Research on Flexible Job Shop Scheduling Based on Improved Two-Layer Optimization Algorithm

To improve the productivity,the resource utilization and reduce the production cost of flexible job shops,this paper designs an improved two-layer optimization algorithm for the dual-resource scheduling optimization problem of flexible job shop considering workpiece batching.Firstly,a mathematical model is established to minimize the maximum completion time.Secondly,an improved two-layer optimization algorithm is designed:the outer layer algorithm uses an improved PSO(Particle Swarm Optimization)to solve the workpiece batching problem,and the inner layer algorithm uses an improved GA(Genetic Algorithm)to solve the dual-resource scheduling problem.Then,a rescheduling method is designed to solve the task disturbance problem,represented by machine failures,occurring in the workshop production process.Finally,the superiority and effectiveness of the improved two-layer optimization algorithm are verified by two typical cases.The case results show that the improved two-layer optimization algorithm increases the average productivity by 7.44% compared to the ordinary two-layer optimization algorithm.By setting the different numbers of AGVs(Automated Guided Vehicles)and analyzing the impact on the production cycle of the whole order,this paper uses two indicators,the maximum completion time decreasing rate and the average AGV load time,to obtain the optimal number of AGVs,which saves the cost of production while ensuring the production efficiency.This research combines the solved problem with the real production process,which improves the productivity and reduces the production cost of the flexible job shop,and provides new ideas for the subsequent research.

Research on Optimization of Dual-Resource Batch Scheduling in Flexible Job Shop

With the rapid development of intelligent manufacturing and the changes in market demand,the current manufacturing industry presents the characteristics of multi-varieties,small batches,customization,and a short production cycle,with the whole production process having certain flexibility.In this paper,a mathematical model is established with the minimum production cycle as the optimization objective for the dual-resource batch scheduling of the flexible job shop,and an improved nested optimization algorithm is designed to solve the problem.The outer layer batch optimization problem is solved by the improved simulated annealing algorithm.The inner double resource scheduling problem is solved by the improved adaptive genetic algorithm,the double coding scheme,and the decoding scheme of Automated Guided Vehicle(AGV)scheduling based on the scheduling rules.The time consumption of collision-free paths is solved with the path planning algorithm which uses the Dijkstra algorithm based on a time window.Finally,the effectiveness of the algorithm is verified by actual cases,and the influence of AGV with different configurations on workshop production efficiency is analyzed.

Modeling and Optimization for Scheduling of Chemical Batch Processes

Chemical batch processes have become significant in chemical manufacturing. In these processes, large numbers of chemical products are produced to satisfy human demands in daily life. Recently, economy globalization has resulted, in growing worldwide competitions in tradi.tional chemical .process industry. In order to keep competitive in the global marketplace, each company must optimize its production management and set up a reactive system for market fluctuation. Scheduling is the core of production management in chemical processes. The goal of this paper is to review the recent developments in this challenging area. Classifications of batch scheduling problems and optimization methods are introduced. A comparison of six typical models is shown in a general benchmark example from the literature. Finally, challenges and applications in future research are discussed.

Batch-to-batch Optimization of Batch Crystallization Processes

It is the fact that several process parameters are either unknown or uncertain. Therefore, an optimal control, profile calculated with developed process models with respect to such process parameters may not give an optimal performance when implemented to real processes. This study proposes a batch-to-batch optimization strategy for the estimation of uncertain kinetic.par.ameters in a batch crystallization process of potassium sulfate production. The knowledge of a crystal size distribution of the product at the end of batch operation is used in the proposed methodology. The updated kinetic parameters are applied for determining an optimal operating temperature policy for the next batch run.

Improved elastase production by Bacillus sp. EL31410—further optimization and kinetics studies of culture medium for batch fermentation

An efficient culture medium producing a bacterial elastase with high yields was developed further following preliminary studies by means of response surface method. Central composite design (CCD) and response surface method-ology were applied to optimize the medium constituents. A central composite design was used to explain the combined effect of three medium constituents, viz, glucose, K2HPO4, MgSO47H2O. The strain produced more elastase in the completely optimized medium, as compared with the partially optimized medium. The fitted model of the second model, as per RSM, showed that glucose was 7.4 g/100 ml, casein 1.13 g/100 ml, corn steep flour 0.616 g/100 ml, K2HPO4 0.206 g/100 ml and MgSO47H2O 0.034 g/100 ml. The fermentation kinetics of these two culture media in the flask experiments were analyzed. It was found that the highest elastase productivity occurred at 54 hours. Higher glucose concentration had inhibitory effect on elastase production. At the same time, we observed that the glucose consumption rate was slow in the completely optimized medium, which can explain the lag period of the highest elastase production. Some metal ions and surfactant additives also affected elastase production and cell growth.

An improved multi-objective optimization algorithm for solving flexible job shop scheduling problem with variable batches

In order to solve the flexible job shop scheduling problem with variable batches,we propose an improved multiobjective optimization algorithm,which combines the idea of inverse scheduling.First,a flexible job shop problem with the variable batches scheduling model is formulated.Second,we propose a batch optimization algorithm with inverse scheduling in which the batch size is adjusted by the dynamic feedback batch adjusting method.Moreover,in order to increase the diversity of the population,two methods are developed.One is the threshold to control the neighborhood updating,and the other is the dynamic clustering algorithm to update the population.Finally,a group of experiments are carried out.The results show that the improved multi-objective optimization algorithm can ensure the diversity of Pareto solutions effectively,and has effective performance in solving the flexible job shop scheduling problem with variable batches.

