Control of a magnetic microrobot navigating in microfluidic arterial bifurcations through pulsatile and viscous flow

International audienceNavigating in bodily fluids to perform targeted diagnosis and therapy has recently raised the problem of robust control of magnetic microrobots under real endovascular conditions. Various control approaches have been proposed in the literature but few of them have been experimentally validated. In this paper, we point out the problem of navigation controllability of magnetic microrobots in high viscous fluids and under pulsatile flow for endovascular applications. We consider the experimental navigation along a desired trajectory, in a simplified millimeter-sized arterial bifurcation, operating in fluids at the low-Reynolds-number regime where viscous drag significantly dominates over inertia. Different viscosity environments are tested (ranging from 100\% water-to-100\% glycerol) under a systolic pulsatile flow compatible with heart beating. The control performances in terms tracking, robustness and stability are then experimentally demonstrated

Robust Control Strategy for a Conduction–Convection System Based on the Scenario Optimization

International audienceThis paper deals with the robust control of an uncertain conduction–convection system in the framework of probabilistic control design based on both the geometric control and the scenario optimization approach. Thus, a robust control strategy that copes with parameter uncertainties is proposed for a heated rod taken as an application example of a conduction–convection system. The design approach consists in two steps. In the first step, assuming a nominal model, a state feedback that yields a stable linear lumped parameter system, of first order, in closed loop is designed by means of geometric control theory. The stability of the resulting closed-loop system is demonstrated based on the perturbation theorem from semigroup theory. The second step consists in defining the input reference of the designed state feedback by a structured robust controller. The parameter tuning of the structured controller is formulated as a semi-infinite (or robust) optimization problem which is, then, relaxed using the scenario approach leading to a standard finite optimization problem. The solution of this scenario optimization problem is achieved using a genetic algorithm. The proposed control strategy is adopted to cope with parameter uncertainties in the problem of heating a steel rod. The effectiveness of the proposed robust control strategy is demonstrated by simulation

Robust control strategy for a conduction-convection system based on the scenario optimization

International audienceThis paper deals with the robust control of an uncertain conduction-convection system in the framework of probabilistic control design based both on the geometric control and the scenario optimization approach. Thus, a robust control strategy that copes with parameter uncertainties is proposed for a heated rod taken as an application example of a conduction-convection system. The design approach consists in two steps. In the first step, assuming a nominal model, a state feedback that yields a stable linear lumped parameter system, of first order, in closed loop is designed by means of geometric control theory. The stability of the resulting closed loop system is demonstrated based on the perturbation theorem from semigroup theory. The second step consists in defining the input reference of the designed state feedback by a structured robust controller. The parameter tuning of the structured controller is formulated as a semi-infinite (or robust) optimization problem which is, then, relaxed using the scenario approach leading to a standard finite optimization problem. The solution of this scenario optimization problem is achieved using a genetic algorithm. The proposed control strategy is adopted to cope with parameter uncertainties in the problem of heating a steel rod. The effectiveness of the proposed robust control strategy is demonstrated by simulation

Robotic Manipulator for Positioning a Magnetic Actuator Dedicated to Drug Delivery in the Cochlea

International audienceThe actuators dedicated to micrometric applications are known for their precision but also for their restricted workspace. The use of a robotic manipulator as a carrier makes it possible to considerably increase this workspace. In this paper, we present a novel robotic system specially designed for positioning a magnetic actuator based on permanent magnets, used as an end-effector of the robot for steering magnetic microrobot throughout the cochlea. Using the classical mathematical tools of serial robotics, we determined the direct and inverse kinematic models of the manipulator, thus defining a reference trajectory to move the microrobot on a space as small as possible and take account of the geometrical specifications based on medical needs. A prototype has been realized with a 3D printer to experimentally validate the numerical results. In addition, the mechanical considerations for the construction of the prototype are presented

Predictive navigation of a magnetic microrobot : instrumentation, control ans validation

