Airplane ABS control synthesis using fuzzy logic

The paper proposes a fuzzy logic controller for an airplane antilock-braking system (ABS). The system benefits by the knowledge of real vehicle speed, as given by the unbraked front wheel of the landing gear. Thus, the slip ratios of rear wheels can be easily inferred by measuring their angular velocities. By taking into account these slip ratios, resulting from control variables applied in the system, a phenomenological scenario - a road label inferring diagram - is conceived to on line decide, via a fuzzy logic reasoning, upon the most suitable new control variable to apply at the current sample step. More precisely, certain threshold values concerns, for each braked wheel, the input variables in the inferring diagram: wheel slip, predicted wheel slip and previous value of control variables. Control variables are thus synthesized in the last component of a standard Mamdani type fuzzy logic control triplet: fuzzifier, rules base and defuzzyfier. A rules base, clustered according to some real road conditions is defined. Supplementary features to improve the braking performance are also described. The simulation results, performed on the mathematical model of a military jet braking, show that proposed ABS algorithm ensures the avoiding of wheel's blockage, even in the worst road conditions.