  This study proposes a novel robotic gripper driven by a single motor. The
main task is to pick up objects in confined spaces. For this purpose, the
developed gripper has three operating modes: grasping, finger-bending, and
pull-in modes. Using these three modes, the developed gripper can rotate and
translate a grasped object, i.e., can perform in-hand manipulation. This
in-hand manipulation is effective for grasping in extremely confined spaces,
such as the inside of a box in a shelf, to avoid interference between the
grasped object and obstacles. To achieve the three modes using a single motor,
the developed gripper is equipped with two novel self-motion switching
mechanisms. These mechanisms switch their motions automatically when the motion
being generated is prevented. An analysis of the mechanism and control
methodology used to achieve the desired behavior are presented. Furthermore,
the validity of the analysis and methodology are experimentally demonstrated.
The gripper performance is also evaluated through the grasping tests.
