with actuators and as such may become inherently dangerous, passive force displays are effective methods for assuring safety. In this paper, we developed a brake using electrorheological (ER) fluid, and showed a passive force display system using ER brakes with two degrees of freedom. We also discuss basic control experiments of the system.

The progress of a project on the research and development of fundamental technologies for accelerator magnets using high Tc superconductors (HTS) is reported. The aim of the project is to establish technologies for cryo-cooler-cooled HTS accelerator magnets wound with coated conductors. At the first stage of the project, the conceptual design study of accelerators was carried out, and the coils of the HTS magnets which are compatible with these accelerators were designed successfully. The required winding technologies were clarified through designing the coils, and the R&D of winding technologies for coils with three-dimensional shape and those with negative bend are in progress. The influence of the tape magnetization, that is, the shielding current on the wide face of coated conductor, on the field quality of magnets was studied.

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To study the influence of coated-conductor magnetization on the field quality of accelerator magnets, we made a small dipole magnet consisting of four racetrack coils wound with GdBCO coated conductors and measured its magnetic field in liquid nitrogen by using rotating pick-up coils. We focused on the dipole and sextupole components (coefficients) of the magnetic field, which vary with time owing to the decay of the magnetization of the coated conductors. About 50 min (3055 s) after the current was ramped up to 50 A, the dipole coefficient normalized by the design value of the dipole component, i.e., the value calculated with the designed coil shape and the uniform current distribution in the coated conductors, increased by 7.4 × 10 −4 , and the sextupole coefficient normalized by the design value of the dipole component increased by 1.8 × 10 −4 . The magnitudes of the dipole and sextupole components depended on the excitation history of the magnet. Electromagnetic field analyses were carried out to calculate the current distributions in coated conductors, considering their superconducting properties; the dipole and sextupole coefficients were then determined from the calculated current distributions. Although the analyses were based on the two-dimensional approximation of the cross-section of the magnet, the temporal behaviours as well as the hysteretic characteristics of the calculated dipole and sextupole coefficients agree qualitatively with those of the dipole and sextupole coefficients measured in the magnet.

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