Event-Based {LQR} with Integral Action

International audienceIn this paper, a state-feedback linear-quadratic regulator (LQR) is proposed for event-based control of a linear system. An interesting property of LQRs is that an optimal response of the system can be obtained in accordance to some specifications, like the actuator limits. An integral action is also added in order to not only restrict the study to null stabilization but also to tracking. The idea is to consider an external control loop and stabilize the integral of the error between the measurement and a desired setpoint to track. However, an event-triggered integral can lead to important overshoots when the interval between two successive events becomes large. Therefore, an exponential forgetting factor of the sampling interval is proposed as a solution to avoid such problems. The whole proposal is tested on a real-time system (a gyroscope) in order to highlight its ability, the reduction of control updates and the respect to the actuator limits

Attitude control of a gyroscope actuator using event-based discrete-time approach

International audienceIn this paper, a discrete state feedback Linear Quadratic Regulator (LQR) for event-triggered control is presented. To ensure zero steady state error in the case of such controllers, one normally extends the states with an integral action. Instead of using integral action, the idea is to estimate the disturbance causing the steady state error and use this to extend the states. A Lyapunov-based event triggering function is proposed. Practical results using a gyroscope actuator are presented and compared to a classical time-triggered controller. The obtained results demonstrate the simplicity and efficiency of the proposed approach

Event-based speed control on a sensor-less miniature thruster

International audienceThe main contribution of this paper is the experimental evaluation of the performance of different event-based control strategies in the case of a sensor-less miniature thruster. While most control engineering applications considers periodic control with equidistant sample intervals, the event-based approach updates the control signal only when required. The performances in terms of thruster power consumption and control update number are evaluated by comparing the event- based control system with respect to the time-based loop for the angular speed regulation of a sensor-less miniature thruster. The experimental results clearly show an important reduction of the control updates while the power consumptions are similar

An analytical approximation scheme to two point boundary value problems of ordinary differential equations

A new (algebraic) approximation scheme to find {\sl global} solutions of two point boundary value problems of ordinary differential equations (ODE's) is presented. The method is applicable for both linear and nonlinear (coupled) ODE's whose solutions are analytic near one of the boundary points. It is based on replacing the original ODE's by a sequence of auxiliary first order polynomial ODE's with constant coefficients. The coefficients in the auxiliary ODE's are uniquely determined from the local behaviour of the solution in the neighbourhood of one of the boundary points. To obtain the parameters of the global (connecting) solutions analytic at one of the boundary points, reduces to find the appropriate zeros of algebraic equations. The power of the method is illustrated by computing the approximate values of the ``connecting parameters'' for a number of nonlinear ODE's arising in various problems in field theory. We treat in particular the static and rotationally symmetric global vortex, the skyrmion, the Nielsen-Olesen vortex, as well as the 't Hooft-Polyakov magnetic monopole. The total energy of the skyrmion and of the monopole is also computed by the new method. We also consider some ODE's coming from the exact renormalization group. The ground state energy level of the anharmonic oscillator is also computed for arbitrary coupling strengths with good precision.Comment: 5 pages, 3 tables, Late

Electrostatics in a simple wormhole revisited

The electrostatic potential generated by a point charge at rest in a simple static, spherically symmetric wormhole is given in the form of series of multipoles and in closed form. The general potential which is physically acceptable depends on a parameter due to the fact that the monopole solution is arbitrary. When the wormhole has Z2-symmetry, the potential is completely determined. The calculation of the electrostatic self-energy and of the self-force is performed in all cases considered.Comment: 16 pages, no figure

On the issue of transparency and reproducibility in nanomedicine.

