Jessica Burgner-Kahrs

• PhD
• Managing Director at University of Toronto

Added to their high dexterity and ability to conform to complex shapes, continuum robots can be further improved to provide safer interaction with their environment. Indeed, controlling their stiffness is one of the most challenging yet promising research topics. We propose a tubular stiffening sheath as a replaceable cover for small-diameter conti...

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. Adaptions of this specific robot design include extens...

Continuum robots are constructed from flexible materials, possess slender shapes, and can perform complex 3D motion. With their miniaturization capacity, high dexterity, and lack of rigid-links, their use in medical applications is increasingly considered. The specificity of their scale, their model differences, as well as the intended application...

In this paper, we propose a dynamic model and control framework for tendon-driven continuum robots with multiple segments and an arbitrary number of tendons per segment. Our approach leverages the Clarke transform, the Euler-Lagrange formalism, and the piecewise constant curvature assumption to formulate a dynamic model on a two-dimensional manifol...

The displacement-actuated continuum robot as an abstraction has been shown as a key abstraction to significantly simplify and improve approaches due to its relation to the Clarke transform. To highlight further potentials, we revisit and extend this abstraction that features an increasingly popular length extension and an underutilized twisting. Fo...

In this letter, we demonstrate that previously proposed improved state parameterizations for soft and continuum robots are specific cases of Clarke coordinates. By explicitly deriving these improved parameterizations from a generalized Clarke transformation matrix, we unify various approaches into one comprehensive mathematical framework. This unif...

Tendon-driven continuum robots (TDCRs) have the potential to be used in minimally invasive surgery and industrial inspection, where the robot must navigate narrow and confined spaces. We propose a model predictive controller (MPC) to leverage the non-linear kinematics and redundancy of TDCRs for whole-body collision avoidance, with real-time capabi...

This article introduces the Clarke transform and Clarke coordinates, which present a solution to the disengagement of an arbitrary number of coupled displacement actuation of continuum and soft robots. The Clarke transform utilizes the generalized Clarke transformation and its inverse to reduce any number of joint values to a two-dimensional space...

For almost all tendon-driven continuum robots, a segment is actuated by three or four tendons constrained by its mechanical design. For both cases, methods to account for the constraints are known. However, for an arbitrary number of tendons, a disentanglement method has yet to be formulated. Motivated by this unsolved general case, we explored sta...

Tendon-driven Continuum Robots (TDCRs) are promising candidates for applications in confined spaces due to their unique shape, compliance, and miniaturization capability. Non-parallel tendon routing for TDCRs have shown definite advantages including segments with higher degrees of freedom, larger workspace and higher dexterity. However, most works...

This extended abstract introduces a novel method for continuous state estimation of continuum robots. We formulate the estimation problem as a factor-graph optimization problem using a novel Gaussian-process prior that is parameterized over both arclength and time. We use this to introduce the first continuous-time-and-space state estimation method...

Tendon-Driven Continuum Robots (TDCRs) have the potential to be used in minimally invasive surgery and industrial inspection, where the robot must enter narrow and confined spaces. We propose a Model Predictive Control (MPC) approach to leverage the non-linear kinematics and redundancy of TDCRs for whole-body collision avoidance, with real-time cap...

Tendon-driven continuum robots (TDCRs), with their flexible backbones, offer the advantage of being used for navigating complex, cluttered environments. However, to do so, they typically require multiple segments, often leading to complex actuation and control challenges. To this end, we propose a novel approach to navigate cluttered spaces effecti...

Experiments on physical continuum robot are the gold standard for evaluations. Currently, as no commercial continuum robot platform is available, a large variety of early-stage prototypes exists. These prototypes are developed by individual research groups and are often used for a single publication. Thus, a significant amount of time is devoted to...

Parallel-continuum robots combine the advantages of both parallel and continuum robotics. They offer a compromise between the inherent compliance and slenderness of continuum robots and the high precision and strength of rigid-link parallel robots. Throughout recent years there has been an increasing research interest in these novel architectures,...

In contrast to conventional robots, accurately modeling the kinematics and statics of continuum robots is challenging due to partially unknown material properties, parasitic effects, or unknown forces acting on the continuous body. Consequentially, state estimation approaches that utilize additional sensor information to predict the shape of contin...

The ability to interact safely with the environment is known as one of the major advantages of soft robots (SRs). Due to their low material stiffness, these continuously deformable robots offer inherent flexibility. These advantages make them suitable for application that involve human-robot collaboration in industrial settings as well as medical a...

The small size, high dexterity, and intrinsic compliance of continuum robots (CRs) make them well suited for constrained environments. Solving the inverse kinematics (IK), that is finding robot joint configurations that satisfy desired position or pose queries, is a fundamental challenge in motion planning, control, and calibration for any robot st...

