Guaranteed control of "Almost-linear" plants

Considering the uncertainty which affects any description of actual plants and considering the fact that a feedback control does not require a very accurate knowledge of the plant behavior, the problem is examined to determine the largest simplification and inaccuracy of the model admissible for a guaranteed feedback control design. Sufficient conditions are derived. The foundations of a closed-loop control with guaranteed maximum error are then established. Finally, the design principles for the state observer and for the control are presented. Plants which can be modeled by linear systems for the purpose of feedback control are defined as "almost-linear."