改进变邻域搜索算法求解动态车辆路径问题

针对动态车辆路径问题DVRP(Dynamic Vehicle Routing Problem)的优化问题,提出一种改进算法。该算法在分析路径寻优问题的局部特性的基础上,利用变邻域搜索算法VNS(Variable Neighbourhood Search)对路径空间进行"局部探索",结合变异机制对路径空间进行"全局开采",最后根据近邻优先原则将动态路径片段安插到适宜的路径中。实验结果验证了算法的有效性。     

A modified particle swarm optimization for economic dispatch with non-smooth cost functions

This paper presents a new approach to economic dispatch (ED) problems with non-smooth cost functions using a particle swarm optimization (PSO) technique. The practical ED problems have non-smooth cost functions with equality and inequality constraints, which makes the problem of finding the global optimum difficult when using any mathematical approaches. Since, standard PSO may converge at the early stage, in this paper, a modified PSO (MPSO) mechanism is suggested to deal with the equality and inequality constraints in the ED problems. To validate the results obtained by MPSO, standard particle swarm optimization (PSO) and guaranteed convergence particle swarm optimization (GCPSO) are applied for comparison. Also, the results obtained by MPSO, PSO and GCPSO are compared with the previous approaches reported in the literature. The results show that the MPSO produces optimal or nearly optimal solutions for the study systems.     

MDVRPTW问题多阶段迭代启发式算法

提出一个求解多车库VRPTW问题的聚类和迭代混合遗传算法。该算法采用三阶段过程：客户聚类分配、路径规划和路径改进,与以往两阶段算法不同,该算法采用混合遗传算法进行路径规划,采用竞争-插入进行路径改进,且路径规划与路径改进有机结合形成迭代路径规划过程。用Cordeau等人提出的算例实验表明该算法能够在可以接受的计算时间内得到可接受的好解。     

求解带时间窗车辆路径问题的改进粒子群算法

通过分析已有粒子群算法对有时间窗约束的车辆路径问题求解质量不高的原因,提出了一种基于粒子交换原理的整数粒子更新方法。采用构造的双层粒子进化算法分别对8个和20个任务点的有时间窗约束的车辆路径问题求解,数值实验结果表明算法的求解精度和耗时均优于已有算法。     

改进粒子群优化算法求解任务指派问题

任务指派问题是典型NP难题,引入粒子群优化算法对其进行求解。建立了任务指派问题的数学模型,给出了粒子群优化算法求解任务指派问题的具体方案。为提高其优化求解效果,引入变异机制及局部更新机制对粒子群优化算法进行改进。实例及数字仿真验证了改进粒子群优化算法的有效性。     

带时间窗的粮食物流车辆路径问题的研究

带时间窗的粮食物流车辆路径问题是一个典型的NP—难问题。针对粮食物流批量大、多点对多点等特点,建立了带时间窗的粮食物流车辆路径问题（Vehicle Routing Problem with Time Windows,VRPTM）的数学模型,进一步构造粒子群算法（Particle Swarm Optimization,PSO）用于问题求解,并将求解结果与遗传算法进行比较。结果表明,粒子群算法可以快速、有效地求得带时间窗的粮食物流车辆路径问题的优化解,降低配送成本。     

Solving the Urban Transit Routing Problem using a particle swarm optimization based algorithm

The Urban Transit Routing Problem (UTRP) comprises an NP-hard problem that deals with the construction of route networks for public transit networks. It is a highly complex and multiply constrained problem, in which the assessment of candidate route networks can be both time consuming and challenging. Except for that, a multitude of potential solutions are usually rejected due to infeasibility. Because of this difficulty, soft computing algorithms can be very effective for its efficient solution. The success of these methods, however, depends mainly on the quality of the representation of candidate solutions, on the efficiency of the initialization procedure and on the suitability of the modification operators used.An optimization algorithm, based on particle swarm optimization, is designed and presented in the current contribution, aiming at the efficient solution of UTRP. Apart from the development of the optimization algorithm, emphasis is also given on appropriate representation of candidate solutions, the route networks in other words, and the respective evaluation procedure. The latter procedure considers not only the quality of service offered to each passenger, but also the costs of the operator. Results are compared on the basis of Mandl's benchmark problem of a Swiss bus network, which is probably the only widely investigated and accepted benchmark problem in the relevant literature. Comparison of the obtained results with other results published in the literature shows that the performance of the proposed soft computing algorithm is quite competitive compared to existing techniques.     

