Manabu Okui

Semi-endoskeleton-type waist assist AB-wear suit equipped with compressive force reduction mechanism

In recent years in Japan, over half of all workers suffered from lower back pain. This has become a social problem that needs to be addressed. To reduce its occurrence, we developed a flexible, high-output waist assist suit called “AB-Wear” in a previous study. The AB-Wear suit can assist human motion and reduce muscular fatigue of the waist. However, the assistive forces of the device generate compressive forces on the backbone, which have adverse effects on the body. Hence, in this study, we propose an exoskeleton-type AB-Wear equipped with a compressive force reduction mechanism, called “semi-endoskeleton-type AB-Wear”. This device has a reduction mechanism similar to a flexible flat spring behind the upper body. Because of this structure, this device can generate an effective assistive force. First, we explain the difference between the semi-endoskeleton-type AB-Wear and the previous device. Then, we model the semi-endoskeleton-type AB-Wear because the model is used for its operation. Moreover, its effectiveness is confirmed using musculoskeletal simulation. Finally it is evaluated by measuring surface electromyography (EMG) on a subjects body to confirm its effectiveness with a real body. The EMGs of the wearer with and without the suit are compared. The usefulness of the AB-Wear is confirmed by simulation and experiment.

The verification of permissible resistant torque considering back-drivability to develop a wearable assist suit

In this paper, permissible resistant torque considering back-drivability is verified to develop a wearable assist suit (WAS). The WAS has a clutch and a variable viscoelasticity joint. In this paper, permissible resistant torque is defined as torque that is acceptable in daily use. As first stage of the WAS development, the paper discusses the relationship between the resistant torque to the knee and the degree of discomfort experienced by the wearer as evaluated through a survey questionnaire experiment. In addition, the influence of the resistant torque on a muscle of the knee extension is considered and confirmed by measuring surface electromyography (surface-EMG).

Aspect ratio consideration and material development for prolonging the lifetime of the straight-fiber-type pneumatic rubber artificial muscle

A pneumatic artificial muscle is a rubber actuator activated by air pressure. It is lightweight and has the high power density compared to other actuators such as motors and fluid powered cylinders. In addition, it can provide high compatibility with human since its flexibility. Authors have developed the Straight-fiber-type pneumatic artificial muscle which has high output and high contraction amount compared to the McKibben type artificial muscle that is widely used. However, the lifetime of the Straight-fiber-type pneumatic artificial muscle has not been considered so far. In this paper, effects of aspect ratio and materials on the lifetime of the artificial muscle are examined for prolonging the lifetime. Firstly, the desirable maximum stretch rate of the material is developed. Secondly, fatigue life is measured by reducing the elongation of the rubber material by changing the aspect ratio of length and inner diameter in the SF-ARM. Finally we measure the influence on the output characteristics by changing aspect ratio. The result shows relationship of the lifetime and the aspect ratio of the artificial muscle. We showed that the artificial muscle’s lifetime and contraction characteristics can be selected according to the application. 1. 緒 言 ソフトアクチュエータは従来のモータや油圧シリンダなどのアクチュエータと異なり構造的な柔軟さを有して おり,身体装着型装置などへの応用が期待されている.現在までに様々な素材や駆動原理を用いたソフトアクチ ュエータが研究されているが(CMC 出版,2017),(山野他,2009),(Lima et al., 2012),(Polygerinos et al., 2015), その中でも空気圧ゴム人工筋肉は,すでに製品化された例がある(Wakimoto et al., 2011),(Tondu et al., 2000), (FESTO,参照日 2017 年 11 月 23 日)など,その出力密度の高さや安定した動作から,最も実用的なソフトア クチュエータの一つである.空気圧ゴム人工筋肉は,ゴム等の弾性構造体に空気等の作動流体を注入して動力を 得るアクチュエータである.出力として収縮が得られ,柔軟であるという特徴から,人間との協調性の高いアク チュエータとして注目されている(則次,高,2005),(只野他,2012),(Okui et al., 2016),(Iikawa et al., 2016). 現在,広く利用されている空気圧ゴム人工筋肉としてMcKibben 型人工筋肉(以下McKibben 型)が挙げられる. これは,ゴムチューブが繊維コードで覆われた構造であり,このゴムチューブに空気圧を印加することで膨張し て,繊維コードを押し広げる.その際,繊維コードの編み込み角度が変わり,軸方向へ収縮する特性を有する. 1 No.17-00299 [DOI:10.1299/transjsme.17-00299], J-STAGE Advance Publication date : 27 December, 2017 *1 正員,中央大学 研究開発機構(〒112-8551 東京都文京区春日 1-13-27) *2 正員,中央大学 理工学部 精密機械工学科 E-mail of corresponding author: a_kojima@bio.mech.chuo-u.ac.jp