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A Classification of Sitting Strategies Based on Seating Pressure Distribution

Automotive Research and Development Division, Hyundai Motor Group, Uiwang, Gyeonggi-do, 437-815, KoreaDriversx92 sitting strategies are considered in car seat design. Existing research has identified representative sitting strategies by visual inspection of seating pressure measurements collected from a small sample size of drivers. The present study recruited 20 female and 20 male participants, measured seating pressure, and classified sitting strategies by cluster analysis. The participantsx92 sitting postures were classified based on seating pressure distribution into mid-back and scapular, mid-back and lumbar, and lumbar sitting strategies for the upper body and hip concentrated, hip and mid-thigh concentrated, and hip and mid-thigh distributed sitting strategies for the lower body. The effects of gender and occupant package layout (OPL) on sitting strategy were nout found significant. The identified sitting strategies would be of use for the design and evaluation of an OPL and a seat.

Development of an Evaluation Method for a Driver’s Cognitive Workload Using ECG Signal

Objective: The present study is to develop an effective evaluation method for a driver’s cognitive workload using electrocardiography (ECG) signal. Background: ECG measures such as heart rate (HR) and heart rate variability (HRV) have been used for cognitive workload evaluation. Since ECG changes by cognitive workload vary largely depending on personal characteristics, an optimal analysis protocol of ECG needs to be tailored to each individual accordingly; however, existing studies have not considered personal characteristics in ECG analysis for cognitive workload evaluation. Method: The proposed evaluation method uses the area under the receiver operating characteristic (ROC) curve (AUC). A preliminary analysis was conducted with ECG data collected in a driving simulator while an n-back task was conducted. AUC analysis was performed for four ECG metrics (mean IBI, SDNN, RMSSD, and RMSE), three window spans (20, 30, and 40 seconds), and three update rates (1, 2, and 3 seconds). Results: It was identified that the optimal ECG analysis parameters of metric, window span, and update rate maximizing the discriminability of cognitive workload evaluation varied between individual drivers. Conclusion: The finding of the present study supports the use of an individually customized ECG analysis protocol for better evaluation accuracy of a drivers’ cognitive workload. Application: The proposed ECG analysis method for cognitive workload evaluation can be applied to development of a safe driving support system.

Evaluation of Driving Posture Prediction in Digital Human Simulation Using RAMSIS

For proper ergonomic evaluation using a digital human model simulation (DHMS) system such as RAMSIS®, postures of a humanoid for designated tasks need to be predicted accurately. The present study (1) evaluated the accuracy of driving postures of humanoids predicted by RAMSIS, (2) proposed methods to improve its accuracy, and (3) examined the effectiveness of the proposed methods. Driving postures of 12 participants in a seating buck were measured by a motion capture system and compared with those predicted by RAMSIS. Significant discrepancies (8.7° to 74.9°) between predicted and measured postures were observed for different body parts and driving tasks. Constraint addition and user-defined posture methods were proposed and their performance was assessed in terms of prediction accuracy. Of the two proposed methods, the user-defined posture method was found preferred by improving the accuracy of posture prediction by 11.5% to 84.9%. Both the posture prediction accuracy assessment protocol and user-defined posture method introduced in the study would be of use for practitioners to improve the accuracy of predicted postures of humanoids in virtual environments.

Wearing Comfort Evaluation of a Summer Flight Suit to Improve Ventilation

This study verified the effect of summer flight ventilation developed in a previous study based on wearing comfort evaluation. Seven healthy males in their twenties volunteered for this experiment conducted in aclimatic cham- ber. The experiment consisted of three consecutive periods of rest (20 minutes), running on a treadmill (10 minutes) and recovery (20 minutes). A comparative evaluation was conducted on the general flight suit which had no ventilation holes and summer flight suit that usesubjective satisfaction measures and objective measures. The subjective satisfaction was evaluated according to the criteria of temperature sensation, wet sensation, thermal comfort and fatigue sensation. The objective satisfaction was measured by skin temperature, microclimate (temperature and humidity), sweat rate and ther- mography. The comparative wearing evaluation identified the summer flight suit decreased the temperature between skin and suit by 0.42 o C (upper arm), 0.9 o C (calf) and the skin temperature by 0.3 o C (shoulder), 0.4 o C (upper arm), 0.5 o C (calf) as compared to the general flight suit. The humidity inside the summer flight suit decreased at head (7.73%), shoulder (5.86%), upper arm (5.26%), and calf (8.73%) compared to the one inside the general flight suit. Thermography showed that the air flowed through ventilation holes (neck and armpit). The design of ventilation holes applied to the summer flight suit can be applicable to overall clothing that requires thermal comfort such as dust-free garments, mechanical cloth- ing and combat uniforms.

Development of a Sizing System of Mass-customized Clothing for Wheelchair Users: Men's Suit Sizes

This study develops a sizing system of mass-customized male suits for wheelchair users. One hundred and three male wheelchair users 21 anthropometric dimensions were measured to identify body shapes and develop a sizing system. The measured wheelchair users body sizes were compared with the average body sizes of Korean males from the 6 th Korean Body Size Survey to understand the body size differences between two groups. As a result of body shape classification using the KSs Drop method, wheelchair user body shapes were classified into four shapes for upper-body (A: 32%, B: 26%, BB: 24%, and Y: 18%), and two shapes for lower-body (B: 70% and A: 30%). The upper-body of wheel- chair users was relatively developed than Korean males; however, the lower-body was relatively stunted. The key dimen- sions of a sizing system were selected as chest circumference, waist circumference, and trunk length, outside leg length based on the correlation analysis between anthropometric measures. The top sizes were determined considering chest and waist circumferences for horizontal sizes, and additionally the trunk length was divided into short, medium, and long groups for vertical sizes. The bottom sizes were selected considering the waist and hip circumferences for horizontal sizes, and additionally their outside leg length was divided into short, medium, and long groups for vertical sizes.