• Journal of the Korean Society of Manufacturing Process Engineers
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• v.17 no.2
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• pp.109-117
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• 2018

The experimental results are presented of an autonomous flight algorithm of a foldable quadcopter with airdrop launching functions. A foldable wing structure enabled the quadcopter to be inserted into a rocket container with limited space. The foldable quadcopter was then separated from the rocket in the air. The flight pattern was tracked using a global positioning system (GPS) with various sensors, including an inertial measurement unit (IMU) module until a designated target position was reached. Extensive field tests were conducted through an international rocket competition, ARLISS 2017, which was held in Black Rock Desert, Nevada, USA. The flight trajectory record of the experiments is stored in electrically erasable programmable read-only memory (EEPROM) embedded in the main control unit. The flight record confirmed that the quadcopter successfully separated from the rocket, executed flight toward the target for a certain length of time, and stably landed on the ground.

• Journal of Astronomy and Space Sciences
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• v.32 no.3
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• pp.269-279
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• 2015

Future space missions will have larger telescopes in order to look deeper into space while improvising on spatial resolution. The primary mirrors for these telescopes will be so large that using a monolithic mirror will be nearly impossible because of the difficulties associated with its fabrication, transportation, and installation on a launch vehicle. The feasibility of launching these huge mirrors is limited because of their small launch fairing diameter. The aerodynamic shape of the fairing requires a small diameter, but the height of the launch vehicle, which is available for designers to utilize, is larger than the fairing diameter. This paper presents the development of an axial deployment mechanism based on the screw jack principle. The mechanism was designed and developed, and a prototype was constructed in order to demonstrate a lab model.

• Journal of rehabilitation welfare engineering & assistive technology
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• v.10 no.2
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• pp.133-139
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• 2016

An electric wheelchair is a assistive device to maneuver on the ground. Tip-over of an electric wheelchair is increasing every year. Dynamic stability metric test item in KS P 7176 has not ensured safety of electric wheelchair on the slope. This study presents design the foldable electric wheelchair that can load in the car and analysis of tip-over measurement which is easily computed for electric wheelchair. Wheelchair frame is designed with a four-bar link mechanism for a foldable structure, and seat module, battery and power driving module can be separated. This analysis is performed during a maneuver on the ground by force-moment stability metric. Several elements, center of gravity position, rotational radius and acceleration, were evaluated how to affect stability metric. This stability metric can reduce tip-over of wheelchair and provide a clue to make of dynamic stability test item.

• Proceeding of KASS Symposium
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• 2006.05a
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• pp.142-152
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• 2006

The purpose of this study is to explore an inquisitive and innovative approach to structure and form, Calatrava's morphogenetic mechanism and to trace the ideas behind his working methods and his theoretical preoccupations. The bridges and buildings of S. Calatrava possess a breathtaking rhythm and of them some are designed to expand and contract like living organisms. The analogy Calatrava has used as a creative tool to mutate human bodies into arcing roof forms and bridge suspensions is introduced to illustrate the morphogenetic process. At the same time, the analysis used developing how to design frame structures foldable with brilliant mathematical solution is also investigated. Consequently, the potentialities of Calatrava's morphogenetic mechanism to invent new systems are generated by methodological hypothesis; analysis and analogy.

• Journal of the Microelectronics and Packaging Society
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• v.29 no.3
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• pp.49-53
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• 2022

Ultra-thin glass (UTG) has been widely used in foldable display as a cover window for the protection of display and has a great potential for rollable display and various flexible electronics. The foldable display is under impact loading by bending and touch pen and exposed to other external impact loads such as drop while people are using it. These external impact loads can cause cracks or fracture to UTG because it is very thin under 100 ㎛ as well as brittle. Cracking and fracture lead to severe reliability problems for foldable smartphone. Thus, this study constructs finite element analysis (FEA) model for the pen drop test which can measure the impact resistance of UTG and conducts mechanical modeling to improve the reliability of UTG under impact loading. When a protective layer is placed to an upper layer or lower layer of UTG layer, stress mechanism which is applied to the UTG layer by pen drop is analyzed and an optimized structure is suggested for reliability improvement of UTG layer. Furthermore, maximum principal stress values applied at the UTG layer are analyzed according to pen drop height to obtain maximum pen drop height based on the strength of UTG.

