Design and Evaluation of a Robotic Forceps With Flexible Wrist Joint Made of PEEK Plastic

This letter presents the design and evaluation of a robotic forceps in which the wrist joint is made of polyetheretherketone (PEEK) plastic. Due to the structural improvement of enclosing a flexible backbone of PTFE tube inside the wrist joint, the developed forceps simultaneously fulfills the requirements of small diameter, bending dexterity, sufficient axial stiffness, and even the control rigidity. The proposed robotic forceps employs pneumatic drive with wire actuation mechanism. For accurate motion control and external force estimation, we developed a novel inverse dynamics model considering the coupled dynamic effect between the wrist joint and the gripper motions. The position control accuracy of the wrist joint bending angle is at the level of 1 degrees and is not affected by the simultaneous open-close motion of the gripper. The translation and grasping forces are beyond 4.5 N, enabling powerful tasks in laparoscopic surgery. Furthermore, the robotic forceps is capable of multi-DOF external force estimation. The estimation accuracy of the translation force is about 0.2 N, and the estimation accuracy of grasping force remains within 0.2 N regardless of the bending angle of the wrist joint. The performance evaluation results demonstrate that the developed forceps is eligible to be used in robotic-assisted laparoscopic surgery.