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This activity is aimed to investigate the application of the fuzzy logic paradigm for the control of dynamic system.
Fuzzy logic in control has been successful used to capture heuristic control laws obtained from human experience or engineering practice in automated algorithm. These control laws are defined by means of linguistic rule, for example "if the pressure is high, then decrease the pump power''. The heuristic approach in the controller design can be appealing for its simplicity, but formal design method can be mandatory in some cases. For this reason a great endeavor is carrying out by several researcher in defining formal design procedures.

The research carried at L.A.R. is aimed to exploit the linguistic interpretation of the fuzzy paradigm as well as to investigate formal design procedure of the fuzzy control system.

Linguistic interpretation of fuzzy system

The fuzzy logic controller paradigm proposed is based an extension of the generalized modus ponens using the operations of disjunction and aggregation of fuzzy sets. Some other work investigates a model-based procedure for the synthesis of a fuzzy logic controller. This algorithm defines the linguistic rules of a fuzzy logic controller, starting from a desired closed loop behavior and a plant model, both described via linguistic statements. To obtain a plant model in a linguistic form, suitable for the above algorithm, a novel identification procedure is under development.The application of a fuzzy logic controller to the control of a complex system is carried on in collaboration with the Institute for Earth-Moving Machinery and Off-RoadVehicles (CNR-Cemoter). This work aims to the fuzzy control of variable displacement pump.

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Fuzzy logic design via sliding mode approach

This research activity starts from some considerations about similarity between a Variable Structure Control with Boundary Layer and a very simple Fuzzy Logic Controller. From these considerations some properties of VSC (Variable Structure Control) are used, in particular the sliding mode dynamics, for the definition of the rules and the membership functions of a Fuzzy Logic Control.

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Analysis of Takagi-Sugeno fuzzy system

This works, done in collaboration with Professor H.B. Verbruggen, Mr. R. Babuska and Mr. S. Stramigioli of the Control Laboratory, Delft University of Technology (The Netherlands), address the theoretical analysis of the so-called Takagi-Sugeno fuzzy model. In detail our research is devoted to investigate restrictive criteria for the stability analysis of the fuzzy model. Moreover the more general problem of the interpolation of complex non-linear dynamic process using simple linear homogeneous and non-homogeneous subsystem is also considered.

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Control system autotuning

This applicative research aims to investigate the potentiality of the fuzzy logic controller coupled with a standard PID algorithm. The control structure is formed by a PID servo--controller which parameters are tuned on--line by a supervisor designed using fuzzy logic paradigm.
The application of this structure to a real plant is currently under test with the collaboration of Pulsar Engineering (Modena, Italy) and Democenter (Modena, Italy).

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