关于约束底盘装载问题的一种启发式方法

已研究多年的底盘装载问题属于ＮＰ完备问题，关于它的解决方法多为启发式方法．本文讨论了约束底盘装载问题，并提出了一种基于计算机的启发式方法．实例表明，该方法能较好地解决约束底盘装载问题．     

A novel hybrid tabu search approach to container loading

The container loading problem, which is significant for a number of industrial sectors, aims to obtain a high space utilisation in the container while satisfying practical constraints. This paper presents a novel hybrid tabu search approach to the container loading problem. A loading heuristic is devised to incorporate heuristic strategies with a handling method for remaining spaces to generate optimal loading arrangements of boxes with stability considered. The tabu search technique, which covers the encoding, evaluation criteria and configuration of neighbourhood and candidate solutions, is used to improve the performance of the loading heuristic. Experimental results with benchmark data show that the hybrid approach provides a better space utilisation than the published approaches under the condition of all loaded boxes with one hundred percent support from below. Moreover, it is shown that the hybrid tabu search can solve problems with the constraints of weight limit and weight distribution with real world data.     

THREE-DIMENSIONAL CONTAINER LOADING USING A COOPERATIVE CO-EVOLUTIONARYGENETIC ALGORITHM

This paper presents the use of a cooperative co-evolutionary genetic algorithm (CCGA) in conjunction with a heuristic rule for solving a 3D container loading or bin packing problem. Unlike previous works, which concentrate on using either a heuristic rule or an optimization technique to find an optimal sequence of packages which must be loaded into the containers, the proposed heuristic rule is used to partition the entire loading sequence into a number of shorter sequences. Each partitioned sequence is then represented by a species member in the CCGA search. The simulation results indicate that the use of the heuristic rule and the CCGA is highly efficient in terms of the compactness of packages in comparison to the results given by a standard genetic algorithm search. In addition, this helps to confirm that the CCGA is also suitable for use in a sequence-based optimization problem.     

求解多车辆装载问题的启发式改进蚁群算法设计

针对启发式优化算法不能较理想地对多车辆大规模装载问题进行优化的局限性,文章设计了一种启发式改进蚁群算法,该算法将单车辆的启发式装载与多车辆装载时的蚁群优化算法有机结合,较好地解决了多车辆大规模装载问题。经过实例验证,该算法具有较高的计算效率和较好的收敛特性。     

一种求解三维集装箱装箱问题的混合遗传算法

在遗传算法的基础上结合传统启发式装箱算法,设计了一个混合遗传算法,该算法既继承了遗传算法的全局搜索好的优点,也克服了遗传算法局部搜索能力差的缺点,能够较好地解决集装箱这类多目标多约束的空间三维分布的问题。     

Bi-objective optimization of three echelon supply chain involving truck selection and loading using NSGA-II with heuristics algorithm

This paper models a three echelon supply chain distribution problem considering multiple time periods, multi-products and uncertain demands. To take the problem closer to reality we consider multiple truck types and focus on the truck selection and loading sub-problem. Truck selection is important because the quantity of goods to be transported varies regularly and also because different trucks have different hiring cost, mileage and speed. Truck loading is important when considering the optimal loading pattern of products having different shapes and sizes on trucks, which themselves have distinct loading capacities. The two objectives considered here are the cost and responsiveness of the supply chain. The distribution problem is solved using the non-dominated sorting genetic algorithm (NSGA-II). However, the genetic algorithms compromise the optimality of the sub-problems while optimizing the entire system. But the optimality of truck selection and loading sub-problem is non-compromisable in nature. Hence a heuristic algorithm is used innovatively along with the NSGA-II to produce much better solutions. To make our model more realistic, the distribution chain is modelled as a push–pull based supply chain having multiple time periods and using demand aggregation over time. Using a separate algorithm also gives the advantage of utilizing the difference in nature of the push and pull part of the supply chain by giving every individual truck different objectives. Real life like data is generated and the optimality gap between the heuristic and non-heuristic approach is calculated. A clear improvement in objectives can be seen while using the heuristic approach.     

Micro-IPLS: Pallet loading on a microcomputer

IPLS is an interactive computerized system developed in 1982 to assist the U.S. Air Force with pallet loading. It uses a dynamic programming based heuristic to solve the two-dimensional problem of loading a rectangular pallet from a set of n rectangular boxes so as to maximize the area covered. Micro-IPLS is a version of IPLS that has been developed recently using Apple Fortran on an Apple II⁺ microcomputer with 64k. This paper discusses the underlying heuristic used by Micro-IPLS and compares its performance to the results obtained by the latest version of IPLS.     

