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Nabil Simaan

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43 papers
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43

AAAI Conference 2026 Conference Paper

Neural-Augmented Kelvinlet for Real-Time Soft Tissue Deformation Modeling

  • Ashkan Shahbazi
  • Kyvia Pereira
  • Jon S. Heiselman
  • Elaheh Akbari
  • Annie C. Benson
  • Sepehr Seifi
  • Xinyuan Liu
  • Garrison Lawrence Horswill Johnston

Accurate and efficient modeling of soft-tissue interactions is fundamental for advancing surgical simulation, surgical robotics, and model-based surgical automation. To achieve real-time latency, classical Finite Element Method (FEM) solvers are often replaced with neural approximations; however, naively training such models in a fully data-driven manner without incorporating physical priors frequently leads to poor generalization and physically implausible predictions. We present a novel physics-informed neural simulation framework that enables real-time prediction of soft-tissue deformations under complex single- and multi-grasper interactions. Our approach integrates Kelvinlet-based analytical priors with large-scale FEM data, capturing both linear and nonlinear tissue responses. This hybrid design improves predictive accuracy and physical plausibility across diverse neural architectures while maintaining the low-latency performance required for interactive applications. We validate our method on challenging surgical manipulation tasks involving standard laparoscopic grasping tools, demonstrating substantial improvements in deformation fidelity and temporal stability over existing baselines. These results establish Kelvinlet-augmented learning as a principled and computationally efficient paradigm for real-time, physics-aware soft-tissue simulation in surgical AI.

IROS Conference 2024 Conference Paper

A Feasibility Study of a Soft, Low-Cost, 6-Axis Load Cell for Haptics

  • Madison Veliky
  • Garrison L. H. Johnston
  • Ahmet Yildiz
  • Nabil Simaan

Haptic devices have shown to be valuable in supplementing surgical training, especially when providing haptic feedback based on user performance metrics such as wrench applied by the user on the tool. However, current 6-axis force/torque sensors are prohibitively expensive. This paper presents the design and calibration of a low-cost, six-axis force/torque sensor specially designed for laparoscopic haptic training applications. The proposed design uses Hall-effect sensors to measure the change in the position of magnets embedded in a silicone layer that results from an applied wrench to the device. Preliminary experimental validation demonstrates that these sensors can achieve an accuracy of 0. 45 N and 0. 014 Nm, and a theoretical XY range of ±50N, Z range of ±20N, and torque range of ±0. 2Nm. This study indicates that the proposed low-cost 6-axis force/torque sensor can accurately measure user force and provide useful feedback during laparoscopic training on a haptic device.

IROS Conference 2024 Conference Paper

A Robotic Mediation Device for Skill Assessment and Training During Colonoscopy

  • Olivia K. Richards
  • Elan Z. Ahronovich
  • Neel Shihora
  • Ahmet Yildiz
  • Jumana Atoum
  • Jie Ying Wu
  • Keith L. Obstein
  • Nabil Simaan

Colonoscopy demands multi-finger coordinated motion to achieve safe navigation. As a result, training for colonoscopists is challenging and skill assessment currently relies on subjective scoring by expert proctors. There is a need to provide tools for skill assessment and aid with training new interventionalists. This paper presents a new concept of an in-hand robotic mediation device that can be used for both skill assessment and training. The robotic device can be used to infer the kinematic motion as well as the power input of a user - both of which are proposed to be used for skill assessment and subtask skill classification. Preliminary results collected expert and novice users performing colonoscopy navigation are used to demonstrate this device as a skill assessment tool. A machine-learning model (classification and regression trees) is used for subtask classification of skill and evaluating the most important classification features. A user study demonstrates the effectiveness of this in hand haptic training and assessment tool. We believe that, in the future, this device will enable accelerated skill assessment and training and possible semi-automation of difficult maneuvers.

ICRA Conference 2023 Conference Paper

Exploring An External Approach to Subretinal Drug Delivery via Robot Assistance and B-Mode OCT

  • Elan Z. Ahronovich
  • Neel Shihora
  • Jin-Hui Shen
  • Karen M. Joos
  • Nabil Simaan

Injections into specific retinal layers of the eye present a serious challenge to surgeons in terms of accuracy and perception. The emergence of new gene therapies further emphasizes the need for effective tools for localized drug delivery. Unlike the dominant approach of delivering drugs via a transvitreal intraocular pathway, this paper demonstrates the feasibility of delivering injections into the space between the choroid and the retina using an external approach. The design of a cooperative robotic system for enabling robot-assisted extraocular subretinal injections is presented. The system uses a distal micromanipulator that can serve as a hand-held tool for OCT-aided injection or attach to a six degree of freedom (DOF) serial robot arm for cooperative manipulation. The kinematics and control of the robot for constrained cooperative control motions to enable safe needle injection is presented and experimentally evaluated. These results suggest that the proposed external drug delivery approach is feasible, thereby enabling the advantages of preserving the integrity of the retina and omitting the necessity for vitrectomy.

ICRA Conference 2023 Conference Paper

Exploring Robot-Assisted Optical Coherence Elastography for Surgical Palpation

  • Yeonhee Chang
  • Elan Z. Ahronovich
  • Nabil Simaan
  • Cheol Song

Optical Coherence Elastography (OCE) is a method that discerns local tissue stiffness using optical information. This method has recently been explored for laryngeal cancer tumor margin detection but has not been widely deployed clinically. Part of the challenge hindering such clinical deployment is the need for controlled high-precision mechanical probing of the tissue. This paper explores the concept of robot-assisted optical coherence elastography(OCE) and presents a preliminary system integration used to demonstrate the approach for stiffness mapping and discerning tumor margins. The approach is demonstrated on a custom Cartesian stage robot, and a custom-built OCE system comprised of an 830 nm broad-band laser with a vector-analysis method for phase gradient estimation and strain imaging. The paper illustrates one of the advantages of robot-controlled probing in terms of increasing the accuracy of the OCE system in a large range of displacement and strain. By leveraging motion information from the robot, online re-calibration of the OCE strain map may be achieved, thereby reducing OCE errors. After calibration, it is shown that the error in estimating the local Young's modulus is 0. 485% in the silicon phantom and 0. 531% in the agar phantom. These results suggest that future integration of optical coherence tomography(OCT) in clinically deployable robots may offer advantages in enabling local stiffness map estimation using OCE.

