Publications

@article{Modes2020b,
title = {Shape Sensing Based on Longitudinal Strain Measurements Considering Elongation, Bending and Twisting},
author = {Vincent Modes and Tobias Ortmaier and Jessica Burgner-Kahrs },
doi = {10.1109/JSEN.2020.3043999},
year = {2021},
date = {2021-03-01},
journal = {IEEE Sensors Journal},
volume = {21},
number = {5},
pages = {6712-6723},
abstract = {The inherent flexibility, the small dimensions as well as the curvilinear shape of continuum robots makes it challenging to precisely measure their shape. Optical fibers with Bragg gratings (FBGs) provide a powerful tool to reconstruct the centerline of continuum robots. We present a theoretical model to determine the shape of such a sensor array based on longitudinal strain measurements and incorporating bending, twisting, and elongation. To validate our approach, we conduct several simulations by calculating arbitrary shapes based on the Cosserat rod theory. Our algorithm showed a maximum mean relative shape deviation of 0.04%, although the sensor array was twisted up to 78 degrees. Because we derive a closed-form solution for the strain curvature twist model, we also give analytical sensitivity values for the model, which can be used in the calculation of error propagation.},
keywords = {continuum robot, modeling, shape sensing},
pubstate = {published},
tppubtype = {article}
}

@article{Rao2021,
title = {How to Model Tendon-Driven Continuum Robots and Benchmark Modelling Performance},
author = {Priyanka Rao and Quentin Peyron and Sven Lilge and Jessica Burgner-Kahrs},
doi = {10.3389/frobt.2020.630245},
year = {2021},
date = {2021-02-02},
journal = {Frontiers in Robotics and AI},
volume = {7},
number = {630245},
pages = {20},
abstract = {Tendon actuation is one of the most prominent actuation principles for continuum robots. To date, a wide variety of modelling approaches has been derived to describe the deformations of tendon-driven continuum robots. Motivated by the need for a comprehensive overview of existing methodologies, this work summarizes and outlines state-of-the-art modelling approaches. In particular, the most relevant models are classified based on backbone representations and kinematic as well as static assumptions. Numerical case studies are conducted to compare the performance of representative modelling approaches from the current state-of-the-art, considering varying robot parameters and scenarios. The approaches show different performances in terms of accuracy and computation time. Guidelines for the selection of the most suitable approach for given designs of tendon-driven continuum robots and applications are deduced from these results.},
keywords = {continuum robot, modeling, tendon actuated, tendon-driven continuum robots},
pubstate = {published},
tppubtype = {article}
}

@article{Lilge2020,
title = {Tendon Actuated Continuous Structures in Planar Parallel Robots: A Kinematic Analysis},
author = {Sven Lilge and Kathrin Nuelle and Georg Böttcher and Svenja Spindeldreier and Jessica Burgner-Kahrs},
doi = {10.1115/1.4049058},
year = {2020},
date = {2020-11-07},
journal = {ASME Journal of Mechanisms and Robotics},
volume = {13},
number = {1},
pages = {011025 (11 pages)},
abstract = {The use of continuous and flexible structures instead of rigid links and discrete joints is a growing field of robotics research. Recent work focuses on the inclusion of continuous segments in parallel robots to benefit from their structural advantages, such as a high dexterity and compliance. While some applications and designs of these novel parallel continuum robots have been presented, the field remains largely unexplored. Furthermore, an exact quantification of the kinematic advantages and disadvantages when using continuous structures in parallel robots is yet to be performed. In this paper, planar parallel robot designs using tendon actuated continuum robots instead of rigid links and discrete joints are proposed. Using the well known 3-RRR manipulator as a reference design, two parallel continuum robots are derived. Inverse and differential kinematics of these designs are modeled using constant curvature assumptions, which can be adapted for other actuation mechanisms than tendons. Their kinematic performances are compared to the conventional parallel robot counterpart. On the basis of this comparison, the advantages and disadvantages of using continuous structures in parallel robots are quantified and analyzed. Results show that parallel continuum robot can be kinematic equivalent and exhibit similar kinematic performances in comparison to conventional parallel robots depending on the chosen design.},
keywords = {design, modeling, parallel continuum robot, tendon actuated, tendon-driven continuum robots},
pubstate = {published},
tppubtype = {article}
}

