Kazuhito Hyodo

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.

Design of tendon-driven mechanisms for fault tolerance from tendon-breaking by using centroid vectors

Tendon-driven mechanisms (TDMs) are mechanisms driven by more tendons than joints. This tendon redundancy is often used for changing the hardware compliance. In contrast, in this paper, the redundancy is used for coping with unexpected tendon breaking. We analyze kinematics of a class of TDMs with asymmetrically spanned tendons and modify it to design a TDM that preserves the controllability even if at least one of the tendons is broken. We validate the proposed method to design several TDMs.