  This work designs a mechanical tool for robots with 2-finger parallel
grippers, which extends the function 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 mechanical tool. Four torsion springs
are attached to the four inner joints of the two parallelograms to open 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. Also, based on the kinematic structure, variety
tooltips were designed for the mechanical tool to perform various tasks. The
kinematic structure can be a platform to apply various skillful gripper
designs. 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 grip objects. The robot may also determine the optimal grasps
and usage according to the requirements of given tasks.
