Thrust Command Scheduling for Uncertainty-Tolerant Control of Gas Turbine Aero-Engines

Uncertainties in measurements and gas path including manufacture tolerance and degradation effects unavoidably influence thrust regulation of gas turbine aero-engines. In this paper, a thrust command scheduling (TCS) controller is proposed based on current measurement precision levels and the improvement of the industrial sensor-based baseline controller, which aims at enhancing the uncertainty tolerance capabilities for a fleet of in-service gas turbine aero-engines. The TCS controller is fulfilled in two steps. A measurement-insensitive thrust mode is selected via random analysis, followed by a two-dimensional thrust command scheduling approach of a family of thrust maps. Industrial baseline controllers with common thrust modes, i.e., low-pressure shaft speed (N1) and engine pressure ratio (EPR) modes are designed as benchmarks. Simulations are conducted on a validated aero-thermal turbofan engine model with publically available uncertainty statistics. Simulation results at the takeoff state on the new and degraded engine fleets reveal that N1 mode is insensitive to measurement uncertainties but owns significant thrust deviation due to degradation effects. Conversely, EPR mode just has the opposite thrust control behavior, compared to N1 mode. The TCS controller regulates the degraded engine fleet with a tight thrust distribution and suppresses the thrust variation of N1 mode via utilizing the remaining N1 margin. Hence, the uncertainty tolerance benefits of the proposed controller are confirmed.