A Kinematic Modeling and Control Scheme for Different Robotic Endoscopes: A Rudimentary Research Prototype

In image-guided robotic surgery, there exist different endoscopes coupled either with specialized surgical robots (SSRs) or general industrial robots (GIRs). In general, SSRs mechanically respect the remote-center-of-motion (RCM) constraints with directly and explicitly controllable degrees-of-freedom (DoFs), whereas GIRs meet the constraints at the algorithmic level in an implicit manner, with a loss of direct control of some RCM DoFs. Conventionally, different robotic endoscopes are treated as different monolithic systems. Then, kinematic models and control schemes are separately established to automate different robotic endoscopes. This means that a similar analysis must be followed for each system, which is tedious and time-consuming. This letter introduces a modular method to analyze the individual kinematics of the robotic holder, the endoscope shaft and the surgical endoscope with RCM constraints explicitly handled. For achieving automation, the integrated kinematics of a generic robotic endoscope is determined by combining the kinematics of the modular elements. Considering that cameras are intrinsically embedded sensors, a visual servo control scheme applicable to different robotic endoscopes is formulated to incorporate four explicit (virtual) DoFs characterizing the RCM constraints in the control law. Simulations and experiments performed using three different robotic endoscopes validate the effectiveness and practicality of the kinematic modeling and control scheme for automatic field-of-view adjustment.