The small size, high dexterity, and intrinsic compliance of continuum robots (CRs) make them well suited for constrained environments. Solving the inverse kinematics (IK), that is finding robot joint configurations that satisfy desired position or pose queries, is a fundamental challenge in motion planning, control, and calibration for any robot st...

Various design modifications have been proposed for tendon-driven continuum robots to improve their stiffness and workspace. One of them is using locking mechanisms to constrain the lengths of rods or passive backbones along the robot. However, physics-based models used to predict these robots' behaviour commonly assume that the curvature of the lo...

Experiments on physical continuum robot are the gold standard for evaluations. Currently, as no commercial continuum robot platform is available, a large variety of early-stage prototypes exists. These prototypes are developed by individual research groups and are often used for a single publication. Thus, a significant amount of time is devoted to...

Continuum robots are promising candidates for interactive tasks in various applications due to their unique shape, compliance, and miniaturization capability. Accurate and real-time shape sensing is essential for such tasks yet remains a challenge. Embedded shape sensing has high hardware complexity and cost, while vision-based methods require ster...

This paper presents the singularity analysis of 3-DOF planar parallel continuum robots (PCR) with three identical legs. Each of the legs contains two passive conventional rigid 1-DOF joints and one actuated planar continuum link, which bends with a constant curvature. All possible PCR architectures featuring such legs are enumerated and the kinemat...

Tendon driven continuum robots are often considered to navigate through- and operate in cluttered environments. While their compliance allows them to conform safely to obstacles, it leads them also to buckle under tendon actuation. In this work, we perform for the first time an extensive elastic stability analysis of these robots for arbitrary plan...

Continuum robots are promising candidates for interactive tasks in medical and industrial applications due to their unique shape, compliance, and miniaturization capability. Accurate and real-time shape sensing is essential for such tasks yet remains a challenge. Embedded shape sensing has high hardware complexity and cost, while vision-based metho...

Continuum robots have the potential to enable new applications in medicine, inspection, and countless other areas due to their unique shape, compliance, and size. Excellent progess has been made in the mechanical design and dynamic modelling of continuum robots, to the point that there are some canonical designs, although new concepts continue to b...

Continuum robots have the potential to enable new applications in medicine, inspection, and countless other areas due to their unique shape, compliance, and size. Excellent progress has been made in the mechanical design and dynamic modeling of continuum robots, to the point that there are some canonical designs, although new concepts continue to b...

Due to the compliance of tendon-driven continuum robots, carrying a load or experiencing a tip force result in variations in backbone curvature. While the spatial robot configuration theoretically needs an infinite number of parameters for exact description, it can be well approximated using Euler Arc Splines which use only six of them. In this let...

We propose a segment design that combines two distinct characteristics of tendon-driven continuum robots, i.e. variable length and non-straight tendon routing, into a single segment by enabling rotation of its backbone. As a result, this segment can vary its helical tendon routing and has four degrees-of-freedom, while maintaining a small-scale des...

Tendon-driven parallel continuum robots (PCR) consist of multiple individual continuous kinematic chains, that are actuated in bending utilizing tendons routed along their backbones. This work derives and proposes a Cosserat rod based kinetostatic modeling framework for such parallel structures that allows for efficiently solving the forward, inver...

In this letter, a novel spatial parallel continuum robot is proposed. It is composed of three tendon-actuated continuum robots as kinematic chains that are coupled at a common end-effector platform by spherical joints. A modular design approach is used, allowing the reconfiguration of each continuum robot's base position and orientation to adapt th...

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 mod...

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 b...

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 para...

Concentric Tube Continuum Robots are among the smallest and most flexible instruments in development for minimally invasive surgery, thereby enabling operations in areas within the human body that are difficult to reach. Unfortunately, integrating state-of-the-art force sensors is challenging for these robots due to their small form factor, althoug...

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 is derived by adapting the descriptions for conventional planar parallel manipulators to incl...

Continuum robots are highly miniaturizable, exhibit non-linear shapes with several curves, and are flexible and compliant. In particular, concentric-tube and tendon-driven continuum robots can be designed on a small scale with diameters of below 10 mm. A small diameter-to-length ratio enables insertion of these robots through small entry points in...

Joint level calibration is an integral part of robotics as it directly influences the achievable accuracy. As opposed to serial robotic arms, continuum robots are not composed of any rigid links or joints, but of elastic materials that undergo bending and torsion. The jointless composition requires dedicated calibration procedures. In this letter,...

This paper presents a novel data-driven approach for sensing forces for Concentric Tube Continuum Robots. By exploiting their inherent flexibility, the deflection of the robot is used to estimate external forces. This work is based on the usage of a Direct Cascade Architecture of Extreme Learning Machines with Ridge-Regression to estimate the tip c...

