Abstract
Robotic Mobile Fulfillment System (RMFS) is a new type of parts-to-picker order picking system and has become the development trend of e-commerce logistics distribution centers. There are usually a large number of tasks need to be allocated to many robots and the picking time for e-commerce orders is usually very tight, which puts forward higher requirements for the efficiency of multirobot task allocation (MRTA) in e-commerce RMFS. Current researches on MRTA in RMFS seldom consider task correlation and the balance among picking stations. In this paper, a task time cost model considering task correlation is built according to the characteristics of the picking process. Then, a multirobot task allocation model minimizing the overall picking time is established considering both the picking time balance of picking stations and the load balance of robots. Finally, a four-stage balanced heuristic auction algorithm is designed to solve the task allocation model and the tasks with execution sequence for each robot are obtained. By comparing with the traditional task time cost model and the algorithm without considering the balance among picking stations, it is found that the proposed model and algorithm can significantly shorten the overall picking time.
Highlights
In the market mechanism, robots negotiate with each other through bidding and complete the task allocation [10]
(3) A four-stage balanced heuristic auction algorithm is designed to solve the task allocation model, which achieves the goal of balancing picking time among picking stations by controlling the sequence of task assignments
Parameter Definition of multirobot task allocation (MRTA) in Robotic Mobile Fulfillment System (RMFS). rough the operation process analysis, we find that a robot can perform multiple tasks at one time, and one task can only be performed by one robot. e MRTA problem in RMFS can be classified as multitask robots and single-robot tasks (MT-SR) problem [23]
Summary
2.1. e Operation Process of e-Commerce RMFS. E-commerce orders have the characteristics of many varieties, small batch, and high frequency. Conveyor belt picker Figure 1: Logistics robot e typical layout of an e-commerce RMFS. Since a robot can serve one or more picking stations and perform one or more tasks at one shelf visit, the time cost of each task should be calculated in different ways. The time cost of robots to perform different tasks is distinguished through refining the task allocation process, especially considering the situation that robots can transport a shelf to serve multiple picking stations at one time. Ajl is the task performed by rj in order l, and |Oj| represents the total number of tasks assigned to rj. Sai represents the picking station where task ai was assigned, which is already known before allocating tasks to robots. Dai represents the Manhattan distance between the shelf of task ai and its picking station. Tijl is the time cost, which means the time used of fulfilling the task ai by robot rj in the lth order
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