• The Journal of Korea Robotics Society
• /
• v.8 no.3
• /
• pp.164-172
• /
• 2013

This paper presents a new concept of a 1-DOF elbow exoskeleton driven by a twisted strings-based actuator. A novel joint actuation mechanism is proposed and its kinematic model is presented along with its experimental evaluation, and guidelines on how to choose the strings suitable for such an exoskeleton are given. We also proposed and experimentally verified a human intention detection method which takes advantage of intrinsic compliance of the mechanism. The study showed that the developed twisted strings-driven elbow exoskeleton is light, compact and have a high payload-to-weight ratio, which suggests that the device can be effectively used in a variety of haptics, teleoperation, and rehabilitation applications.

• The Journal of Korea Robotics Society
• /
• v.14 no.3
• /
• pp.221-227
• /
• 2019

This paper studies an effect of vibration on twisted string actuation inside conduit at high curvature angles. In our previous work. we have mentioned that twisted string actuators can be used to transmit power even at significant curvature angles of the conduit. However, several undesirable effects, namely pull-back, hysteresis, and chattering, were present during actuation due to friction between strings and the internal sheath of the conduit. This paper reports the results of experimental study on effects of vibration on twisted string actuation inside curved conduits. We have demonstrated that applying vibration generated near natural frequency of the system during the stages of twisting and untwisting cycles helped reduce pull-back and hysteresis and increase string contraction. In case when sheath was deflected by $180^{\circ}$ under a constant load of 3 kg, we were able to achieve over 40% decrease in pull-back and 30% decrease in hysteresis, compared with no vibration case.

• Journal of Institute of Control, Robotics and Systems
• /
• v.21 no.6
• /
• pp.524-530
• /
• 2015

Early wearable robotic devices were big, powerful and manipulator-like. Recently, various applications of wearable robotics have shown a greater demand for lower weight and compliancy. One approach to achieve these objectives is the use of novel actuators such as twisted string actuators. These actuator are very light, quiet, mechanically simple and compliant. Therefore, they can drastically decrease the weight and size of robotic systems such as exoskeletons. However, one drawback of this actuator is its nonlinear transmission ratio, which is established as a ratio between the angle of twisting of the strings and their resulting contraction. In this paper, we propose a transmission mechanism with rotational motion as the output incorporating a twisted string actuator (TSA). The designed mechanism allows the linearization of the relationships between the input and output displacements and forces of a TSA. The proposed design has been validated theoretically and through a set of computer simulations. A detailed analysis of the performance of the proposed mechanism is presented in this paper along with a design guideline.

• Journal of Sericultural and Entomological Science
• /
• v.46 no.1
• /
• pp.32-37
• /
• 2004

Gayageum and Geomungo are the traditional stringed music instrument in Korea. These strings are usually made of raw silk. This study was carried out to investigate the optimum condition for silk string producing method using several kind of silk and setting temperature of silk string. If the ply of strings and twisting condition were same, tenacity and elongation of every silk strings were similar, in spite of silk strings prepared by physically different raw silk. On the other hand, in setting treatment of twisted string, it was disclosed that the proper setting temperature of silk strings were 11$0^{\circ}C$ for 20 min.

• The Journal of Korea Robotics Society
• /
• v.19 no.3
• /
• pp.244-253
• /
• 2024

This paper presents a novel stem-cutting device using a twisted string actuation system combined with the cinch bag-typed gripper proposed in previous research. The suggested cutting device was developed to cut the stem of a tomato using two motors. The relationship between contact time and motor angle was mathematically induced, and the contacting time was verified through the experiments. The contact time has decreased as the offset of each pair of strings at the disk increases. The contact time and its deviation were reduced by increasing the radius of the twisted string bundle, and the motor torque to exert an equivalent cutting force was surged at the same time. The proposed cutting mechanism with 16 strands of twisted string bundle and 40 mm of offset can cut the given tomato stems and stalks, exerting up to 132.4 N of cutting force in 4.6 to 6.5seconds.

