Chen, Yuerong

de Koster, Rene

Gong, Yeming Yale

Zou, Bipan

English

Georgia Southern University: Digital Commons@Georgia Southern

Classification: Internal16th International Material Handling Research ColloquiumDresden, Saxony, Germany, June 20-23, 2023Sorting with robots: where to drop off the parcel?Rene de Koster, Yuerong Chen, Bipan Zou, Yeming GongErasmus University RotterdamHuazhong UST, Zhongnan U of Economics and Law, EM LyongAssign destinations to drop-off points in Robotic Sorting System (RSS) to maximize throughput capacity, considering robot congestion.Sorting using an RSS can be cheaper than conventional sorters (e.g. tilt tray), because of smaller footprint and building. It is also more flexible (adding/removing destinations and robots).However, systems can be congested. See below (China Postal; TPT in sec for a given drop-off point):Sorting at DepponTools: 1) OQN model estimating TT, including congestion, for given assignment 2) use this in MIP to determine optimal assignmentModel, Step 1:Result: TT(𝒙𝒙), with given assignment𝒙𝒙 = 𝑥𝑥𝑖𝑖,𝑗𝑗 , 𝑖𝑖 = 1, . . ,𝑀𝑀, 𝑗𝑗 = 1, … ,𝑁𝑁:Validation: errors <3%.Iteratively solve tandem queues with finite buffers:Dallery &Frein (1993)Solve resulting OQN using QNA of  Whitt (1983)Model, Step 2, Optimize assignmentMin 𝑇𝑇𝑇𝑇 𝒙𝒙�𝑗𝑗=1𝑁𝑁𝑥𝑥𝑖𝑖,𝑗𝑗 = 1, 𝑖𝑖 = 1, . . ,𝑀𝑀�𝑖𝑖=1𝑀𝑀𝑥𝑥𝑖𝑖,𝑗𝑗 = 1, 𝑗𝑗 = 1, . . ,𝑁𝑁𝑥𝑥𝑖𝑖,𝑗𝑗 =1, if destination 𝑖𝑖 is assigned to drop-off point 𝑗𝑗, 0 otherwiseFor given assignment and buffer capacities.Assumption: 𝑁𝑁 = 𝑀𝑀 = 𝐿𝐿 × 𝑊𝑊Solution: ALNS (Ropke& Pisinger, 2006)Results 1: Optimize assignment at Deppon Express (Shanghai)Data: 30 randomly selected days during 5 months from November 2018 to March 2019current (HC) optimized (ALNS)Throughput time reduction: 25%, congestion time reduction: 73%Develop assignment heuristic: BA (Balance destinations over drop-offs). ALNS is still significantly betterResults 2: Minimize cost, for given Throughput Capacity (TC) λmin𝐶𝐶𝑇𝑇 𝑛𝑛,𝑅𝑅,𝑝𝑝 = 𝐶𝐶𝑙𝑙𝑙𝑙 � 𝑛𝑛 + 𝐶𝐶𝑅𝑅 � 𝑅𝑅Such that: 𝑇𝑇𝐶𝐶 ≥ λ𝑛𝑛 = #insertion stations, 𝑅𝑅 = #robots, 𝑊𝑊, 𝐿𝐿, λ given.Solution: change OQN model, step 1 into closed queuing network and solve using AMVA method (Buitenhek et al., 2000).Results: 1) ALNS is better than BA and HC (=Deppon)2) BA outperforms HC at lowTCs, at high TCs HC is better.Future work: extend todifferent topologies10-years total multi-annual cost,𝑊𝑊 = 6, 𝐿𝐿 = 4,𝐶𝐶𝑙𝑙𝑙𝑙 = €12.5K, 𝐶𝐶𝑅𝑅 = €25K

Sorting with robots: where to drop off the parcel?

https://digitalcommons.georgiasouthern.edu/cgi/viewcontent.cgi?article=1075&context=imhrc

Sorting with robots: where to drop off the parcel?

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