ICRA Conference 2023 Conference Paper

Induced Vertex Motion As a Performance Measure for Surgery in Confined Spaces

  • Neel Shihora
  • Nabil Simaan

While in the design phase of a robotic system for the procedures performed in surgical confined spaces or hard-to-reach-deep surgical fields, designers can leverage a systematic method to compare the design alternatives for tele-surgical manipulators quantitatively. Unlike most of the work in the literature, we propose an approach for comparing design alternatives by considering the spurious motions along the length of the manipulator in lieu of existing approaches looking at only the end-effector dexterity measures. We propose a performance measure quantifying these spurious motions while the end-effector executes the application-critical tasks such as suturing and tying a knot. A good manipulator design should yield minimal swept volume along its length portions within the confined space. If informed about these spurious motions, that design would lead to reduced force on the internal organs, reducing the pain and discomfort as well as occurrences of extracorporeal inter-manipulator collisions. To validate the proposed approach, we present two illustrative simulation case studies: (1) two planar rigid link serial robots performing the task of following a desired trajectory and (2) two different architectures of tele-surgical manipulators performing the task of passing a circular suture needle under the fulcrum constraints. The results show the applicability of the proposed performance measure in determining the suitability of a particular design alternative for a given task. Although results are promising, using this measure alone for design optimization may compromise overall device dexterity. Therefore, this measure needs to be incorporated into a weighted optimization framework for robot design.

ICRA Conference 2023 Conference Paper

Model-Based Pose Estimation of Steerable Catheters under Bi-Plane Image Feedback

  • Jared Lawson
  • Rohan Chitale
  • Nabil Simaan

Small catheters undergo significant torsional deflections during endovascular interventions. A key challenge in enabling robot control of these catheters is the estimation of their bending planes. This paper considers approaches for estimating these bending planes based on bi-plane image feedback. The proposed approaches attempt to minimize error between either the direct (position-based) or instantaneous (velocity-based) kinematics with the reconstructed kinematics from bi-plane image feedback. A comparison between these methods is carried out on a setup using two cameras in lieu of a bi-plane fluoroscopy setup. The results show that the position-based approach is less susceptible to segmentation noise and works best when the segment is in a non-straight configuration. These results suggest that estimation of the bending planes can be accompanied with errors under 30°. Considering that the torsional buildup of these catheters can be more than 180°, we believe that this method can be used for catheter control with improved safety due to the reduction of this uncertainty.

IROS Conference 2023 Conference Paper

Task and Configuration Space Compliance of Continuum Robots via Lie Group and Modal Shape Formulations

  • Andrew L. Orekhov
  • Garrison L. H. Johnston
  • Nabil Simaan

Continuum robots suffer large deflections due to internal and external forces. Accurate modeling of their passive compliance is necessary for accurate environmental interaction, especially in scenarios where direct force sensing is not practical. This paper focuses on deriving analytic formulations for the compliance of continuum robots that can be modeled as Kirchhoff rods. Compared to prior works, the approach presented herein is not subject to the constant-curvature assumptions to derive the configuration space compliance, and we do not rely on computationally-expensive finite difference approximations to obtain the task space compliance. Using modal approximations over curvature space and Lie group integration, we obtain closed-form expressions for the task and configuration space compliance matrices of continuum robots, thereby bridging the gap between constant-curvature analytic formulations of configuration space compliance and variable curvature task space compliance. We first present an analytic expression for the compliance of a single Kirchhoff rod. We then extend this formulation for computing both the task space and configuration space compliance of a tendon-actuated continuum robot. We then use our formulation to study the tradeoffs between computation cost and modeling accuracy as well as the loss in accuracy from neglecting the Jacobian derivative term in the compliance model. Finally, we experimentally validate the model on a tendon-actuated continuum segment, demonstrating the model's ability to predict passive deflections with error below 11. 5% percent of total arc length.

ICRA Conference 2023 Conference Paper

Torque-Limited Manipulation Planning through Contact by Interleaving Graph Search and Trajectory Optimization

  • Ramkumar Natarajan
  • Garrison L. H. Johnston
  • Nabil Simaan
  • Maxim Likhachev
  • Howie Choset

Robots often have to perform manipulation tasks in close proximity to people (Fig 1). As such, it is desirable to use a robot arm that has limited joint torques so as to not injure the nearby person. Unfortunately, these limited torques then limit the payload capability of the arm. By using contact with the environment, robots can expand their reachable workspace that, otherwise, would be inaccessible due to exceeding actuator torque limits. We adapt our recently developed INSAT algorithm [1] to tackle the problem of torque-limited whole arm manipulation planning through contact. INSAT requires no prior over contact mode sequence and no initial template or seed for trajectory optimization. INSAT achieves this by interleaving graph search to explore the manipulator joint configuration space with incremental trajectory optimizations seeded by neighborhood solutions to find a dynamically feasible trajectory through contact. We demonstrate our results on a variety of manipulators and scenarios in simulation. We also experimentally show our planner exploiting robot-environment contact for the pick and place of a payload using a Kinova Gen3 robot. In comparison to the same trajectory running in free space, we experimentally show that the utilization of bracing contacts reduces the overall torque required to execute the trajectory.

IROS Conference 2021 Conference Paper

Feasibility of Remote Landmark Identification for Cricothyrotomy Using Robotic Palpation

  • Neel Shihora
  • Rashid Yasin
  • Ryan Walsh
  • Nabil Simaan

Cricothyrotomy is a life-saving emergency intervention that secures an alternate airway route after a neck injury or obstruction. The procedure starts with identifying the correct location (the cricothyroid membrane) for creating an incision to insert an endotracheal tube. This location is determined using a combination of visual and palpation cues. Enabling robot-assisted remote cricothyrotomy may extend this life-saving procedure to injured soldiers or patients who may not be readily accessible for on-site intervention during search-and-rescue scenarios. As a first step towards achieving this goal, this paper explores the feasibility of palpation-assisted landmark identification for cricothyrotomy. Using a cricothyrotomy training simulator, we explore several alternatives for in-situ remote localization of the cricothyroid membrane. These alternatives include a) unaided telemanipulation, b) telemanipulation with direct force feedback, c) telemanipulation with superimposed motion excitation for on-line stiffness estimation and display, and d) fully autonomous palpation scan initialized based on the user’s understanding of key anatomical landmarks. Using the manually digitized cricothyroid membrane location as ground truth, we compare these four methods for accuracy and repeatability of identifying the landmark for cricothyrotomy, time of completion, and ease of use. These preliminary results suggest that the accuracy of remote cricothyrotomy landmark identification is improved when the user is aided with visual and force cues. They also show that, with proper user initialization, landmark identification using remote palpation is feasible - therefore satisfying a key prerequisite for future robotic solutions for remote cricothyrotomy.

