Antiskid control for aircraft via extremum-seeking

Gear walk instability studies using flexible multibody dynamics simulation methods in SIMPACK

“…Achieving a shorter stopping distance becomes critical on wet or icy runways and during rejected take-offs (RTO). It may also be designed to enhance passenger comfort through reducing strut vibrations and improving tire wear through smoother braking, as secondary objectives [22]. For this purpose a simple and somewhat idealized anti-lock braking algorithm has been implemented at the DLR which works as follows: A sensor at the landing gear wheels measures the actual speed and the slip which is fed to the control system along with the desired velocity and the desired slip.…”

“…The nature of this dependence is not well understood even after numerous experiments. If we assume that other factors are fixed the friction coefficient can be represented as a function of slip ratio [10,22] and has a unique maximum. During braking it is possible that the wheels get locked.…”

Slope seeking: a generalization of extremum seeking

“…This is a generalization of the method of extremum seeking [1][2][3][4][5][6], that involves driving the plant output to an extremum of the reference-to-output map, i.e., a point on the reference-to-output map corresponding to a slope of zero. Motivations for the development of slope seeking are: problems where operation at the extremum of the plant reference-to-output map is susceptible to destabilization under finite disturbances, such as maximum pressure rise in deep hysteresis aeroengine compressors [7], antiskid braking for aircraft [8], minimum power demand formation flight [9], and problems in nuclear fusion where there is a need to stay away from the extremum (such as a maximal energy release condition) [10]. In fact, work on aircraft Contract/grant sponsor: AFOSR Contract/grant sponsor: ONR Contract/grant sponsor: NSF antiskid control [8] used a slope set point in its extremum seeking loop.…”

“…Motivations for the development of slope seeking are: problems where operation at the extremum of the plant reference-to-output map is susceptible to destabilization under finite disturbances, such as maximum pressure rise in deep hysteresis aeroengine compressors [7], antiskid braking for aircraft [8], minimum power demand formation flight [9], and problems in nuclear fusion where there is a need to stay away from the extremum (such as a maximal energy release condition) [10]. In fact, work on aircraft Contract/grant sponsor: AFOSR Contract/grant sponsor: ONR Contract/grant sponsor: NSF antiskid control [8] used a slope set point in its extremum seeking loop. In all these problems, there is significant uncertainty in the models, and the set-points are unknown.…”

Aircraft Anti-Skid Brake Control Based on High-Speed on-off Valve

“…In order to prevent the occurrence of such phenomena, anti-skid brake control has become the necessary function in the aircraft brake system. Anti-skid control mainly by monitoring the status of wheels (slip velocity or slip ratio) to determine whether the skid occurred, and then adjust the brake pressure to stop the wheels into the state of skid, ensure the brake safety and improve the brake efficiency [5,6]. Pressure servo valve can output the pressure which is proportional to the control signal, and has the high frequency response, suitable for direct pressure control.…”