| Traditional control system design focuses on stability and performance only; in other words, the control design process ignores the effects of aging, fatigue, and damage in the materials involved. Motivated by this, in the 1990's life extending control (LEC) appeared. Its main purpose is to extend the life of critical plant components, or to reduce maintenance cost, while simultaneously ensuring that a set of specific performance requirements are satisfied.; In this research, two main topics in LEC, damage modeling and LEC design, are studied for a boiler-turbine system. The following is a list of the research contributions: (1) Two new continuum fatigue modeling theories are discussed, and an improved Rainflow cycle-counting method is applied for on-line model-based life extending control. (2) A new LEC control system structure is proposed. (3) Sytem identification method is used to reduce system complexity. (4) Linear quadratic regulator and model predictive control are used to design LEC for a boiler system. (5) Simulations are presented with linear and nonlinear models. |
