Static low tire pressure detection system for aircraft

• US 4,506,328 A
• Filed: 07/30/1982
• Issued: 03/19/1985
• Est. Priority Date: 07/30/1982
• Status: Expired due to Fees

• Current Assignee: Sundstrand Data Control, Inc. (Rtx Corporation)
• Original Assignee: Sundstrand Data Control, Inc. (Rtx Corporation)
• Inventors: Bateman, Charles D.
• Primary Examiner(s): NOT, DEFINED
• Application Number:
  US06/403,454
• Time in Patent Office: 963 Days
• Field of Search: 364/463, 364/567, 340/58, 73/146, 73/65, 244/100 R
• US Class Current: 340/443
• CPC Class Codes: G01G 19/07 for weighing aircraft

Abstract

A static low tire pressure detection system for detecting the presence of a low tire mounted on a structural member of an aircraft, such as a bogie beam or nose axle, includes a pair of inclinometers mounted on the structural member and adapted to sense the bend therein. The signals from the inclinometers are stored in a memory once the aircraft is at rest on the ground to provide reference signals indicating the angle of the structural member with respect to an inertial reference and the weight carried thereby. The reference signals are compared against later-developed signals representing instantaneous angle and weight on the structural member to develop difference signals. The difference signals are used to generate an indication of tire pressurization, which is then checked to determine whether the tire pressurization is within acceptable limits. If the tire pressure is outside of the acceptable limits, then an indicating device is energized to provide a warning of a potentially dangerous condition to the aircraft operating personnel.

Claims

1. A low tire pressure detection system for detecting an underpressurized condition of a tire mounted on a structural member of an aircraft when the structural member is at rest, comprising:

first and second inclinometers disposed in spaced-apart relationship on the structural member with the sensitive axes of the inclinometers being parallel to one another, the first and second inclinometers developing first and second output signals representing the angle of the structural member at first and second locations with respect to a reference plane;

means for summing the first and second output signals to develop a weight signal representing the weight on the member;

means for subtracting the first and second output signals to develop an angle signal representing the overall angle of the structural member with respect to the reference plane;

means for storing the weight and angle signals developed at a particular time;

means for comparing subsequent weight and angle signals with the stored weight and angle signals to derive weight and angle difference signals; and

means for deriving an indication of tire pressurization including a lookup table in which is stored a plurality of tire pressure signals and means for addressing the lookup table with the weight and angle difference signals to cause the lookup table to develop a signal representing tire pressurization.

2. The low tire pressure detection system of claim 1, wherein the means for deriving includes a look up table in which is stored a plurality of tire pressure values as a function of the angle and weight difference signals.

3. The low tire pressure detection system of claim 1, further including means for comparing the derived tire pressure value against a tire pressure limit to determine whether a low tire pressure condition exists.

4. The low tire pressure detection system of claim 1, further including a variable gain amplifier coupled to the angle difference signal having a gain factor K dependent upon the weight carried by the structural member for deriving a pressure signal representing tire pressure.

5. The low tire pressure detection system of claim 4, further including means for comparing the pressure signal with a tire pressure limit to determine whether a low tire pressure condition exists.

6. The low tire pressure detection system of claim 1, further including means for updating the stored weight and angle signals when a subsequent weight signal is less than the stored weight signal.

7. The low tire pressure detection system of claim 1, further including means for sensing movement of the member and means for inhibiting storage of the weight and angle signals while the member is moving.

8. The low tire pressure detection system of claim 7, wherein the movement sensing means includes means for detecting the presence of particular frequency components in the angle difference signal.

9. The low tire pressure detection system of claim 8, wherein the movement sensing means includes means for generating an inhibit signal when the particular frequency components are present in the angle difference signal.

10. The low tire pressure detection system of claim 8, wherein the detecting means includes a band pass filter for integrating the angle difference signal.

11. The low tire pressure detection system of claim 10, wherein the detecting means includes means for detecting whether the amplitude of the integrated angle difference signal exceeds a predetermined value.

12. A low tire pressure detection system for detecting the existence of an underpressurized tire carried by a structural member of an aircraft, comprising

first and second accelerometers disposed on opposite ends of the structural member having their sensitive axes disposed 180°

with respect to one another for generating first and second accelerometer signals representing the bend of the structural member;

means for summing the first and second accelerometer signals to derive a weight signal;

means for subtracting the first and second accelerometer signals to derive an angle signal;

means for storing the angle signal when the weight signal is at a minimum during an interval;

means for comparing the stored angle signal with subsequent angle signals to develop an angle difference signal; and

means for deriving an indication of tire pressure from the weight signal and the angle difference signal.

13. The low tire pressure detection system of claim 12, wherein the deriving means includes a variable gain amplifier coupled to the angle difference signal and to the weight signal having a gain factor K dependent upon the weight on the structural member.

14. A low tire pressure detection system for detecting the existence of an underpressurized tire carried by a structural member of an aircraft, comprising:

15. first and second accelerometers disposed on opposite ends of the structural member having their sensitive axes disposed 180°

with respect to one another for generating first and second accelerometer signals representing the angle of the structural member at first and second locations;

means for summing the first and second accelerometer signals to derive a weight signal;

means for subtracting the first and second accelerometer signals to derive an angle signal;

means for storing the angle and weight signals when the weight signal is at a minimum during an interval;

means for comparing the stored angle and weight signals with subsequent angle and weight signals to develop angle and weight difference signals;

means for deriving a first indication of tire pressure from the weight signal and the angle difference signal; and

means for deriving a second indication of tire pressure including a lookup table in which is stored a plurality of tire pressure signals and means for addressing the lookup table with the weight and angle difference signals to cause the lookup table to develop a signal representing tire pressurization.

16. A low tire pressure detection system for detecting an underpressurized condition of a tire mounted on a weight-supporting structural member, comprising:

first and second transducers mounted on the member for developing first and second transducer signals dependent upon the weight supported by the member;

means coupled to the first and second transducers for developing a weight signal representing the weight carried by the structural member;

17. first means coupled to the first and second transducers for subtracting the first and second transducer signals to derive an angle signal representing the angle of the member relative to a reference;

means for detecting movement of the structural member;

means for storing the weight and angle signals when the structural member is not moving;

second means for subtracting subsequent weight and angle signals with the stored weight and angle signals to derive weight and angle difference signals; and

means for deriving an indication of tire pressurization including a lookup table in which is stored a plurality of tire pressure signals and means for addressing the lookup table with the weight and angle difference signals to cause the lookup table to develop a signal representing tire pressurization.

18. A low tire pressure detection system for detecting an underpressurized condition of a tire mounted on a structural member of an aircraft when the aircraft is not moving comprising:

means operatively connected to the structural member for generating a first signal representing the weight on the structural member;

means operatively connected to the structural member for generating a second signal representing a mechanical characteristic of the structural member functionally related to the weight of the aircraft;

means for storing said first and said second signals at a first time; and

means for generating at a second time a signal representative of tire pressurization including a lookup table in which is stored a plurality of signals representing tire pressures and means for addressing the lookup table in accordance with the stored first and second signals and the first and second signals.

19. A system for sensing movement of an aircraft having landing gear on the ground comprising:

means operatively connected to a structural member of the landing gear for generating a signal representing a mechanical characteristic of the structural member functionally related to the weight of the aircraft, the signal having a particular frequency when the aircraft is moving; and

means responsive to the frequency of said signal for generating a logic signal indicating aircraft movement on the ground when the particular frequency is present.