Laurent Catoire

Modeling of the interaction force between the instrument and the trocar in minimally invasive surgery

Trocars used in Minimally Invasive Surgery (MIS) are equipped with a sealing mechanism. During the motion of an instrument through a trocar, the sealing mechanism deforms itself. None of the friction models presented in the literature capture the macroscopical deformation of the seal mechanism. Therefore a specific hybrid model is developed to describe the movement of an instrument through a trocar. The only geometrical assumption of this model is the axial symmetry of the two bodies. It can thus be applied to all problems with the same symmetry. Two operating modes are distinguished, corresponding to the deformation of the sealing mechanism on the one hand, and to the sliding phase through the trocar on the other hand. The model is identified and validated using experimental data recorded on a dedicated test setup.

Design of a static output feedback controller for bilateral teleoperation

Abstract Traditional H ∞ design methods available in commercial softwares lead to controllers which present the same order as the model of the plant. Considering the high order of teleoperation systems, implementing such controllers may require the use of order-reduction methods. To avoid this extra step in the design, we propose to produce fixed-order controllers directly based on a full-order model of the system. In this paper, a zero-order (static output feedback) controller is designed for a teleoperation system. The design procedure, based on a cone complementary formulation is described and applied to a 22 nd -order model of the system. The resulting controller is implemented on a one degree of freedom teleoperation system. The experimental results obtained with this simple control structure validate the use of very low order control structures in the case of teleoperation systems with the extra advantage, with respect to conventional H ∞ design techniques, that the involved and time-consuming order reduction step is avoided.

Disturbance-observer-based user force estimation for bilateral teleoperated needle insertion

The work reported in this paper is part of a project aiming at designing a teleoperated tool to perform a needle insertion task through an endoscope. The focus is on the design of the master interface. The proposed mechanical design ensures that the gesture performed by the operator is as close as possible to the original clinical gesture. As this design does not allow for an easy measurement of the interaction force with the operator, a software sensor is used to estimate this force from an encoder measurement. It relies on a disturbance observer (DOB), for which a systematic design approach is presented. The DOB requires the velocity of the one dof master device as input. A comparative study between four possible approaches is performed in order to determine the most appropriate method to estimate this velocity. A method relying directly on the encoder pulses appears to surpass the classical velocity estimators.

Identification of a hybrid model for simulation of the instrument/trocar interaction force

Trocars used in Minimally Invasive Surgery (MIS) are equipped with a sealing mechanism. During the motion of an instrument through a trocar, the sealing mechanism deforms itself. The Extended Maxwell Slip model has been developed in order to capture the deformation of the sealing mechanism. Two operating phases are distinguished, corresponding to the deformation of the sealing mechanism on the one hand, and to the sliding phase through the trocar on the other hand. This article addresses the identification procedure for this model. The deformation phase uses a PieceWise Affine (PWA) model. This model is identified using a PWARX (PieceWise ARX) identification technique namely the clustering based technique. Identification and validation are achieved using experimental data recorded on a dedicated test setup.

Simulation and implementation of bilateral teleoperated needle insertion via an endoscope

This paper describes the design of a 1 dof teleoperation system aiming at performing a needle insertion task through an endoscope. The mechanical design of the master accounts for issues of ergonomics and performance (low inertia and friction force), while issues of ergonomics and instrumentations guided the design of the slave device. A complete simulator of the master / slave device together with its environment was developed, with particular focus on the major sources of friction. It was used for validation of the control scheme. Experimental results of a needle insertion task in a phantom multilayer tissue demonstrate the effectiveness of the device for detecting force variations due to puncturing of a tissue. Besides, the experimental signal recordings exhibit a good fit with the simulator outputs, which testifies the validity of this simulator.