Jacques Gangloff

Model predictive control for compensation of cyclic organ motions in teleoperated laparoscopic surgery

During teleoperated laparoscopic surgery with robots, periodic deformations of organs due to respiratory movements may be critical disturbances for surgeons manipulating the robot. Indeed, the surgeon has to manually compensate for these motions if accurate gestures are needed, like, e.g., during suturing. This paper proposes a repetitive model predictive control scheme for driving a surgical robot toward the reference trajectory defined by the surgeon while rejecting cyclic disturbances due to the respiratory motion. A new cost function is proposed for an unconstrained generalized predictive control scheme based on a multiple input-output model of the surgical robot. Contributions of the controller output to the reference tracking task and to the disturbance rejection task are split and computed separately, so that their respective efficiency can be independently weighted. The proposed control scheme is validated through simulations and experimental in vivo results using a surgical robot.

High-speed visual servoing of a 6-d. o. f. manipulator using multivariable predictive control

This paper presents a new approach to model and control high-speed 6-d.o.f. visual servo loops. The modeling and control strategy take into account the dynamics of the velocity-controlled 6-d.o.f. manipulator as well as a simplified model of the camera and acquisition system in order to significantly increase the bandwidth of the servo loop. Multi-input multi-output generalized predictive control (GPC) is used to optimally control the visual loop with respect to the proposed dynamical model. The predictive feature of the GPC is used for optimal trajectory following in Cartesian space. Experimental results on a 6-d.o.f. industrial robot are presented that validate the proposed model. The visual sensor used in the experiments is a high-speed camera that acquires 120 non-interlaced images. Using this camera, a sampling rate of 120 Hz is achieved for the visual loop. Furthermore, a precise synchronization method is used to reduce the delays due to image transfer and processing. The experiments show a drastic improvement of the loop performance with respect to more classical control strategies for 6-d.o.f. visual servo loops.

Towards robotized beating heart TECABG: Assessment of the heart dynamics using high-speed vision

Active robotic filtering is probably the solution for beating heart Totally Endoscopic Coronary Artery Bypass Grafting (TECABG). In this work, we assess the heart motion dynamics by simultaneous use of high-speed imaging of optical markers attached to the heart, ECG signals and ventilator airflow acquisitions. Our goal is to assess the heart motions (shape, velocity, acceleration) in order to be able to make more accurate specifications for a novel, dedicated robot that could follow these motions in real time. Furthermore, using two additional inputs (ECG and airflow), we propose a novel robust prediction algorithm that could be used with a predictive control algorithm to improve the tracking accuracy.

Motion Prediction for Computer-Assisted Beating Heart Surgery

Off-pump totally endoscopic coronary artery bypass grafting is a milestone for cardiac surgery, and still a technical challenge. Indeed, the fast and complex cardiac motion makes this operating method technically demanding. Therefore, several robotic systems have been designed to assist the surgeons by compensating for the cardiac motion and providing a virtually motionless operating area. In the proposed systems, the servoing schemes often take advantage of a prediction algorithm that supplies the controller with some future heart motion. This prediction enlarges the control-loop bandwidth, thus allowing a better motion compensation. Obviously, improving the prediction accuracy will lead to better motion-compensation results. Thus, a current challenge in computer-assisted cardiac surgery research is the design of efficient heart-motion-prediction algorithms. In this paper, a detailed survey of the main existing prediction approaches is given and a classification is provided. Then, a novel prediction technique based on amplitude modulation is proposed, and compared with other techniques using in vivo collected datasets. A final discussion summarizes the main features of all the proposed approaches.

A Parallel Robotic System with Force Sensors for Percutaneous Procedures Under CT-Guidance

This paper presents a new robotic framework for assisted CT-guided percutaneous procedures with force feedback and automatic patient-to-image registration of needle. The purpose is to help practitioners in performing accurate needle insertion while preserving them from harmful intra-operative X-rays imaging devices. Starting from medical requirements for needle insertions in the liver under CT-scan, a description of a dedicated parallel robot is made. Its geometrical and physical properties are explained. The design is mainly based on the accuracy and safety constraints. A real prototype is presented that is currently tested.

