Operation of forearm support-type lift assist system (FOLAS) by using pneumatic pressure in air cushions.

The objective of this study is to develop an operation method of forearm-support type lift assist system (FOLAS)using pneumatic pressure in air cushions. The FOLAS has air cushions, which work as a buffer between the machine and the user's forearm, and the user's operating intention can be indirectly detected by measuring the variation of the pneumatic pressure inside the air cushions. Force control to compensate the weight of a lifted object was adopted for the vertical operation of the FOLAS on the assumption that force applied to an air cushion has proportional relationship to pneumatic pressure in the air cushion. Position control using overlap length between movable cushion and fixed cushion was adopted for the horizontal operation, and the overlap length was estimated by the pneumatic pressure ratio in the air cushions. Independence between the vertical and horizontal operation manners that commonly utilize pneumatic pressure in the movable cushion was verified through basic experiments. An experiment for the operational performance showed that the FOLAS could be operated according to the operator's intention. In an experiment for a lifting motion, the FOLAS could move continuously supporting the operator's forearm and reduce the muscle activation of elbow muscle.