Tubular continuum robots can follow complex curvilinear paths to reach restricted areas within the body. Using teleoperation, these robots can help minimize incisions and reduce trauma. However, drawbacks include the lack of haptic feedback and a limited view of the situs, often due to camera occlusion. This work presents novel auditory display to...

Purpose Laser-induced thermotherapy in the brain is a minimally invasive procedure to denature tumor tissue. However, irregularly shaped brain tumors cannot be treated using existing commercial systems. Thus, we present a new concept for laser-induced thermotherapy using a concentric tube robotic system. The planning procedure is complex and consis...

Background Evidence suggests that transoral robot‐assisted surgery is becoming increasingly common, yet current systems are incapable of sufficiently reaching the glottis or subglottic areas. This paper presents a teleoperated tubular continuum robot prototype for laryngeal surgery in a feasibility study. Methods A tubular continuum robot prototyp...

Laparoscopic partial nephrectomy for localized renal tumors is an upcoming standard minimally invasive surgical procedure. However, a single-site laparoscopic approach would be even more preferable in terms of invasiveness. While the manual approach offers rigid curved tools, robotic single-site systems provide high degrees of freedom manipulators....

This paper deals with the development of vision-based controller for a continuum robot architecture. More precisely, the controlled robotic structure is based on three concentric tube robot (CTR), an emerging paradigm to design accurate, miniaturized, and flexible endoscopic robots. This approach has grown considerably in the recent years finding a...

Dual-arm continuum robots have been considered mainly for teleoperation where human perception and cognition permitted coordination and collision-free motions. This paper describes theoretical investigations on automation of dual-arm robots constituted of two concentric tube continuum manipulators. An optimization algorithm is developed in order to...

Dense arrays of Draw Tower Gratings (DTG®s) have been produced in 7 core multicore fiber. They are measured with a standard spectrometer based readout system using Wavelength Division Multiplexing. We demonstrate that these sensor arrays can be used for curvature and shape sensing in continuum robotics and the accuracy for the measurement of both p...

This paper presents a computer-assisted planning workflow for robotic laser induced thermal therapy in the brain (LITT). A tubular continuum robot is used to position a laser probe for thermoablation, as conventional multiple straight trajectories are insufficient to treat polycyclic intracranial lesions with stereotactically placed probes. A multi...

Continuum manipulators possess the ability to travel on nonlinear paths and avoid obstacles in confined environments. A variety of designs were proposed for several applications, such as minimally invasive surgery or inspections and maintenance in hazardous spaces. While hyperredundant robots can follow a path on the large scale, path following beh...

Intracerebral hemorrhage evacuation using a tubular aspiration robot promises benefi�ts over conventional approaches to release the pressure of an hemorrhage within the brain. The blood of the hemorrhage is evacuated through preplanned, coordinated motion of a flexible, curved, concentric tube that aspirates from within the hemorrhage. To achieve m...

Transurethral access to the kidney is mostly utilized to perform endoscopy for diagnostics and stone removal. This minimally invasive procedure is challenging, especially for those patients whose kidney branches out into fine structures. Often, existing flexible instruments are lacking manipulability, robustness, and the field of view is limited. I...

Single port laparoscopic surgeries are the next step towards minimal invasiveness after conventional laparoscopy with several incisions. However, current conventional and single port instruments as well as robotic systems offer only a straight instrument deployment possibility, which results in limited visualization and triangulation. In the partic...

This paper presents a miniature wrist that can be integrated into needle-sized surgical instruments, including concentric tube robots. The wrist consists of a nitinol tube with asymmetric cutouts that is actuated by a single tendon to provide high distal curvature. We derive and experimentally validate kinematic and static models for the wrist, and...

This letter presents a new heuristic 3-D volume coverage path planning (VCPP) algorithm for robotic intracerebral hemorrhage evacuation. In contrast to existing 3-D planning techniques, the proposed algorithm generates 3-D paths without first decomposing the volume into series of 2-D planning problems. It considers the morphology of the volume to b...

Continuum manipulators possess the ability to move along nonlinear paths and avoid obstacles in confined environments. However, existing designs have some inherent restrictions: limited range of curvatures or fixed segment lengths. Hence, to achieve motion along a tortuous path in a confined environment in a follow-the-leader manner requires though...

Intracerebral hemorrhage evacuation using a tubular aspiration robot enables minimally-invasive surgery. To suction out blood from within, a 3D motion plan has to be determined prior to evacuation as well as intraoperatively based on CT images. In this paper, our previously proposed 3D motion planner is extended by a new objective, such that it all...

During manual cochlear implant electrode insertion the surgeon is at risk to damage the intracochlear fine-structure, as the electrode array is inserted through a small opening in the cochlea blindly with little force-feedback. This paper addresses a novel concept for cochlear electrode insertion using tubular manipulators to reduce risks of causin...

