Linear Dynamic Mathematical Model and Identification of Micro Turbojet Engine for Turbofan Power Ratio Control

Abstract

Micro turbojets can be used for propulsion of civilian and military aircraft, consequently their investigation and control is essential. Although these power plants exhibit nonlinear behaviour, their control can be based on linearized mathematical models in a narrow neighbourhood of a selected operating point and can be extended by using robust control laws like H∞ or Linear Quadratic Integrating (LQI). The primary aim of the present paper is to develop a novel parametric linear mathematical model based on state space representation for micro turbojet engines and the thrust parameter being Turbofan Power Ratio (TPR). This parameter is used by recent Rolls-Royce commercial turbofan engines but can be applied for single stream turbojet power plants as well, as it has been proven by the authors previously. An additional goal is to perform the identification for a particular type based on measurements of a real engine. This model has been found suitable for automatic control of the selected engine with respect of TPR, this has been validated by simulations conducted in MATLAB® Simulink® environment using acquired data from transient operational modes.

Sliding Mode Control for Micro Turbojet Engine Using Turbofan Power Ratio as Control Law

“…In [41] the authors have established the mathematical model and have shown an identification that was performed for a single selected nominal operating point. Then, using multiple stable operating points from the same measurement, the entire range has been modeled, where the originally constant matrix members have been replaced by interpolated values determined from the discrete points.…”

“…The main hypothesis of the present work is that TPR is applicable to single stream turbojets as the basis of thrust control system because it is proportional to the thrust output. Despite the apparent contradiction between the designation of TPR and the turbojet application, the authors have already proven in [41] that the TPR allows its usage for control of turbojet engines and it has a considerable advantage over conventional rotor speed or Engine Pressure Ratio (EPR) as well.…”