Following our call to join in the discussion over the suitability of implementing a reporting checklist for bio-nano papers, the community responds

Event-based control dedicated to robotic systems

La théorie du contrôle a d'abord été conçue pour des contrôleurs analogiques. Il était alors pertinent de synthétiser un contrôleur dans une représentation continue. De nos jours, les systèmes numériques ont majoritairement remplacés les systèmes analogiques pour différentes raisons (coût, résistance au bruit, intégration,...). Les signaux sont alors maintenus constants entre le cadencement périodique fixé par une horloge numérique.La commande événementielle vise à améliorer l’échantillonnage périodique en proposant une méthode dans laquelle les mises à jour sont déclenchées par une fonction événement.Dans cette thèse, de nouvelles méthodes de synthèse de contrôleurs evenementiels sont présentés et testés sur des systèmes temps-réels.La contribution la plus originale étant l'utilisation d'une commande événementielle appliquée à un problème d'anticollision entre une quadrirotor et un environnement supposé connu.Control system theory has first been built for analog controllers. In this context, it was relevant to use a continuous framework to design a control feedback function. Nowadays, digital technologies are supplanting analog solutions due to several advantages (cost, noise, resistance, integration...). Signal is held constant between periodic triggers given by a digital clock.Event-based (or event-triggered) control aims to improve the periodic sampling scheme by proposing a method in which updates are triggered by an event function.In this thesis new event-based designs are detailled and tested on real-time systems.The most original contribution of this thesis is the use of an event-triggered design for a problem of collision avoidance between a quadrotor and a known environment

Commande événementielle : applications aux systèmes robotiques

Control system theory has first been built for analog controllers. In this context, it was relevant to use a continuous framework to design a control feedback function. Nowadays, digital technologies are supplanting analog solutions due to several advantages (cost, noise, resistance, integration...). Signal is held constant between periodic triggers given by a digital clock.Event-based (or event-triggered) control aims to improve the periodic sampling scheme by proposing a method in which updates are triggered by an event function.In this thesis new event-based designs are detailled and tested on real-time systems.The most original contribution of this thesis is the use of an event-triggered design for a problem of collision avoidance between a quadrotor and a known environment.La théorie du contrôle a d'abord été conçue pour des contrôleurs analogiques. Il était alors pertinent de synthétiser un contrôleur dans une représentation continue. De nos jours, les systèmes numériques ont majoritairement remplacés les systèmes analogiques pour différentes raisons (coût, résistance au bruit, intégration,...). Les signaux sont alors maintenus constants entre le cadencement périodique fixé par une horloge numérique.La commande événementielle vise à améliorer l’échantillonnage périodique en proposant une méthode dans laquelle les mises à jour sont déclenchées par une fonction événement.Dans cette thèse, de nouvelles méthodes de synthèse de contrôleurs evenementiels sont présentés et testés sur des systèmes temps-réels.La contribution la plus originale étant l'utilisation d'une commande événementielle appliquée à un problème d'anticollision entre une quadrirotor et un environnement supposé connu

Effect of high-intensity interval training on total, abdominal and visceral fat mass: a meta-analysis

International audienceBackground High-intensity interval training (HIIT) is promoted as a time-efficient strategy to improve body composition.Objective The aim of this meta-analysis was to assess the efficacy of HIIT in reducing total, abdominal, and visceral fat mass in normal-weight and overweight/obese adults.Methods Electronic databases were searched to identify all related articles on HIIT and fat mass. Stratified analysis was performed using the nature of HIIT (cycling versus running, target intensity), sex and/or body weight, and the methods of measuring body composition. Heterogeneity was also determinedResults A total of 39 studies involving 617 subjects were included (mean age 38.8 years +/- 14.4, 52% females). HIIT significantly reduced total (p = 0.003), abdominal (p = 0.007), and visceral (p = 0.018) fat mass, with no differences between the sexes. A comparison showed that running was more effective than cycling in reducing total and visceral fat mass. High-intensity (above 90% peak heart rate) training was more successful in reducing whole body adiposity, while lower intensities had a greater effect on changes in abdominal and visceral fat mass. Our analysis also indicated that only computed tomography scan or magnetic resonance imaging showed significant abdominal and/or visceral fat-mass loss after HIIT interventions.Conclusion HIIT is a time-efficient strategy to decrease fat-mass deposits, including those of abdominal and visceral fat mass. There was some evidence of the greater effectiveness of HIIT running versus cycling, but owing to the wide variety of protocols used and the lack of full details about cycling training, further comparisons need to be made. Large, multicenter, prospective studies are required to establish the best HIIT protocols for reducing fat mass according to subject characteristics