@article{Nuelle2020,
title = {Modeling, Calibration, and Evaluation of a Planar Parallel Continuum Robot based on Tendon Actuation},
author = {Kathrin Nuelle and Tim Sterneck and Sven Lilge and Dhezu Xiong and Jessica Burgner-Kahrs and Tobias Ortmaier},
doi = {10.1109/LRA.2020.3010213},
year = {2020},
date = {2020-07-17},
journal = {IEEE Robotics & Automation Letter},
volume = {5},
number = {4},
pages = {5811 - 5818},
abstract = {In this work, a novel planar parallel continuum robot (PCR) is introduced, consisting of three kinematic chains that are coupled at a triangular end-effector platform and include tendon-actuated continuum segments. The kinematics of the resulting structure are derived by adapting the descriptions for conventional planar parallel manipulators to include constant curvature bending of the utilized continuous segments. To account for friction and non-linear material effects, a data-driven model is used to relate tendon displacements and curvature of the utilized continuum segments. A calibration of the derived kinematic model is conducted to specifically represent the constructed prototype. This includes the calibration of geometric parameters for each kinematic chain and for the end-effector platform. During evaluation, positioning repeatability of 1.0% in relation to one continuum segment length of the robot, and positioning accuracy of 1.4%, are achieved. These results are comparable to commonly used kineto-static modeling approaches for PCR. The presented model achieves high path accuracies regarding the robot's end-effector pose in an open-loop control scenario.},
keywords = {calibration, control, design, modeling, parallel continuum robot, tendon actuated, tendon-driven continuum robots},
pubstate = {published},
tppubtype = {article}
}

@article{Chikhaoui2019,
title = {Comparison of Modeling Approaches for a Tendon Actuated Continuum Robot with Three Extensible Segments},
author = {Mohamed Taha Chikhaoui and Sven Lilge and Simon Kleinschmidt and Jessica Burgner-Kahrs},
doi = {10.1109/LRA.2019.2893610},
year = {2019},
date = {2019-01-17},
journal = {IEEE Robotics & Automation Letters},
volume = {4},
number = {2},
pages = {989 - 996},
abstract = {Continuum robots actuated by tendons are a widely researched robot design offering high dexterity and large workspaces relative to their volume. Their flexible and compliant structure can be easily miniaturized, making them predestined for applications in difficult-to-reach and confined spaces. Adaption of this specific robot design includes extensible segments leading to an even higher manipulability and enabling so-called follow-the-leader motions of the manipulator. In this letter, kinematic modeling for a tendon actuated continuum robot with three extensible segments is investigated. The focus is drawn on the comparison of two of the most widely used modeling approaches both for freespace and loaded configurations. Through extensive experimental validation, the modeling performances are assessed qualitatively and quantitatively in terms of the shape deviation, Euclidean error at segment ends, and computation time. While Cosserat rod modeling is slightly more accurate than beam mechanics modeling, the latter presents significantly lower computation time.},
keywords = {continuum robot, extensible, modeling, tendon actuated},
pubstate = {published},
tppubtype = {article}
}

@article{Burgner-Kahrs2015a,
title = {Continuum Robots for Medical Applications - A Survey},
author = {Jessica Burgner-Kahrs and Caleb D Rucker and Howie Choset},
doi = {10.1109/TRO.2015.2489500},
year = {2015},
date = {2015-11-02},
journal = {IEEE Transactions on Robotics},
volume = {31},
number = {6},
pages = {1261-1280},
abstract = {In this paper, we describe the state of the art in continuum robot manipulators and systems intended for application to interventional medicine. Inspired by biological trunks, tentacles, and snakes, continuum robot designs can traverse confined spaces, manipulate objects in complex environments, and conform to curvilinear paths in space. In addition, many designs offer inherent structural compliance and ease of miniaturization. After decades of pioneering research, a host of designs have now been investigated and have demonstrated capabilities beyond the scope of conventional rigid-link robots. Recently, we have seen increasing efforts aimed at leveraging these qualities to improve the frontiers of minimally invasive surgical interventions. Several concepts have now been commercialized, which are inspiring and enabling a current paradigm shift in surgical approaches toward flexible access routes, e.g., through natural orifices such as the nose. In this paper, we provide an overview of the current state of this field from the perspectives of both robotics science and medical applications. We discuss relevant research in design, modeling, control, and sensing for continuum manipulators, and we highlight how this work is being used to build robotic systems for specific surgical procedures. We provide perspective for the future by discussing current limitations, open questions, and challenges.},
keywords = {computational design, continuum robot, control, design, minimally-invasive surgery, modeling, motion planning, survey, trajectory planning},
pubstate = {published},
tppubtype = {article}
}