Un grand nombre de traitements sont aujourd'hui disponibles pour la cancérologie, dont l'objectif est d'éliminer tous les tissus cancéreux en minimisant les dommages occasionnés sur les tissus sains. La chimio-embolisation est considérée comme un régime de traitement localisé, préconisé pour certains cancers. Cependant, le ciblage des tumeurs profondément enfouies par chimio-embolisation est actuellement limité en raison de la taille des cathéters. Compte tenu des échelles envisagées, l'utilisation des microrobots magnétiquement guidés est l'une des approches les plus prometteuses. L'objectif de cette thèse consiste à développer les outils permettant à des microrobots endovasculaires (ou transporteurs magnétiques), de naviguer dans le corps humain, en utilisant les gradients magnétiques d'un appareil IRM clinique amélioré. Pour cela, une compréhension approfondie de l'environnement d'évolution du microrobot est une étape au préalable, en vue d'établir des stratégies de navigation adéquates. La variation des paramètres physiologiques de l'humain et l'utilisation d'un scanner IRM nécessitent d'une part, une robustesse du contrôleur vis-à-vis des erreurs de modélisation, et d'autre part, l'anticipation du comportement du système. A cet effet, la commande prédictive, trouve ici toute son efficacité pour résoudre les problèmes de poursuite. En outre, une plateforme d'instrumentation a été conçue au sein du laboratoire en vue de démontrer les concepts proposés, et de valider les stratégies de navigation prédictives développées dans nos travaux. Puis, dans un deuxième temps, nous avons intégré ces approches dans une plateforme d'IRM clinique.Today, many cancer treatments are available, whose goal is to kill the cancerous tissue and to minimize damage to healthy tissue. Chemoemobilization is considered as a targeting treatment recommended for some cancers. However, targeting tumor deeply buried using chemoemobilization is currently limited due to the size of the microcatheters. Taking into account the scales considered, the use of magnetically guided microrobots is one of the most promoting approaches. The objective of this thesis is to develop tools for endovascular microrobots (or carriers), navigate in the human body using magnetic gradients of an improved clinical MRI. For this, understanding microrobot evolution environment is a first step, in order to develop appropriate navigation strategies. The variation of the human physiological parameters and the use of MRI scanner require a robustness of the controller to the modeling errors, and the anticipation of the system behavior. For this, predictive control is fully effective to solve the tracking problem. In addition, an instrumentation platform was designed to demonstrate the proposed concepts and to validate the predictive navigation strategies developed in our work. Then, in a second step, we investigated these approaches in clinical MRI platform

Navigation prédictive d'un microrobot magnétique : Instrumentation, commande et validation

Today, many cancer treatments are available, whose goal is to kill the cancerous tissue and to minimize damage to healthy tissue. Chemoemobilization is considered as a targeting treatment recommended for some cancers. However, targeting tumor deeply buried using chemoemobilization is currently limited due to the size of the microcatheters. Taking into account the scales considered, the use of magnetically guided microrobots is one of the most promoting approaches. The objective of this thesis is to develop tools for endovascular microrobots (or carriers), navigate in the human body using magnetic gradients of an improved clinical MRI. For this, understanding microrobot evolution environment is a first step, in order to develop appropriate navigation strategies. The variation of the human physiological parameters and the use of MRI scanner require a robustness of the controller to the modeling errors, and the anticipation of the system behavior. For this, predictive control is fully effective to solve the tracking problem. In addition, an instrumentation platform was designed to demonstrate the proposed concepts and to validate the predictive navigation strategies developed in our work. Then, in a second step, we investigated these approaches in clinical MRI platform.Un grand nombre de traitements sont aujourd'hui disponibles pour la cancérologie, dont l'objectif est d'éliminer tous les tissus cancéreux en minimisant les dommages occasionnés sur les tissus sains. La chimio-embolisation est considérée comme un régime de traitement localisé, préconisé pour certains cancers. Cependant, le ciblage des tumeurs profondément enfouies par chimio-embolisation est actuellement limité en raison de la taille des cathéters. Compte tenu des échelles envisagées, l'utilisation des microrobots magnétiquement guidés est l'une des approches les plus prometteuses. L'objectif de cette thèse consiste à développer les outils permettant à des microrobots endovasculaires (ou transporteurs magnétiques), de naviguer dans le corps humain, en utilisant les gradients magnétiques d'un appareil IRM clinique amélioré. Pour cela, une compréhension approfondie de l'environnement d'évolution du microrobot est une étape au préalable, en vue d'établir des stratégies de navigation adéquates. La variation des paramètres physiologiques de l'humain et l'utilisation d'un scanner IRM nécessitent d'une part, une robustesse du contrôleur vis-à-vis des erreurs de modélisation, et d'autre part, l'anticipation du comportement du système. A cet effet, la commande prédictive, trouve ici toute son efficacité pour résoudre les problèmes de poursuite. En outre, une plateforme d'instrumentation a été conçue au sein du laboratoire en vue de démontrer les concepts proposés, et de valider les stratégies de navigation prédictives développées dans nos travaux. Puis, dans un deuxième temps, nous avons intégré ces approches dans une plateforme d'IRM clinique

