基于排队论的港口运输装卸服务系统优化方法研究

An optimized method for the loading/unloading system of port transportation based on queuing theory

直接用汽车将集装箱运往港口堆场是集装箱货物运输的一种重要方式。在货物由内陆地区货运站到港口码头堆场的运输工作中,运输车辆与装卸机械是构成港口运输装卸服务系统最基本的生产要素。为减少运输车辆和装卸机械在运输生产过程中由于等待而产生的非生产停歇时间,控制车辆的等待费用和机械的装卸费用,获得最好的系统效率和生产效益,必须合理组织装卸机械和运输车辆的协调配合工作。在集装箱运输组织和管理中,运输车辆与装卸机械协调配合下装卸机械数量的确定,通常采用在一个连续和足够大的时间内以运输车辆和装卸机械两方面工作节奏相一致为条件进行建模的方法求解。这种方法存在的问题是车辆的周转时间和装卸停歇时间均采用平均值来计算,没有充分考虑车辆到达和装卸时间随机性的影响。本文运用排队论的理论方法,在建立港口运输装卸服务排队系统基础上,根据装卸机械数与等待费用和服务费用的变动关系,以系统在单位时间内承担的总费用最小作为决策目标来确定装卸机械的数量。以此实现运输车辆与装卸机械的协调配合,最终达到提高生产效率和效益、增强港口竞争力的目的。由于充分考虑了运输车辆运行时间和装卸机械装卸时间的随机性,因此该决策更具有科学性和合理性。

Transporting containers to port storage by cars is one of the important ways of container freight transportation. In transporting freight from the inland freight stations to the port storage fields, cars and loading/unloading machinery is the most basic production elements of the load/unloading service system in port transportation. To reduce the not-production resting time that started from the process of transportation, to control the waiting and loading/unloading cost, to attain the optimum system efficiency and benefit, it is needed to cooperate the loading/unloading machinery and the cars reasonably. In the container organization and management, to decide the quantity of the load/ unloading machinery and cars, the mathematical model is often established under the condition of the same working pace between the cars and the machinery for a period of continuous and sufficient time. The problem of this strategy is the calculation the turnover time and loading/unloading time is mean value, it does not pay attention to the cars arriving and the loading/unloading time. In this article, according to the changing ralationship between the machinery quantity and the waiting and serv ice costs, and based on establishing port transportation load/unloading queuing system, queuing theory was used to determined the quantity of loading/unloading machinery for realizing the ordinary operation between the cars and the load/unloading machinery by taking the minimum of total costs in the unit time as the decision goal, this strategy could finally improve the efficiency and benefit, and increase the port＇s competitive capacity. Because of including all of the randomness of the transportation time and loading/unloading time, this decision is more scientific and reasonable.