Accurate and precise control of catheters inside a vasculature is a difficult yet important task. Current manual approaches require significant surgical skill. Over the years, surgeons build up a sort of mental kinematic map telling them how to handle the catheter in order to steer the catheter tip safely through the vessel system. The input-output behaviour of the catheter is complex and depends heavily on its configuration within and contacts with the vasculature. This paper introduces an alternative approach to control robotic catheters. The input-output behaviour or so-called differential kinematics are derived from a patient-specific vasculature model, following a minimum-energy argumentation. The validity of the proposed approach is demonstrated experimentally. Whereas the performance of model-based approaches is obviously greatly influenced by the correctness of estimated parameters, within this work we show experimentally how reasonable performance can already be achieved within the setup that was constructed. We expect that there is still ample room for improvement by, e.g., putting more sophisticated identification, modeling and collision detection schemes into place.

This paper introduces a framework for constraint-based force/position control of robots that exhibit large nonlinear structural compliance and that undergo large deformations. Controller synthesis follows hereto the principles of the Task Frame and instantaneous Task Specification using Constraints (iTaSC) formalisms. iTaSC is found particularly suitable due to its ability to express and combine control tasks in a natural way. Control tasks can be formulated as combinations of target positions, velocities, or forces expressed in an arbitrary number and type of coordinate frames. The proposed framework is applied to a mixed mechatronic system composed of a traditional rigid-link robot whose end-effector is a continuum (flexible) link. A selection of different position/force control tasks is prepared to demonstrate the validity and general nature of the proposed framework.

This paper presents a mathematical formulation for calculation of the compliance of continuum type of robots. The mathematical model of the continuum robot is built following the Cosserat rod theory and focuses on a single section Cosserat rod under arbitrary loading. The compliance of the robot is described as a set of ordinary differential equations with split boundary conditions. This new set of compliance equations is directly coupled to the solution of the forward kinematics of the robot. After solving the forward kinematics problem, these solutions can be directly used to compute the compliance. A particular class of continuum robots in which the compliance of the robot can be formulated as an initial value problem and solved in a single numerical integration is discussed. The paper provides experimental validation of the proposed method.

Minimally invasive endovascular procedures including robotically assisted intervention require effective intraoperative guidance. This is mainly achieved through intraoperative imaging such as fluoroscopy. Concerns over excessive x-ray radiation and nephrotoxicity due to repeated injection of contrast agents have motivated the development of effective catheter navigation schemes based on limited imaging data. This paper presents a catheter navigation technique based on probabilistic fusion of in situ real-time electromagnetic tracking with physically-based simulation of the mechanical characteristics of the catheter. A catheter with multiple electromagnetic sensors placed along its length has been developed. The sensor data and the catheter insertion-length are used as the boundary condition for determining the shape and position of the catheter within the vasculature. A probabilistic framework based on a Kalman Filter is used to combine the information from the catheter motion algorithm and the electromagnetic tracking data. This provides continuous visualization of the catheter within the lumen without the need of continuous fluoroscopy and contrast injection. The proposed approach has been validated with detailed in vitro experiments demonstrating the potential clinical application of the technique.

Recent discovery of a cracked and leaking Reactor Pressure Vessel Head (RPVH) nozzles have raised concerns about the structural integrity of RPVH nozzles in the pressurized water reactor (PWR) nuclear power plants. In order to remove crack abnormalities in the areas of nozzle J-Groove Weld on reactor pressure vessel head, we have developed an “Automated Robotic Grinding” (ARG) system which removes the surface cracks of the J-Groove Weld nozzles. Cracks are removed by the means of grinding of the J-Groove Weld performed both automatically and remotely. A manipulator was designed to be attached to the nozzle of the reactor head and enable the grinder tool to move according to cylindrical coordinate system with three degrees of freedom. Control system allows a synchronized motion of the manipulator axes and remote operation of the ARG manipulator. The inputs for grinding are the surface area coordinates of the crack and the maximum depth of the crack. Due to the limited accessibility in the area around the CRDM nozzle, the system is designed to include combined sensor and actuator. The grinder tool is first used as a sensor in a procedure to automatically detect the surface topology in the given area of the J-Groove Weld and then as an actuator which grinds with predefined depth, leaving the surface smooth and free of sharp edges. In this paper we present main features of the ARG system as well as main features of the grinding procedure.