Computer aided analysis applications in furniture ergonomics with human centered design approach: study for selected seats

Human-centered design is a design and management process where people's needs are prioritized while developing any product and problem solving is approached from a human perspective at every stage. In this study, it is aimed to apply computer aided analysis in furniture ergonomics with a human-centered design approach. Within the scope of the study, "seating furniture" (single sofa), which is considered to be the most ergonomically important furniture and where people establish one-to-one relationship, was chosen to work. For this purpose, 8 different single seat model obtained from a manufacturer that has large-scale operations in Turkey, and 18 controlled group seats produced by different ergonomic parameters were evaluated with 3 different methods including a practical survey (perceptual measurement) and pressure measurement mat ( physiological evaluation) and human-based product development software "Anybody Modeling System (AMS)" (biomechanical evaluation). In the first stage of the study, 18 controlled experimental group seats with different ergonomic parameters were produced in order to determine the effects of factors such as sitting depth, sitting height, backrest inclination angle and armrest height on the comfort of people of different sizes (5, 10, 95 percentiles). The comfort values of the control group seats were obtained numerically by a questionnaire study to measure the comfort levels in different parts of the body, which was applied to 40 volunteer participants consisting of 20 men and 20 women. At this stage, thanks to the statistical analysis of the data obtained, the factors affecting comfort and the relationships between these factors were examined, and mathematical equations were developed in which the comfort value can be predicted according to ergonomic parameters and human percentile. Later, the same questionnaires were applied to the same volunteer participants for the ergonomic evaluation of the firm seats, and the comfort values of the firm seats were estimated with mathematical equations developed from control group seats data. In the second stage of the study, pressure mapping analyzes (PMAT) were carried out using sponges with 3 different densities (28, 32, 35 dns) commonly used in the production of upholstered furniture in the 18 controlled group seats, with the participation of 3 types of individuals selected from volunteer participants for physiological evaluation. In the results of the pressure mapping analysis, it was determined that the effect of density differences between sponges on the comfort was not significant. According to the results of the pressure mapping analysis performed on the company seats, it was determined that the women in short stature feel uncomfortable and feel the most uncomfortable in models 3 and 6, and the height increase in male participants also has a positive effect on comfort. In the third stage of the study, for biomechanical analysis, the musculoskeletal systems of the male and female volunteers participating in the study were scaled according to 10 static anthropometric data taken from each participant and modeled in a 1/1 scale (3 male 3 female models). In this way, the sitting action and thus the sitting posture was modeled in a virtual environment for both controlled group seats and firm seats, by obtaining the muscle and joint forces occurring in the musculoskeletal systems of the participants, the most comfortable sitting element where the least energy is consumed, thus the sitting posture quantitatively determined. According to the results, it was determined that the most effective factor on comfort was the backrest inclination angle, and the increase in the backrest inclination angle reduced joint reaction forces (lumbar region) and muscle activation of both female and male participants in all percentiles. As a result of the study, the factors that affect comfort (size, form, angle, relations between dimensions, materials, upholstery etc.) were analyzed in detail in the most comfortable single seat models, and the optimum criteria required for ergonomic seat design were revealed. As a result, with the application of human-centered design and computer-assisted ergonomic analysis, suggestions for increasing the quality of life of users using more ergonomic products are presented.