• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.6
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• pp.535-540
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• 2015

The location of the pivot between the backrest and seat pan of a reclining chair should be identical to the hip joint center to prevent unpleasant user experiences during tilting motion. However, mechanical friction occurs in the pin-in-slot joints that are installed under the seat pan as an alternative to the hinge joint. This reduces the reaction force between the backrest and the occupant's back when reclining and returning to an upright position, which causes the occupant's discomfort. In this study, bearings, rollers, and sliders were suggested as alternatives for the pin component, and the percentage of the reaction force on the backrest was measured while reclining the backrest and subsequently returning it to an upright position. The results show when bearings, rollers, and sliders were used for the pin-in-slot joint, the percentages of the reaction force were $59.7{\pm}10.3$, $47.2{\pm}13.6$, and $30.3{\pm}18.1$, respectively, indicating that the friction of the bearing was the lowest among the three pin components. Because the three alternatives have different manufacturing costs, synthetic judgment requires the consideration of not only mechanical friction but also user experience.

• Journal of the Korea Furniture Society
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• v.10 no.1
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• pp.13-21
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• 1999

All chairs are uncomfortable in the long run and some chairs become uncomfortable more rapidly than others. In a particular chair, some people feel more uncomfortable than others. Comfort will depend upon the interaction of chair, user, and task characteristics. In this study, we intended to design a comfortable office chair by investigating anthropometric and biomechanical aspects for Koreans. We determine the design dimensions by analysis the anthropometric data. With these body parameters, we determined the design dimensions such as seat height, seat depth, seat width, seat backrest width, etc. This research, hopefully contributes to the development of ergonomic chair and improvement of the chair design technologies.

• International journal of advanced smart convergence
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• v.7 no.3
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• pp.110-118
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• 2018

This study aimed to examine the postures and behaviors of high school sophomores in Gyeongnam Province in daily life and the relations between back pain and sitting postures, and to identify undesirable behaviors and postures in daily life, and the following conclusions were obtained. The relation between back pain and cupping the chin in one of the two hands in rotation or sitting with the legs crossed or sitting on a chair with the back and hip not leaning against the backrest was statistically significant (p<0.05). The results above indicated that high school sophomores in South Korea spend most of the day sitting on a chair in school and that undesirable behaviors using one side of the body, such as cupping the chin in one of the two hands in rotation or sitting with the legs crossed, cause back pain. In addition, those who sit on a chair with the back and hip leaning against the backrest experienced less back pain than those who did not, and exercises after school were found to be helpful to prevent back pain.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.5
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• pp.527-533
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• 2010

The feeling that is evoked when products are handled has become increasingly important in the design of products primarily used by humans. In the traditional product design process, prototypes are built several times in order to evaluate the feeling evoked during use. However, these design processes can be optimized by adopting a haptic simulator that can serve as a prototype. The design method based on the use of the haptic simulator is called haptics-aided design (HAD), which is the main subject of this paper. Here, a new HAD method that can be effectively used to design a custom-made chair is proposed. A haptic simulator, which is composed of a haptic chair and an intuitive graphical user interface, was developed. The simulator can adjust the impedance of the backrest and seat pan of a chair in real time. The haptic chair was used instead of real prototypes in order to evaluate the comfort of the initially designed seat pan and backrest on the basis of their stiffness and damping values. It was shown that the HAD method can be effectively used to design a custom-made chair and can be extended to other product design processes.

• Journal of Drive and Control
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• v.20 no.2
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• pp.1-6
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• 2023

This study aims to develop a Korean dental chair hydraulic circuit by improving the existing equipment in order to localize foreign leading companies' products. The suggested Hydraulic circuit can be applicable to varied sectors where height and backrest angle control of chair-type equipment are required. The study followed the steps below. First, three kinds of foreign hydraulic circuits were analyzed and three kinds of Korean dental chair hydraulic circuits were suggested. Second, it was determined whether the three kinds of Korean hydraulic circuits operate normally through SimulationX, a software specialized in multi domain analysis, and the effectiveness of each circuit was examined.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.860-864
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• 2008

In modern society, people tend to spend their time on various types of chairs. However, it is not easy for a designer to design a comfortable chair, because satisfaction with the chair depends not only on the quantitative elements such as size, but also on the qualitative element such as the user's feeling. To deal with these problems, there have been many studies on designing an ergonomics chair. In this paper, the hapticaided design (HAD) system was adopted to design the ergonomics chair. Based on the HAD system, the designer can experience whether the chair is comfortable or not through the haptic device, and also can modify the design parameters instantaneously. The haptic chair capable of controlling the design parameters in real time was proposed as a haptic simulator. The controllable parameters such as the seat height, reclining angle, stiffness of the backrest, and so on were selected based on the previous researches related to ergonomics chairs. It will reduce the development cost and time by replacing the process of making the real mock-up and prototype with the haptic chair.