Physiological motion rejection in flexible endoscopy using visual servoing

Flexible endoscopes are used in many surgical procedures and diagnostic exams, like in gastroscopy or coloscopy. They have also been used recently for new surgical procedures using natural orifices called NOTES. While these procedures are very promising for the patients, they are quite awkward for the surgeons. The flexible endoscope allows the access to operating areas which are not easily reachable, with small or no incisions; but the manipulation of the system is complex. In order to help the practicians during NOTES or classical interventions with flexible endoscopes, we propose to motorize the system so as to partially robotize the movements. This paper presents the problems in the use of the flexible endoscope and explains how the system can be used to stabilize the endoscope on an area of interest despite physiological motions and therefore to improve the manipulation of the system.

Cardiolock: An active cardiac stabilizer. First in vivo experiments using a new robotized device

Off-pump Coronary Artery Bypass Grafting (CABG) is still a technically difficult procedure. The mechanical stabilizers used for local suppression of the heart excursion have been demonstrated to exhibit significant residual motion, which could lead to a lack of accuracy in performing the surgical task, particularly when using a minimally invasive surgery (MIS) approach. We therefore propose a novel active stabilizer to compensate for the residual motion whose architecture is compatible with MIS. An experimental evaluation of a commercially available totally endoscopic stabilizer is first presented to demonstrate the unsatisfactory behavior of this device. Then, the interaction between the heart and a mechanical stabilizer is assessed in vivo using an animal model. Finally, the principle of active stabilization, based on the high-speed vision-based control of a piezo-actuated compliant mechanism, is presented, along with in vivo experimental results obtained using a prototype to demonstrate its efficiency.

Toward robotized beating heart TECABG: assessment of the heart dynamics using high-speed vision

Active robotic filtering is a promising solution for beating heart Totally Endoscopic Coronary Artery Bypass Grafting (TECABG). n this work, we assess the heart motion dynamics using simultaneously igh speed imaging of optical markers attached to the heart, ECG signals and ventilator airflow acquisitions. Our goal is to make an assessment of the heart motion (shape, velocity, acceleration) in order to be able to make more accurate specifications for a dedicated robot that could follow this motion in real-time. Furthermore, using the 2 additional inputs (ECG, airflow), we propose a prediction algorithm of the motion that could be used with a predictive control algorithm to improve the tracking accuracy.

Active Stabilization for Robotized Beating Heart Surgery

In this paper, control strategies for an active stabilizer dedicated to beating heart coronary artery bypass grafting are investigated. The active stabilizer, which consists of a piezoactuated compliant mechanism, has to be controlled to compensate for the displacements induced by the beating heart in order to provide the surgeon with a locally motionless myocardium surface. Three controllers, including different levels of prior knowledge about the heart motion, are presented. Their performance with respect to modeling uncertainties, arising unknown interactions of the stabilizer with its positioning mechanism, and the heart, is studied through simulations, as well as laboratory and in vivo experiments. Finally, the selection of the most adequate control scheme and the performance of the device from a clinical point of view are discussed.

CTBot: A stereotactic-guided robotic assistant for percutaneous procedures of the abdomen

This article presents positioning results of a stereotactic robotic assistant for percutaneous needle insertions in the abdomen. The robotic system, called the CT-Bot, is succinctly described. This mechanically safe device is compatible with medical requirements and offers a novel approach robotic needle insertion with computed tomography guidance. Our system does self-registration using only visual information from a fiducial marker. The theoretical developments explain how the pose reconstruction is done using only four fiducial points and how the automatic registration algorithm is achieved. The results concern the automatic positioning of the tip of a needle with respect to a reference point selected in a CT-image. The accuracy of the positioning result show how interesting this system is for clinical use.