Apparatus for generating a reference signal in a brake control system

• US 4,720,794 A
• Filed: 07/01/1982
• Issued: 01/19/1988
• Est. Priority Date: 07/25/1979
• Status: Expired due to Term

• Current Assignee: Crane Company
• Original Assignee: Crane Company
• Inventors: Skarvada, Thomas
• Primary Examiner(s): Harkcom, Gary V.
• Application Number:
  US06/394,130
• Time in Patent Office: 2,028 Days
• Field of Search: 364/425, 364/426, 303/20, 303/93-95, 303/100, 303/106, 303/109
• US Class Current: 701/74
• CPC Class Codes: B60T 8/17616 Microprocessor-based systems

Abstract

An apparatus for generating a reference signal in a brake control system stores a reference signal representative of a reference braking condition and compares this reference signal with a conditioned wheel signal. Depending on the outcome of the comparison, the reference signal is either updated to correspond to a reduced reference braking condition or ramped to correspond to an increased braking condition. The reference signal is not simultaneously ramped and updated, and is, therefore, precisely controlled. In a first embodiment, the amount by which the reference signal is ramped is a function of the past history of the reference signal: each time the reference signal is ramped the ramp rate is increased and each time the reference signal is updated the ramp rate is decreased. The apparatus of this embodiment generates the conditioned wheel signal from the wheel signal by averaging the maximum and minimum wheel signals in a preselected group and by then reducing this average by an amount proportional to the difference between the maximum and minimum wheel signals. In this way undesirable oscillations, such as those due to pitching of the wheel truck, are filtered out. In a second embodiment the conditioned wheel signal is set equal to the minimum wheel signal in a preselected group, and the reference signal is set equal to the conditioned wheel signal in the event the reference signal is less than the conditioned wheel signal.

Claims

1. An apparatus for generating a reference signal representative of a reference braking condition in a brake control system for a braked wheel, said brake control system including means for generating a wheel signal having a plurality of values which vary in time and are each representative of a respective measurement of a braking condition of the braked wheel at a separate respective time period, said apparatus comprising:

means for determining the value of the wheel signal corresponding to a maximum braking condition from a plurality of values of the wheel signal occurring during a first time interval;

means for generating a conditioned wheel signal indicative of the value corresponding to the maximum braking condition; and

means for generating a reference signal representative of a reference braking condition as a function of the conditioned wheel signal.

2. The apparatus of claim 1 wherein the determining means comprises:

means for storing the plurality of values of the wheel signal during the first time interval;

means for comparing the stored values with one another to determine stored value having an extreme magnitude in a predetermined direction; and

means for supplying the stored value having the extreme magnitude to the generating means as the value corresponding to the maximum braking condition.

3. The apparatus of claim 1 or 2 wherein the reference signal generating means comprises:

means for setting a next value of the reference signal to a value corresponding to the conditioned wheel signal when the conditioned wheel signal is indicative of a lesser braking condition than is a current value of the reference signal.

4. The apparatus of claim 1 or 2 wherein the conditioned wheel signal is indicative of a conditioned wheel velocity, wherein the reference signal is indicative of a reference velocity, and wherein the reference signal generating means comprises:

means for setting a next value of the reference signal to a value corresponding to the conditioned wheel signal when the conditioned wheel signal is indicative of a greater velocity than is a current value of the reference signal.

5. The apparatus of claim 1 wherein the plurality of values comprises at least seven values.

6. The apparatus of claim 1 or 5 wherein the first time interval comprises at least 0.07 seconds.

7. The apparatus of claim 1 or 5 wherein the first time interval is greater than 1/20 of a second and less than 1/10 of a second.

8. An apparatus for generating a reference signal representative of a reference velocity in a brake control system for a braked wheel, said brake control system including means for generating a velocity signal having a plurality of values which vary in time and are each representative of a respective measurement of the rotation velocity of said braked wheel at a separate respective time period, said apparatus comprising:

means for determining the minimum value of the velocity signal from a plurality of values of the velocity signal occurring during a first time interval;

means for generating a conditioned velocity signal indicative of the minimum value; and

means for generating a reference signal representative of a reference velocity as a function of the conditioned velocity signal.

9. The apparatus of claim 8 wherein the determining means comprises:

means for storing the plurality of values of the velocity signal during the first time interval;

means for comparing the stored values with each other to determine the minimum stored value; and

means for supplying the minimum stored value to the generating means as the minimum value.

10. The apparatus of claim 8 wherein the reference signal generating means comprises:

means for setting a next value of the reference signal to a value corresponding to the conditioned velocity signal when the conditioned velocity signal is indicative of a greater velocity than is a current value of the reference signal.

