  This study proposes a novel robotic gripper with variable grasping
configurations for grasping various objects. The fingers of the developed
gripper incorporate multiple different surfaces. The gripper possesses the
function of altering the finger surfaces facing a target object by rotating the
fingers in its longitudinal direction. In the proposed design equipped with two
fingers, the two fingers incorporate three and four surfaces, respectively,
resulting in the nine available grasping configurations by the combination of
these finger surfaces. The developed gripper is equipped with the functions of
opening/closing its fingers for grasping and rotating its fingers to alter the
grasping configuration -all achieved with a single motor. To enable the two
motions using a single motor, this study introduces a self-motion switching
mechanism utilizing magnets. This mechanism automatically transitions between
gripper motions based on the direction of the motor rotation when the gripper
is fully opened. In this state, rotating the motor towards closing initiates
the finger closing action, while further opening the fingers from the fully
opened state activates the finger rotation. This letter presents the gripper
design, the mechanics of the self-motion switching mechanism, the control
method, and the grasping configuration selection strategy. The performance of
the gripper is experimentally demonstrated.
