Recent studies show that there is no guarantee for conventional Min-Max structure containing linear compensators to keep engine limitations in transient state, while limit violation can make dangerous events. Careful analysis indicates that despite the design of limitation loops overshoot-free to reduce the possibility of limit violation, exceeding the limits can occur for some variables affected by engine acceleration or deceleration, when other loop controllers are active. In this study, the limit values of these variables are taken into account in controller design of other loops using state feedback techniques and convex optimization problems, and their dynamic compensators are removed from the Min-Max structure. Thus, in addition to improvement of Min-Max limit protection, computational burden also decreases owing to loop reduction. The condition for limit protection in steady state and thrust tracking assurance is also specified. Simulations carried out with linear and nonlinear turbofan engine model show efficient performance of the proposed methodology in comparison with traditional Min-Max and Min-Max/sliding mode control (SMC) approaches.
