Design and Realization of Forceps With 3-D Force Sensing Capability for Robot-Assisted Surgical System

Force sensing plays an important role in minimally invasive surgery, which enables surgeons to differentiate tissue stiffness and apply appropriate manipulation forces to avoid additional damages. However, due to size constraints, the implementation of force sensing on the surgical instruments is very difficult. In this paper, a novel type of surgical forceps consisting of double grippers is proposed for directly measuring the 3-D pulling force and grasp force at the tips of surgical instrument for the robot-assisted surgical system. For the design of forceps, a new structural decoupling sensor with 2-D force sensing capability is first developed. And then, it is integrated with the common gripper to be a single part. Mathematical models for the force-strain curves are obtained by a surface piecewise fitting method. After a notion produced that 3-D force can be characterized by double low-dimensional force sensing elements, a new 3-D force decoupling algorithm is presented based on the double grippers of the designed forceps. Furthermore, the validity of the design is evaluated by the finite-element analysis. Finally, for the machined prototype, several static calibration experiments and verifications are conducted using weights. Experimental results have shown that the proposed forceps possess higher performance of direct force sensing, and for the range of 2.5 N, the accuracies of X, Y, and Z axes are approximately 0.023 N, 2.2 mN, and 0.093 N, respectively, satisfying the actual requirements.