MSD-Based NMPC Aircraft Anti-Skid Brake Control Method Considering Runway Variation

Abstract

In this paper, a nonlinear model predictive control (NMPC) method based on mixed slip-deceleration (MSD) with runway identification is proposed to prevent the aircraft wheels from locking up and improve the braking performance under time-varied runway conditions. The MSD control algorithm reduces the dependence of control performance on slip rate estimation accuracy and retains a good slip rate control performance. The proposed NMPC control method guarantees optimal braking torque on each wheel by individually controlling the slip rate of each wheel near the optimal point. A nonlinear brake control model based on aircraft ground taxiing dynamics is derived. In this model, the tire-runway friction coefficient–slip rate model under different runway conditions and vertical force variation caused by brake are considered. A runway identification algorithm based on friction coefficient and friction coefficient slope is used to identify the real-time runway status, based on which the prediction model and optimization function of the proposed control scheme are modified. The wheel slip stable zone and the system maximum brake torque are regarded as time-domain constraints of the NMPC for safety considerations and physical limitations. The control objectives of the NMPC include longitudinal deceleration, braking performance, and preservation of crew comfort. The proposed MSD-based NMPC controller is verified by a tricycle-geared aircraft model using MATLAB/Simulink software. Simulation results of different control schemes on a specific mixed runway show good performances of the proposed control method. The proposed control method provides a new efficient solution for aircraft wheel braking on variable runway.