Patent ID: 6684147
Filing Date: 2004-01-27
Classification: B60T

Abstract:
A sliding, integral, and proportional controller for providing anti-skid braking control for an aircraft having a plurality of tires and brakes, comprising:a reference velocity subsystem generating a reference velocity signal based upon an input wheel velocity signal; a velocity error ratio subsystem generating a modified slip ratio signal (Smod) based upon a ratio of the difference between the reference velocity and the wheel velocity to the reference velocity; and a main controller subsystem receiving the reference velocity signal and the modified slip ratio signal, the main controller subsystem generating a control command output signal indicative of a command braking pressure responsive to the reference velocity signal and the modified slip ratio signal, wherein the main controller subsystem comprises: a one dimensional sliding mode controller subsystem to determine an estimated net wheel torque signal; an adaptive threshold subsystem for generating an adaptive threshold based upon the modified slip ratio signal (Smod) and a clock signal; a first integral gain subsystem for comparing the estimated net wheel torque signal with the adaptive threshold to determine dominance between the tire drag torque and braking torque, and outputting a corresponding gain value; a second integral gain subsystem exponentially generating a deep skid signal (DS) when the Smod is greater than a predetermined limit and wheel velocities indicating a deep skid situation based upon the modified slip ratio signal (Smod), the wheel velocity signal (Vw), the reference velocity signal (Vref), the tire rolling radius, a predetermined deep skid limitation (Slim) of the Smod signal, and first and second function coefficients; a third integral gain subsystem to modify the initial braking command signal to avoid Smod signals that are too small or negative; a proportional controller subsystem generating an output signal to prevent sudden deep skids; and a pressure limiter for limiting the command braking pressure.