ICRA Conference 2020 Conference Paper

Kinematic Modeling and Compliance Modulation of Redundant Manipulators Under Bracing Constraints

  • Garrison L. H. Johnston
  • Andrew L. Orekhov
  • Nabil Simaan

Collaborative robots should ideally use low torque actuators for passive safety reasons. However, some applications require these collaborative robots to reach deep into confined spaces while assisting a human operator in physically demanding tasks. In this paper, we consider the use of in-situ collaborative robots (ISCRs) that balance the conflicting demands of passive safety dictating low torque actuation and the need to reach into deep confined spaces. We consider the judicious use of bracing as a possible solution to these conflicting demands and present a modeling framework that takes into account the constrained kinematics and the effect of bracing on the endeffector compliance. We then define a redundancy resolution framework that minimizes the directional compliance of the end-effector while maximizing end-effector dexterity. Kinematic simulation results show that the redundancy resolution strategy successfully decreases compliance and improves kinematic conditioning while satisfying the constraints imposed by the bracing task. Applications of this modeling framework can support future research on the choice of bracing locations and support the formation of an admittance control framework for collaborative control of ISCRs under bracing constraints. Such robots can benefit workers in the future by reducing the physiological burdens that contribute to musculoskeletal injury.

IROS Conference 2020 Conference Paper

Solving Cosserat Rod Models via Collocation and the Magnus Expansion

  • Andrew L. Orekhov
  • Nabil Simaan

Choosing a kinematic model for a continuum robot typically involves making a tradeoff between accuracy and computational complexity. One common modeling approach is to use the Cosserat rod equations, which have been shown to be accurate for many types of continuum robots. This approach, however, still presents significant computational cost, particularly when many Cosserat rods are coupled via kinematic constraints. In this work, we propose a numerical method that combines orthogonal collocation on the local rod curvature and forward integration of the Cosserat rod kinematic equations via the Magnus expansion, allowing the equilibrium shape to be written as a product of matrix exponentials. We provide a bound on the maximum step size to guarantee convergence of the Magnus expansion for the case of Cosserat rods, compare in simulation against other approaches, and demonstrate the tradeoffs between speed and accuracy for the fourth and sixth order Magnus expansions as well as for different numbers of collocation points. Our results show that the proposed method can find accurate solutions to the Cosserat rod equations and can potentially be competitive in computation speed.

ICRA Conference 2019 Conference Paper

A Multi-modal Sensor Array for Safe Human-Robot Interaction and Mapping

  • Colette Abah
  • Andrew L. Orekhov
  • Garrison L. H. Johnston
  • Peng Yin 0001
  • Howie Choset
  • Nabil Simaan

In the future, human-robot interaction will include collaboration in close-quarters where the environment geometry is partially unknown. As a means for enabling such interaction, this paper presents a multi-modal sensor array capable of contact detection and localization, force sensing, proximity sensing, and mapping. The sensor array integrates Hall effect and time-of-flight (ToF) sensors in an I 2 C communication network. The design, fabrication, and characterization of the sensor array for a future in-situ collaborative continuum robot are presented. Possible perception benefits of the sensor array are demonstrated for accidental contact detection, mapping of the environment, selection of admissible zones for bracing, and constrained motion control of the end effector while maintaining a bracing constraint with an admissible rolling motion.

ICRA Conference 2018 Conference Paper

Design Considerations and Redundancy Resolution for Variable Geometry Continuum Robots

  • Colette Abah
  • Andrew L. Orekhov
  • Nabil Simaan

Current multi-backbone continuum robots are limited to a constant cross-sectional diameter. This paper proposes a design alternative that overcomes this limitation. The ability to change the diameter of a continuum robot expands the repertoire of kinematic redundancy and enables kinematic parameter adaptation to optimize performance. A continuum robot design based on the angulated scissor mechanism is presented along with its position analysis. An exploration of admissible design parameter values for a given continuum robot segment with a desired maximum curvature while maintaining an open bore along its center is also carried out. A design presenting how this mechanism can be incorporated into a continuum robot is shown and a strategy for minimizing joint forces and avoiding joint limits is formulated as a gradient descent redundancy resolution problem in a simulation case study. The simulation results show that varying the diameter can significantly reduce joint forces while preserving the workspace and avoiding joint limits. This work is a first step towards continuum robots with situational awareness that will use their sensing capabilities to adapt their structure in order to optimize task execution performance.

ICRA Conference 2018 Conference Paper

Trajectory-Optimized Sensing for Active Search of Tissue Abnormalities in Robotic Surgery

  • Hadi Salman
  • Elif Ayvali
  • Rangaprasad Arun Srivatsan
  • Yifei Ma
  • Nico Zevallos
  • Rashid Yasin
  • Long Wang 0007
  • Nabil Simaan

In this work, we develop an approach for guiding robots to automatically localize and find the shapes of tumors and other stiff inclusions present in the anatomy. Our approach uses Gaussian processes to model the stiffness distribution and active learning to direct the palpation path of the robot. The palpation paths are chosen such that they maximize an acquisition function provided by an active learning algorithm. Our approach provides the flexibility to avoid obstacles in the robot's path, incorporate uncertainties in robot position and sensor measurements, include prior information about location of stiff inclusions while respecting the robot-kinematics. To the best of our knowledge this is the first work in literature that considers all the above conditions while localizing tumors. The proposed framework is evaluated via simulation and experimentation on three different robot platforms: 6-DoF industrial arm, da Vinci Research Kit (dVRK), and the Insertable Robotic Effector Platform (IREP). Results show that our approach can accurately estimate the locations and boundaries of the stiff inclusions while reducing exploration time.

