A particle swarm optimization based memetic algorithm for dynamic optimization problems

Recently, there has been an increasing concern from the evolutionary computation community on dynamic optimization problems since many real-world optimization problems are dynamic. This paper investigates a particle swarm optimization (PSO) based memetic algorithm that hybridizes PSO with a local search technique for dynamic optimization problems. Within the framework of the proposed algorithm, a local version of PSO with a ring-shape topology structure is used as the global search operator and a fuzzy cognition local search method is proposed as the local search technique. In addition, a self-organized random immigrants scheme is extended into our proposed algorithm in order to further enhance its exploration capacity for new peaks in the search space. Experimental study over the moving peaks benchmark problem shows that the proposed PSO-based memetic algorithm is robust and adaptable in dynamic environments.     

A new hybrid approach for dynamic continuous optimization problems

A new hybrid approach for dynamic optimization problems with continuous search spaces is presented. The proposed approach hybridizes efficient features of the particle swarm optimization in tracking dynamic changes with a new evolutionary procedure. In the proposed dynamic hybrid PSO (DHPSO) algorithm, the swarm size is varied in a self-regulatory manner. Inspired from the microbial life, the particles can reproduce infants and the old ones die. The infants are especially reproduced by high potential particles and located near the local optimum points, using the quadratic interpolation method. The algorithm is adapted to perform in continuous search spaces, utilizing continuous movement of the particles and using Euclidian norm to define the neighborhood in the reproduction procedure. The performance of the new proposed approach is tested against various benchmark problems and compared with those of some other heuristic optimization algorithms. In this regard, different types of dynamic environments including periodic, linear and random changes are taken with different performance metrics such as real-time error, offline performance and offline error. The results indicate a desirable better efficiency of the new algorithm over the existing ones.     

A parallel boundary search particle swarm optimization algorithm for constrained optimization problems

During the past decade, considerable research has been conducted on constrained optimization problems (COPs) which are frequently encountered in practical engineering applications. By introducing resource limitations as constraints, the optimal solutions in COPs are generally located on boundaries of feasible design space, which leads to search difficulties when applying conventional optimization algorithms, especially for complex constraint problems. Even though penalty function method has been frequently used for handling the constraints, the adjustment of control parameters is often complicated and involves a trial-and-error approach. To overcome these difficulties, a modified particle swarm optimization (PSO) algorithm named parallel boundary search particle swarm optimization (PBSPSO) algorithm is proposed in this paper. Modified constrained PSO algorithm is adopted to conduct global search in one branch while Subset Constrained Boundary Narrower (SCBN) function and sequential quadratic programming (SQP) are applied to perform local boundary search in another branch. A cooperative mechanism of the two branches has been built in which locations of the particles near boundaries of constraints are selected as initial positions of local boundary search and the solutions of local boundary search will lead the global search direction to boundaries of active constraints. The cooperation behavior of the two branches effectively reinforces the optimization capability of the PSO algorithm. The optimization performance of PBSPSO algorithm is illustrated through 13 CEC06 test functions and 5 common engineering problems. The results are compared with other state-of-the-art algorithms and it is shown that the proposed algorithm possesses a competitive global search capability and is effective for constrained optimization problems in engineering applications.     

Sequential approximation optimization assisted particle swarm optimization for expensive problems

In this paper, an efficient sequential approximation optimization assisted particle swarm optimization algorithm is proposed for optimization of expensive problems. This algorithm makes a good balance between the search ability of particle swarm optimization and sequential approximation optimization. Specifically, the proposed algorithm uses the optima obtained by sequential approximation optimization in local regions to replace the personal historical best particles and then runs the basic particle swarm optimization procedures. Compared with particle swarm optimization, the proposed algorithm is more efficient because the optima provided by sequential approximation optimization can direct swarm particles to search in a more accurate way. In addition, a space partition strategy is proposed to constraint sequential approximation optimization in local regions. This strategy can enhance the swarm diversity and prevent the preconvergence of the proposed algorithm. In order to validate the proposed algorithm, a lot of numerical benchmark problems are tested. An overall comparison between the proposed algorithm and several other optimization algorithms has been made. Finally, the proposed algorithm is applied to an optimal design of bearings in an all-direction propeller. The results show that the proposed algorithm is efficient and promising for optimization of the expensive problems.     

