Design and Verification of Force Launch Patterns for Reducing Mental Load in Artificial Muscle Assist Devices

Seventeen percent of the Japanese workforce per- forms physical labor, and there is a need to reduce the physical burden of this work. Assist devices using artificial muscles, which are lightweight and easy to install, are effective in reducing the burden of physical labor. However, when an assist device is used for lifting a load, for example, the assist torque must be quickly raised to a certain level, which may lead to discomfort for the user, reduced operability. Therefore, this research conducted an experiment to verify whether controlling the assist torque of an assist device using artificial muscles according to the previously measured exerted muscle strength pattern of the lifting motion can reduce the mental load compared to a case where the assist torque is suddenly raised. Participants in the experiment were asked to receive assistance from the assist device, and the results were evaluated based on subjective evaluation and the sum of squares of the joint angular jerk, an index of discomfort. The results showed that there was no significant difference in subjective mental load, but the sum of squares of joint angular jerk decreased significantly.