IROS Conference 2017 Conference Paper

Continuum robots for multi-scale motion: Micro-scale motion through equilibrium modulation

  • Giuseppe Del Giudice
  • Long Wang 0007
  • Jin-Hui Shen
  • Karen M. Joos
  • Nabil Simaan

Existing robots for multi-scale motion (MSM) are unsuitable for micro-surgery in deep surgical sites where miniaturization and traversal of often tortuous anatomical passageways is required. Also, new emerging surgical paradigms for natural orifice surgery and image-based diagnosis and guidance at the micro-scale level promise to provide accurate verification of tumor resection margins. To overcome the limitations of current robot architectures, and to enable image-based biopsy and micro-surgery in confined spaces, we present a new concept of continuum robots with equilibrium modulation (CREM). CREM robots are a modification of multi-backbone continuum robots that achieve micro-motion by using indirect actuation through modulation of their static equilibrium by change of the distribution of their cross-sectional flexural rigidity. As a first step towards modeling the micro-scale kinematics of these robots, solutions for micro-motion tracking are presented and verified to achieve tracking accuracies of better than 2μm. Preliminary evaluation of the micro-motion capabilities of a first prototype demonstrates motion resolutions at 1μm level and hysteresis of less than 10μm - despite the use of inexpensive actuators with significant backlash. Finally, a demonstration of a first effort at integrating such a robot with a custom-made optical coherence tomography (OCT) probe is presented.

IROS Conference 2017 Conference Paper

Minimal visual occlusion redundancy resolution of continuum robots in confined spaces

  • Nima Sarli
  • Nabil Simaan

Minimally invasive surgery in confined spaces often requires the coordinated use of endoscopes and surgical tools while minimizing visual occlusions. In a robotic system such visual occlusion avoidance has to be achieved autonomously while keeping the surgical end-effector as close as possible to the center of the field of view of the endoscope. This paper presents an investigation of use of redundancy resolution to solve the problem of visual occlusion. Specifically, the paper addresses hard cases where a continuum robot or an ablation catheter emanate from a narrow access channel containing an endoscope. A redundancy resolution method accounting for the kinematics of the continuum robot and allowing for rotation of an angled lens endoscope is presented. A potential field method is used to guide all portions of the continuum arm outside of the visualization cone of the endoscope and a gradient descent method is used to guide the rotation of the endoscope to keep the end-effector as close as possible to the center of the visual field of the endoscope. A simulation case study demonstrates the utility of our method using a recently designed transurethral bladder cancer surgery system as a demonstration platform. Although the context of the problem is bladder surgery utilizing a continuum robot, the method can be generalized to any redundant robot that requires to accomplish a task with minimal visual occlusion.

ICRA Conference 2016 Conference Paper

Complementary model update: A method for simultaneous registration and stiffness mapping in flexible environments

  • Rangaprasad Arun Srivatsan
  • Elif Ayvali
  • Long Wang 0007
  • Rajarshi Roy 0005
  • Nabil Simaan
  • Howie Choset

Registering a surgical tool to an a priori model of the environment is an important first step in computer-aided surgery. In this paper we present an approach for simultaneous registration and stiffness mapping using blind exploration of flexible environments. During contact-based exploration of flexible environments, the physical interaction with the environment can induce local deformation, leading to erroneous registration if not accounted for. To overcome this issue, a new registration method called complementary model update (CMU), is introduced. By incorporating measurements of the contact force, and contact location, we minimize a unique objective function to cancel out the effect of local deformation. We are thus able to acquire the necessary registration parameters using both geometry and stiffness information. The proposed CMU method is evaluated in simulation and using experimental data obtained by probing silicone models and an ex vivo organ.

ICRA Conference 2016 Conference Paper

Concurrent nonparametric estimation of organ geometry and tissue stiffness using continuous adaptive palpation

  • Preetham Chalasani
  • Long Wang 0007
  • Rajarshi Roy 0005
  • Nabil Simaan
  • Russell H. Taylor
  • Marin Kobilarov

Surgeons often manually palpate tissue or organs in order to find tumors or other anatomical structures. Information about organ geometry and tissue stiffness gained from palpation can also be extremely useful in robotic surgery for diagnosis, surgical guidance, and registration to other preoperative information. However, it is not always easy to obtain, even if the robot is equipped with force sensors. This paper reports our approach for concurrent estimation of stiffness and surface geometry, using a continuous motion similar to a sweeping palpation motion used by surgeons. Our method relies on force data captured by a tactile sensor rigidly attached to an end-effector probe. We use Gaussian processes to simultaneously estimate geometry and stiffness. The method is not tied to any specific robotic platform and is consistent with a variety of palpation strategies. For simplicity, we discuss the results based on two different palpation primitives. This is our first step towards developing an adaptive high fidelity model reconstruction and path optimization technique.

ICRA Conference 2016 Conference Paper

Investigation of effects of dynamics on intrinsic wrench sensing in continuum robots

  • Rajarshi Roy 0005
  • Long Wang 0007
  • Nabil Simaan

Multi-backbone continuum robots have been demonstrated to possess wrench sensing capabilities by measuring the actuation load on each backbone and then using elaborate statics models. The ability to sense forces of interaction allows these robots to also control their interaction with the environment. In past studies, the force sensing models were subject to quasi-static assumptions. The goal of this paper is threefold: to update the wrench sensing model taking into account dynamic forces, to investigate the effect of these dynamic forces on the wrench sensing abilities of these robots and to present design atlases that help designers with the determination of critical dimensions ensuring bounded effect of dynamics on wrench sensing. The paper presents a simplified dynamics model using a Lagrangian formulation. This dynamics model is then used to update the wrench estimation model for a single-segment continuum robot. Finally, a set of normalized parameters is used to produce design atlases that help designers predict the effect of dynamics on the wrench estimation model. These results will allow improved performance in force sensing and control for multi-backbone continuum robots. Employing the methods presented in the paper, continuum robots, that have previously demonstrated excellent distal dexterity, will be able to control their force interaction with the anatomy better in future - thereby improving safety and the finesse of surgery.