混合改进搜索策略的鸡群优化算法

针对鸡群算法易陷入局部最优和出现早熟收敛的情况,提出一种混合改进搜索策略的鸡群优化算法。该算法通过种内和种间竞争,确定子群规模及等级次序,子群角色通过竞争繁殖进行动态更新。种群进化寻优中引入全局最优引导策略和动态惯性策略,个体的寻食学习通过动态惯性策略进行自我调整,并同时接受子群与种群中的最优个体引导,以平衡局部搜索和全局搜索之间的关系。仿真实验结果表明,与基本鸡群算法和粒子群算法等相比,改进后的鸡群算法能有效提高算法的收敛精度和收敛速度。     

Multi-strategy ensemble particle swarm optimization for dynamic optimization

Optimization in dynamic environments is important in real-world applications, which requires the optimization algorithms to be able to find and track the changing optimum efficiently over time. Among various algorithms for dynamic optimization, particle swarm optimization algorithms (PSOs) are attracting more and more attentions in recent years, due to their ability of keeping good balance between convergence and diversity maintenance. To tackle the challenges of dynamic optimization, several strategies have been proposed to enhance the performance of PSO, and have gained success on various dynamic optimization problems. But there still exist some issues in dynamic optimization which need to be studied carefully, i.e. the robustness of the algorithm to problems of various dynamic features. In this paper, a new multi-strategy ensemble particle swarm optimization (MEPSO) for dynamic optimization is proposed. In MEPSO, all particles are divided into two parts, denoted as part I and part II, respectively. Two new strategies, Gaussian local search and differential mutation, are introduced into these two parts, respectively. Experimental analyses reveal that the mechanisms used in part I can enhance the convergence ability of the algorithm, while mechanisms used in part II can extend the searching area of the particle population to avoid being trapped into the local optimum, and can enhance the ability of catching up with the changing optimum in dynamic environments. The whole algorithm has few parameters that need to be tuned, and all of them are not sensitive to problems. We compared MEPSO with other PSOs, including MQSO, PHPSO and Standard PSO with re-initialization, on moving peaks Benchmark and dynamic Rastrigin function. The experimental results show that MEPSO has pretty good performance on almost all testing problems adopted in this paper, and outperforms other algorithms when the dynamic environment is unimodal and changes severely, or has a great number of local optima as dynamic Rastrigin function does.     

一种采用完全Logistic混沌的PSO-GA优化方法

为了提高粒子群优化算法的性能,提出了一种完全Logistic混沌粒子群优化与遗传算法的混合优化方法。该方法将具有伪随机性与遍历性特征的Logistic混沌应用到粒子群算法的粒子位置和速度初始化、惯性权重优化、随机常数以及局部最优解邻域点产生的全过程,并在粒子速度和位置更新后再与遗传算法相混合,进行选择和交叉操作。三种典型Benchmark函数的实验结果验证了所提方法的有效性,该方法具有更好的寻优能力与收敛速度。     

一种新的自适应动态文化粒子群优化算法

为了克服粒子群优化算法在解决复杂问题时易陷入局部最优的缺陷, 提出了一种新的自适应动态文化粒子群优化算法。该算法引入评价粒子群早熟收敛程度的指标来判断种群空间粒子群状态, 以确定影响函数对种群空间粒子群的作用时机, 当算法陷入局部最优时, 自适应地利用影响函数对种群空间进行变异更新, 从而有效发挥文化粒子群算法的双演化双促进机制。并且根据种群的早熟收敛程度自适应地调整粒子的惯性权重, 使种群在进化过程中始终保持惯性权重的多样性, 在算法的全局收敛性与收敛速度之间作一个很好的折中。最后对四个经典的测试函数进行仿真, 结果表明该算法具有很强的搜索能力, 收敛速度和收敛精度也有所提高。     

