Keijiro Yamamoto

Stand alone wearable power assisting suit - sensing and control systems

A stand alone wearable power assisting suit was developed, which gives nurses the extra muscle they need to lift their patients and avoid back injuries. The suit consists of shoulders, arms, back, waist and legs units to be fitted on the nurses body. The arms, waist and legs have pneumatic rotary actuators driven directly by micro air pumps supplied by portable Ni-Cd batteries. The muscle forces are sensed by a new muscle hardness sensor utilizing a sensing tip mounted on a force sensing film device. The embedded microcomputer calculates the necessary joint torque for maintaining a position according to the equations derived from static body mechanics using the joint angles, and the necessary joint torque is combined with the output signals of the muscle sensors to make control signals. The suit was applied practically to a human body and movement experiments that weights in the arms were held and take up and down was performed. Each unit of the suit could transmit assisting torque directly to each joint verifying its practicability.

Self-sustained Oscillation Phenomena of Fluidic Flowmeters

In order to clarify the metering characteristics of the fluidic flowmeters employing selfsustained oscillation, the oscillating jets in a feedback oscillator and a target oscillator were visualized and the differential pressures across the jets were measured.The experiment clarified that the fluidic oscillators could be classified into three types, i.e., feedback type, reflection type and recirculation type oscillators. The jet oscillation was caused by external feedback control pressures in the feedback type oscillator. On the other hand, the internal feedback pressure difference, produced mainly by a partly reflected jet flow from the target, sustains the jet’s oscillation in the reflection type oscillator. In the recirculation type oscillator, the jet oscillation was caused by the internal feedback pressure difference produced by a jet flow recirculating along the side wall of the target oscillator under the influence of the reflected jet flow.The jet oscillation of the target oscillator was influenced by forced pulsation of the jet flow as follows. The strength of the reversed jet flow and reflected jet flow was affected directly with the pulsation of the jet and a synchronization phenomenon appeared, in which the oscillation frequency was matched with the pulsation frequency of the jet flow.The ranges of dimensional parameters maintaining the oscillation of the target oscillator were revealed. It was found that the target oscillator with crescent target could produce steady oscillation in a wider region of dimensional parameters.

Relation between Sensory Evaluation of the Grasping Cylinder with Lifting Hand and the Arch of Hand.

In order to realize the grasping mechanism of hand which grasps cylinder with lifting hand, the relationships between the optimum diameter of grasping cylinder and arches formed by fingers and palm was investigated. The optimum grasping diameter of the lifting hand was approximately 30 mm at no weighted condition, the diameter increase with increasing the lifting weight of pipes, then saturated about 40 mm at 30 N. It was found that the arches formed by a palm-forc fingers except for a thumb was more closely connected with the optimum grasping diameter than the arches formed by a thumb-a forefinger. From these results, in view of the arch formation, the grasping mechanism with lifting hand and its weight dependence was discussed.

Relationship Between Handle Size of Milling Machine and Comfortableness to Handle Operation.

In order to clarify the relationship between handle size of milling machine and comfortableness to handle operation, sensory evaluation test and the measurement of cutting force and contact pattern between hand and handle have been performed. It was proved that the handles of larger sizes were evaluated as more comfortable, the subjects operating large handle with both hands could operate with large cutting force and short operation time, and the subjects operating handle with one hand could not rotate continuously the handle. It was thought that the comfortableness to handle operation depends on the large contact area between hand and handle and small load on hand.