ICRA Conference 2016 Conference Paper

Using Bayesian optimization to guide probing of a flexible environment for simultaneous registration and stiffness mapping

  • Elif Ayvali
  • Rangaprasad Arun Srivatsan
  • Long Wang 0007
  • Rajarshi Roy 0005
  • Nabil Simaan
  • Howie Choset

One of the goals of computer-aided surgery is to register intraoperative data to preoperative model of the anatomy, and hence add complementary information that can facilitate the task of surgical navigation. In this context, mechanical palpation can reveal critical anatomical features such as arteries and cancerous lumps which are stiffer than the surrounding tissue. This work uses position and force measurements obtained during mechanical palpation for registration and stiffness mapping. Prior approaches, including our own, exhaustively palpated the entire organ to achieve this goal. To overcome the costly palpation of the entire organ, a Bayesian optimization framework is introduced to guide the end effector to palpate stiff regions while simultaneously updating the registration of the end effector to an a priori geometric model of the organ, hence enabling the fusion of intraoperative data into the a priori model obtained through imaging. This new framework uses Gaussian processes to model the stiffness distribution and Bayesian optimization to direct where to sample next for maximum information gain. The proposed method was evaluated with experimental data obtained using a Cartesian robot interacting with a silicone organ model and an ex vivo porcine liver.

ICRA Conference 2015 Conference Paper

Characterization of resection dexterity in transurethral resection of bladder tumor: A kinematic study

  • Nima Sarli
  • Tracy Marien
  • S. Duke Herrell
  • Nabil Simaan

Transurethral resection of bladder tumors (TURBT) presents surgeons with challenges of limited tool dexterity. This paper investigates the limitations of dexterity and resection reach and accuracy within the intra-vesicular space of the bladder. The paper assumes the kinematics and geometry of current tools used for TURBT. The study presents a kinematic modeling framework and a simulation evaluation that aim to elucidate the limitations of current surgical tools. The kinematic framework also proposes a method for analyzing resection dexterity and accuracy in different regions of the bladder. The results demonstrate resection dexterity deficiencies in the areas neighboring the bladder neck and substantially higher dexterity in superior regions. In addition, the results of this work provide a currently missing quantified dexterity evaluation baseline for expected performance during manual TURBT against which future devices and robotic-assisted systems for resection can be compared.

ICRA Conference 2014 Conference Paper

Force-based flexible path plans for robotic electrode insertion

  • Jason Pile
  • George B. Wanna
  • Nabil Simaan

Rapidly deployable surgical robots pose minimal interruption to surgical workflow and require minimal setup time and equipment to support deployment. This paper explores the concept of rapid deployment through the use of in-vivo sensory information to adapt a pre-operative surgical plan and to increase robustness against registration and misalignment errors during robot deployment. Robotic insertion of cochlear implant electrode arrays is presented as a benchmark application demonstrating this concept. Two key ideas are presented within the context of this application: First, a hybrid position and admittance controller is used to define an insertion path plan that is modified based on in-vivo force measurements in order to reduce sensitivity to misalignment errors. Secondly, a new concept allowing the use of force cues to determine the onset of advance-off stylet electrode array insertion is presented. The new controller is tested with electrode insertions in both plastic models and human cadaveric specimens. The experiments show that insertion forces may be maintained or reduced compared to preplanned trajectories relying solely on the initial registration.

ICRA Conference 2013 Conference Paper

Characterization of constraints in flexible unknown environments

  • Samrat Bhattacharyya
  • Nabil Simaan

Robot manipulation in unstructured environments depends on understanding the geometric and physical constraints that the environment imposes on the robot. While approaches like simultaneous localization and mapping (SLAM) allow robots to understand geometric constraints, the understanding of environmental physical manipulation constraints is largely unaddressed when exploring unstructured flexible environments. The aim of this paper is to investigate algorithms that enable robots to autonomously perform exploratory manipulation tasks to comprehend physical constraints that guide safe manipulation. To achieve this goal we break new ground in the area of constraint exploration in unknown flexible environments. We propose using spatial stiffness, represented using screw theory, as a measure of mechanical constraints in the context of flexible environments. This paper focuses on developing a compact representation of global workspace constraints using locally measured stiffness properties. Additionally, we propose methods for identifying and classifying the various types of mechanical constraints that may exist in an elastic workspace, using only local stiffness properties. Used in tandem, these methods form a real-time compatible approach for exploring and mapping constraints of a flexible unknown environment.

ICRA Conference 2013 Conference Paper

Characterization of friction and speed effects and methods for detection of cochlear implant electrode tip fold-over

  • Jason Pile
  • Nabil Simaan

Perimodiolar electrode arrays for cochlear implant surgery present surgeons with challenges during their insertion into the cochlea. These challenges stem from the inherent flexibility of these arrays and the fragile intracochlear anatomy and has opened opportunities for high precision robotic systems. This paper investigates effects of insertion speed on insertion forces using perimodiolar electrode arrays in human temporal bones and complements previously published results on insertion force and speed relationships when using straight outer-wall electrode arrays. The paper presents a custom-made parallel robot equipped with a high resolution force/moment sensor as an insertion platform. Experimental results using 42 insertions in 8 temporal bones are analyzed and grouped by insertion speed. Our results show a reduction in insertion forces up to insertion speeds of 1 mm/s. The second aspect of this paper is the investigation of the feasibility of using insertion force and speed data to sense conditions predicting the onset of electrode tip fold over, a complication resulting in poor placement of electrode contacts. It is shown that tip folding can be detected by features taken from insertion force data when employing a support vector machine classifier. The capability to detect such errors in a procedure is a critical component to the development of a practical surgical tool.

ICRA Conference 2013 Conference Paper

Constrained motion control of multisegment continuum robots for transurethral bladder resection and surveillance

  • Andrea Bajo
  • Ryan B. Pickens
  • S. Duke Herrell
  • Nabil Simaan

Constrained motion control of robotic end-effectors is essential for safe operation in confined spaces such as the urinary bladder. This paper presents the clinical motivation for the development of new control algorithms for robotic-assisted transurethral bladder resection and surveillance using multisegment continuum robots. The anatomy, workspace, and access constraints for this procedure are identified and used as a guideline for the design of the telesurgical system and its control architecture. Constraints are mapped into the configuration space of the robot rather than in task space simplifying the modeling and the enforcement of virtual fixtures. The redundancy resolution is autonomously modified in order to exploit the remaining degrees of freedom using task priority. These methods are validated on a glass model of urinary bladder.

