System design for forearm support-type lift assist system (FOLAS): An intuitively-operated power assist system without wearing

In labor-intensive fields, lifting a heavy object up and down is regarded as a frequently performed motion which imposes a physical strain on workers, and power assist systems are expected to address such a problem. The objectives of this paper are to introduce system design for forearm support-type lift assist system (FOLAS) and to verify its basic functionality and usefulness in lifting motion support. The FOLAS mechanical structure is largely divided into the forearm support and parallel motion arm; The forearm support can transfer the FOLAS driving force to operator's forearms to assist lifting motion. The air cushion attached on the forearm support can indirectly detect interaction force between FOLAS and operator through a pneumatic pressure sensor as well as receive operator's forearm softly. We adopt the PSDs for load existence detection, and the FOLAS recognizes an operator receives a load when the PSD data indicates less than the preset threshold. The forearm support is mounted on the 2-DOF parallel motion arm that enables the forearm support to be maintained in a horizontal position with fewer actuators. Such mechanical characteristics enable the FOLAS to assist lifting motion without wearing, i.e., fixing his/her body on the system, and an operator can maneuver it intuitively feeling a lifted object. Experiments for lifting motion with the FOLAS operation were performed, and we could verify its basic functionality and usefulness.