Designing a Mechanical Tool for Robots With Two-Finger Parallel Grippers

This letter designs a mechanical tool for robots with two-finger parallel grippers, which extends the functionality of the robotic gripper without additional requirements on tool exchangers or other actuators. The fundamental kinematic structure of the mechanical tool is two symmetric parallelograms, which transmit the motion of the robotic gripper to the tooltips. Four torsion springs are attached to the four inner joints of the two parallelograms to reopen the tool as the robotic gripper releases. The forces and transmission are analyzed in detail to make sure the tool reacts well with respect to the gripping forces and the spring stiffness. Based on the kinematic structure, various tooltips were designed for the mechanical tool to perform different tasks. The designed tool could be treated as a normal object and be picked up and used by automatically planned grasps. A robot may locate the tool through the AR markers attached to the tool body, grasp the tool by selecting an automatically planned grasp, and move the tool from any arbitrary pose to a specific pose to perform various tasks. The robot may also determine the optimal grasps and usage according to the requirements of given tasks.