Abstract
In the workplace, there are many tasks that are performed with the arms raised posture, and this movement causes shoulder and arm disorders. In this research, we developed an assistive device to reduce shoulder muscle fatigue during arm raising. The Remote Center of Motion (RCM) mechanism was used in this device to achieve a structure without a frame around the shoulder and to align the rotational axis of the machine with the rotational axis of the shoulder joint. The assist force of the device was determined by calculation to compensate the load torque generated around the shoulder when lifting the arm. The gas spring was selected as the power source of the device. The placement and selection of the gas springs were also determined by calculation. A prototype of the designed device was fabricated, and experiments were conducted to measure muscle activity during the arm raising operation and to evaluate the effectiveness of the assist. The subjects were three healthy male adults. The experimental results showed that muscle activity in the anterior deltoid was reduced by 38% compared to that without the device in the dynamic posture experiment.
