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This work considers the path planning problem for a team of identical robots evolving in a known environment. The robots should satisfy a global specification given as a Linear Temporal Logic (LTL) formula over a set of regions of interest. The proposed method exploits the advantages of Petri net models for the team of robots and B\"uchi automata modeling the specification. The approach in this paper consists in combining the two models into one, denoted Composed Petri net and use it to find a sequence of action movements for the mobile robots, providing collision free trajectories to fulfill the specification. The solution results from a set of Mixed Integer Linear Programming (MILP) problems. The main advantage of the proposed solution is the completeness of the algorithm, meaning that a solution is found when exists, this representing the key difference with our previous work in [1]. The simulations illustrate comparison results between current and previous approaches, focusing on the computational complexity., Comment: submitted to IEEE Transactions on Automatic Control, 2022

International audience; MCS (Minimal Cut Sequences) computation is the main objective of qualitative safety analysis of dynamic systems. This paper shows first that the existing definitions of MCS are not suitable when systems are repairable and reconfigurable, then proposes a new definition for this class of systems. This proposal is illustrated on a case study from power industry. Comparison of the obtained MCS to those which are yielded by algorithms based on previous definitions permits to highlight the relevance of the approach.

International audience; Vibration sensitivity is an important specification for oscillators dedicated to space or airborne systems. For some crystallographic material, some physical constant are not yet measured. So, computation of stress coefficients of frequency is not possible. This paper presents a simple experimentation which allows the determination of the six stress coefficients of frequency for each high-overtone bulk acoustic resonators configuration. The first three coefficient are sαmn are -2.9×10-12/Pa, 4.3×10-10/Pa and 9.4×10-11/Pa. The relative standard deviation can be high due to experimental uncertainty.

International audience; Vibration sensitivity is an important specification for oscillators dedicated to space or airborne systems. Vibration sensitivity can be due to the resonator, the oscillator loop or non-oscillator components like wire, for instance. Commonly, the main source of acceleration sensitivity is due to the resonator. Active compensation can be used to decrease this effect, but such systems are not easily miniaturized. This paper presents computations of the stress sensitivity coefficients of frequency for the high-overtone bulk acoustic resonators and the design of a simple packaging to minimize vibration sensitivity. The final goal is to control vibration sensitivity of the high-overtone bulk acoustic resonators with dedicated packaging. The computed results are compared to experimental ones. The agreement between theoretical and experimental results is about 50%.

Vibration sensitivity is an important specification for oscillators dedicated to space or airborne systems. Vibration sensitivity can be due to from resonator, oscillator loop or non-oscillator components as wire for example. Commonly, the main source of acceleration sensitivity is due to the resonator. Active compensation can be used to decrease this effect, but such systems are not easily miniaturized. This paper presents quality factor and temperature coefficient of frequency of three different high-overtone bulk acoustic resonator and phase noise of corresponding oscillators and the first result of oscillator vibration sensitivity based on high-overtone bulk acoustic resonator. Three resonators based on different material are tested.

This work presents a comparison between three different High-overtone Bulk Acoustic Resonators based on different materials. Furthermore, the goal of this work is to realize a High-overtone Bulk Acoustic Resonators presented a temperature coefficient of frequency less than 10 ppm over a wide range of temperature around a turnover temperature, and a Q.f product higher than 5×10 13 Hz. After a discussion about the choice of materials to achieve such resonator and the description of our microfabrication, three High-overtone Bulk Acoustic Resonators based on a Lithium of Niobate, Quartz, Lithium of Tantalate, AlN and Sapphire materials are compared in term of the temperature coefficient of frequency, the Q.f product and the phase noise. The new HBAR exhibits a Q.f product around 3.7×10 13 Hz, a turnover around 55°C with a parabolic shape and a temperature coefficient of frequency around +/-4 ppm/K.

Distribution of very low phase noise and low spurious microwave Local Oscillator (LO) is needed for most of the radar or electronic warfare applications. In this paper we study the capability to optically carry low phase noise LO, thanks to a directly-modulated optical link, while subjected to severe environmental conditions. First the optical link is compared to a coaxial cable link in terms of additive phase noise: subsequently the absolute amplitude and phase noise under random vibration are compared. It should be noticed that even in case of a wide band optical link, the phase noise floor difference between optical and coaxial cable is small even for short distance links. Secondly, the absolute amplitude and phase noise of the optical and coaxial cable link are measured with the entire optical link or only with some components of the link (10 GHz LO, optical single mode fiber (SMF), laser and photodiode) under random vibration. The phase noise degradation is almost the same when the optical or the coaxial link is under vibration and the main degradation is always due to the Local Oscillator whatever the technology is (OEO: Opto-Electronic Oscillator or traditional quartz oscillator). Some ways of improvement of optical link g-sensitivity that can be useful for OEO will be discussed. Thanks to recent experimentations done by DGA, it has been shown that very low phase noise microwave LO signals can be carried on optical link without any phase noise degradation due to the link while subjected to random vibration.

International audience; The aim of the paper is to provide an optimal placement of sensors for inhabitant location tracking in smart homes, by using only motion detectors. In particular, motion detectors are binary sensors largely used in ambient assisted living applications because they are low cost, non-intrusive and privacy sensors. An approach to optimize the placement of motion detectors in a real home environment by adopting a two-dimensional grid is presented. In this context, the real coverage area of a sensor is computed by considering the obstacles and respecting the specified coverage performance requirements. The optimization problem is formalized and solved as an Integer Linear Programming (ILP) problem and a case study is presented to show the efficacy of the proposed approach.

International audience; Timed Event Graphs (TEGs) are a specific class of Petri nets that have been thoroughly studied given their useful linear state representation in (Max,+) algebra. Unfortunately, TEGs are generally not suitable for modeling systems displaying resources sharing (or conflicts). In this paper, we show that if a system with conflicts is modeled using a NCTEG (Networked Conflicting Timed Event Graphs), it is quite possible to obtain an equivalent (Max,+) representation. More precisely, we prove that the evolution of a NCTEG satisfies linear time-varying (Max,+) equations. In case of cyclic NCTEGs, which are a natural model of many repetitive systems, we provide a standard time-invariant (Max,+) representation. As an application of the proposed approach to exhibit its interest, we consider the case of Jobshops. We first propose a generic NCTEG-based model of these systems and subsequently apply the corresponding (Max,+) representation to evaluate some of their performances.

International audience; This paper deals with identification of automated Discrete Event Systems (DES). A method for processing sequences of input/output signals from PLC-based controlled DES is proposed; it yields an interpreted Petri net model describing the closed-loop behavior of the automated DES. This new method extends a previously presented approach by taking into account the technological characteristics of industrial controllers and the data collection requirements. Based on polynomial-time algorithms, the method is implemented as an efficient software tool; its use is illustrated through a case study dealing with an automated manufacturing system.