| Summary: | 碩士 === 國立臺灣科技大學 === 工業管理系 === 102 === With the vast development of network, wireless fidelity and cloud technology, the usage of smart devices that depend on 3G, 4G or Wi-Fi technology increase dramatically in recent years. Since the launch of iPad in 2010, tablets have led the trend and have been becoming indispensable handheld mobile devices in our daily life. Tablets, which are regarded as handheld mobile equipment, need to be held on the bracing hand in order to be operated easily. Since the development trend of tablets is set to making the size larger, the weight of tablets becomes a critical issue to consider from human factors engineering perspective. Another issue needs to be thought through is whether different holding postures on the bracing hand can cause damages to the muscle and skeleton under long period of operation.
The purpose of the study is to investigate the effects of forearm limb’s loading under different weights and different holding postures. Four tablet prototypes based on weight are designed in the experiment. Two independent variables, including four different weights of the tablet prototypes and two bracing types of handheld, are considered in the experimental design.Specifically, there are 4 levels for weight :450g,500g, 550g, and 600g; and there are 2 levels for holding postures, namely Thumb Wrap Posture and Thumb Extended with Thenar Support. The psychophysical measurements of the dependent variables are the signal of myoelectricity for forearm limb and the angle of wrist under different weights and holding postures. Borg scales and the open-question questionnaire from users’ perceived exertion and fatigue are used as the subjective assessment.
The experiment result shows that 550g is a upper bound of load, which implies that when the device weight is heavier than 550g it might cause significant impact on forearm limb loading. With this result, a design of tablet no more than 550g is advised to not increase the risk of damages to forearm limb. The experiment result also shows that the posture of Thumb Wrap Posture has less loading than that of Thumb Extended with Thenar Support, which suggests that the former posture is recommended than the latter posture for the bracing hand. However, subjective assessment of fatigue did not show any statistically significant difference among four different weights.
In conclusion, 550g is a upper bound of load and Thumb Wrap Posture shows less fatigue than Thumb Extended with Thenar Support when using tablets. The experiment results provide helpful information for designers to improve the user experiences both psychologically and physically.
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