A novel aircraft anti-skid brake control method based on runway maximum friction tracking algorithm

Abstract

As a dominant type of disturbance during aircraft braking, variation in maximum friction between the runway and the tires largely affects the efficiency of aircraft anti-skid braking systems (ABS). Conventional aircraft anti-skid braking control method, such as pressure-bias-modulated (PBM), are unable to identify and track the changing maximum friction between the runway and the tires, which results in reduced braking efficiency and long braking distances. This paper presents a novel anti-skid braking control method which can identify and track the maximum friction using only wheel angular velocity and brake pressure signals. An extended braking stiffness (XBS)-based runway maximum friction identification method is proposed to determine the runway maximum friction, where XBS is the differential of the friction to the differential of the slip ratio. Tracking differentiator (TD) is employed to derive the corresponding differential signals, which enables XBS to be calculated efficiently, without compromising calculation accuracy. By analyzing the dynamic characteristic of the wheel, a runway friction characteristic observation function is designed to observe changing friction characteristic during the entire braking. To be able to track the varying maximum friction in real time, a runway maximum friction tracking algorithm is designed, which can realize accurate brake pressure control according to the change in runway friction characteristic. The Lyapunov function is employed to prove the stability of the designed controller. Simulation tests are carried out under multiple sets of changes in runway friction characteristic. The comparison simulation test with PBM algorithm shows that the designed control method greatly improves the braking efficiency. Ground inertia test bench experiments are also conducted to further verify the correctness and effectiveness of the proposed aircraft anti-skid brake control method. Simulation and experiment results prove that the proposed control method is able to identify and track the varying maximum friction provided by different runways. The results of experiment also demonstrate that the control method still has good robustness and performance, even with the objective noise of the system.