Design and Control of Parallel Gripper with Linear and Curved Trajectory Consisting of Only Revolute Pairs

A parallel gripper that can grasp an object notjust between the fingers, using the linear trajectory, but also in front of the fingers, using the curved trajectory, is proposed. With an aim to make it dust-and-waterproof, the link structure is designed to combine two mechanisms consisting of only revolute pairs, called the Chebyshev’s lambda mechanism and double parallel link. The former constrains the fingertips on the trajectory and the latter always keeps the gripping face of the fingertip vertical. As a trigger of grasping motion, it is also possible to detect contact between the fingertip and grasping target on the basis of the actuators’ backdrive, without any sensors on the fingertip. Kinematic analysis, control methods, and experiments with a fabricated gripper are also presented.