Problems on feedback control of uncertain systems : a theoretical interpretation

The main problem in control theory is the definition of the optimal control law that must be applied to a physical system in order to obtain a desired behavior. A general approach to this problem is developed. The meanings of ″system″ and approximating ″model″ are clarified. The correct use of an observer, as the device which measures the uncertainty about the internal structure of the system and about the environmental influences on the system itself, is defined. The concept of ″equilibrium″ of a controlled system is introduced and some necessary and sufficient conditions in order that such an equilibrium may be reached, are stated.