Purpose: Organ-level registration is critical to image-guided therapy in soft tissue. This is especially important in organs such as the kidney which can freely move. We have developed a method for registration that combines three-dimensional locations from a holographic conoscope with an endoscopically obtained textured surface. By combining thes...

The aim of this study was to investigate the applicability of tubular manipulators as an actuator mechanism for intracochlear positioning of the electrode array (EA) of a cochlear implant (CI). This is motivated by the vision of an atraumatic insertion of the EA into the inner ear (cochlea) without any damage to the intracochlear structures in comb...

Anecdotally, surgeons sometimes observe large errors when using image guidance in endonasal surgery. We hypothesize that one contributing factor is the possibility that operating room personnel might accidentally bump the optically tracked rigid body attached to the patient after registration has been performed. In this paper we explore the registr...

For those minimally invasive surgery where conventional surgical instruments cannot reach the surgical site due to their straight structure and rigidity, concentric tube continuum robots are a promising technology because of their small size (comparable to a needle) and maneuverability. These flexible, compliant manipulators can easily access hard...

Tubular continuum robots, which are composed of multiple concentric, precurved, elastic tubes, provide more dexterity than traditional surgical instruments at the same diameter. The tubes can be precurved such that the resulting manipulator fulfills surgical task requirements. Up to now the only material used for the component tubes of those manipu...

Tubular continuum robots are the smallest among continuum robots. They are composed of multiple, precurved, superelastic tubes. The design space for tubular continuum robots is infinite: each one of the component tubes can be individually parameterized in terms of its length, segmental curvatures, diameter, and material properties. Ad-hoc selection...

Concentric tube robots exhibit complex workspaces due to the way their component tubes bend and twist as they interact with one another. This paper explores ways to compute and characterize their workspaces. We use Monte Carlo random samples of the robot's joint space and a discrete volumetric workspace representation, which can describe both reach...

Steerable needles have the potential to improve the effectiveness of needle-based clinical procedures such as biopsy and drug delivery by improving targeting accuracy and reaching previously inaccessible targets that are behind sensitive or impenetrable anatomical regions. We present a new needle steering system capable of automatically reaching ta...

Mechanics-based models of concentric tube continuum robots have recently achieved a level of sophistication that makes it possible to begin to apply these robots to a variety of real-world clinical scenarios. Endonasal skull base surgery is one such application, where their small diameter and tentacle-like dexterity are particularly advantageous. I...

This article presents initial experiences using vibratory touchscreens and audible sounds to communicate graphical concepts in mathematics education to students with visual impairments. These studies are motivated by the prospect of displaying graphical and mathematical concepts typically taught in a highly visual manner through nonvisual channels....

Background: Registered medical images can assist with surgical navigation and enable image-guided therapy delivery. In soft tissues, surface-based registration is often used and can be facilitated by laser surface scanning. Tracked conoscopic holography (which provides distance measurements) has been recently proposed as a minimally invasive way t...

Concentric tube continuum robots provide an infinite-dimensional design space, consisting of individual tube space curves and other tube parameters. Even when design choices are made to restrict the design space to a small number of discrete parameters, ad hoc selection of parameter values to achieve coverage of a desired volume, in the presence of...

The high incidence of intracerebral hemorrhages, together with a 40% mortality rate, provide strong motivation for enhancements in the treatment methods available to physicians. To minimize the disruption to healthy brain tissue associated with gaining access to the surgical site that is imposed by traditional open or endoscopic surgical interventi...

The high incidence of intracerebral hemorrhages, together with a 40% mortality rate, provide strong motivation for enhancements in the treatment methods available to physicians. To minimize the disruption to healthy brain tissue associated with gaining access to the surgical site that is imposed by traditional open or endoscopic surgical interventi...

Concentric tube continuum robots provide an infinite-dimensional design space, consisting of individual tube space curves and other tube parameters. Even when design choices are made to restrict the design space to a small number of discrete parameters, ad hoc selection of parameter values to achieve coverage of a desired volume, in the presence of...

New approaches to intracerebral hemorrhage management are motivated by its high incidence and 40% mortality rate. Surgery is sometimes attempted to decompress the brain, although patient outcomes are similar regardless of whether surgery occurs. We hypothesize that surgical decompression is not more effective because current open surgical technique...

Introduction: Access to the anterior skull base via transsphenoidal routes is employed for a multitude of pathologic entities, the most common being for pituitary disorders. The rise of endoscopy has offered significant advantages over the classical sublabial route. However, significant limitations remain due the largely rigid coaxial constraints o...

We present a novel robotic approach for the rapid, minimally invasive treatment of Intracerebral Hemorrhage (ICH), in which a hematoma or blood clot arises in the brain parenchyma. We present a custom image-guided robot system that delivers a steerable cannula into the lesion and aspirates it from the inside. The steerable cannula consists of an in...