The Design of Phugoid Mode Stabilization in Angle of Attack Protection Control Law

Abstract

To achieve the requirement of maintaining the angle of attack, the design of the angle of attack (AOA) protection control law often causes instability in the pitch attitude and generates phugoid mode oscillations. Conversely, adding a damping ratio of phugoid to suppress the oscillations would reduce the stability of the angle of attack and the maneuverability of the aircraft. Therefore, when designing the AOA protection control law, it is necessary to choose the appropriate damping ratio to allow the aircraft to have a certain balance between maneuverability and stability. At present, people do not pay enough attention to this, but the resulting aviation accidents make this problem urgent to be solved. In this paper, based on the general modeling process, the linear model of a sample aircraft is established. Different gain values are designed according to the different needs of different flight phases for aircraft maneuverability and stability. The simulation shows that in the flight phase, the phugoid mode stabilization control law designed by the eigenstate assignment method (EA) can reduce the phugoid oscillation effectively, while in the landing flare phase when maneuverability is more important, it provides a greater degree of maneuverability.