Rotable inventory calculation method
First Claim
Patent Images
1. A method of optimizing rotable inventory, comprising:
- interfacing a processor with a user interface, the user interface and the processor communicating with a computer having a computer readable storage medium including instructions for executing an algorithm to determine an optimized inventory level, the algorithm comprising the steps of;
selecting a desired customer service level;
obtaining at least one characteristic of a part repair lead-time distribution, wherein the at least one characteristic is a mean μ and
a variance σ
of the part repair lead-time distribution;
computing on the computer a proposed inventory level based on said at least one characteristic, wherein computing a proposed inventory level includes recomputing a probability term β
having a distribution reflected by a difference term Δ
β
and calculating the proposed inventory level as I=A·
(R−
W)−
μ
+Δ
β
·
σ
, wherein I is the proposed inventory level, A is a part arrival value, R is a maximum repair time and W is a desired turnaround time window;
determining a calculated customer service level corresponding to the proposed inventory level;
comparing the calculated customer service level with the desired customer service level; and
selecting the proposed inventory level as the optimized inventory level when the calculated customer service level is within a selected convergence threshold with respect to the desired customer service level.
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Abstract
A method for conducting a repairable inventory analysis calculates the minimum number of repairable parts to be held in inventory while still being able to satisfy the demand for spare parts even in view of uncertain repair lead times. The method uses a set of equations that relates a customer service level to arbitrary probability distribution functions of a repair lead-time and a part arrival process. The distributions are then searched to locate the optimal inventory level in the distribution.
34 Citations
16 Claims
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1. A method of optimizing rotable inventory, comprising:
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interfacing a processor with a user interface, the user interface and the processor communicating with a computer having a computer readable storage medium including instructions for executing an algorithm to determine an optimized inventory level, the algorithm comprising the steps of; selecting a desired customer service level; obtaining at least one characteristic of a part repair lead-time distribution, wherein the at least one characteristic is a mean μ and
a variance σ
of the part repair lead-time distribution;computing on the computer a proposed inventory level based on said at least one characteristic, wherein computing a proposed inventory level includes recomputing a probability term β
having a distribution reflected by a difference term Δ
β
and calculating the proposed inventory level as I=A·
(R−
W)−
μ
+Δ
β
·
σ
, wherein I is the proposed inventory level, A is a part arrival value, R is a maximum repair time and W is a desired turnaround time window;determining a calculated customer service level corresponding to the proposed inventory level; comparing the calculated customer service level with the desired customer service level; and selecting the proposed inventory level as the optimized inventory level when the calculated customer service level is within a selected convergence threshold with respect to the desired customer service level. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A method of maintaining an optimized rotable inventory level, comprising:
determining an optimized inventory level, the determining step occurring on a computer having a computer readable storage medium storing instructions for; selecting a desired customer service level; obtaining at least one characteristic of a part repair lead-time distribution, wherein the at least one characteristic is a mean μ and
a variance σ
of the part repair lead-time distribution;computing on the computer a proposed inventory level based on said at least one characteristic, wherein computing a proposed inventory level includes recomputing a probability term β
having a distribution reflected by a difference term Δ
β
and calculating the proposed inventory level as I=A·
(R−
W)−
μ
+Δ
β
·
σ
, wherein I is the proposed inventory level, A is a part arrival value, R is a maximum repair time and W is a desired turnaround time window;determining a calculated customer service level corresponding to the proposed inventory level; comparing the calculated customer service level with the desired customer service level; and selecting the proposed inventory level as the optimized inventory level when the calculated customer service level is within a selected convergence threshold with respect to the desired customer service level; and maintaining an inventory level responsive to said optimized inventory level. - View Dependent Claims (13, 14, 15)
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16. A computer readable storage medium including a set of instructions that causes a computer to perform the following steps:
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interfacing a user interface with a processor storing data on a memory to be used by the processor to execute an algorithm; executing the algorithm on the processor to determine an optimized inventory level, the algorithm comprising the steps of; selecting a desired customer service level; obtaining at least one characteristic of a part repair lead-time distribution, wherein the at least one characteristic is a mean μ and
a variance σ
of the part repair lead-time distribution;using the computer readable storage medium on a computer to compute a proposed inventory level based on said at least one characteristic, wherein computing a proposed inventory level includes recomputing a probability term β
having a distribution reflected by a difference term Δ
β
and calculating the proposed inventory level as I=A·
(R−
W)−
μ
+Δ
β
·
σ
, wherein I is the proposed inventory level, A is a part arrival value, R is a maximum repair time and W is a desired turnaround time window;determining a calculated customer service level corresponding to the proposed inventory level; comparing the calculated customer service level with the desired customer service level; and selecting the proposed inventory level as the optimized inventory level when the calculated customer service level is within a selected convergence threshold with respect to the desired customer service level.
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Specification