ICRA Conference 2013 Conference Paper

Design, calibration and preliminary testing of a robotic telemanipulator for OCT guided retinal surgery

  • Haoran Yu
  • Jin-Hui Shen
  • Karen M. Joos
  • Nabil Simaan

This paper presents an experimental system for demonstrating a new concept for retinal micro-vascular surgery. This concept involves the use of stents to maintain the structural integrity in artery/vein crossings. A design of an 11 degree of freedom robot that includes a 6 DoF Stewart-Gough platform, a two DoF differential wrist, and a three DoF actuator for deployment of stent and bridge vessel separators is proposed as a validated robotic system for ophthalmic microsurgery. The robot also allows for quick exchange of surgical graspers and the integration of a custom made B-mode OCT probe. The paper presents the kinematic modeling and calibration of the robot for demonstration of ocular and intraocular manipulation. The system telemanipulation framework is constructed and experimental evaluations of stent deployment and membrane peeling are shown with a verification of results using OCT probe images. We believe these preliminary results demonstrate new technology that may enable micro-vascular stenting for treatment of branch retinal vein occlusion while offering a general platform for dexterous retinal surgery.

ICRA Conference 2013 Conference Paper

Robotic-assisted micro-surgery of the throat: The trans-nasal approach

  • Andrea Bajo
  • Latif M. Dharamsi
  • James L. Netterville
  • C. Gaelyn Garrett
  • Nabil Simaan

Minimally Invasive Surgery of the throat is predominantly performed trans-orally. Although trans-oral (TO) access provides a scarless access into the airways, its outcomes are affected by complications, high cost, and long setup time. This paper investigates the clinical motivation for trans-nasal (TN) access to the throat and presents the design and hybrid position/compliant motion control of a rapidly deployable endo-nasal telerobotic system. The system exploits a unique ⊘5 mm surgical slave with force sensing capabilities used to enable semi-automating the insertion process. Working channels allow the deployment of surgical tools such as a fiberscope, positioning sensors, grippers, suction tubes, cautery, and laser fibers. The treatment of vocal fold paralysis is chosen as a benchmark application and a feasibility study for collagen injection is conducted. Experiments on a realistic human intubation trainer demonstrated successful and safe TN deployment of the end-effector and the feasibility of robotic-assisted treatment of vocal nerve paralysis. We believe this system constitutes a first step toward low-cost office-based head and neck surgical procedures.

ICRA Conference 2012 Conference Paper

Constrained filtering with contact detection data for the localization and registration of continuum robots in flexible environments

  • Stephen Tully
  • Andrea Bajo
  • George Kantor
  • Howie Choset
  • Nabil Simaan

This paper presents a novel filtering technique that uses contact detection data and environmental stiffness estimates to register and localize a robot with respect to an a priori 3D surface model. The algorithm leverages geometric constraints within a Kalman filter framework and relies on two distinct update procedures: 1) an equality constrained step for when the robot is forcefully contacting the environment, and 2) an inequality constrained step for when the robot lies in the free-space of the environment. This filtering procedure registers the robot by incrementally eliminating probabilistically infeasible state space regions until a high likelihood solution emerges. In addition to registration and localization, the algorithm can estimate the deformation of the surface model and can detect false positives with respect to contact estimation. This method is experimentally evaluated with an experiment involving a continuum robot interacting with a bench-top flexible structure. The presented algorithm produces an experimental error in registration (with respect to the end-effector position) of 1. 1 mm, which is less than 0. 8 percent of the robot length.

ICRA Conference 2012 Conference Paper

Integration and preliminary evaluation of an Insertable Robotic Effectors Platform for Single Port Access Surgery

  • Andrea Bajo
  • Roger E. Goldman
  • Long Wang 0007
  • Dennis L. Fowler
  • Nabil Simaan

In this paper, we present the integration and preliminary evaluation of a novel Insertable Robotic Effectors Platform (IREP) for Single Port Access Surgery (SPAS). The unique design of the IREP includes planar parallel mechanisms, continuum snake-like arms, wire-actuated wrists, and passive flexible components. While this design has advantages, it presents challenges in terms of modeling, control, and telemanipulation. The complete master-slave resolved-rates telemanipulation framework of the IREP along with its actuation compensation is presented. Experimental evaluation of the capabilities of this new surgical system include bi-manual exchange of rings, pick-and-place tasks, suture passing and knot tying. Results show that the IREP meets the minimal workspace and dexterity requirements specified for laparoscopic surgery, it allows for dual-arm operations such as tool exchange and knot tying in confined spaces. Although it was possible to tie a surgeon's knot with minimal training, suture passing was difficult due to the limited axial rotation of the distal wrists.

IROS Conference 2011 Conference Paper

A learning algorithm for visual pose estimation of continuum robots

  • Austin Reiter
  • Roger E. Goldman
  • Andrea Bajo
  • Konstantinos Iliopoulos
  • Nabil Simaan
  • Peter K. Allen

Continuum robots offer significant advantages for surgical intervention due to their down-scalability, dexterity, and structural flexibility. While structural compliance offers a passive way to guard against trauma, it necessitates robust methods for online estimation of the robot configuration in order to enable precise position and manipulation control. In this paper, we address the pose estimation problem by applying a novel mapping of the robot configuration to a feature descriptor space using stereo vision. We generate a mapping of known features through a supervised learning algorithm that relates the feature descriptor to known ground truth. Features are represented in a reduced sub-space, which we call eigen-features. The descriptor provides some robustness to occlusions, which are inherent to surgical environments, and the methodology that we describe can be applied to multi-segment continuum robots for closed-loop control. Experimental validation on a single-segment continuum robot demonstrates the robustness and efficacy of the algorithm for configuration estimation. Results show that the errors are in the range of 1°.

