Publications
2025
- A System for Endoscopic Submucosal Dissection Featuring Concentric Push-Pull ManipulatorsPeter Connor, Carter Hatch, Khoa Dang, and 4 more authorsIn 2025 IEEE International Conference on Robotics and Automation (ICRA), May 2025
Endoscopic Submucosal Dissection (ESD) is an effective minimally invasive approach to removing colon cancer, yet it is underutilized, since it is challenging to learn and perform. To promote the adoption of ESD by making it easier, we propose a system in which two small, flexible robotic manipulators are delivered through a colonoscope. Our system differs from prior robotic systems aimed at this application in that our manipulators are small enough to fit through a clinically used colonoscope. By not re-engineering the colonoscope, we maintain overall system diameter at the current clinical gold standard, and streamline the path to eventual clinical deployment. Our concentric push-pull robot (CPPR) manipulators offer dexterity and simultaneously provide a conduit for grasper or cutting tool deployment. Each manipulator in our system consists of two push-pull tube pairs, and we describe how they are actuated. We describe for the first time our approach to compensating for undesirable CPPR tip motion induced by differences in the tubes’ transmission stiffness. We also evaluate the workspace of the manipulators and demonstrate teleoperation in a point-touching experiment. Lastly, we demonstrate the ability of the system to resect tissue via ex vivo animal experiments.
- Stiff yet Bendy: Tubular Transmissions for Driving Surgical Robots through Flexible EndoscopesKhoa T. Dang, Carter Hatch, Peter Connor, and 5 more authorsJournal of Medical Robotics Research, Jun 2025
Concentric push–pull robots delivered through flexible endoscopes work best if their laser-cut transmission tubes have high axial stiffness, high torsional stiffness and low bending stiffness. This paper simultaneously addresses all three output stiffness values in the transmission design problem, explicitly considering axial stiffness, whereas prior work on laser-cut tube design has focused on the bending/torsional stiffness ratio. We demonstrate an inherent trade-off present in existing laser-cut patterns: it is difficult to simultaneously achieve high axial stiffness and low bending stiffness because these properties are very tightly correlated. To break this correlation and design all three stiffness independently, we propose a new type of laser material removal pattern that leverages local stiffness asymmetry (EIxx≠≠ EIyy) in discrete bending segments separated by segments of solid tube. These discrete asymmetric segments are then rifled down the tube to achieve global stiffness symmetry. We parameterize the design and provide a study of the properties through finite-element analysis. We also consider the effect of interference between the tubes when the discrete segments are not aligned. Results show that our discrete asymmetric segment concept can achieve high axial stiffness and torsional stiffness better than previously suggested laser patterns while maintaining equally low bending stiffness. We also experimentally validated the proposed design’s properties and actuation performance with professionally manufactured prototype Nitinol tubes for use in an endoscopic robot system.
2024
- Design of Transmission Tubes for Surgical Concentric Push-Pull RobotsKhoa T. Dang, Stephen Qiu, Carter Hatch, and 5 more authorsIn 2024 International Symposium on Medical Robotics (ISMR), Jun 2024
The performance of concentric push-pull robots passing through endoscopes is best if their laser-cut transmission tubes exhibit high axial stiffness, high torsional stiffness, and low bending stiffness. In this paper we simultaneously consider all three output stiffness values in the design problem, explicitly considering axial stiffness, whereas prior work has focused on the bending/torsional stiffness ratio. We show that it is very challenging for existing laser-cut patterns to simultaneously achieve high axial stiffness and low bending stiffness because these stiffnesses are tightly coupled. To break this coupling and balance all three stiffness factors independently, we propose a new laser material removal design approach that leverages local stiffness asymmetry (EIx≠ EIy) in discrete bending segments separated by segments of solid tube. These discrete asymmetric segments are then rifled down the tube to achieve global stiffness symmetry. We parameterize the design and provide a study of the properties through finite-element analysis. We also consider the effect of interference between the tubes when the discrete segments are not aligned. Results show that our discrete asymmetric segment concept can achieve high axial stiffness and torsional stiffness better than previously suggested laser patterns while maintaining equally low bending stiffness.
2023
- Assessing the Impact of VR Interfaces in Human-Drone InteractionMaitrey Gramopadhye, Arran Zeyu Wang, Leonard Shearer, and 2 more authorsXR-ROB Workshop, Jun 2023
Drones are a uniquely useful type of robot that allows aerial exploration and surveying. However, they require substantial training to operate effectively. Previous research has introduced novel drone interfaces, but have not substantively compared these interfaces. In this paper, we explore the impact and differences of VR and 2D interfaces on layman human-drone interaction. We measured performance on three environmental exploration tasks in an indoor environment. Participants were introduced to the interfaces and then asked to read random sequences of digits from 1 meter away. The simple task had the participant read one sequence, while the complex task had the participant read four sequences in positions around the room. This required participants to demonstrate moderate levels of competence while operating the drone. Our results suggest that our VR interface has a comparable performance to a smartphone interface across all three tasks. Despite this, VR interfaces show potential to reduce barriers to drone operation and should be the focus of future research.
- Computational Analysis of Design Parameters for a Bimanual Concentric Push-Pull RobotUniversity of North Carolina at Chapel Hill, US, Tony Qin, Peter Connor, and 9 more authorsIn Proceedings of The 15th Hamlyn Symposium on Medical Robotics 2023, Jun 2023
Colorectal cancer is a pervasive disease: an estimated 4.6% of men and 4.2% of women will suffer from it in their lifetime [1]. Precancerous polyps can be small (<5 mm) medium (6-9 mm) or large (>10 mm) [2]. Small polyps are most frequent, but polyps too large for immediate endoscopic removal during screening occur 135,000 times per year in the US alone [1]. There are two primary options for removing these polyps: endoscopic removal or partial colectomy. Endoscopic procedures, such as endoscopic submucosal dissection (ESD), are less invasive and reduce the risk of infection, reoccurence, and other adverse events [3]. Despite this, approximately 50,000 patients each year undergo partial colectomies for polyps which could have been removed endoscopically [4]. A primary obstacle to wider use of endoscopic pro- cedures is how challenging they are for physicans to perform, due to the limited dexterity of existing trans- endoscopic tools [5]. Currently tools come straight out the tip of the colonscope and moving them requires moving the tip of the colonoscope [6]. To enable tools to move independent of the colonoscope, we propose an endoscopically deployable, flexible robotic system, as shown in Fig. 1. This system deploys a flexible robotic arm through each channel of a standard 2-channel colonoscope. Each arm is composed of a setup sheath followed by a steerable sheath, with each sheath built using a concentric push-pull robot (CPPR) [7]. Each arm has a hollow central lumen through which tools (e.g. forceps, electrosurgery probes, etc.) can be passed. This design adds dexterity and provides the physician with two independent manipulators, with the goal of making ESD easier to perform.