SEA-based Humanoid Finger-functional Parallel Gripper with Two Actuators: PG2 Gripper

—The ﬂexible grasping, force sensing, and in-hand ma- nipulating abilities of the gripper are theoretically signiﬁcant and practically valuable to solve. However, it is still difﬁcult for most existing grippers to realize these three functions simultaneously. This paper proposed a novel humanoid ﬁnger-functional parallel gripper with two actuators based on overlapping parallelogram mechanisms and the series elastic actuator (SEA). Based on the in-hand manipulation principle for the ordinary contour object, an in-hand manipulation algorithm for grasping force and position decoupling was designed. Then, to adjust the posture and position of objects within parallel ﬁngers, the rolling and sliding conditions of objects based on the molecular-mechanical friction theory were analyzed. Combined with the proposed in- hand manipulating conditions and algorithm, the PG2 gripper can control the grasping force and manipulate the ordinary contour object in-hand controllably. Evaluation experimental results showed that the force-position control of the PG2 gripper was decoupled stably and the gripper had high accuracy in controlling force and position. Finally, the physical features perception experiments and the in-hand manipulating experiment were carried out to demonstrate the utility of the proposed manipulating methods and algorithm, and in-hand manipulating and grasping force sensing abilities of the gripper. The possible applications of this gripper include tasks that need accurate force-position control or manipulating and sensing in-hand remotely.