• Journal of Institute of Control, Robotics and Systems
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• v.16 no.2
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• pp.202-205
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• 2010

When we render 3D sound images using headphones or speakers, the main key of this technology is the Head-related transfer function (HRTF) database. Even though there are various HRTF databases, they have some drawbacks such as detrimental effects caused by imperfect measuring environment and insufficient measurement points. Moreover there is no database with Korean subjects. We are planning to develop the HRTF database for Korean. As a first step to establish the HRTF database aimed at Korean, the new HRTF measurement system with minimized aforementioned drawbacks is designed. In this paper, the newly designed HRTF measurement system is introduced and the overall effects caused by the diffraction of the apparatus, especially the headrest and backrest of the chair, are analyzed. The backrest of the chair does not distort the HRTFs significantly while the headrest makes significant distortion on the HRTFs and it could have significant effects on directional perception. We determined acceptable head rotation angle and head position of the subject for accurate HRTF measurement based on the experiments with B&K HATS. We conclude that the 3 degrees of the head rotation and the 1.5cm front/back/left/right shift of the head do not distort the HRTFs significantly.

• Journal of the Institute of Convergence Signal Processing
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• v.19 no.3
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• pp.104-109
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• 2018

A non-intrusive ECG and BCG measurement system is introduced. The system is built on a auxiliary backrest of a chair. The developed system is aimed to non-intrusive assessment of cardiovascular dynamic indices such as pulse arrival time(PAT) and pre-ejection period (PEP). In the system, capacitive active electrodes and capacitive grounding were used for the non-intrusive indirect-contact ECG measurement, and EMFi pressure sensor was used for the non-intrusive BCG measurement. The capacitive active electrodes and the EMFi sensor were attached on the backrest. Using the system, ECG and BCG were successfully acquired. The measured BCG showed peaks that following ECG R peaks. It was shown that the time interval between Q wave in ECG and first peak in BCG correlates Pre-ejection period measured by impedance-cardiogram. The results showed that the introduced system can be used for the non-intrusive various cardiovascular information including ECG, PAT, PEP.

• Journal of Korea Entertainment Industry Association
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• v.14 no.7
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• pp.469-476
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• 2020

This study was conducted on college students with low back pain to find out how a backrest exercise program affects the pain and balance of students. Thirty-two students at K University in Gwangju City were randomly classified with backrests and without backrests group respectively. Each group conducted the program for lasted three times a week for a total of 30 minutes for four weeks. Visual Analog Scale (VAS) was measured for pain assessment before and after arbitration, and the Korean Oswestry Disability Index (KODI) was measured for functional disability assessment. TETRAX is used to measure the weight distribution index and posture stability. According to the results of the experiment, the Visual Analog Scale (VAS) and the Korean Oswestry Disability Index (KODI) and weight distribution index showed significant differences over time, but the posture stability was no significant difference. The results of this study show that the lower limb exercise program is effective in back pain, dysfunction and weight distribution index, and it is believed that the pain reduction is significant when performed by distal movement in the area of back pain, It can be applied effectively to reduce low back pain in college students who spend a lot of time sitting down.

• Journal of the Ergonomics Society of Korea
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• v.33 no.2
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• pp.167-174
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• 2014

Objective: This research focuses on the working environment of office workers and aims to propose an ideal seating posture and chair design. Background: Generally, office workers having to seat in a fixed posture for long periods of time tend to suffer from an increased rate of musculoskeletal disorders. Method: The measurement and survey of 123 office workers on their working conditions and literature survey will lead to a suggestion of an ideal seating posture and workstation design theory. Results: Work environment satisfaction appeared low for chair and desks. Work-related pain over the last year was experienced among 47.2% of the respondents in shoulder (34.2%), neck (30.9%). Observation of working posture revealed that only 27.6% of workers utilize backrest during work. Conclusion: Office work embodies many situations where risks of musculoskeletal disorders may be high. Thus, the seated workplace must be set up to allow proper seating posture for workers. Application: The results of this study can be applied as baseline data for preventing musculoskeletal disorders of office workers.