Three-Dimensional Controlled Motion of a Microrobot using Magnetic Gradients

International audienceThis paper presents the endovascular navigation of a ferromagnetic microdevice using magnetic resonance imaging (MRI)-based predictive control. The concept was studied for the future development of microrobots designed to perform minimally invasive interventions in remote sites accessible through the human cardiovascular system. A system software architecture is presented illustrating the different software modules to allow three-dimensional (3-D) navigation of a microdevice in blood vessels, namely: (i) vessel path extraction, (ii) magnetic gradient steering, (iii) tracking and (iv) closed-loop navigation control. First, the navigation path of the microrobot into the blood vessel is extracted using the Fast Marching Method from the pre-operation images (3-D MRI imaging) to guide the microrobot from the injection point to the tumor area through the anarchic vessel network. Based on the pre-computed path, a Model Predictive Controller is proposed for robust time-multiplexed navigation along a 3-D path in the presence of pulsative flow. The simulation results suggest the validation of the proposed image processing and control algorithms

3D MRI-based predictive control of a ferromagnetic microrobot navigating in blood vessels

International audienceThis paper presents an endovascular navigation of a ferromagneticmicrodevice using a MRI-based predictive control. The concept wasstudied for future development of microrobot designed to performminimally invasive interventions in remote sites accessible throughthe human cardiovascular system. A system software architecture ispresented illustrating the different software modules to allow 3Dnavigation of a microdevice in blood vessels, namely: (i) vesselpath extraction, (ii) magnetic gradient steering, (iii) trackingand (iv) closed-loop navigation control. First, the navigation pathof the microrobot into the blood vessel is extracted using Fast MarchingMethod (FMM) from the pre-operation images (3D MRI imaging) to guidethe microrobot from the injection point to the tumor area throughthe anarchic vessel network. Based on the pre-computed path, a ModelPredictive Controller (MPC) is proposed for robust navigation alonga 3D path. The simulation results suggest the validation of the proposedimage processing and control algorithms

Untethered microrobot control in fluidic environment using magnetic gradients

International audienceNavigating in bodily fluids to perform targeted diagnosis and therapy has recently raised the problem of robust control of magnetic microrobots under real endovascular conditions. Various control approaches have been proposed in the literature but few of them have been experimentally validated. In this paper, we point out the problem of navigation controllability of magnetic microrobots in high viscous fluids and under pulsatile flow for endovascular applications. We consider the experimental navigation along a desired trajectory, in a simplified millimeter-sized arterial bifurcation, operating in fluids at the low-Reynolds-number regime where viscous drag significantly dominates over inertia. Different viscosity environments are tested (ranging from 100% water-to-100% glycerol) under a systolic pulsatile flow compatible with heart beating. The control performances in terms tracking, robustness and stability are then experimentally demonstrated