Method of maintaining optimal braking and skid protection for a two-wheeled vehicle having a speed sensor failure on a single wheel
The method of maintaining optimal braking and skid protection for a two-wheeled vehicle wheel with a wheel speed sensor failure involves providing pulsed braking pressure to the affected wheel with the wheel speed sensor failure. If an incipient or initial skid on another wheel with a functioning wheel speed sensor has occurred, the pulsed braking pressure to the affected wheel is limited to the brake pressure command that caused the last incipient or initial skid on the other wheel, scaled by a factor for safety. Otherwise the pulsed braking pressure to the affected wheel is limited to be no greater than the greatest commanded brake pressure to the other wheel. The pulsed braking pressure is also limited to be less than the brake pressure commanded to the affected wheel.
1. A method for controlling antiskid braking of a plurality of wheels in a group of wheels of an aircraft, said plurality of wheels having a corresponding plurality of wheel speed sensors associated therewith, respectively, said plurality of wheel speed sensors configured to generate wheel speed signals of said corresponding plurality of wheels, respectively, for antiskid control of said plurality of wheels, based upon said wheel speed signals, the method comprising the steps of:
determining that a first wheel speed sensor of said plurality of wheel speed sensors associated with a corresponding first wheel of said plurality of wheels is not functioning to generate wheel speed signals;
determining that a second wheel speed sensor of said plurality of wheel speed sensors associated with a corresponding second wheel of said plurality of wheels is functioning to generate wheel speed signals;
determining a commanded braking pressure of said second wheel;
determining whether an incipient or initial skid of said second wheel associated with said commanded braking pressure of said second wheel has occurred, based upon said wheel speed signals from said second wheel speed sensor;
storing said commanded braking pressure of said second wheel as a brake pressure limit of said first wheel if said skid of said second wheel associated with said commanded braking pressure has occurred;
determining a maximum brake pressure of said first wheel as a predetermined fraction of said brake pressure limit of said first wheel;
determining a highest commanded braking pressure of said second wheel;
storing said highest commanded braking pressure of said second wheel as said maximum brake pressure of said first wheel if an incipient or initial skid of said second wheel associated with said commanded braking pressure of said second wheel has not occurred;
determining a modulated brake pressure as a second predetermined fraction of said maximum brake pressure of said first wheel; and
providing modulated pressure pulses of the modulated brake pressure to said first wheel.
2. The method of claim 1 , further comprising the steps of:
monitoring a commanded braking pressure of said first wheel;
comparing said modulated brake pressure to said first wheel with said commanded brake pressure of said first wheel; and
limiting said modulated brake pressure to be less than said commanded braking pressure of said first wheel.
3. The method of claim 2 , wherein said step of limiting said modulated brake pressure comprises limiting said modulated brake pressure as a third predetermined fraction of said commanded braking pressure of said first wheel.
4. The method of claim 1 , wherein said step of providing modulated pressure pulses of the modulated brake pressure to said first wheel comprises modulating said modulated pressure pulses with a constant period and duty cycle between a return pressure and said modulated pulsed pressure.
5. A method for controlling antiskid braking of first and second paired wheels of an aircraft, said first and second paired wheels having corresponding first and second wheel speed sensors associated therewith, respectively, said first and second wheel speed sensors configured to generate wheel speed signals of said corresponding first and second paired wheels, respectively, for antiskid control of said first and second paired wheels, based upon said wheel speed signals, the method comprising the steps of:
determining that the first wheel speed sensor is not functioning to generate wheel speed signals;
determining that the second wheel speed sensor is functioning to generate wheel speed signals;
monitoring a commanded braking pressure of said second wheel;
determining whether an incipient or initial skid of said second wheel associated with said commanded braking pressure of said second wheel has occurred, based upon said wheel speed signals from said second wheel speed sensor;
storing said commanded braking pressure of said second wheel as a brake pressure limit of said first wheel if said skid of said second wheel associated with said commanded braking pressure has occurred;
determining a maximum brake pressure of said first wheel as a predetermined fraction of said brake pressure limit of said first wheel;
determining a highest commanded braking pressure of said second wheel;
storing said highest commanded braking pressure of said second wheel as said maximum brake pressure of said first wheel if an incipient or initial skid of said second wheel associated with said commanded braking pressure of said second wheel has not occurred;
determining a modulated brake pressure as a second predetermined fraction of said maximum brake pressure of said first wheel; and
providing modulated pressure pulses of the modulated brake pressure to said first wheel.
6. The method of claim 5 , further comprising the steps of:
monitoring a commanded braking pressure of said first wheel;
comparing said modulated brake pressure to said first wheel with said commanded brake pressure of said first wheel; and
limiting said modulated brake pressure to be less than said commanded braking pressure of said first wheel.
7. The method of claim 6 , wherein said step of limiting said modulated brake pressure comprises limiting said modulated brake pressure as a third predetermined fraction of said commanded braking pressure of said first wheel.
8. The method of claim 5 , wherein said step of providing modulated pressure pulses comprises modulating said modulated pressure pulses with a constant period and duty cycle between a return pressure and said modulated pulsed pressure.