• Journal of fish pathology
• /
• v.9 no.2
• /
• pp.127-135
• /
• 1996

Acanthochondria spirigera is redescribed based on the specimens recovered from the Lophiomus setigerus in the southern coast of Korea. This parasitic copepoda is distinguished from congeners by the possession of spirally twisted egg-strings. Acanthochondria spirigera(Chondracanthidae, Poecilostomatoida) is the first recorded species from Korea. This parasitic copepod was not found on the fish in May. Relative density and prevalence also decreased from January to May. A. spirigera live symbiotically within the pharyngeal cavity of the L. setigerus, and eat oesophageal mucous string of their hosts. The male of the parasitic copepoda is dwarf, and found on the ventral surface of genital segment of the female.

• Journal of the Korean Society of Costume
• /
• v.67 no.2
• /
• pp.88-100
• /
• 2017

This study is for the textiles of at Sun Am Temple and characteristic of embroidery. Tak Ui was composed of orange body and green upper cover, and had no strings. The body plate was covered with embroidery, with Gauze base, and upper part was appliqued, by cutting dragon pattern, cloud pattern on satin damask. The thread for embroidery was silk floss, silk twisted thread, rapped gold thread, and rapped silk thread. For padding, it was used cotton thread in the part of dragon's scales. It was used satin stitch, outline stitch, split stitch, couching, and counted stitch, etc. as method of embroidery. In particular, it embroidered counted stitch of diamond shape consecutively on the whole of Tak Ui, it does so with counted stitch of same effect of weaving Brocade in the part of cloud. Besides, it is one of the characteristic for couching rapped silk thread. Such lead embroidery is the popular method in the Ming dynasty of China, in the 16~17 century. The design of Tak Ui is dragon, cloud, and wave in the theme. In the center, 'Seong-su-man-nyeon' was placed on the heads of dragon. This is similar to Dragon Robe of Four-petalled medallion patterns, period of Ming dynasty in China. Therefore, it confirmed that Tak Ui was remodeled the embroidered textiles, made for royal robe, originally, with Tak Ui at temple.

• Korean Journal of Heritage: History & Science
• /
• v.54 no.3
• /
• pp.52-67
• /
• 2021

This study is an attempt to explore the roles of and the collaborative relationship between Daheojang and Maedeupjang. Daheojang and Maedeupjang share a similar manufacturing process. However, in modern times, Daheojang totally disappeared, and Maedeupjang was designated as an intangible cultural property. The present study will investigate the role of Daheojang and Maedeupjang based on the literature of the Joseon dynasty. Daheojang were craftsmen who made bands and strings of woven or twisted silk strands. They made mangsu and tassels or made knots to produce magnificent artifacts. Maedeupjang complete all steps of the process, from refining, dyeing, combining threads, daheo, maedeup, to the tassel. Daheojang in the Joseon dynasty was the center of this process. Daheojang belonged to almost all Uigwe because it used items ranging from large uso to cushion straps. Dahoe is a craft with various items and techniques. It has been widely used to produce majestic items like formal dresses, ritual ceremony pieces, and mountings, as well as daily items like jodae, pocket straps, and norigae. Based on the records of Uigwe in the late Joseon dynasty, the study explored the collaborative relationship between Daheojang and Maedeupjang. Sambang, the room where both Daheojang and Maedeupjang belong, was the room to produce the royal chair. The royal chair essentially includes large uso. The large uso is an artifact that ties a knot in a thick circle more than two meters long. While Daheojang made rounded daheo, Maedeupjang made delicate and balanced knots. Also, they produced royal inscriptions together with a royal seal with decorative mangsu and a seal of thick rounded daheo. In order to learn about traditional technology, it is necessary to study the system of the times and social trends. Therefore, the study focused on Daheojang, who were common master craftsmen during the Joseon dynasty but now are not familiar to most people.