Data-driven Learning Intelligent Control for Flexible Surgical Manipulators


Automate Surgical Tasks for A Flexible Serpentine Manipulator via Learning Actuation Space Trajectory from Demonstration

Background: Accurate motion control of flexible surgical manipulators is crucial in tissue manipulation tasks. Tendon-driven serpentine manipulator (TSM) is one of the most widely adopted flexible mechanisms in MIS for its enhanced maneuverability in torturous environment. TSM, however, exhibits high nonlinearities and conventional analytical kinematics model is insufficient to achieve high accuracy.
Methods: To account for the system nonlinearities, we applied data driven approach to encode the system inverse kinematics. Three regression methods: Extreme Learning Machine (ELM), Gaussian Mixture Regression (GMR) and K-Nearest Neighbors Regression (KNNR) were implemented to learn a nonlinear mapping from the robot 3D position state to the control inputs.
Results: The performance of the three algorithms were evaluated both in simulation and physical trajectory tracking experiments. KNNR performs the best in the tracking experiments with the lowest RMSE of 2.1275mm.
Conclusions: The proposed inverse kinematics learning methods provide an alternative and efficient way to accurately model the challenging tendon driven flexible manipulator.
Keywords: Tendon-driven serpentine manipulator; surgical robotics; Inverse kinematics; Heuristic Methods

Demo video at:


  • W. Xu; J. Chen; H. Y. Lau & H. Ren Data-driven Methods towards Learning the Highly Nonlinear Inverse Kinematics of Tendon-driven Surgical Manipulators International Journal of Medical Robotics and Computer Assisted Surgery , 2016, 1-13
  • W. Xu; J. Chen; H. Y. Lau & H. Ren Automate Surgical Tasks for A Flexible Serpentine Manipulator via Learning Actuation Space Trajectory from Demonstration ICRA2016, IEEE International Conference on Robotics and Automation, 2016, –

Soft Robotic Manipulators: fabrication & applications


Flexible robotic manipulators have been widely used in minimally invasive surgery (MIS) and many other applications requiring closer inspection and operation. Although a variety of manipulators enabled by different mechanism have been developed, few of them can preserve softness, thinness and decent bending capability simultaneously. We develop miniature soft robotic manipulators made of hyper-elastic silicone rubber. Along with the manipulator design, novel fabrication methods are proposed and elaborated. Detailed characterizations are specified to show the bending capability of the manipulator given different air pressure. Specifically, our manipulator, as thin as 6 mm, is able to achieve 360° directional bending, and, when given pressure over 70kPa, it can reach 180° bending angle and around 5mm bending radius easily. Due to its innate compliance and small dimension, this type of robotic manipulator can deliver safe and comfortable interactions with the subjects. More significantly, the novel fabrications in this paper diversify the fabrication methods for soft pneumatic robots and actuators (SPRA) and further scale down their sizes.
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Multi-channel iTubot-BAT


The overall objective of this project is to develop and evaluate the key technologies of Transnasal Artificial Tentacles, a new approach involving research on the tentacle-like robotic and sensing technologies. This is aiming to create a compliant, flexible, multiple-sensorized, immersive, intraoperative targeting and guidance system for constrained transnasal endoscopic surgeries in a confined workspace.
Minimally invasive surgery-based nasopharyngeal cancer treatment is promising, but currently, it is not a common treatment choice because of the absence of suitable tools. In this project, a multi-channel concentric tube robot is proposed for the treatment of nasopharyngeal cancer based on natural orifice translumenal endoscopic surgery. The proposed system has three channels, i.e. two manipulation channels and one vision channel, and all the three channels are confined by a 10 mm active sheath. The robot is controlled by human-in-the-loop bimanual teleoperation under active endoscopic guidance. The reduced sheath diameter and the steerable vision channel improve the functionality of the system and distinguish our design from the prior art. The feasibility of the system has been evaluated through a series of simulations and experiments. Results show that the proposed system is capable to conduct cooperative tasks in a confined space and the miniaturized manipulator is suitable for transnasal procedures. Besides, comparisons with other types of flexible surgical robots are discussed to further demonstrate the superiority of the proposed system in the target clinical applications.


Singapore Millennium Foundation
PI: Jan/11/2015 – Jan/10/2018


Yu H, Wu L, Wu K, Lim CM and Ren H (2016), “Development of a Multi-Channel Concentric Tube Robotic System With Active Vision for Transnasal Nasopharyngeal Carcinoma Procedures”, IEEE Robotics and Automation Letters., Jan, 2016. Vol. 1(2), pp. 1172-1178.