Design of turbofan engine controller based on non-linear analysis

The design of a turbofan engine controller was considered. The analysis tool was based on a non-linear digital simulation. The parameters of this controller were specified satisfying engine performance requirements and limits, at a wide range of operating conditions. The study points out to the critical operating conditions and criteria for the choice of the various controller gains. A new simple scaling parameter was introduced to adapt the combined controller-engine gains to the operating conditions. Two different methods were investigated to prevent the engine limits being exceeded. The first employed direct or indirect redundant controllers of the physical limits. These additional controllers would be activated at critical conditions overriding the main controller. The second method used fuel acceleration schedules to prevent limits exceedence. It proved more adaptable to operating conditions, leading to a better performance besides being simpler.