Xavier Brun

A Robust Differentiator-Controller Design for an Electropneumatic System

In this paper, a robust differentiator via sliding mode is studied. A comparative study between the robust differentiator and a classical one is presented. Experimental results of the proposed differentiator in the context of third order sliding mode controller for an electropneumatic system are given to illustrate the developments.

Does forceps training on a birth simulator allow obstetricians to improve forceps blade placement

OBJECTIVEnThe aim of this study was to evaluate whether forceps training on a birth simulator allows obstetricians to improve forceps blade placement.nnnSTUDY DESIGNnAnalysis was based on 600 forceps blade placements performed by ten trainees on a simulator. The trajectories used by the trainees were assessed using reference spheres that reflected an optimal bimalar placement. Three definitions of success were used: small-sphere success, medium-sphere success and large-sphere success were respectively defined by the forceps blade tip being within 5, 10 or 15mm of the center of the sphere (the small-sphere being nested within the medium-sphere and the small and medium being nested within the large-sphere). Wilcoxon paired analysis was performed to compare the first (50 trajectories) and final (50 trajectories) sets of five forceps placements. Graphical representation and linear regression were used to visualize the learning process.nnnRESULTSn596 trajectories were available for analysis. During the last set of five forceps the success rate was respectively 28%, 72% and 86% for small-sphere, medium-sphere and large-sphere success with the right blade and 8%, 32% and 70% for the left blade. Wilcoxon analysis showed a highly significant improvement for all kinds of success in the right blade and for large-sphere success in the left blade. Linear regression slopes were significant. Using a projection, the theoretical numbers of placements needed to achieve a 100% success rate for small-sphere, medium-sphere and large-sphere were respectively 80, 45 and 35.nnnCONCLUSIONnThese results strongly suggest that performing forceps blade placement on birth simulator allows obstetricians to improve their skills.

Adaptive Higher Order Sliding Modes for Two-dimensional Derivative Estimation

In this paper, some recent technical of the derivatives noisy transient signals estimation is extended to the two-dimensional case. This technique, which called higher order sliding modes is mostly used in the synthesis of robust controllers and is also shown a good results in the synthesis of the rth order robust dierentiators. In this work, such dierentiators are used as an edge detection method into image application. The proposed algorithm use an adaptive mechanism for tuning up its parameters in real time, in order to increase the efficiency of basic scheme. Some comparative study with a conventional methods of edge detection is performed.

Assessment of forceps use in obstetrics during a simulated childbirth

In obstetrics, manipulations are mainly learned during real deliveries. To minimize the risks linked to such training, we propose a childbirth simulator as a teaching tool in hospitals. More specifically, we focus on training with forceps during obstetric manipulation.

Comparative analysis of pick & place strategies for a multi-robot application

This paper deals with a comparative analysis of different pick & place strategies. The purpose is to give some rules to obtain a good sizing in terms of components (number of robots, conveyor speed) and control laws (individual scheduling rules of each robot, collaborative strategy of all the robots) of a multi-robot cell. This approach is validated by the use of a new simulation tool combining a behavioral simulation of multiple robots and the product flows. This simulation tool takes into account not only the end effector, but also the robots collaborative aspect to ensure the desired overall performance for a given task.

Dynamic Gains Differentiator for Hydraulic System Control

This paper deals with online numerical differentiation of a noisy time signal where new higher order sliding mode differentiators are proposed. The key point of these algorithms is to include a dynamic on the differentiator parameters. These dynamics tune-up automatically the algorithm gains in real-time. Convergence properties of the new schemes are derived using a Lyapunov approach. Their effectiveness is illustrated via simulations and experimental tests, where comparative studies are performed between classical schemes and the new ones. Such algorithms are also used in the feedback control of an electrohydraulic system.

A piecewise-affine approach to the analysis of non-linear control laws for pneumatic systems

This paper concerns the control of pneumatic actuators, which are nowadays of widespread use in the industry. A problem related to the use of such actuators is the so-called “stick-slip”, due to the presence of dry friction on the system. A switching control law has been proposed in the literature in order to avoid this phenomenon, without giving a formal proof of the closed-loop stability of the system; the absence of a proof was due to the difficulty of finding a Lyapunov function, and to the fact that the state converges not to a single point but to a set. In this article, we prove stability by modelling the pneumatic system and its switching control law as a piecewise affine system. This formalism allows the use of a variety of specific techniques, which we have extended in order to cast the proof of the convergence of the state as a Linear Matrix Inequality (LMI) test. The paper contains the description of our experimental setup and the results obtained by applying the aforementioned method.

Exponential Stability With Decay Rate Estimation for Linear Difference Equations

This technical note addresses the stability analysis of linear systems governed by continuous-time difference equations with multiple delays. We propose new sufficient conditions for L2-exponential stability and exponential stability within the Lyapunov-Krasovskii framework. These conditions are delayindependent, and provide constructive exponential decay rate estimates of the system response. It is also shown that these conditions are less conservative than previous results in the literature.

A piecewise-polynomial approach to the stability analysis of non-linear switching controllers in presence of sliding modes with application to pneumatic systems

This paper concerns the stability analysis of non-linear, switching control laws for pneumatic actuators. A first approach to the problem has been proposed by the authors in [1], under the hypothesis of a simplified model of friction. The approach is based on casting the closed-loop system into a piecewise-affine form. However, if a more realistic friction model is introduced, the method in [1] proves to be too conservative, and unfit to deal with the sliding modes that can occur with this new model. This paper proposes a new method for proving the stability on the system by introducing a less conservative class of Lyapunov function, namely piecewise-polynomial ones. At the end of the paper, we show how such a method can be successfully applied to our experimental setup.

Development of a methodology for performance analysis and synthesis of control strategies of multi-robot pick & place applications

This paper deals with a new simulation tool for the improvement of multi-robot pick & place applications performance combining behavioral simulation of multiple robots and products flows. A novelty of the proposed work is to take into account in the simulation not only the scheduling rules of each robot, but also the robots collaborative aspect to ensure the desired overall performance for a given task. The transition from simulation to implementation of pick & place strategies is also an issue tackled in this paper. By using a typical example consisting of comparing techniques to optimize the workflow, the utility of the simulation tool is proven. First experimental results validate the simulation results.