Hiroaki Kuno

Development of String Type Flexible Displacement Sensor to Measure the Movement of Robot and Human Body

An importance of wearable devices in the field of medical treatment such as nursing care and rehabilitation has been strongly recognized. Also, the development of the power assisted device has been done to support the nursing care work for the elderly. The purpose of our study is to develop a flexible displacement sensor and bending sensor which can measure the movement of human body, flexible actuator or flexible joint of the robot by mounting on the surface of them. The developed string type flexible displacement sensor (FDS for short) consists of two fixed electrodes, a slide electrode and a nylon string coated with carbon (NSCC for short). It works as a flexible potentiometer by sliding the slide electrode along NSCC. We confirmed that the proposed sensor worked well by carrying out the position control of a McKibben artificial muscle with the tested sensor. We also proposed the flexible bending sensor that can measure the bending angle for various bending directions such as the movement of flexible joint of robot. The sensor consists of four tested FDSs, a coil spring and two plastic covers. The NSCCs are installed through the coil spring. We investigated the relation between bending angle and output voltages from four FDSs both experimentally and theoretically. As a result, we confirmed that the proposed sensor can work well and the proposed analytical model can predict well the bending angle and bending direction.

Characteristic activities of lower limbs with body weight support ratio

In this study, we investigated a lower limbs muscle activity during body weight support treadmill training (BWSTT). Informed consent was obtained from 16 healthy men. Experimental system consists of force plate, treadmill, three-dimensional motion analysis system, electromyograph, and body weight support device. Body weight support (BWS) was set every 15% increase from 0% to 45%. Walking speed was 4.17km/h. The measurement data were reaction forces, joint angles, joint moments and lower limbs muscle activities. The vertical reaction force shows two peaks. Two peaks decreased with increase of BWS together. Joint angles did not show significant changes with BWS. However, only the extension of hip angle was decreased with BWS. The peaks of joint moment were decreased. Decrease of ankle joint moment was greatest compared with other moment. Decrease of peaks of muscle activity by BWS was observed during stance phase, and did not almost change during swing phase.

A pilot study of the stability of the ankle joint moment and M-wave evoked by intermittent stimulation

We examined the stability of the ankle joint moment (AM) and M-wave amplitude evoked by electrical stimulation of the gastrocnemius and soleus muscle. The use of functional electrical stimulation (FES) is associated with some problems, including the fact that the muscle activity evoked by electrical stimulation decreases with muscle fatigue. Also, when electrical stimulation is delivered via surface electrodes, the stimulation reaching the muscle can vary according to the impedance between the electrode and the skin. In this paper, we performed experiments to (1) examine the relation between AM and stimulation intensity and between M-wave amplitude and stimulation intensity; (2) determine the change in this relation over a long duration; and (3) identify a strategy to allow the muscle to recover from fatigue. In the first experiment, M-wave amplitude and AM changed similarly with respect to the stimulation voltage. In the second experiment, the pattern of the M-wave and AM both showed downward. The pattern, however, was not similar at the soleus. In the third experiment, M-wave and AM remained almost constant compared with fatigued response in the second experiment. We showed that it is possible to generate a stable AM using electrical stimulation of the muscle. To ensure the stability of AM, it is necessary to consider the characteristics of the muscle (e.g., the proportion of fast and slow twitch fibers), the stimulation area, and the state of the muscles (e.g., fatigue).