Closed-Loop Pose Control and Automated Suturing of Continuum Surgical Manipulators With Customized Wrist Markers Under Stereo Vision

The use of continuum manipulators in surgical applications can be beneficial because of their inherent safety from their structural compliance. However, the tip pose (position and orientation) accuracy of a continuum manipulator can be low when an external load or disturbance is applied. Closed-loop pose control is preferred to improve the pose accuracy. Considering the requirements stemmed from sterilization and medical device electromagnetic compatibility, the approach of fully utilizing the vision feedback from a stereo endoscopic camera for such a closed-loop pose controller is adopted. Wrist markers are attached to the end-effectors of the surgical continuum manipulators for pose information detection. And these wrist markers are designed in a well-considered way to generate enough variants. The closed-loop pose controller is then designed based on a stereo vision tracking algorithm that detects the position and orientation of the wrist marker. A switching feature is also incorporated into the controller to handle the situation when the closed-loop control is disrupted due to the visual occlusion or the operation transition in dual-arm manipulation. Experimental verification showed that the average errors of the pose feedback are 0.65 mm for the position and 1.05° for the orientation. The experiments of trajectory following under a 120-gram external load and automated dual-arm suturing were also conducted to verify the effectiveness of the proposed controller.