A comparative study between dynamic adapted PSO and VNS for the vehicle routing problem with dynamic requests

Combinatorial optimization problems are usually modeled in a static fashion. In this kind of problems, all data are known in advance, i.e. before the optimization process has started. However, in practice, many problems are dynamic, and change while the optimization is in progress. For example, in the dynamic vehicle routing problem (DVRP), new orders arrive when the working day plan is in progress. In this case, routes must be reconfigured dynamically while executing the current simulation. The DVRP is an extension of a conventional routing problem, its main interest being the connection to many real word applications (repair services, courier mail services, dial-a-ride services, etc.). In this article, a DVRP is examined, and solving methods based on particle swarm optimization and variable neighborhood search paradigms are proposed. The performance of both approaches is evaluated using a new set of benchmarks that we introduce here as well as existing benchmarks in the literature. Finally, we measure the behavior of both methods in terms of dynamic adaptation.     

基于密度聚类构建物流配送问题的毁灭移除算法

研究多车型大规模物流配送问题,针对企业配送门店规模大且聚集的特点,在自适应大规模邻域搜索（ALNS）框架下提出一种新的邻域映射方式：基于密度聚类的毁灭移除算法。ALNS包含毁灭与重建两个阶段,通过不断对当前解进行破坏和重建得到更好解。在毁灭阶段,随机选择一条路线进行密度聚类得到簇集合,然后按簇对路线上的门店进行移除;重建阶段随机选择贪婪插入法或Regret-2插入法将移除的门店插入到合适的路线上得到新配送方案。通过国际基准测试案例验证了所提算法的有效性,与已有算法对比,基于密度聚类的毁灭移除算法的ALNS算法求解结果比案例已知最优解平均误差更低,求解质量更优;应用于实际场景中,该算法能在有限时间内求得较好的配送方案。     

Dynamic vehicle routing using genetic algorithms

Many difficult combinatorial optimization problems have been modeled as static problems. However, in practice, many problems are dynamic and changing, while some decisions have to be made before all the design data are known. For example, in the Dynamic Vehicle Routing Problem (DVRP), new customer orders appear over time, and new routes must be reconfigured while executing the current solution. Montemanni et al. [1] considered a DVRP as an extension to the standard vehicle routing problem (VRP) by decomposing a DVRP as a sequence of static VRPs, and then solving them with an ant colony system (ACS) algorithm. This paper presents a genetic algorithm (GA) methodology for providing solutions for the DVRP model employed in [1]. The effectiveness of the proposed GA is evaluated using a set of benchmarks found in the literature. Compared with a tabu search approach implemented herein and the aforementioned ACS, the proposed GA methodology performs better in minimizing travel costs. Franklin T. Hanshar is currently a M.Sc. student in the Department of Computing and Information Science at the University of Guelph, Ontario, Canada. He received a B.Sc. degree in Computer Science from Brock University in 2005. His research interests include uncertain reasoning, optimization and evolutionary computation. Beatrice Ombuki-Berman is currently an Associate Professor in the Department of Computer Science at Brock University, Ontario, Canada. She obtained a PhD and ME in Information Engineering from University of The Ryukyus, Okinawa, Japan in 2001 and 1998, respectively. She received a B.Sc. in Mathematics and Computer Science from Jomo Kenyatta University, Nairobi, Kenya. Her primary research interest is evolutionary computation and applied optimization. Other research interests include neural networks, machine learning and ant colony optimization.     

