| Summary: | 碩士 === 朝陽科技大學 === 工業工程與管理系 === 107 === Manual Material Handling （MMH） is an important feature of most industries and services in a variety of workplaces in many countries. However, performing long-hour MMH tasks continuously may cause muscle fatigue and reduce the force exertion capability, thus increasing the risk of developing musculoskeletal disorders.
In this study, the subjects were asked to evaluate the maximum acceptable frequency of the conveyor belt operation using psychophysical method under the combination of three weights (1.5 Kg、1 Kg、0.5 Kg) and two asymmetric angles (45∘and 90∘). The frequency was evaluated twice and the lower frequency was selected as the MAF. The average MAF (standard deviation) of the subjects selected in the combinations of 0.5Kg45°, 0.5Kg90°, 1Kg45°, 1Kg90°, 1.5Kg45°, 0.5Kg90° are 26.73(3.41), 24.27(3.13), 23.45(2.62), 24.27(3.41), 21.82(3.57), 19.91(2.43). The subjects in this study also performed two 25-minute repetitive conveyor belt operations on each weight-angle combination with selected MAF. During the operation, the electromyography module and the physiological strain monitoring system were used to collect physiological strain. In addition, the psychological strains were also evaluated uising psychological questionnaires right after the experiment. The results showed that the physiological and psychological strains measured did not exceed selected workloads criteria, indicating that the MAFs selected using psychophysical method could be recommended as lifting frequencies for conveyor belt operations handling lighter weight objects.
Keywords: conveyor belt operation, maximum acceptable handling frequency, manual material handling, Electromyography (EMG), physiological strain, psychological strain
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