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Towards Autonomous Wireless Sensors Systems in Civil Engineering: Paving the Way to an “Energy Oriented Design Methodâ€

V. LE CAM, M. LOSSEC, R. LE MAULF, L. LEMARCHAND, W. MARTIN, M. LE PEN

Abstract


Last years, SHM and similar non-destructive techniques communities have developed and published solutions and efforts regarding wireless and smart sensors solutions. Those numerous works clearly demonstrate the immediate gain that wireless solutions imply especially when applied to civil engineering structures: cost-effectiveness, simplicity, more mobile and reusable devices, etc. As an evidence, the main input constraint when designing a wireless instrumentation (sensor or other) refers to energy saving. In that prolific domain, numerous solutions are designed with more or less positive results. Most known or commercialized solutions refers to improved and optimized electronic design that save energy. But, in most of the case, the consequence resides in sensors that offer lower sampling rate (up to some Hz), lower computing abilities, and limited wireless communications: distances, rates, durations.... Moreover some other functionalities are forgotten when sensor is too focused on energy: synchronization, intelligence. The aim of this paper is to pave the ground of methods and approaches that refers to energy harvesting to make wireless sensors able of high level functionalities. More than some general considerations, this paper also includes real and technical feedback that French Public Works Laboratory (IFSTTAR) obtained through the application of its generic and wireless sensor platform (PEGASE) in collaboration with SATIE Laboratory (from ENS-Cachan). This article first makes the distinction between the sensor's sub-entities from the energy point of view: sources, charge, storage. Then, in view of optimal dimensioning (solar cells, battery capacity), concept of degree of freedom is introduced as well as a concept of quality index from energy point of view. The article proposes a method that details

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