Dexterity Assessment for Wrist Joints of Surgical Robots: A Statics-Based Evaluation Method

The continuum manipulators are the most common wrist joint design in surgical robots. However, there is currently no complete and accurate evaluation system to evaluate the performance of the continuum manipulator. In this article, a static model-based assessment method is proposed to evaluate the dexterity of continuum manipulator. Compared with conventional approaches, the methodology presented in this article demonstrates superior accuracy and scientific rigor, contributing to the establishment of a comprehensive framework for the evaluation of the dexterity of continuum manipulators. First, static models for three commonly encountered continuum manipulators are established. Based on the Bernoulli–Euler beam theory, the static models for the cable-driven continuum manipulator and hybrid continuum manipulator are established, taking into account the large deformations of the manipulators. Compared with the traditional constant curvature model, the average error is reduced from 0.67% to 0.33%. The static model for the concentric tube manipulator (CTM) is established by solving differential equations and based on differential element method. The average error is reduced from 3.09% to 0.90%. Subsequently, the effective workspace of the continuum manipulators is defined based on operational requirements. Based on the established static models and the service sphere theory, a more accurate dexterity assessment method is proposed within the effective workspace. Finally, the assessment of the dexterity is conducted for the three types of continuum manipulators. Simulation results indicate that within the effective workspace, the average dexterity is 0.4571 for the cable-driven continuum manipulator, 0.2495 for the hybrid continuum manipulator, and 0.1753 for the CTM. This article is of paramount significance in refining the comprehensive performance evaluation framework for surgical robots.