Solving a furnace loading problem

This paper presents a heuristic solution procedure for the furnace loading problem in metallurgical industry. The problem is decomposed into two stages: ingot order selection and candidate ingot loading. The 2-stage problems are then iteratively solved. It is shown that practical sized problems can be efficiently solved using the proposed approach.     

Heuristic procedures and mathematical models for cell loading and scheduling in a shoe manufacturing company

This paper focuses on cell loading and scheduling issues in a shoe manufacturing company. It involves a three-phase solution methodology where first number of cells is determined, then cells are loaded and finally detailed scheduling is performed. Three different family definitions are used (subfamilies, families and superfamilies) during the cell loading process. Three cell loading heuristic procedures (H1, H2, and H3), a simple cell scheduling heuristic and two-level mathematical models are proposed and then compared with respect to makespan. An important observation is that better post-loading schedules did not lead to better post-scheduling results. As a result, the best schedule can only be known after both cell loading and cell scheduling functions are performed. The results showed that H1 led to the best post-scheduling makespan values and they were on the average within 3% of the optimal solution. The execution time for H1 was less than four seconds for the problems tested in the experimentation and this can be considered negligible for a manufacturing setting.     

具有承载能力约束的集装箱装入问题的求解方法

对有承载能力约束的三维集装箱装入问题进行了描述,定义了货物承载约束的表示形式,并在全局寻优能力很强的集装箱装入的禁忌搜索算法中加入承载能力的计算和检查方法,设计了相关的处理策略.在优化空间利用率的同时减少或杜绝货物损坏现象的发生.实验结果表明,该算法对有承载能力约束的三维集装箱装入问题的有效性和实用性.     

同类货物集装箱装载问题的启发式算法

提出了求解同类货物集装箱装载问题的一种启发式算法.算法中采用了层的思想,集装箱的每个面都可用来构建层.通过对二维布局、层高组合和用来构建层的集装箱面的选择等三个方面的优化求解,得到了具有较高装载率的集装箱装载方案.实例结果表明,该算法是求解同类货物集装箱装载问题的一种行之有效的方法.     

一种求解集装箱装载问题的启发式算法

所谓集装箱装载问题,就是将若干大小不同的长方体盒子装进一个大小已知的长方体容器,其目标是最大化容器的积裁率.对这一问题,国内外学者利用不同的哲学思想,提出了诸如遗传算法、模拟退火算法等求解算法.本文提出一种求解此问题的基于最大穴度优先原则的启发式算法.算法中使用了两个重要的策略:最大穴度原则和最小边度原则.用一些公开的算例对算法性能进行了实算测试,测试结果表明:算法所得结果的容器积载率高,是求解集装箱装载问题的有效算法.     

Extended guided tabu search and a new packing algorithm for the two-dimensional loading vehicle routing problem

In this paper, we develop an extended guided tabu search (EGTS) and a new heuristic packing algorithm for the two-dimensional loading vehicle routing problem (2L-CVRP). The 2L-CVRP is a combination of two well-known NP-hard problems, the capacitated vehicle routing problem, and the two-dimensional bin packing problem. It is very difficult to get a good performance solution in practice for these problems. We propose a meta-heuristic methodology EGTS which incorporates theories of tabu search and extended guided local search (EGLS). It has been proved that tabu search is a very good approach for the CVRP, and the guiding mechanism of the EGLS can help tabu search to escape effectively from local optimum. Furthermore, we have modified a collection of packing heuristics by adding a new packing heuristic to solve the loading constraints in 2L-CVRP, in order to improve the cost function significantly. The effectiveness of the proposed algorithm is tested, and proven by extensive computational experiments on benchmark instances.     

An AND/OR-graph Approach to the Container Loading Problem

The container loading problem consists of packing boxes of various sizes into available containers in such a way as to optimize an objective function. In this paper we deal with the special case where there is just one available container and the objective is to maximize the total volume (or the total utility value, supposing that each box has a utility value) of the loaded boxes. We firstly present three heuristic solution methods for the unconstrained problem. Two of them solve the original three-dimensional problem by layers and by stacks reducing it into several problems with lower dimensions. The third one consists of representing possible loading patterns as complete paths in an AND/OR-graph. Bounds and heuristics are proposed in order to reduce the solution space. A proper heuristic is also given to treat the constrained problem by using the AND/OR-graph approach. Moreover, computational results are presented by solving a number of examples.     

