48 research outputs found
Snake-Like Robots for Minimally Invasive, Single Port, and Intraluminal Surgeries
The surgical paradigm of Minimally Invasive Surgery (MIS) has been a key
driver to the adoption of robotic surgical assistance. Progress in the last
three decades has led to a gradual transition from manual laparoscopic surgery
with rigid instruments to robot-assisted surgery. In the last decade, the
increasing demand for new surgical paradigms to enable access into the anatomy
without skin incision (intraluminal surgery) or with a single skin incision
(Single Port Access surgery - SPA) has led researchers to investigate
snake-like flexible surgical devices. In this chapter, we first present an
overview of the background, motivation, and taxonomy of MIS and its newer
derivatives. Challenges of MIS and its newer derivatives (SPA and intraluminal
surgery) are outlined along with the architectures of new snake-like robots
meeting these challenges. We also examine the commercial and research surgical
platforms developed over the years, to address the specific functional
requirements and constraints imposed by operations in confined spaces. The
chapter concludes with an evaluation of open problems in surgical robotics for
intraluminal and SPA, and a look at future trends in surgical robot design that
could potentially address these unmet needs.Comment: 41 pages, 18 figures. Preprint of article published in the
Encyclopedia of Medical Robotics 2018, World Scientific Publishing Company
www.worldscientific.com/doi/abs/10.1142/9789813232266_000
Task and Configuration Space Compliance of Continuum Robots via Lie Group and Modal Shape Formulations
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
Design Considerations and Robustness to Parameter Uncertainty in Wire-Wrapped Cam Mechanisms
Collaborative robots must simultaneously be safe enough to operate in close
proximity to human operators and powerful enough to assist users in industrial
tasks such as lifting heavy equipment. The requirement for safety necessitates
that collaborative robots are designed with low-powered actuators. However,
some industrial tasks may require the robot to have high payload capacity
and/or long reach. For collaborative robot designs to be successful, they must
find ways of addressing these conflicting design requirements. One promising
strategy for navigating this tradeoff is through the use of static balancing
mechanisms to offset the robot's self weight, thus enabling the selection of
lower-powered actuators. In this paper, we introduce a novel, 2 degree of
freedom static balancing mechanism based on spring-loaded, wire-wrapped cams.
We also present an optimization-based cam design method that guarantees the
cams stay convex, ensures the springs stay below their extensions limits, and
minimizes sensitivity to unmodeled deviations from the nominal spring constant.
Additionally, we present a model of the effect of friction between the wire and
the cam. Lastly, we show experimentally that the torque generated by the cam
mechanism matches the torque predicted in our modeling approach. Our results
also suggest that the effects of wire-cam friction are significant for
non-circular cams
Endovascular Detection of Catheter-Thrombus Contact by Vacuum Excitation
Objective: The objective of this work is to introduce and demonstrate the
effectiveness of a novel sensing modality for contact detection between an
off-the-shelf aspiration catheter and a thrombus. Methods: A custom robotic
actuator with a pressure sensor was used to generate an oscillatory vacuum
excitation and sense the pressure inside the extracorporeal portion of the
catheter. Vacuum pressure profiles and robotic motion data were used to train a
support vector machine (SVM) classification model to detect contact between the
aspiration catheter tip and a mock thrombus. Validation consisted of benchtop
accuracy verification, as well as user study comparison to the current standard
of angiographic presentation. Results: Benchtop accuracy of the sensing
modality was shown to be 99.67%. The user study demonstrated statistically
significant improvement in identifying catheter-thrombus contact compared to
the current standard. The odds ratio of successful detection of clot contact
was 2.86 (p=0.03) when using the proposed sensory method compared to without
it. Conclusion: The results of this work indicate that the proposed sensing
modality can offer intraoperative feedback to interventionalists that can
improve their ability to detect contact between the distal tip of a catheter
and a thrombus. Significance: By offering a relatively low-cost technology that
affords off-the-shelf aspiration catheters as clot-detecting sensors,
interventionalists can improve the first-pass effect of the mechanical
thrombectomy procedure while reducing procedural times and mental burden
A learning algorithm for visual pose estimation of continuum robots
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°