ICRA Conference 2011 Conference Paper

Algorithms and design considerations for robot assisted insertion of Perimodiolar Electrode Arrays

  • Jason Pile
  • Mei Yi Cheung
  • Jian Zhang 0074
  • Nabil Simaan

This paper evaluates the potential for using robotic assistance for the insertion of commercial Perimodiolar Electrode Arrays (PEA's) that use a stylet and a pre-curved electrode body. We propose an algorithm for coordinated robotic insertion of the pre-curved electrode body and pulling of the stylet in order to provide partial control over the PEA shape. However, for robotic insertion to be a viable option for PEA's, an understanding of the statistical variability of their characteristics is essential. This paper investigates the kinematics of PEA's, their shape variability, and their expected performance during robotic insertion. An investigation of the required number of Degrees of Freedom (DoF) and the workspace is presented. A study of shape variability is carried out for characterizing shape repeatability across different insertion trials using the same electrode array. Also a study of shape variability is carried out between different electrode arrays. We simulate and evaluate the expected performance of three and four DoF robotic instruments for PEA insertion. The results support our proposed algorithm for coordinated insertion of the electrode array body and pulling of the stylet. They show that existing commerical perimodiolar arrays provide good shape repeatability. These results also point to the need for designing robotic insertion tools with at least four DoF. We believe that these results provide guidelines for future robotic instrument design for cochlear implant PEA's.

ICRA Conference 2011 Conference Paper

Compliant motion control for continuum robots with intrinsic actuation sensing

  • Roger E. Goldman
  • Andrea Bajo
  • Nabil Simaan

Novel minimally invasive surgical paradigms accessing deep surgical sites present a new challenge of safe instrument insertion and navigation. This paper addresses this challenge by presenting a new framework for compliant motion control of multi-backbone continuum robots subject to whole-arm contacts. This control framework does not rely on knowledge of contact locations along the length of a continuum robot. Instead, the forces at joint level are applied as controller inputs to generate compliant motion. The paper first presents a new mapping of the external wrenches to a generalized force in the configuration space of a single-stage multi-backbone continuum robot. A closed-form analytic expression for the passive stiffness of a multi-backbone continuum robot segment is also presented. A controller, robust to uncertainties of the system model, is proposed to provide compliant motion of the continuum robot segment by using the generalized force and stiffness definitions. Stability, convergence, and controller properties are shown through experimental validation. The presented framework defines a method for providing compliant motion to continuum robots without explicit knowledge of the environment. We believe this work enables new control algorithms for rapidly deployable surgical robots and supports novel surgical paradigms by increasing safety during unstructured interaction with flexible anatomy.

ICRA Conference 2011 Conference Paper

Configuration and joint feedback for enhanced performance of multi-segment continuum robots

  • Andrea Bajo
  • Roger E. Goldman
  • Nabil Simaan

Multi-segment continuum robots offer enhanced safety during surgery due to their inherent passive compliance. However, they suffer poor position tracking performance due to flexibility of their actuation lines, structural compliance, and actuation coupling effects between segments. The need for control methods addressing accurate tracking for multi segment continuum robots is magnified by increased precision requirements of surgical procedures employing these structures. To address this need, this paper proposes a tiered controller that uses both extrinsic and intrinsic sensory information for improved performance of multi-segment continuum robots. The higher tier of this controller uses configuration space feedback while the lower tier uses joint space feedback and a feed-forward term obtained with actuation compensation techniques. We prove the stability of this controller using Lyapunov's direct method and experimentally evaluate its performance on a three-segment multi-backbone continuum robot. Results demonstrate its efficacy in enhancing regulation and tracking performance. It is shown that the controller mitigates the effects of actuation coupling between robot's sub-segments and decreases phase lag. These results suggest that this tiered controller will enhance telemanipulation performance of multi-segment continuum robots.

ICRA Conference 2010 Conference Paper

Design, simulation and evaluation of kinematic alternatives for Insertable Robotic Effectors Platforms in Single Port Access Surgery

  • Jienan Ding
  • Kai Xu 0005
  • Roger E. Goldman
  • Peter K. Allen
  • Dennis L. Fowler
  • Nabil Simaan

This paper presents the task specifications for designing a novel Insertable Robotic Effectors Platform (IREP) with integrated stereo vision and surgical intervention tools for Single Port Access Surgery (SPAS). This design provides a compact deployable mechanical architecture that may be inserted through a single Ø15 mm access port. Dexterous surgical intervention and stereo vision are achieved via the use of two snake-like continuum robots and two controllable CCD cameras. Simulations and dexterity evaluation of our proposed design are compared to several design alternatives with different kinematic arrangements. Results of these simulations show that dexterity is improved by using an independent revolute joint at the tip of a continuum robot instead of achieving distal rotation by transmission of rotation about the backbone of the continuum robot. Further, it is shown that designs with two robotic continuum robots as surgical arms have diminished dexterity if the bases of these arms are close to each other. This result justifies our design and points to ways of improving the performance of existing designs that use continuum robots as surgical arms.

ICRA Conference 2010 Conference Paper

Finding lost wrenches: Using continuum robots for contact detection and estimation of contact location

  • Andrea Bajo
  • Nabil Simaan

This paper presents a novel modeling framework for contact detection and estimation of contact location on multi-backbone continuum robots. The paper presents modified kinematics for constrained continuum robots and introduces the concept of Fixed Centrode Deviation (FCD) for continuum robots. It is shown that the change in fixed centrode locus may be used for detection of contact and for contact location estimation. An alternative method for contact detection using Joint Force Deviation (JFD) is investigated and a lower bound for contact detectability is derived while considering uncertainties in joint forces. An estimation framework for the location of contact is presented based on FCD and the constrained kinematics Jacobian of the continuum robot. These methods are validated by simulation and experiments. This framework may be used for enhancing the safety of robotic surgical slaves and for exploration of unknown environments such as in scenarios of search and rescue.

ICRA Conference 2009 Conference Paper

Design and synthesis of wire-actuated universal-joint wrists for surgical applications

  • Saleem Abdul Hamid
  • Nabil Simaan

This paper presents synthesis methods and performance measures for wire-actuated wrists using a universal-joint constraining linkage. Performance measures based on the isotropy of the wrench-closure workspace are derived and used in generating design atlases as a function of non-dimensional design parameters. The performance indices that are optimized include wrench-closure workspace, isotropy of the wrench-closure workspace, and kinematic conditioning index. Stiffness is used to define a safety margin from singularities of wrench closure. A design example of a wire-actuated surgical wrist is presented and validated through simulation. The methods presented in this paper are useful for quick dimensional synthesis of wire-actuated wrists with predefined wrench-closure workspaces.

