Abstract
Abstract Although the automatic manufacturing technique is broadly adopted by modern manufacturing industry, manual materials handling task is still necessary. This study aims to evaluate the potential risk from inappropriate MMH task design and working posture, and determine the effects and correlations among human movement, muscle activity and body discomfort rating. For the experiment design, an experiment with 12 heath male subjects was conducted. The experimental factors include (1) carrying load weight: 7kg and 14kg (2) shelf height: knee height, elbow height and shoulder height (3) box size: big size and small size. The response variables are (1) gait parameters in time and space, (2) joint motion for the kinetic and kinematics analysis, (3) muscle activity levels with EMG, (4) subjective body part discomfort rating. The results indicate that weight factor had significantly effect on gait speed, steps per minute, gait cycle time, the ratio of stance time and swing time, maximal flexion angle of knee joint and the range of motion(ROM) of elbow joint. Shelf height had significantly effects on hip flexion and elbow ROM. Box size factor had significantly effect on stride length, gait cycle time, the ratio of stance time and swing time, knee joint elbow ROM. For the muscle activity levels with EMG, load weight and shelf height both affected the %MVC significantly. When the subjects carrying a load of 14kg, the muscle activity and the subjective body part discomfort rating are both higher than that of 7kg. The box size had effect on the body part discomfort rating of upper extremity and back. For the kinetic and kinematics analysis, the shelf height around elbow height was better than the other two height levels. The finding of this study can be used to generate digital human model motion based on real human motion data and key frame information. Thus, the MMH task simulation in virtual reality environment can represent the actual situation.