AGV Route Re-Planning Using Lay-By Areas to Resolve Deadlocks

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Solution Overview

Problem

Automated Guided Vehicles (AGVs) in plants and logistics facilities often experience deadlocks when accidents or obstacles occur, leading to blocked routes and inability to move.

Innovation Solution

A route planning apparatus with a search unit that connects AGVs to lay-by areas and a re-planning unit that re-routes them to target sites such that initial routes do not collide with each other, using methods like A* algorithm, minimum cost flow processing, or selecting lay-by areas and moving objects based on distance and availability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If AGVs follow fixed routes to target sites, then route planning is simple and efficient, but deadlocks occur when accidents or obstacles block the routes

Engineering Contradiction:

Improveroute planning efficiencyVSAvoiddeadlock avoidance

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The system pre-identifies lay-by areas as potential waiting positions before deadlocks occur. When a deadlock is detected, AGVs are redirected to these pre-designated areas rather than attempting to navigate through blocked routes, enabling quick resolution without complex real-time recalculation

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

Lay-by areas serve as intermediary zones between target sites and blocked routes. AGVs temporarily park in these intermediary areas while waiting for obstacles to clear, acting as a buffer that prevents complete system shutdown and enables gradual recovery

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If AGVs are redirected to lay-by areas to avoid deadlocks, then deadlock avoidance improves, but route complexity and re-planning time increase

Engineering Contradiction:

Improvedeadlock avoidanceVSAvoidroute planning complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The route planning problem is segmented into two independent phases: (1) detecting deadlock and redirecting to lay-by areas, and (2) re-planning from lay-by areas to target sites. This segmentation allows each phase to be handled with simpler, more focused algorithms rather than attempting to solve the entire routing problem simultaneously

Inventive Principle:

Principle #1Segmentation

3Loss of time

If multiple AGVs are re-routed simultaneously, then deadlock resolution is faster, but route collisions between AGVs increase

Engineering Contradiction:

Improvedeadlock resolution timeVSAvoidroute collision

Core Design Contradiction:

Loss of timeVSObject-affected harmful factors

Solution Approach 1:

The system implements feedback mechanisms where AGVs communicate their intended routes and current positions to the route planning apparatus. Before finalizing re-routing decisions, the system checks for potential collisions and adjusts paths accordingly, ensuring that simultaneous re-routing of multiple AGVs does not create new conflicts

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The route planning system dynamically adjusts re-routing sequences based on real-time conditions. Rather than applying a fixed re-routing algorithm to all AGVs simultaneously, the system prioritizes AGVs based on their proximity to lay-by areas, current position, and potential for conflict, enabling coordinated movement that minimizes collisions

Inventive Principle:

Principle #15Dynamics

Data Source

PatentUS11782446B2Route planning apparatus, route planning method, and computer-readable recording medium

Publication Date: 2023.10.10 NEC CORP

AI summary

Provided is a route planning apparatus including a search unit 2 configured to search for a first route that connects each moving object and a lay-by area, when a deadlock is detected in a route plan of one or more moving objects 20, and a re-planning unit 3 configured to re-plan a second route from each moving object 20 to a target site such that the first routes which have been respectively found for the moving objects 20 do not collide with each other.