Robust control of gas generator in a 1.5 MW gas turbine engine

This paper describes the robust control design of a gas generator engine. A nonlinear model of the engine has been developed within Simulink from details previously presented by Hill (1987). State space H _∞ control designs are performed using a linearised model to represent the key components in the single loop control configuration. The performance criteria are specified in terms of stability margins, bandwidth and desired response of the engine to large step input. The engine is subject to constraints on its manipulated variable (i.e. the throttle valve angle) which cause integral windup. The H_∞ design is simplified to a classical PI controller. A technique so-called utilise saturation feedback is used to reduce the effect of the integral windup. The results show that the PI control produces results similar to H_∞ at low speeds but that H_∞ gives better robustness and performance at higher speeds. Nonlinear simulations with parameter changes support the conclusion that the design is robust