Life extending control of large-scale dynamical systems

This tutorial paper provides an introduction to the evolving field of Life Extending Control (LEC) where the objective is to achieve a desired trade-off between structural durability and dynamic performance of complex dynamical systems. The paper also presents a procedure for synthesis of fuzzy-logic-based LEC systems via feedback of on-line predictions of damage and damage rate. The proposed control system has a two-tier structure. Linear sampled-data controller(s) tracks a reference trajectory vector in the lower tier while a fuzzy-logic-based damage controller at the upper tier makes a trade-off between system performance and structural damage in critical plant components. The above LEC concept and several different design methodologies have been tested by simulation experiments on a reusable rocket engine, and the airframe structures of rotorcraft and tactical aircraft. The LEC concept is being actively pursued by NASA Glenn Research Center and several gas turbine engine manufacturers including General Electric, Pratt & Whitney, and Allied Signal. Some of these activities are reported in the four accompanying papers of this tutorial session.