Binary particle swarm optimization (BPSO) based state assignment for area minimization of sequential circuits

State assignment (SA) for finite state machines (FSMs) is one of the main optimization problems in the synthesis of sequential circuits. It determines the complexity of its combinational circuit and thus area, delay, testability and power dissipation of its implementation. Particle swarm optimization (PSO) is a non-deterministic heuristic that optimizes a problem by iteratively trying to improve a candidate solution with regard to a given measure of quality. PSO optimizes a problem by having a population of candidate solutions called particles, and moving them around in the search-space according to a simple mathematical formulae. In this paper, we propose an improved binary particle swarm optimization (BPSO) algorithm and demonstrate its effectiveness in solving the state assignment problem in sequential circuit synthesis targeting area optimization. It will be an evident that the proposed BPSO algorithm overcomes the drawbacks of the original BPSO algorithm. Experimental results demonstrate the effectiveness of the proposed BPSO algorithm in comparison to other BPSO variants reported in the literature and in comparison to Genetic Algorithm (GA), Simulated Evolution (SimE) and deterministic algorithms like Jedi and Nova.     

混合蚁群算法在车辆路径问题中的应用

蚁群算法在求解车辆路径问题过程中存在搜索时间长、易于陷入局部最优解的问题。为此,设计并实现一种混合蚁群算法。引入变异算子增强算法的全局搜索能力,采用2-opt法优化阶段最优解的子路径。通过对信息素的挥发因子进行动态调整,从而有效控制信息量的变化速度。实例仿真结果表明,该算法具有较好的求解效率和寻优效果。     

基于车辆路径问题的蚁群遗传融合优化算法

在对车辆路径问题（VRP）分析的基础上,为之建立了数学模型,提出了一种适合求解该问题的蚁群遗传融合优化算法。该算法首先采用蚁群算法产生阶段最优解,然后利用遗传算法的变异算子对阶段最优解进一步优化。仿真结果表明,该算法能高效解决VRP,并且优化效果较好。     

自动化立体仓库货位分配与作业调度集成优化

针对动态提高单载具堆垛机式自动化立体仓库拣选效率的问题,文中提出了一种基于共享货位存储与动态订单拣选策略下的货位分配与作业调度集成优化方法。将动态移库优化扩展到仓库的整个拣选生命周期,建立以双指令循环下堆垛机拣选任务所需的总作业时间最短为评价目标的数学模型,提出了一种基于K-Medoids聚类的粒子群优化(Particle Swarm Optimization,PSO)算法,用K-Medoids算法通过产品与订单的相关性进行初始货位的聚类分析,筛除劣质解的货位范围,并在K-Medoids聚类算法生成的解类簇基础上获得精确解。实验结果表明,考虑动态移库可以使仓库拣选效率提高20%,且该算法与传统PSO算法相比求解时间下降66%左右。     

A modified particle swarm optimization for aggregate production planning

Particle swarm optimization (PSO) originated from bird flocking models. It has become a popular research field with many successful applications. In this paper, we present a scheme of an aggregate production planning (APP) from a manufacturer of gardening equipment. It is formulated as an integer linear programming model and optimized by PSO. During the course of optimizing the problem, we discovered that PSO had limited ability and unsatisfactory performance, especially a large constrained integral APP problem with plenty of equality constraints. In order to enhance its performance and alleviate the deficiencies to the problem solving, a modified PSO (MPSO) is proposed, which introduces the idea of sub-particles, a particular coding principle, and a modified operation procedure of particles to the update rules to regulate the search processes for a particle swarm. In the computational study, some instances of the APP problems are experimented and analyzed to evaluate the performance of the MPSO with standard PSO (SPSO) and genetic algorithm (GA). The experimental results demonstrate that the MPSO variant provides particular qualities in the aspects of accuracy, reliability, and convergence speed than SPSO and GA.     

引入多级扰动的混合型粒子群优化算法

为解决粒子群优化算法易陷入局部最优值的问题,提出一种引入多级扰动的混合型粒子群优化算法.该算法结合两种经典改进粒子群优化算法的优点,即带惯性参数的标准粒子群优化算法和带收缩因子的粒子群优化算法,在此基础上,引入多级扰动机制：在更新粒子位置时,引入一级扰动,使粒子对解空间的遍历能力得到加强;若优化过程陷入“局部最优”的情况,则引入二级扰动,使得优化过程继续,从而摆脱局部最优值.使用了6个测试函数——Sphere函数、Ackley函数、Rastrigin函数、Styblinski-Tang函数、Duadric函数及Rosenbrock函数来对所提出的混合型粒子群优化算法进行仿真运算和对比验证.模拟运算的结果表明：所提出的混合型粒子群优化算法在对测试函数进行仿真时,其收敛精度和收敛速度都优于另外两种经典的改进粒子群优化算法;另外,在处理多峰函数时,本算法不易被局部最优值所限制.     

