[Plant Simulation Study #26] – AMR Routing Logic (3): Deadlock Resolution and Optimization

[Plant Simulation Study #26] – AMR Routing Logic (3): Deadlock Resolution and Optimization

 

Implementing Logic to Prevent AMR Collision and Deadlock in Siemens Plant Simulation

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📘 Overview

This post addresses the deadlock issue that occurred in the previous study ([Plant Simulation Study #25]) involving Autonomous Mobile Robots (AMRs).
It also demonstrates how to optimize the dynamic routing logic of AMRs in more complex environments.

💡 Key Objectives

• Solve AMR deadlock problems at intersections
• Implement node selection logic that considers occupied states
• Verify efficient movement in a complex grid network

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📺 Watch the Video

🎥 [YouTube] Plant Simulation Study (26) – AMR Destination Routing Logic (3): Deadlock Resolution and Optimization
👉 https://youtu.be/wdn4ei89zZw

 

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🧩 1. Analyzing and Fixing the Cause of Deadlock

⚠️ Problem

In the previous version, multiple AMRs would stop face-to-face at intersections, causing a complete deadlock.
The issue stemmed from AMRs’ DistanceCTRL zone being triggered during rotation, halting movement even when the path ahead was clear.

🧠 Solution Strategy

To eliminate this issue, the DistanceCTRL trigger during rotation was removed.
By disabling the zone check while turning, AMRs can now move smoothly without freezing mid-rotation.

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🔧 Main Code Snippet

param IsInsideZone : boolean, ZoneNumber : integer
-- param DistanceIsBelowLimit: boolean

if ?.AGVPool /= void

////////////Delete here//////////////
    /*if ZoneNumber = 1
        var numMUInZone1 = ?.getSafetyZoneContent(1).dim

        if IsInsideZone
            if numMUInZone1 = 1 then ?.StoppingCounter += 1 end
        else
            if numMUInZone1 = 0 then ?.StoppingCounter -= 1 end
        end
    end*/ 
////////////////////////////////////    


    var numMUInZone2 = ?.getSafetyZoneContent(2).dim

    if numMUInZone2 > 0
	    ?.Speed := ?.Origin.speed * 0.01
	    if ?.curveSpeed /= -1
		    ?.curveSpeed := ?.Origin.curveSpeed  * 0.01
	    end
    else
	    ?.Speed := ?.Origin.Speed
	    if ?.curveSpeed /= -1
		    ?.curveSpeed := ?.Origin.curveSpeed
	    end
    end
end

 

✅ By removing this small section, AMRs can move through intersections without triggering unintended stops — effectively preventing deadlock conditions.

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⚙️ 2. Logic Implementation and Testing

🔨 Implementation

Modify the AMR_destination_move method with the updated logic.
When an AMR encounters an occupied node, it waits (waitfor) until the node becomes available, then continues its path automatically.

🎬 Simulation Results

• AMRs no longer collide or block each other at intersections.
• Occupied nodes are skipped automatically → Deadlock completely resolved.
• Smooth stop-and-go motion achieved through efficient pathfinding.

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🧭 3. Testing in a Complex Grid Model

🧩 Extended Experiment

The same logic was applied to a large grid-based environment with multiple nodes and intersections.

🚀 Results

• AMRs moved through the complex network without collisions or bottlenecks.
• Each robot maintained a safe distance and optimized its route dynamically.
• Verified a stable, deadlock-free flow under heavy traffic conditions.

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🧭 4. Bonus: Auto-Generating and Connecting Nodes

Instead of manually creating nodes one by one, we implemented an automatic node generation script that builds an entire network based on variable inputs.

🧱 Node Generation Logic

for var i := 1 to 노드컬럼수
	for var p := 1 to 노드로우수
		var node := .ShuttleRack.M.duplicate(root)
		node._3D.Position := [i * 노드간간격 ,- p * 노드간간격 ,0]
		이동가능노드[I,P] := node
		DataTable[1,DataTable.ydim+1] := node
	next
next

for var t1 := 1 to 이동가능노드.xdim
	for var t2 := 1 to 이동가능노드.ydim
		if t1 /= 이동가능노드.xdim and t2 /= 이동가능노드.ydim
			.ShuttleRack.커넥터.connect(이동가능노드[t1,t2],이동가능노드[t1+1,t2])
			.ShuttleRack.커넥터.connect(이동가능노드[t1,t2],이동가능노드[t1,t2+1])
		elseif t1 = 이동가능노드.xdim and t2 /= 이동가능노드.ydim
			.ShuttleRack.커넥터.connect(이동가능노드[t1,t2],이동가능노드[t1,t2+1])
		elseif t2 = 이동가능노드.ydim and  t1 /= 이동가능노드.xdim
			.ShuttleRack.커넥터.connect(이동가능노드[t1,t2],이동가능노드[t1+1,t2])
		end
	next
next

for var t1 := 이동가능노드.xdim downto 1
	for var t2 := 이동가능노드.ydim downto 1
		if t1 /= 1 and t2 /= 1
			.ShuttleRack.커넥터.connect(이동가능노드[t1,t2],이동가능노드[t1-1,t2])
			.ShuttleRack.커넥터.connect(이동가능노드[t1,t2],이동가능노드[t1,t2-1])
		elseif t1 = 1 and t2 /= 1
			.ShuttleRack.커넥터.connect(이동가능노드[t1,t2],이동가능노드[t1,t2-1])
		elseif t2 = 1 and  t1 /= 1
			.ShuttleRack.커넥터.connect(이동가능노드[t1,t2],이동가능노드[t1-1,t2])
		end
	next
next

🧹 Node Deletion Logic

 

for var t1 := 1 to 이동가능노드.xdim
	for var t2 := 1 to 이동가능노드.ydim
		이동가능노드[t1,t2].deleteObject
	next
next
dataTable.delete

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✨ Conclusion

This study demonstrates a simple yet powerful method to prevent AMR deadlocks in Siemens Plant Simulation by refining node-based logic and eliminating DistanceCTRL triggers during rotation.
It also shows how to automatically generate node networks through parameterized logic, making model scalability much easier.

✅ Key Takeaways

• Disable DistanceCTRL trigger during AMR rotation
• Automatically create and connect nodes using parameters
• Achieve full deadlock-free and optimized AMR pathfinding

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🏷️ Tags / SEO Keywords

#PlantSimulation #AMR #Deadlock #RoutingLogic #DigitalTwin #Simulation #SmartFactory #SiemensTecnomatix #Optimization