A brake in which the magnetorheologic fluid (MRF) is used has a simple structure and good responsibility. Therefore, MR brake is expected to perform a good adaptability for human-coexistence system. Being applied in an ankle-foot orthosis, however, conventional MR brake is too large to fit. Then, in this study we developed a shear-type MR brake with multi layer disks and minute gaps (50 micrometers) to realize compactness and high performance. This paper describes the development of a shear type compact MR brake and a new controllable ankle-foot orthosis with this brake. Furthermore, we design algorithm to control an ankle. We assist gait of a patient by changing a brake force.

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.

Ankle-Foot Orthoses (AFOs) are orthotic devices supporting movements of ankles for disabled people for example hemiplegia, peroneal nerve palsy, etc. In our research, we have developed the intelligently controllable AFO (I-AFO) which can control its ankle torque by using compact Magneto-rheological fluid (MRF) brakes. In this paper, we describe the gait-control tests with I-AFO for a patient of the Guillain-Barre syndrome. The subject has difficulty in his voluntary movement of the peripheral part of the inferior limb, and there are physical limitations on his ankle. By applying the I-AFO, his gait control was improved by the prevention of drop-foot in the swing-phase and the forward promotion in the stance-phase.

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