基于K-均值聚类的协同进化粒子群优化算法

针对粒子群优化（PSO）算法优化高维问题时,易陷入局部最优,提出一种基于K-均值聚类的协同进化粒子群优化（KMS-CCPSO）算法。该算法通过引入K-均值算法扩大种群的局部搜索范围,采用柯西分布和高斯分布相结合的方法更新粒子的位置。实验结果表明,该算法具有较好的优化性能,其优势在处理高维问题上更为明显。     

粒子群Memetic算法求解多峰函数优化

针对目前多峰函数优化问题较难找到全部局部最优解的情况,提出了一种粒子群Memetic算法。算法结合了粒子群优化的全局搜索能力和爬山法的局部搜索能力,增强了算法搜索最优解的能力。实验结果表明,该算法求解精度较高,且收敛速度较快。     

多峰搜索的动态微粒群算法

对多峰搜索问题提出了一类动态微粒群算法。该算法通过变换函数将多峰问题中的所有峰变为等高峰,从而保证每个峰都有同等机会被找到;在搜索过程中采用群体规模动态可调的进化方式,使得初始群体可以任意指定,从而克服了标准微粒群算法由于无法事先知道多峰函数峰值点个数而很难确定合适群体大小的困难。实验表明了该算法可以尽可能多地找到峰值点。     

融合分区和局部搜索的多模态多目标优化

为解决多模态多目标优化中种群多样性维持难和所得等价解数量不足问题,基于分区搜索和局部搜索,本研究提出一种融合分区和局部搜索的多模态多目标粒子群算法(multimodal multi-objective particle swarm optimization combing zoning search and local search,ZLS-SMPSO-MM)。在所提算法中,整个搜索空间被分割成多个子空间以维持种群多样性和降低搜索难度;然后,使用已有的自组织多模态多目标粒子群算法在每个子空间搜索等价解和挖掘邻域信息,并利用局部搜索能力较强的协方差矩阵自适应算法对有潜力的区域进行精细搜索。通过14个多模态多目标优化问题测试,并与其他5种知名算法进行比较;实验结果表明ZLS-SMPSO-MM在决策空间能够找到更多的等价解,且整体性能要好于所比较算法。     

A novel multi-swarm algorithm for optimization in dynamic environments based on particle swarm optimization

Optimization in dynamic environment is considered among prominent optimization problems. There are particular challenges for optimization in dynamic environments, so that the designed algorithms must conquer the challenges in order to perform an efficient optimization. In this paper, a novel optimization algorithm in dynamic environments was proposed based on particle swarm optimization approach, in which several mechanisms were employed to face the challenges in this domain. In this algorithm, an improved multi-swarm approach has been used for finding peaks in the problem space and tracking them after an environment change in an appropriate time. Moreover, a novel method based on change in velocity vector and particle positions was proposed to increase the diversity of swarms. For improving the efficiency of the algorithm, a local search based on adaptive exploiter particle around the best found position as well as a novel awakening–sleeping mechanism were utilized. The experiments were conducted on Moving Peak Benchmark which is the most well-known benchmark in this domain and results have been compared with those of the state-of-the art methods. The results show the superiority of the proposed method.     

Gradient-based adaptive particle swarm optimizer with improved extremal optimization

Most real-world applications can be formulated as optimization problems, which commonly suffer from being trapped into the local optima. In this paper, we make full use of the global search capability of particle swarm optimization (PSO) and local search ability of extremal optimization (EO), and propose a gradient-based adaptive PSO with improved EO (called GAPSO-IEO) to overcome the issue of local optima deficiency of optimization in high-dimensional search and reduce the time complexity of the algorithm. In the proposed algorithm, the improved EO (IEO) is adaptively incorporated into PSO to avoid the particles being trapped into the local optima according to the evolutional states of the swarm, which are estimated based on the gradients of the fitness functions of the particles. We also improve the mutation strategy of EO by performing polynomial mutation (PLM) on each particle, instead of on each component of the particle, therefore, the algorithm is not sensitive to the dimension of the swarm. The proposed algorithm is tested on several unimodal/multimodal benchmark functions and Berkeley Segmentation Dataset and Benchmark (BSDS300). The results of experiments have shown the superiority and efficiency of the proposed approach compared with those of the state-of-the-art algorithms, and can achieve better performance in high-dimensional tasks.     

