Estimation of the grasping torque of robotic forceps using the robust reaction torque observer

In this paper, the estimation of the grasping torque of robotic forceps without the use of a force/torque sensor is discussed. To estimate the grasping torque when the robotic forceps driven by a rotary motor with a reduction gear grasps an object, a novel robust reaction torque observer is proposed. The robust reaction torque observer is developed according to the following steps. First, cancellation of the estimation error torque, which causes an overshoot during the torque estimation, is performed. Second, identification of the load torques caused by the reduction gear and the component parts of the robotic forceps are conducted and their cancellations are performed. Finally, the mass of the load added to the gripper is calculated from the estimated grasping torque. The proposed RRTO was experimentally evaluated.