[in Japanese]

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[in Japanese]

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[in Japanese]

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[in Japanese]

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[in Japanese]

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[in Japanese]

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[in Japanese]

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[in Japanese]

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The maintenance of standing balance requires information on the environment if the environment contains uncertainty. From this point of view, we have proposed a learning scheme for locomotion pattern by use of the information on the ground reaction forces. The motion pattern is represented by the weighted sum of basis functions, where learning corresponds to the determination of their weights. However, there are no discussions on what kind of basis function is effective. In this paper, we select trigonometric function, polynomial function and radial basis function as families of the basis functions, and compared the learning result by computer simulations using each function family. As a result, the effectiveness of the trigonometric functions or radial basis functions is confirmed.

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This study aims to apply passive walking to the biped robot. We examined the stabilization method of a passive walking robot with three dimensional weight shifts in a frontal and a sagittal plane to resemble a human gait. As a result, it was demonstrated that the passive walking was stabilized when both the robotic motions in a frontal plane and in a sagittal plane were synchronized. Then we analytically examined the control method of the quasi-passive walk in an arbitrary environment utilizing the van der Pol equation. Finally, it was determined that the biped quasi-passive walking robot was able to be controlled by periodic input generated by an oscillator.

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This study examined the safety and accessibility of stairs for elderly people. A motion capture system was used to measure the heel trajectory while descending the stairs. In our earlier study, we found that the heel trajectories tended to become more linear the faster the subjects descended the stairs, so we developed a mathematical model to reflect the linear trajectory. Using this model, we could calculate the K-value, which is the shortest distance between the heel and the stair nosing. The value varied with the dimensions of the stairs, the tread and the rise, and other foot positioning parameters for normal descending and non-normal descending. A negative K-value indicated that the heel trajectory might hit the stair nosing if the subject descended hastily. In this study, it was assumed that such stair dimensions could be dangerous.
As a result, the stair dimensions recommended by “The act on buildings accessible and usable for the elderly and physically disabled” were judged to be safe provided that elderly peopled descended normally. In addition, we considered that the elderly could not descend normally stairs with dimensions of a rise of less than 10 cm and a tread of more than 30 cm, which are used in public places.
The dimensions recommended by the “Guidelines of housing design device to cope with aged society” were judged to be rather dangerous. However it was unsuitable that stair dimensions of our recommendation need more capacity for housing in Japan.

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This study investigated issues related to initial stability after stem fixation. Finite element models of the AI-Hip cementless stem were constructed for computer simulation.
Boundary and initial conditions were (i) Rigid contact of the distal end of the model femur with a rigid base. (ii) Stepping load of 1800 N was applied to the proximal top of the stem. (iii) A load of 1440 N was pulled from the greater trochanter of the femur as muscle force. (iv) Torsion load of 18.9 Nm was applied to the proximal femur as the intra-rotation.
As a result, the relative micromotion of the AI-Hip cementless stem showed a value as low as that for a conventional stem. The calculated von Mises stress was below the level of von Mises stress that would cause destruction of femur and the stem.
Based on the relative micromotion and von Mises stress level, the AI-Hip cementless stem showed initial stability. However, there is a high risk in evaluating stem stability from only a limited element analysis result. This study should be compared with the experimental results obtained from clinical practice.

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Photoplethysmography (PPG) built in a PC mouse was used to determine the cardiovascular responses to emotional and physical stressors. Subjects (N=7) were asked to hold the PPG mouse during mental arithmetic test (mental stress: MSt), Valsalva test and cold pressor test (physical stress: PSt), and recovery period from the exercise (post exercise: pEx). In each protocol, PPG and ECG were simultaneously recorded. Negative peaks in the PPG (N wave) were detected as the R waves in the ECG, and N-N intervals and R-R intervals were measured respectively. As a result, there was a close correlation between the N-N intervals and the R-R intervals (coefficient of determination: R² = 0.962). The amplitude of N wave decreased in MSt and PSt, which to the contrary increased in pEx. These results suggest that the pulse wave is monitored and the vasoconstriction can be determined as a response to the stressors by using of the PPG mouse.

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