11. The apparatus of claim 8 wherein the plurality of values comprises at least seven values.

12. The apparatus of claim 8 or 11 wherein the first time interval comprises at least 0.07 seconds.

13. The apparatus of claim 8 or 11 wherein the first time interval is greater than 0.05 seconds as less than 0.1 second.

14. In a brake control system for a braked wheel, comprising means for generating a wheel signal having a plurality of values which vary in time and are each indicative of a respective measurement of the rotational behavior of said braked wheel at a respective time, means for generating a brake control signal as a function of the wheel signal and a reference signal representative of a reference braking condition, and means for modifying a braking action applied to the braked wheel in response to the brake control signal, the improvement comprising:

means for determining the value of the wheel signal having an extreme magnitude in a predetermined direction occurring during a first time interval;

means for generating a conditioned wheel signal indicative of the extreme magnitude; and

means for generating the reference signal representative of the reference braking condition as a function of the conditioned wheel signal.

15. The improvement of claim 14 wherein the reference signal generating means operates to generate the reference signal at a value no greater than that corresponding to the conditioned wheel signal.

16. The improvement of claim 14 wherein the reference signal generating means comprises:

means for setting a next value of the reference signal to a value corresponding to the conditioned wheel when the conditioned wheel signal is indicative of a lesser braking condition than is a current value of the reference signal.

17. The improvement of claim 14 or 15 wherein the wheel signal is indicative of wheel velocity and the reference signal is indicative of a reference velocity.

18. The improvement of claim 14 or 15 wherein the first time interval is in the range of 1/20 of a second to 1/10 of a second.

19. The improvement of claim 18 wherein the first time interval is 0.07 seconds.

20. In a brake control system for a braked wheel, comprising means for generating a digital wheel signal on a periodic basis, each value of the wheel signal indicative of a measured value of the rotational velocity of said braked wheel at a respective time, means for generating a brake control signal as a function of the wheel signal and a reference signal representative of a reference velocity, and means for modifying a braking action applied to the braked wheel in response to the brake control signal, the improvement comprising:

a computer;

means, included in the computer, for storing a plurality of values of the wheel signal occurring during a first time period;

p1 means, included in the computer, for determining the minimum one of the stored values of the wheel signal;

means, included in the computer, for generating a conditioned wheel signal corresponding to the minimum one of the stored values; and

means, included in the computer and responsive to the conditioned wheel signal, for generating the reference signal as a function of the conditioned wheel signal.

21. The improvement of claim 20 wherein the reference signal generating means comprises:

means for setting a next value the reference signal to a value corresponding to the conditioned wheel signal when the conditioned wheel signal is indicative of a greater velocity than is a current value of the reference signal.

22. The improvement of claim 20 or 21 wherein the storing means acts to store only every other value of the wheel signal occurring during the first time period.

23. The improvement of claim 20 or 21 wherein the storing means stores greater than 5 values of the wheel signal.

24. The improvement of claim 20 or 21 wherein the duration of the first time period is in the range between 1/20 of a second and 1/10 of a second.

25. The improvement of claim 20 or 21 wherein the duration of the first time interval is 0.07 second.

26. In a brake control system for a braked wheel, comprising means for generating a digital wheel signal on a periodic basis, each value of which is indicative of a measured value of the rotational behavior of said braked wheel at a respective time, means for generating a brake control signal as a function of the wheel signal and a reference signal representative of a reference braking condition, and means for modifying a braking action applied to the braked wheel in response to the brake control signal, the improvement comprising:

a computer;

means, included in the computer, for maintaining a wheel signal block which includes a plurality of stored values, each of which is indicative of a selected respective one of the plurality of values of the wheel signal occurring in a selected time period, which plurality of values includes the most recently generated value of the wheel signal;

means, included in the computer, for searching the when signal block to select the stored value associated with value of the wheel signal indicative of the greatest braking condition;

means, included in the computer, for generating a conditioned wheel signal as a function of the selected stored value; and

means, included in the computer, for generating the reference signal as a function of the conditioned signal.

28. The improvement of claim 26 or 27 wherein the maintaining means acts to store only every other value of the wheel signal occurring during the selected time period in the wheel signal block.

29. The improvement of claim 26 or 27 wherein the maintaining means stores greater than 5 values of the wheel signal in the wheel signal block.

30. The improvement of claim 26 or 27 wherein the duration of the selected time period is in the range between 1/20 of a second and 1/10 of a second.

31. The improvement of claim 26 or 27 wherein the duration of the selected time period is substantially equal to 0.07 second.

27. In a brake control system for a braked wheel, comprising means for generating a digital wheel signal on a periodic basis, each value of the wheel signal being indicative of a measured value of the rotational velocity of said braked wheel at a respective time, means for generating a brake control signal as a function of the wheel signal and a reference signal representative of a reference velocity, and means for modifying a braking action applied to the braked wheel in response to the brake control signal, the improvement comprising:

a computer;

means, included in the computer, for maintaining a wheel signal block which includes a plurality of stored values, each of which is indicative of a selected respective one of the plurality of values of the wheel signal occurring in a selected time period, which plurality of values includes the most recently generated value of the wheel signal;

means, included in the computer, for searching the wheel signal block to select the stored value associated with value of the wheel signal indicative of the minimum velocity;

means, included in the computer, for generating a conditioned wheel signal which corresponds to the selected stored value; and

means, included in the computer, for generating the reference signal as a function of the conditioned wheel signal.