A MIMO Sliding Mode Approach to Limit Protection in Aero-Engines

This paper proposes a scheme for limit protection in aero-engines with two control inputs and two regulated variables. The strategy extends existing results based on single-input sliding mode regulators and the min-max switching logic. The proposed multi-input strategy is able to manage engine limits effectively and offers better transient response than the traditional min-max architecture with linear regulators. The paper presents design guidelines for the multivariable sliding mode controller and the switching logic. The influence of key parameters is described and a simulation-based comparative study is made between the proposed approach and the existing single-input approach. It is shown that the multi-input technique has two clear advantages over the single-input approach, namely the ability to track fan speed (or other output related to thrust) even with harsh constrains, and the possibility of faster responses with smaller fuel flows by adjusting a secondary setpoint reference.