Nonlinear Robust Control of Turbofan Engine Based on Improved Active Disturbance Rejection Control with Cascade Observer

The turbofan engine is a crucial power source for combat aircraft and it works in a complex and variable environment, requiring the development of control methods with strong robustness. This paper adopts an improved active disturbance rejection control (ADRC) method to design a steady-state controller for the throttling state of engine within a large envelope range. First, the steady-state control problem of the engine in throttling state is analyzed and a linear active disturbance rejection controller is designed based on the system characteristics. To improve the noise suppression ability of conventional ADRC, a cascade extend state observer is applied to adjust the amplitude frequency characteristics, which enhances the high-frequency (> 100 rad/s) noise suppression ability. Finally, digital simulation and verification is conducted in a complete flight route and the results are compared with conventional proportional integral differential and fuzzy control methods. The simulation results show that the regulating time of the controller based on ADRC is between 1.68 s and 3.68 s with a given power level angle variation law at H = 0 km, Ma = 0. The improved ADRC is superior in control robustness when the flight condition changes comparing with the traditional proportional integral differential and fuzzy control in the time-domain indicators. When there is a step change in the speed command, the adjustment time of ADRC is shortened by at least 17.3% and the overshoot of the entire process does not exceed 0.2%.