Inventory Mirroring for Fulfillment Networks

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Solution Overview

Problem

Online retailers face challenges in determining the optimal number of distribution centers to stock each SKU due to limited capacity at each center, which affects fulfillment costs and delivery speed, making it infeasible to stock every SKU at every distribution center.

Innovation Solution

A method and system for determining an inventory mirroring plan that clusters distribution centers and calculates the number of clusters needed to minimize total shipping costs for each SKU, using k-medoid clustering and integer programming to optimize the placement of SKUs across the network.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If every SKU is stocked at every distribution center, then delivery speed is improved, but capacity constraints make this approach infeasible

Engineering Contradiction:
Improvedelivery speedVSAvoidcapacity constraint
Core Design Contradiction:
SpeedVSQuantity of substance

Solution Approach 1:

The patent applies local quality by differentiating inventory placement strategies for different SKUs based on their specific characteristics. High-velocity SKUs are mirrored across multiple distribution centers to enable fast local delivery, while low-velocity SKUs are concentrated at fewer centers. This creates non-uniform inventory distribution tailored to local demand patterns at each distribution center, resolving the contradiction between delivery speed and capacity constraints.

Inventive Principle:
Principle #3Local quality

Solution Approach 2:

The patent changes the parameter of inventory mirroring factor for different SKUs. By calculating optimal mirroring factors based on velocity, demand patterns, and capacity constraints, the system dynamically adjusts how many copies of each SKU are placed at each distribution center. This parameter differentiation enables the system to achieve fast delivery for high-priority items while respecting overall capacity limitations.

Inventive Principle:
Principle #35Parameter changes

2Speed

If SKUs are mirrored across multiple distribution centers, then delivery speed is improved, but fulfillment costs increase

Engineering Contradiction:
Improvedelivery speedVSAvoidfulfillment cost
Core Design Contradiction:
SpeedVSLoss of energy

Solution Approach 1:

The patent optimizes the mirroring factor parameter for each SKU to balance delivery speed and fulfillment cost. By calculating the optimal number of distribution centers to stock each SKU based on velocity and demand patterns, the system avoids excessive mirroring of low-velocity items while ensuring adequate coverage for high-velocity items. This parameter optimization resolves the contradiction by achieving necessary delivery speed improvements without incurring disproportionate fulfillment costs.

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The patent applies different mirroring strategies to different SKUs based on their local characteristics. High-velocity SKUs receive higher mirroring priority to enable fast delivery, while low-velocity SKUs are concentrated at fewer centers to reduce fulfillment costs. This localized differentiation resolves the contradiction by allocating mirroring resources where they generate the most value in terms of delivery speed improvement relative to cost.

Inventive Principle:
Principle #3Local quality

3Speed

If the number of distribution centers stocking each SKU is increased, then delivery speed is improved, but the complexity of inventory management increases

Engineering Contradiction:
Improvedelivery speedVSAvoidinventory management complexity
Core Design Contradiction:
SpeedVSDevice complexity

Solution Approach 1:

The patent uses calculated mirroring factors to determine the optimal number of distribution centers for each SKU, avoiding arbitrary or excessive mirroring decisions. This parameter-based approach provides a systematic framework that reduces management complexity compared to ad-hoc decisions, while still achieving the delivery speed improvements needed for high-velocity SKUs.

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The patent differentiates inventory management complexity by SKU characteristics. High-velocity SKUs that require multi-center mirroring receive more sophisticated management attention, while low-velocity SKUs use simpler concentration strategies. This localized management approach resolves the contradiction by applying complexity only where it generates sufficient value in terms of delivery speed.

Inventive Principle:
Principle #3Local quality

Data Source

PatentUS10540621B2Inventory mirroring
Publication Date: 2020.01.21 WALMART APOLLO LLC
  • US10540621B2 patent drawing
  • US10540621B2 patent drawing
  • US10540621B2 patent drawing

AI summary

A method of determining an inventory mirroring plan for a set of distinct items in a fulfillment network. The fulfillment network can include a plurality of distribution centers. The method can include determining, for each distinct item of the set of distinct items and for each demand zone of a set of demand zones, a location-specific demand. The method also can include determining, for each of a number of clusters ranging from 1 to a predetermined maximum number of clusters, a k-cluster profile that partitions the plurality of distribution centers in the fulfillment network into k distribution center clusters. The method further can include determining, for each of the number of clusters and for each demand zone of the set of demand zones, a closest distribution center cluster of the k distribution center clusters that is nearest to the demand zone. The method also can include determining, for each of the number of clusters and for each demand zone of the set of demand zones, an average zone distance from the demand zone to the closest distribution center cluster. The method further can include determining a solution value of the number of clusters for each distinct item that minimizes a sum of a total shipping cost of each distinct item, subject to a total distinct item capacity of the plurality of distribution centers in the fulfillment network.