Design of a power assist system for lifting objects based on human´s weight perception and changes in system´s time constant

In this paper, we designed a simple 1 DOF power assist system for lifting objects based on human´s perception of object weight. We hypothesized that, human´s perception of weight due to inertial force might be different from the perceived weight due to gravitational force. We then compared human´s load force rates for lifting objects manually with that for lifting objects with the power assist system. We found the load force rates much lower for the power assisted objects. We then hypothesized whether or not mechanical time constant of the power assist system is a factor that reduces heaviness of objects lifted with it. The results show that, higher mechanical time constant lowers the perceived heaviness as well as peak load forces. Uses of the findings in design of power assist robots for lifting heavy objects in industries may improve interactions with humans.