Robust control of a 1.5 MW free turbine engine

This paper describes the robust control design of a 1.5 MW free turbine wit h complex load. A non-linear model of the engine with load has been develop ed within Simulink from details previously presented. State space H-infinit y control designs are performed using a linearized model to represent the k ey components in the multiloop control configuration. The performance crite ria are specified in terms of stability margins, bandwidth and desired resp onse of the engine to a severe load disturbance. The engine is subject to c onstraints on its manipulated variable (i.e. the throttle valve angle). The H-infinity design is simplified to a classical proportional-plus-integral (PI) controller. The results show that the PI control produces results simi lar to H-infinity at low speeds but that H-infinity gives better robustness and performance at higher speeds. Non-linear simulations with parameter ch anges support the conclusion that the design is robust.