• Journal of Institute of Control, Robotics and Systems
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• v.17 no.7
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• pp.668-673
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• 2011

This paper presents design and control of a wheelchair robot for handicapped or elderly persons. Novel multi-functional design concepts are introduced. The first function is to balance the chair always parallel to the flat ground so that the driver feels comfortable when he/she drives on the slope. The second function is to help the driver to stand up by pushing the chair so that the driver can get out from the chair with ease. The third design is to make it foldable for easy carrying for automobiles. The last function is an immediate stop and start protection. Experimental studies are conducted to demonstrate the feasibility and functionality of each mechanical design.

• Archives of design research
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• v.19 no.6 s.68
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• pp.5-8
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• 2006

Inversion therapy has been used to relieve backpain, decrease pressure on the discs between vertebrae and stretch musdes as early as 400 BC. Gravity Guidance Inversion Table was introduced in 1960's and has been commercialized mostly for relieving backpain. in United States. But this machine needs to adjusted and possible sudden movement can cause severe injury to the users. In the 1990's, motor assisted inversion cram was introduced in Germany. But this inversion cram is too heavy and inconvenient to be used at home. In these days, the inversion machine become popular equipment in fitness clubs and health care places for relieving backpain as well as stretching muscles. And there is a growing need for home use version of motorized inversion machine. In this study, the motorized inversion machine was developed to be used for stretching exercise at home. The design became compact, simple and foldable as the results of adapting the wabble mechanism. And the machines are optimally designed by analyzing the torques applied to the machine by diverse physical size of users.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2000.11b
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• pp.489-497
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• 2000

Since Chinese cabbages weigh 3 to 5kgf and are big in size at the time of harvest, handling operations such as harvesting, loading and unloading including transportation require the highest labor demand among all other cultivation processes. Recently, though several cabbage harvesters were developed in Japan and Europe, those harvesters were not suitable for Chinese cabbages cultivated in Korea because of the size and shape. The cabbage harvester is almost meaningless without any proper cabbage piling and pallet unloading mechanism. Most harvesters developed so far adopted a sort of slide and free falling way in collecting cabbages into the pallet. Three or four labors are usually required for cleaning incoming cabbages and loading those in the pallet. Because of the required time for piling cabbages without severe damage and the required space capacity to carry empty and loaded pallets, harvesting speed should be adjusted in accordance with time required for consecutive operations. Up to now, any automatic or semi-automatic collecting device has not been developed in the world to pile cabbages on the layer one by one into the pallet in the ordered way with little damage and to unload pallet from the harvester continuously during the harvest process. To compromise system expenses and function, Semi-automatic cabbage piling and pallet unloading mechanism was devised and it required one labor. The foldable mesh pallet with a size of 1050mm x 1050mm x 1000mm and holding capacity of around 70 cabbages was utilized. The prototype for piling and unloading mechanism was composed of three parts such as feeding device, automatic piling device with retractable bellows, and pallet unloading device. Prior to developing the prototype, the geometric properties and the amount of the damage of the cabbage caused during the piling operation were investigated. Considering the height of the pallet, a series of cabbage carrying plates were mounted to the bracket chain to lift and to carry cabbages to the loading device. Indoor laboratory experiments showed that the cabbage carrying chain conveyor worked successfully. Considering the conveying speed 0.46m/sec of the pull up belt from the cabbages on the ground, the speed of cabbage carrying chain conveyor worked property in the range of 0.26m/sec to 0.36m/sec. The system allowed the operator to modify the position of cabbage slightly. Overall system worked successfully resulting into almost same capacity without severe damage to the cabbage as human did.