ICRA Conference 2009 Conference Paper

Model and parameter identification of friction during robotic insertion of cochlear-implant electrode arrays

  • Jian Zhang 0074
  • Samrat Bhattacharyya
  • Nabil Simaan

Robot-assisted cochlear implant surgery was proposed and proved to be efficient in reducing insertion forces on acrylic scala tympani models. During experiments, the authors discovered that the insertion force not only depends on the shape discrepancy between the scala tympani and the inserted electrode array, but also on the insertion speed. This paper presents a friction model that describes the whole insertion process and investigates the relationship between the insertion speed and the insertion force. Experimental and statistical results show the effectiveness of the model. Applying the friction model generates safety insertion force boundaries for future insertions and gives the optimal insertion speed. It also provides predictive force information for insertion speed feedback control law design which may be applied to robot-assisted cochlear implant surgeries.

IROS Conference 2009 Conference Paper

System design of an Insertable Robotic Effector Platform for Single Port Access (SPA) Surgery

  • Kai Xu 0005
  • Roger E. Goldman
  • Jienan Ding
  • Peter K. Allen
  • Dennis L. Fowler
  • Nabil Simaan

This paper presents a novel design and preliminary kinematic analysis of an Insertable Robotic Effector Platform (IREP) for Single Port Access (SPA) Surgery. The IREP robot can be deployed into body cavity through a Ø15mm skin incision to perform SPA procedures. It consists of two snake-like continuum robots as slave surgical assistants for tissue manipulation, two parallelogram mechanisms for the continuum robots' placement, and one controllable stereo vision module with integrated light source for depth perception and tool tracking. Design considerations and alternatives, calculations and preliminary simulations of this 17-DoF surgical robotic system are presented in this paper. The overall control system hierarchy for tele-manipulation using the IREP robot is also presented.

ICRA Conference 2007 Conference Paper

Design and Theoretical Evaluation of Micro-Surgical Manipulators for Orbital Manipulation and Intraocular Dexterity

  • Wei Wei
  • Roger E. Goldman
  • Nabil Simaan
  • Howard F. Fine
  • Stanley Chang

This paper addresses the design considerations and dexterity evaluation of a novel hybrid two-armed micro-surgical slave robot equipped with intraocular dexterity devices. A unified framework for the kinematic modeling of this robot is presented while using the kinematic constraints stemming from the constrained motion of the eye. An augmented Jacobian describing the kinematics of the eye and the relative motion of each one of the two Intra-Ocular Dexterity Robots (IODR) is presented. Using this framework, the capabilities of this two-armed robot in performing dexterous intraocular operations are evaluated and compared to a similar robot without intra-ocular dexterity. The Kinematic Conditioning Index (KCI) for the proposed robot is shown to be significant. The results presented show an increase of approximately 33% and 47% in translational and rotational KCI respectively.

ICRA Conference 2006 Conference Paper

Actuation Compensation for Flexible Surgical Snake-like Robots with Redundant Remote Actuation

  • Kai Xu 0005
  • Nabil Simaan

This paper presents two actuation compensation methods for a snake-like robot implementing multi flexible backbones and actuation redundancy. This snake-like robot is designed for distal dexterity enhancement in MIS surgery of the throat. Actuation compensation is required to account for the flexibility of the actuation lines that connect this snake-like robot with its remote actuation units. The paper presents both a naive model-based compensation approach and a combined model-based recursive linear-estimation approach that uses data gathered from external measurements of the snake-like unit configuration such as vision. The kinematic and static model of this multi-backbone snake-like unit is reviewed and a simplified redundancy resolution is implemented in the error compensation model. The results show that the performance of the snake-like unit is significantly improved when compensation is implemented. The combined model-based recursive linear estimation method showed 1deg accuracy in path tracking. Finally, an updated Jacobian that accounts for the required compensation is presented. All the work done here strides the crucial step towards a successful clinical task such as suturing in the throat

ICRA Conference 2005 Conference Paper

Snake-Like Units Using Flexible Backbones and Actuation Redundancy for Enhanced Miniaturization

  • Nabil Simaan

This paper reports some recent analysis and modeling results obtained while developing a tele-robotic system for minimally invasive surgery of the throat. One of the main enabling components of this system is a Distal Dexterity Unit that implements a novel design using a flexible multi-backbone snake-like unit with actuation redundancy and push-pull actuation. The design of this snake-like unit is compared to other alternative designs that use a single flexible-backbone and wire-actuation. A unified kinematic and virtual work model is used to perform this comparison between a multi-backbone snake like unit with an equal-diameter snake-like unit using a single flexible backbone and wire actuation. The comparison is presented for several actuation redundancy resolutions that minimize the load on the flexible backbones. The results show that the multi-backbone design is superior to the alternative wire-actuated designs using a single flexible backbone. The advantages manifest in smaller required actuation forces on the backbones and, as a result, a reduced risk of buckling of the backbones and enhanced potential downsize scalability.

ICRA Conference 2004 Conference Paper

A Dexterous System for Laryngeal Surgery

  • Nabil Simaan
  • Russell H. Taylor
  • Paul Flint

This work presents a design overview of a novel high DoF (degrees-of-freedom) system being developed for minimally invasive surgery of the throat. The system is designed to allow remote operation of 2-3 tools with high tip dexterity to enable suturing and soft-tissue manipulation while using the patient's mouth as the only entry port. The slave is a 34 DoF unit equipped with three snake-like distal dexterity units for surgical tool manipulation. Each of these units is a multi-backbone snakelike mechanism equipped with a detachable milli parallel manipulator allowing interchangeable tools to be used. The paper presents the outline of the kinematic analysis of the snake-like units and proposes one possible actuation redundancy resolution to allow further downsize scalability while reducing the risk of buckling of the primary backbone of the snake-like units. Finally, The work presents a first early experiment with a prototype of the snake-like unit.

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