Comparison between software simulation and HIL simulation of antiskid brake system for aircrafts

Today, most fixed-wing aircrafts are equipped with an antiskid brake system (ABS). The ABS can modulate braking moments in the wheels optimally whenever an aircraft lands. So it can reduce landing distance and increase safeties. The ABS for an aircraft is mainly composed of braking moment modulators (hydraulic servo valves) and brake control unit in addition to the conventional hydraulic brake system. In this paper, a Mark IV type-fully digital-brake controller is studied. For the development of its control algorithms, a 5 degree of freedom (DOF) aircraft landing model is composed in the form of the Matlab/Simulink model at first. Then antiskid control algorithms using wheel decelerations and slips are made. The developed algorithms are tested in software simulations using state-flow toolboxes in the Matlab/Simulink model. Also, the hardware in-the-loop simulation (HILS) systems are made using real-time simulators, where hydraulic brake systems of a real aircraft, braking moment modulator and its controller are included as hardware components. Algorithms tested in software simulations are coded and downloaded into a newly developed digital signal processing (DSP) controller and the dynamics models are downloaded to real-time simulators and the simulations have been done in the same road conditions as software simulations. Both the software and HIL simulation results are presented.