A new continuous model for job-shop scheduling

In this paper arguments are presented for the use of a new continuous model for job-shop scheduling. In this model each job is regarded as infinitely divisible. Formulating the job-shop problem in this way leads to optimal control problems of a type which recent work has shown to be efficiently solvable. Solutions to these continuous problems can be used to generate heuristic loading rules. Some simulation results from small job-shops are presented. These demonstrate that loading rules based on the continuous model perform well in practice.     

Scheduling of collaborative operations of yard cranes and yard trucks for export containers using hybrid approaches

Optimizing collaborative operations for yard cranes (YCs) and yard trucks (YTs) is vital to the overall performance of a container terminal. This research investigates four different hybrid approaches developed for dealing with yard crane scheduling problem (YCSP) and yard truck scheduling problem (YTSP) simultaneously for export containers in the yard side area of a container terminal. First, these approaches use a load-balancing heuristic to assign containers to YCs evenly. Following this, each of them employs a specific heuristic/metaheuristic, such as genetic algorithm (GA), particle swarm optimization (PSO) or subgroups PSO (SGPSO), to generate alternative container loading sequences for each YC. Finally, a simulation model is used to simulate loading and transporting of these export containers, evaluate alternative planning results, and finally output the best planning result. Experiments have been conducted to compare these hybrid approaches. The results show Hybrid4 (SGPSO) outperforms Hybrid1 (Sort-by-bay), Hybrid2 (GA), and Hybrid3 (PSO) in terms of makespan.     

求解三维装箱问题的混合模拟退火算法

提出了一个高效求解三维装箱问题(Three Dimensional Container Loading Problem 3D-CLP)的混合模拟退火算法.三维装箱问题要求装载给定箱子集合的一个子集到容器中,使得被装载的箱子总体积最大.文中介绍的混合模拟退火算法基于三个重要算法:(1)复合块生成算法,与传统算法不同的是文中提出的复合块不只包含单一种类的箱子,而是可以在一定的限制条件下包含任意种类的箱子.(2)基础启发式算法,该算法基于块装载,可以按照指定装载序列生成放置方案.(3)模拟退火算法,以复合块生成和基础启发式算法为基础,将装载序列作为可行放置方案的编码,在编码空间中采用模拟退火算法进行搜索以寻找问题的近似最优解.文中采用1500个弱异构和强异构的装箱问题数据对算法进行测试.实验结果表明,混合模拟退火算法的填充率超过了目前已知的优秀算法.     

A two-stage tabu search algorithm with enhanced packing heuristics for the 3L-CVRP and M3L-CVRP

The Three-Dimensional Loading Capacitated Vehicle Routing Problem (3L-CVRP) addresses practical constraints frequently encountered in the freight transportation industry. In this problem, the task is to serve all customers using a homogeneous fleet of vehicles at minimum traveling cost. The constraints imposed by the three-dimensional shape of the goods, the unloading order, item fragility, and the stability of the loading plan of each vehicle are explicitly considered. We improved two well-known packing heuristics, namely the Deepest-Bottom-Left-Fill heuristic and the Maximum Touching Area heuristic, for the three-dimensional loading sub-problem and provided efficient implementations. Based on these two new heuristics, an effective tabu search algorithm is given to address the overall problem. Computational experiments on publicly available test instances show our new approach outperforms the current best algorithms for 20 out of 27 instances. Our approach is also superior to the existing algorithm on benchmark data for the closely related problem variant M3L-CVRP (which uses a slightly different unloading order constraint compared to 3L-CVRP).     

集装箱堆场预倒箱问题的混合优化算法

堆场出口箱区通常通过集装箱的预倒箱操作来提高后续装船作业的效率. 为此, 开发了由邻域搜索算法与整数规划算法组成的两阶段混合算法对预倒箱问题进行优化, 第1 阶段通过启发式规则压缩末终堆存状态空间, 第2 阶段通过整数规划算法缩短第1 阶段得到的预倒箱序列的长度. 两个阶段循环交替进行以快速求得最优的预倒箱序列. 借助不同种类仿真算例的实验结果及与现有研究方法下所得结果的对比, 验证了混合优化算法的有效性和实用性.     

基于空间分解的集装箱布局启发式算法及布局空间利用率规律

针对集装箱布局提出了一种利用三叉树结构表达三维矩形物体布局状态空间的方法。通过将布避空间依据分割,每次放入相对于当前布局空间来说是满足特定折最优布局块,将该布局块定位于当前布局空间后部的左下角,来完成不同大小的三维矩形全的布局方案的确定,并给出试验结果。