Design and Kinematics Analysis of a Robotic Pediatric Neuroendoscope Tool Body

Endoscopy is often used to treat hydrocephalus, a common pediatric neurosurgical condition. Rigid endoscopic tools used in these procedures have many limitations. In this article, we propose four novel designs for a steerable two degree-of-freedom robotic tool body to be deployed through a rigid endoscope and a handheld controller for such a tool body. Each of these designs make use of tendon-driven joints known as asymmetric notch joints, while varying tendon routing techniques. Furthermore, we design a compact handheld controller for this steerable tool body, which consists of dc motors driving lead screws to actuate the tendons for each of the robot's joints. A disturbance observer-based control system for these motors is designed to allow the motor to reach the desired tendon displacements under various loading conditions. Next, we analyze the kinematics of the bidirectional asymmetric notch joint, deriving a relationship between the joint angle and corresponding tendon displacement. Finally, we test each of our four proposed designs for interjoint coupling and provide some insights into the results of our tests. We find that tendon routing strategies play an important role in minimizing tendon coupling for meso-scale continuum tendon-driven robots and combining the properties of each of these asymmetric joints can prove to be beneficial in improving the performance of such two degree-of-freedom robots.