Design of transient state control mode based on rotor acceleration

Control mode based on rotor acceleration has been used in many advanced aero-engines to improve the performances of transient process. Under this control mode, acceleration and deceleration performances of all same type engines are consistent ignoring the variances of manufacture, materials and performance degradation. In this paper, we proposed a complete design process of N-dot transient controller for a two-spool civil turbofan engine. Firstly, the surge margin and exhaust gas temperature (EGT) margin were considered in the schedule design. It was designed by an extrapolation approach which has a similar acceleration process to the original Wf/Ps3 transient control process. Then, a set of PI controllers were designed separately using differential evolution algorithm for corresponding engine´s set-points from idle to maximum rotor speed. These controllers constituted a control component using gain scheduling. When the aero-engine´s performance degenerated, we compared the accelerate control process between N-dot control and Wf/Ps3 control. Simulation results demonstrated that, collaborating with the limit protection controllers, the N-dot control method is more suitable for aero-engine´s transient process even though it could cause a large decrease in surge margin as well as large increase in EGT. In addition, the controllers in this paper had a large practice value, as the dynamic characteristics of actuator, sensor and the filter were all considered in the N-dot control design.