We proposed and have been studying a multiple-dof leg rehabilitation system which employs a wire-driven mechanism. Using a parallel wire mechanism, multiple-dof motion can be achieved with relatively low powered actuators compared with the mechanisms that use conventional rigid links. Also, since wire-driven mechanisms are light and flexible, it makes the system human-friendly. Our eventual goal is to develop a rehabilitation system that carries out 6-dof motions of hip, knee and ankle joint. In order to achieve this goal, we are taking a gradual approach. In this paper, we describe a 2-dof experimental system which we designed and built. Target motions of the 2-dof system are flexion/extension of both hip and knee joints. We also mention a 4-dof experimental system which was built by extending degrees of freedom of the system. Target motions of the system are hip joint flexion/extension, hip joint abduction/adduction. hip joint external/internal rotation, and knee joint flexion/extension. Experiments showed that the multiple-dof joint exercise can be carried out using the proposed system.

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Venous blood oxygen saturation in tissues is important to estimate tissue metabolisms. In the present study, noninvasive method to measure venous blood oxygen saturation in tissues was developed using a near-infrared-light absorption technique. A sensor of reflection type consisted of an optical fiber(connected to two light-emitting diodes)and three photo diodes. Light absorption signals were obtained from the sensor with and without loading of a 100g-weight at the hill of thumb in five healthy subjects. When the venous blood oxygen saturation in tissues was calculated on the basis of the differences in the absorption signals, the venous blood oxygen saturations in tissues obtained from the present method were well correlated with those obtained from blood samples at the cubital vein.

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