Method for analyzing and forecasting component replacement

• US 6,278,920 B1
• Filed: 06/19/2000
• Issued: 08/21/2001
• Est. Priority Date: 06/19/2000
• Status: Expired due to Term

• Current Assignee: Horizon Event, LLC
• Original Assignee: James O. Hebberd
• Inventors: Hebberd, James O.
• Primary Examiner(s): Nguyen, Tan
• Assistant Examiner(s): Marc-Coleman, Marthe
• Application Number:
  US09/597,675
• Time in Patent Office: 428 Days
• Field of Search: 701/29, 701/30, 701/31, 701/34, 701/35, 701/36, 701/39, 701/33, 340/500, 324/500, 324/509, 324/512, 702/108, 702/116, 702/127
• US Class Current: 701/29
• CPC Class Codes: G05B 23/0283 Predictive maintenance, e.g. involving the monitoring of a system and, based on the monitoring results, taking decisions on the maintenance schedule of the monitored system; Estimating remaining useful life [RUL] preventive maintenance, i.e. planning maintenance according to the available resources without monitoring the system G06Q10/06
• CPC Class Codes: G06Q 10/06 Resources, workflows, human or project management; Enterprise or organisation planning; Enterprise or organisation modelling

Abstract

A computerized method for quantifying confidence in a replacement schedule for components that must be routinely replaced within a fleet of aircraft or like equipment includes programming a computer to accept predetermined input data, including anticipated life expectancy T, indicated reliability R₁, the population P of the component in the fleet, and the number of failed units F replaced over a time increment t. The method computes the minimum-mean-time-between-removals θ₁, and the upper limit on unreliability P_u based upon such input data. The computer compares two or more of such factors to a series of Gamma Confidence Level look-up tables, and either determines a Gamma Confidence Level for the user, or prompts the user to modify the input data so that a Gamma Confidence Level can be determined. If the resulting Gamma Confidence Level is too low, the anticipated life expectancy T is reduced, and the method is repeated. The component is scheduled for replacement when the usage of the component reaches the computed minimum-mean-time-between-removals θ₁.

Claims

1. A method for establishing a confidence level in a replacement schedule for a component used within a group of machines, said method comprising the steps of:

a. selecting an anticipated life expectancy T for the component;

b. establishing an indicated reliability R₁ for the component;

c. establishing a time increment t over which one or more units of the component produced a failure;

d. establishing a number of failed units F of the component that had to be replaced over the time increment t;

e. determining a number P of units the population of the component in active use within a particular group of such machines;

f. computing a minimum-mean-time-between-removals θ

₁ based upon the anticipated life expectancy T and the indicated reliability R₁;

g. computing an upper limit on unreliability P_u based upon time increment t and the minimum-mean-time-between-removals θ

₁;

h. searching a plurality of Gamma Confidence Level look-up tables based upon three factors, namely, the number of failed units F, the population of the component within a particular group of machines, and the upper limit on unreliability P_u to determine whether such three factors simultaneously appear within one or more of the plurality of Gamma Confidence look-up tables;

i. if the three factors do not simultaneously appear on any of the plurality of Gamma Confidence lookup tables, then raising the indicated reliability R₁ in step b., and repeating steps f., g., and h. until the three factors simultaneously appear on one of the plurality of look-up tables;

j. determining, based upon steps h. and i., the Gamma Confidence Level for the population of the component within the group of machines;

k. if the Gamma Confidence Level determined in step j. is 75% or less, then reducing the anticipated life expectancy T, and repeating steps f., g., and h. until the Gamma Confidence Level is 75% or higher; and

l. replacing the component within the particular group of machines when the usage of the component reaches the minimum-mean-time-between-removals θ

₁ computed in step f.

2. The method recited by claim 1 wherein said step of establishing an indicated reliability R₁ for the component is based in part upon the anticipated life expectancy T for the component selected in step a.

3. The method recited by claim 2 wherein said step of establishing an indicated reliability R₁ for the component includes the step of computing indicated reliability R₁ according to the formula

4. The method recited by claim 1 wherein said steps f., g., h., i. and j. are performed by a computer, and wherein said method includes the step of inputting to the computer the values established in steps a., b., c., d. and e.

5. The method recited by claim 1 wherein said method is repeated at periodic intervals to reassess the Gamma Confidence Level using current input data.

6. The method recited by claim 1 wherein said method is repeated after each removal of the component for cause to reassess the Gamma Confidence Level using current input data.