Ahmed HAFAIFA

<H3>Application of Fuzzy Logic to the Compressor Anti-Surge Control </H3>

{In this work, we treat the problems related to chemical and petrochemical 
plants of a certain complex process taking the centrifugal compressor as an 
example, a system being very complex by its physical structure as well as 
its behaviour surge phenomenon). We propose to study the application 
possibilities of the recent control approaches to the compressor behaviour, 
and evaluate their contribution in the practical and theoretical fields 
consequently. Facing to the studied industrial process complexity, we 
choose to make recourse fuzzy logic for analysis and treatment of its 
control problem owing to the fact
that these technique constitute the only framework in which the types of 
imperfect knowledge can jointly be treated (uncertainties, inaccuracies, 
... ..) offering suitable tools to characterise them. In the particular 
case of the centrifugal compressor, these imperfections are interpreted by 
modelling errors, the neglected dynamics, no modelisable dynamics and the 
parametric variations.
The purpose of this paper is to produce a total robust nonlinear controller 
design method to stabilize the compression process at its optimum steady 
state by manipulating the gas flow rate. In order to cope with both the 
parameter uncertainty and the structured non linearity of the plant, the 
proposed method consists of a linear steady state regulation that ensures 
robust optimal control and of a nonlinear
compensation that achieves the exact input/output linearization