TRL Research: Recent Episodes
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A cable-driven parallel manipulator has been chosen to suspend and navigate instruments over a phenotyping research facility at the University of Nebraska. This paper addresses the static analysis and dimensional optimization of this system. Analysis of the system was performed with catenary simplification to create force equilibrium equations and define a mathematical model. The model incorporates flexibility due to catenary sag of the cables. Cable axial stiffness was not included because stiffness is dominated by catenary flexibility for the expected cable tensions. The model was used to optimize system dimensions, and a twelfth-scale system was constructed to verify the model as well as enable dynamic and control system experimentation during full-scale system construction. Miniature end-effectors were used to obtain end-effector orientation and cable tension measurements which were comparable to model predictions. The mathematical model was thereby shown to be accurate for the purpose of system static analysis.
We have proposed a long-term, non-invasive, non-restrictive method of delivering and implanting a biosensor within the body via a swallowable implantation capsule robot (ICR). The design and preliminary validation of the ICR's primary subsystem—the sensor deployment system—is discussed and evidence is provided for major design choices. The purpose of the sensor deployment system is to adhere a small biosensor to the mucosa of the intestine long-term, and the modality was inspired by tapeworms and other organisms that employ a strategy of mechanical adhesion to soft tissue via the combined use of hooks or needles and suckers. Testing was performed to refine the design of the suction and needle attachment as well as the sensor ejection features of the ICR. An experiment was conducted in which needle sharpness, needle length, and vacuum volume were varied, and no statistically significant difference was observed. Finally, preliminary testing, coupled with prior work within a live porcine model, provided evidence that this is a promising approach for implanting a biosensor within the small intestine.
Colonoscopy is a diagnostic procedure to detect pre-cancerous polyps and tumors in the colon and is performed by inserting a long tube equipped with a camera and biopsy tools. Despite the medical benefits, patients undertaking this procedure often complain about the associated pain and discomfort. These sufferings are mostly due to the rough handling and excessive physical force during the tube insertion. The overall goal of this work is to minimize the invasiveness of traditional colonoscopy. In pursuit of this goal, this work presents the development of a semi-autonomous colonoscopic robot with minimally invasive locomotion. The proposed robotic approach allows physicians to mainly concentrate on the diagnosis rather than the mechanics of the procedure. In this paper, an innovative locomotion approach for robotic colonoscopy is addressed. Our locomotion approach takes advantage of longitudinal expansion of a latex tube to propel the robot’s tip along the colon. This soft and compliant propulsion mechanism, in contrast to minimally-invasive mechanisms used in, for example, inchworm-like robots, has shown promising potential. In the preliminary ex-vivo experiments, the robot successfully advanced 1.5 meters inside an excised curvilinear porcine colon with average speed of 28 mm/sec, traversing four 90-degree curves. The robot creates less than 6 N of normal force at its tip when it is pressurized with 90 kPa. This maximum force generates pressure of 44.17 mmHg at the tip, which is significantly lower than safe intraluminal human colonic pressure of 80 mmHg. The robot design inherently prevents loop formation in the colon, which is recognized as the main cause of post procedural pain in patients. Overall, the robot has shown great promise in an ex-vivo experimental setup. The design of an autonomous control system and in vivo experiments are left as future work.
Background: In single-port access surgeries, robot size is crucial due to the limited space. Thus, a robot may be designed underactuated. Suturing, in contrast, is a complicated task and requires full actuation. This study aims to overcome this shortcoming by implementing an optimization-based algorithm for autonomous suturing for an underactuated robot. Methods: The proposed algorithm approximates the ideal suturing trajectory by slightly reorienting the needle while the deviation of the needle with ideal suturing remains as minimized as possible. The deviation of the path taken by a custom robot with respect to the ideal trajectory varies, depending on the suturing start location within the workspace as well as the needle size. Results: A quantitative analysis reveals that in 13% of the investigated workspace, the accumulative deviation was less than 10 mm. In the remaining workspace, the accumulative deviation was less than xx mm. Likewise, the accumulative deviation of a needle with radius of 10 mm was 2.2 mm as opposed to 8 mm when the radius is 20 mm. Conclusions: The optimization-based algorithm maximized the accuracy of a four-DOF robot to perform a path-constrained trajectory and illustrates the accuracy-workspace correlation.
The aims of robotic colonoscopy are typically to reduce the risk of perforation, reduce exam time, and to increase patient comfort. Here is a robot under development at UNL and UNO that potentially achieves these aims.