Productivity analysis and non-linear gain scheduling approach for multi-species bioprocesses with product inhibition

International audienceBioprocesses with product inhibition are known to allow species coexistence. In this work, we first study the productivity of the different possible equilibria, depending on the operating conditions, and show that single species offers the best performances. Then, we propose a control strategy to stabilize the dynamics about the desired equilibria, in presence of instability. Based on output feedback linearization, we propose a family of controllers and a gain-scheduling approach to adapt the controller. Finally, we illustrate our approach on numerical simulations, showing that the attraction basin of the closed-loop system is improved by considering the gain-scheduling approach

A comparative study of three validities computation methods for multimodel approach

The multimodel approach offers a very satisfactory results in modelling, diagnose and control of complex systems. In the modelling case, this approach passes by three steps: the determination of the model’s library, the validities computation and the establishment of the final model. In this context, this paper focuses on the elaboration of a comparative study between three recent methods of validities computation. Thus, it highlight the method that offers the best performances in term of precision. To achieve this goal, we apply, these three methods on two simulation examples in order to compare their performances

As relações entre valor agregado e riqueza na Análise-diagnóstico de sistemas agrários

A Análise-Diagnóstico de Sistemas Agrários (ADSA) é um método de estudo empregado na extensão rural e em pesquisas sobre dinâmicas locais da agricultura. Neste método normalmente é considerado que a agregação de valor é equivalente à geração de riqueza. O objetivo deste artigo é analisar os problemas provocados pela consideração do valor agregado como um indicador da produção de riquezas na ADSA. Uma demonstração formal de que valor agregado e riqueza são distintos é realizada a partir de um modelo de programação linear, com base no materialismo histórico. Esta demonstração é ilustrada por um exemplo numérico e, após, as relações entre valor agregado e riqueza são discutidas a partir da análise de alguns trabalhos que empregam a ADSA. Conclui-se que uma adoção generalizada de sistemas de produção com alta capacidade de agregação de valor, como em geral proposto a partir da ADSA, pode implicar em uma diminuição da produção de riquezas. No entanto, a crítica a este aspecto da ADSA não implica em subestimar a grande relevância deste método de análise regional da agricultura

Embedding OLTC nonlinearities in predictive Volt Var Control for active distribution networks

International audienceVolatile productions and consumptions generate a stochastic behavior of distribution grids and make its supervision difficult to achieve. Usually, the Distributed Generators reactive powers are adjusted to perform decentralized voltage control. Industrial controllers are generally equipped with a local affine feedback law, which settings are tuned at early stage using local data. A centralized and more efficient tuning method should aim to maximize the probability that all the node voltages of distribution grids remain within prescribed bounds. When the characteristics of the stochastic power forecasts are known, the centralized algorithm allows to update the settings on a regular time basis. However, the method requires to solve stochastic optimization problem. Assuming that stochastic variables have Gaussian distributions, a procedure is given which guarantees the convergence of the stochastic optimization. Convex problems drastically reduce the difficulty and the computational time required to reach the global minimum, compared to nonconvex optimal power flow problems. The linear controllers with optimized parameters are compared to traditional control laws using simulations of a real distribution grid model. The results show that the algorithm is reliable and moreover fast enough. Hence, the proposed method can be used to update periodically the control parameters

A selective gate for very high-rate analog pulses

International audienceA gate for analog pulses has been developed which allows to perform a precise time-selection among a very high-rate flow of incoming signals