A particle swarm optimization for the vehicle routing problem with simultaneous pickup and delivery

This paper proposes a formulation of the vehicle routing problem with simultaneous pickup and delivery (VRPSPD) and a particle swarm optimization (PSO) algorithm for solving it. The formulation is a generalization of three existing VRPSPD formulations. The main PSO algorithm is developed based on GLNPSO, a PSO algorithm with multiple social structures. A random key-based solution representation and decoding method is proposed for implementing PSO for VRPSPD. The solution representation for VRPSPD with n customers and m   vehicles is a (n+2m)$(n+2m)$-dimensional particle. The decoding method starts by transforming the particle to a priority list of customers to enter the route and a priority matrix of vehicles to serve each customer. The vehicle routes are constructed based on the customer priority list and vehicle priority matrix. The proposed algorithm is tested using three benchmark data sets available from the literature. The computational result shows that the proposed method is competitive with other published results for solving VRPSPD. Some new best known solutions of the benchmark problem are also found by the proposed method.     

Leaf constrained minimal spanning trees solved by modified quantum-behaved particle swarm optimization

Given an undirected, connected, weighted graph, the leaf-constrained minimum spanning tree (LCMST) problem seeks a spanning tree of minimum weight among all the spanning trees of the graph with at least l leaves. In this paper, we have proposed an approach based on Quantum-Behaved Particle Swarm Optimization (QPSO) for the LCMST problem. Particle swarm optimization (PSO) is a well-known population-based swarm intelligence algorithm. Quantum-behaved particle swarm optimization (QPSO) is also proposed by combining the classical PSO philosophy and quantum mechanics to improve performance of PSO. In this paper QPSO has been modified by adding a leaping behavior. When the modified QPSO (MQPSO), falls in to the local optimum, MPSO runs a leaping behavior to leap out the local optimum. We have compared the performance of the proposed method with ML, SCGA, ACO-LCMST, TS-LCMST and ABC-LCMST, which are reported in the literature. Computational results demonstrate the superiority of the MQPSO approach over all the other approaches. The MQPSO approach obtained better quality solutions in shorter time.     

基于多粒子群算法的WSNs覆盖优化策略研究*

为了改善无线传感网络的性能,提高网络的覆盖率,在粒子进化的多粒子群算法的基础上,提出了一种无线传感网络覆盖的优化策略。该策略通过多个粒子群彼此独立地搜索解空间, 提高了算法的寻优能力,有效地避免了基本粒子群算法容易出现的“早熟”问题,提高了算法的稳定性。仿真实验表明,与基本粒子群算法、传统遗传算法和新量子遗传算法的优化效果相比较,其覆盖率分别提高了8.39％、3.07％和0.75％;收敛速度提高了25.3％、23.8％和23.8％。因此粒子进化的多粒子群优化策略具有比这三种算法更好的覆盖优化效果。     

A particle swarm optimization approach with refinement procedure for nurse rostering problem

This study attempts to develop a model satisfying the rules of a typical hospital environment based both on published research data and on requirements of a local hospital under study. A mathematical formulation for the studied nurse rostering problem (NRP) is presented first. Due to the combinatorial nature of the NRP model, a particle swarm optimization (PSO) approach is proposed to solve this highly complicated NRP. The structure of the problem constraints is analyzed and used as base for generating workstretch patterns. These patterns serve as the base for generating fast initial solutions, and will later be improved upon by the proposed PSO algorithm. This study also proposes a simple yet effective procedure for attempting possible refinements on the solutions obtained by the PSO before reporting the final solutions. When fair shift assignment is considered as the decision objective, computational results show that the proposed PSO algorithm with refinement procedure is able to produce optimal solutions in all real test problems in a very efficient manner.