A quadratic inequality approach for design of robust controller for a parametric uncertain jet engine

The control logic of a modern jet engine is comprised of many control loops and the control system must account for the uncertainties in the model used in its design. The paper presents a quadratic inequality based methodology for designing a robust controller for a parametrically uncertain jet engine. The inequalities are used for the generation of controller bounds to achieve robust stability and tracking specifications prior to loop shaping. The design is done in the frequency domain and the evolved robust controller controls the system that does not have a distinct set of poles and zeros but a range over which each of the poles and zeros might lie. The methodology has multifarious advantages as it can be easily implemented, does not require template generation and provides the designer with a good insight into the QFT (quantitative feedback theory) bounds at any given design frequency and controller phase. The approach is demonstrated for the design of the speed control loop of a parametrically uncertain twin spool jet engine.