Dexterity Analysis of Three 6-DOF Continuum Robots Combining Concentric Tube Mechanisms and Cable-Driven Mechanisms

Continuum robots are increasingly used in minimally invasive surgeries. To date, the concentric tube mechanism and the cable-driven mechanism have been two prevalent mechanisms for constructing continuum robots. As these two mechanisms complement each other, it is worth exploring the possibility of combining them together. In this paper, we investigate the dexterity of three continuum robots combining both mechanisms. Indices based on the concept of orientability are introduced to analyze the distribution of the dexterity. A Monte Carlo method is used to calculate the dexterity distribution across the workspace. Particularly, directional dexterity indices are put forward to describe the dexterity along different axes. Results imply that evenly allocating degrees of freedom (DOFs) among the segments achieves the best workspace and dexterity. Otherwise, assigning more DOFs to the proximal segment tends to enlarge the workspace and adding more DOFs to the distal segment tends to improve the dexterity. In addition, the dexterity along different axes can vary significantly and thus requires special attention when applying the robot to specific surgical procedures.