Abstract-In this paper, a methodology to design controllers able to cope with different load conditions on an Ethernet network is introduced. Load conditions induce time-varying delays between measurements and control. To face these variations an interpolated, delay-dependent gain scheduling law is used. The lack of synchronization is solved by adopting an event-based control approach. The dual-rate control action computation is carried out at a remote controller, whereas control actions and measurements are taken out locally at the controlled process site. Stability is proved in terms of probabilistic linear matrix inequalities. TrueTime simulations in an Ethernet case show the benefit of the proposal, which is later validated on an experimental test-bed Ethernet environment.Index Terms-Multirate control systems, network delay, networked control system, PID controller, stability analysis.

This paper presents a control strategy to face time-varying delays induced in a Networked Control System (NCS). The delay is divided into two parts: the largest one (an integer multiple of the bus cycle) is compensated by means of an adaptive multi-rate Smith predictor, and the smallest one (whose value is strictly smaller than the bus cycle) via a gain scheduling approach based on root locus contour and linearization techniques. The gains to be scheduled belong to a multi-rate PID controller. Control system stability is studied by means of Lyapunov theory. Simulation results and the implementation on a test-bed Profibus-DP environment illustrate that this control structure can maintain NCS performance and stability, despite the considered delays.

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La gasolina comercial es una mezcla de componentes obtenidos de la destilación del petróleo. El reto del Sistema de Optimización y Control es maximizar el margen económico del proceso utilizando la mezcla de componentes más barata, satisfaciendo la composición de las mezclas, los inventarios, la disponibilidad de las unidades de producción y las restricciones hidráulicas de las líneas. La complejidad de estos sistemas de mezcla ha ido aumentando debido a la competencia creciente en el sector, las refinería más competitivas realizan las mezclas con componentes que provienen directamente de unidad sin pasar por almacenamiento intermedio, método rundown, se disminuyen inventarios y se aumenta el beneficio. En este artículo se presenta un método innovador consistente en aplicar distintos niveles de automatización emulando la estrategia de control en cascada. Los resultados obtenidos en simulación han permitido aplicar el método propuesto en una instalación real, donde se ha podido contrastar la bondad del método y su generalización a un sistema con dimensionamiento real.

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