基于自主学习和精英群的多子群粒子群算法

为了提高动态多子群粒子群算法中粒子学习的自主性,提出一种基于自主学习和精英群的粒子群算法.该算法借鉴教育心理学自主学习的理念,用基础群中粒子自主选择学习对象的操作代替子群的重组操作,并通过精英群局部搜索的配合来达到寻优的目的.将所提出的算法应用于6个测试函数,并与动态多子群PSO等算法进行了比较,比较结果表明,新算法在提高收敛速度、精度和寻优时间等方面具有良好的性能。     

Evolutionary swarm cooperative optimization in dynamic environments

A hybrid approach called Evolutionary Swarm Cooperative Algorithm (ESCA) based on the collaboration between a particle swarm optimization algorithm and an evolutionary algorithm is presented. ESCA is designed to deal with moving optima of optimization problems in dynamic environments. ESCA uses three populations of individuals: two EA populations and one Particle Swarm Population. The EA populations evolve by the rules of an evolutionary multimodal optimization algorithm being used to maintain the diversity of the search. The particle swarm confers precision to the search process. The efficiency of ESCA is evaluated by means of numerical experiments.     

一种新的求解动态连续优化的分层粒子群算法

为了高效求解动态连续优化问题,提出一种分层粒子群优化算法。该算法将动态函数定义域分成Q个子空间,每个空间用一个粒子群作为第一层进行独立搜索,Q个子空间的最优粒子再组成一个全局粒子群进行全局搜索,以达到全局牵引的作用,同时提出探测环境和响应环境的策略。利用经典的动态函数对算法进行测试,结果表明所提出算法能够迅速适应环境变化和跟踪最优解的变化,效果令人满意。     

A discrete version of particle swarm optimization for flowshop scheduling problems

Particle swarm optimization (PSO) is a novel metaheuristic inspired by the flocking behavior of birds. The applications of PSO to scheduling problems are extremely few. In this paper, we present a PSO algorithm, extended from discrete PSO, for flowshop scheduling. In the proposed algorithm, the particle and the velocity are redefined, and an efficient approach is developed to move a particle to the new sequence. To verify the proposed PSO algorithm, comparisons with a continuous PSO algorithm and two genetic algorithms are made. Computational results show that the proposed PSO algorithm is very competitive. Furthermore, we incorporate a local search scheme into the proposed algorithm, called PSO-LS. Computational results show that the local search can be really guided by PSO in our approach. Also, PSO-LS performs well in flowshop scheduling with total flow time criterion, but it requires more computation times.     

Binary optimization using hybrid particle swarm optimization and gravitational search algorithm

The PSOGSA is a novel hybrid optimization algorithm, combining strengths of both particle swarm optimization (PSO) and gravitational search algorithm (GSA). It has been proven that this algorithm outperforms both PSO and GSA in terms of improved exploration and exploitation. The original version of this algorithm is well suited for problems with continuous search space. Some problems, however, have binary parameters. This paper proposes a binary version of hybrid PSOGSA called BPSOGSA to solve these kinds of optimization problems. The paper also considers integration of adaptive values to further balance exploration and exploitation of BPSOGSA. In order to evaluate the efficiencies of the proposed binary algorithm, 22 benchmark functions are employed and divided into three groups: unimodal, multimodal, and composite. The experimental results confirm better performance of BPSOGSA compared with binary gravitational search algorithm (BGSA), binary particle swarm optimization (BPSO), and genetic algorithm in terms of avoiding local minima and convergence rate.     

一种动态分级的混合粒子群优化算法

针对粒子群算法早熟收敛和搜索精度不高的问题,提出一种动态分级的混合粒子群优化算法．该算法采取３种级别的并行粒子群算法,分别用于全局搜索和局部搜索及二者的结合,并根据搜索阶段动态调整各种级别中并行变量的数目．在全局搜索中,将混沌机制引入算法中以增强算法的全局搜索能力;在局部搜索中,采用单纯形法对适应度最优解进行局部寻优．仿真实验表明,该算法比其他优化算法具有更好的性能．