Modeling And H_? Control Of Speed Tracking Problem Of Turbofan Engine

The aero-engine is a strongly nonlinear complex dynamic system. It is often affected by the interference signal or measurement noise in practical work, as a result, the speed control is hard to realize with the purpose of tracking the target speed. Meanwhile, the range of the engine parameter is quite large in the process of flight. It is also difficult to guarantee the whole system stability within full flight envelopes using a single linear parameter-varying (LPV) controller designed by traditional methods. In view of the above two points, related research has been rarely reported on aero-engines. In this article, switching control theory and H? theory of robust control will be applied to design controllers based on modeling. Therefore, the tracking problem of high pressure rotor speed can be solved.First of all, a component-level turbofan engine model is set up on the basis of gas dynamics theory and energy conservation. Interaction equations are built to make all components constrain mutually and produce linkage effects from air inlets to exhaust nozzles. Secondly, the method of Newton-Rapson is used to solve nonlinear equations. Then, a small deviation linearization model is set up by means of 'power extract' based on the nonlinear model, which can facilitate the controller design. Finally, the equilibrium manifold model is discretized to establish a discrete LPV system in order to implement the simulation. An appropriate way of mapping is chosen to guarantee the model much closer to the original system accurately.Switching control is applied to divide the flight envelopes into several subsystems by state-dependent switching in order to reduce conservatism. Hysteresis switching law is used to improve the performance of switched systems and avoid chattering. Common Lyapunov function can be calculated from solving linear matrix inequalities (LMIs) to guarantee the stability of switched systems with a sufficient theoretical criterion. An output feedback parameter-dependent controller is obtained to guarantee the H? performance which is also applied to the nonlinear model. The simulation results are given to show that the high pressure rotor speed can track the reference signal without errors, which proves the validity of the proposed method.