Constrained Run-to-Run Optimization for Batch Process Based on Support Vector Regression Model

An iterative (run-to-run) optimization method was presented for batch processes under input constraints. Generally it is very difficult to acquire an accurate mechanistic model for a batch process.Because support vector machine is powerful for the problems characterized by small samples,nonlinearity, high dimension and local minima, support vector regression models were developed for the end-point optimization of batch processes. Since there is no analytical way to find the optimal trajectory, an iterative method was used to exploit the repetitive nature of batch processes to determine the optimal operating policy. The optimization algorithm is proved convergent. The numerical simulation shows that the method can improve the process performance through iterations.

OPERATION AND OPTIMIZATION OF BATCH DISTILLATION FOR A BINARY SYSTEM

Batch distillation,basically different from continuous distillation which is a steady stateprocess,appears to be an unsteady state process in its mathematical description.The theoreticalanalysis of its operation comprises a concomitant consideration of the stage-wise separation andthe equations of material balance as well as enthalpy balance.Based upon the batch distillationpractice of NMP-water system,this paper reveals the necessity and advantage of a computerizedtreatment for this purpose.Numerical results not only explain the experimental phenomena andprovide a design scheme,but also lead to the optimization of the operation condition.

Optimized air-ground data fusion method for mine slope modeling

Refined 3D modeling of mine slopes is pivotal for precise prediction of geological hazards.Aiming at the inadequacy of existing single modeling methods in comprehensively representing the overall and localized characteristics of mining slopes,this study introduces a new method that fuses model data from Unmanned aerial vehicles(UAV)tilt photogrammetry and 3D laser scanning through a data alignment algorithm based on control points.First,the mini batch K-Medoids algorithm is utilized to cluster the point cloud data from ground 3D laser scanning.Then,the elbow rule is applied to determine the optimal cluster number(K0),and the feature points are extracted.Next,the nearest neighbor point algorithm is employed to match the feature points obtained from UAV tilt photogrammetry,and the internal point coordinates are adjusted through the distanceweighted average to construct a 3D model.Finally,by integrating an engineering case study,the K0 value is determined to be 8,with a matching accuracy between the two model datasets ranging from 0.0669 to 1.0373 mm.Therefore,compared with the modeling method utilizing K-medoids clustering algorithm,the new modeling method significantly enhances the computational efficiency,the accuracy of selecting the optimal number of feature points in 3D laser scanning,and the precision of the 3D model derived from UAV tilt photogrammetry.This method provides a research foundation for constructing mine slope model.

Computational Optimization of Manufacturing Batch Size and Shipment for an Integrated EPQ Model with Scrap

This paper employs mathematical modeling and algebraic approach to derive the optimal manufacturing batch size and number of shipment for a vendor-buyer integrated economic production quantity (EPQ) model with scrap. Unlike the conventional method by using differential calculus to determine replenishment lot size and optimal number of shipments for such an integrated system, this paper proposes a straightforward algebraic approach to replace the use of calculus on the total cost function for solving the optimal production- shipment policies. A simpler form for computing long-run average cost for such a vendor- buyer integrated EPQ problem is also provided.

Modelling and Multi-Objective Optimal Control of Batch Processes Using Recurrent Neuro-fuzzy Networks

In this paper, the modelling and multi-objective optimal control of batch processes, using a recurrent neuro-fuzzy network, are presented. The recurrent neuro-fuzzy network, forms a ＂global＂ nonlinear long-range prediction model through the fuzzy conjunction of a number of ＂local＂ linear dynamic models. Network output is fed back to network input through one or more time delay units, which ensure that predictions from the recurrent neuro-fuzzy network are long-range. In building a recurrent neural network model, process knowledge is used initially to partition the processes non-linear characteristics into several local operating regions, and to aid in the initialisation of corresponding network weights. Process operational data is then used to train the network. Membership functions of the local regimes are identified, and local models are discovered via network training. Based on a recurrent neuro-fuzzy network model, a multi-objective optimal control policy can be obtained. The proposed technique is applied to a fed-batch reactor.

Batch Process Modelling and Optimal Control Based on Neural Network Model

This paper presents several neural network based modelling, reliable optimal control, and iterative learning control methods for batch processes. In order to overcome the lack of robustness of a single neural network, bootstrap aggregated neural networks are used to build reliable data based empirical models. Apart from improving the model generalisation capability, a bootstrap aggregated neural network can also provide model prediction confidence bounds. A reliable optimal control method by incorporating model prediction confidence bounds into the optimisation objective function is presented. A neural network based iterative learning control strategy is presented to overcome the problem due to unknown disturbances and model-plant mismatches. The proposed methods are demonstrated on a simulated batch polymerisation process.

Strategies for Optimizing Feed Rate of Fed-Batch Yeast Fermentation by Fuzzy-Neural Network

In this paper,a novel fuzzy neural network model,in which an adjustable fuzzy sub-space was designed by uniform design,has been established and used in fed-batch yeast fermentationas an example.A brand-new optimization sub-network with special structure has been built andgenetic algorithm,guaranteeing the optimization in overall space,is introduced for the feed rateoptimization.On the basis of the model network,the optimal substrate concentration and theoptimal amount of fed-batch at different periods have been studied,aided with the optimizationnetwork and the genetic algorithm separately.The above results can be used as a basis for theestablishment of a fuzzy neural network controller.

面向部分工序无序加工的柔性作业车间批量调度方法

实际的车间调度问题往往具有更高的复杂度,调度算法需要考虑更多的约束条件,因此增加了问题的求解难度。为解决柔性作业车间批量调度场景中不同批次、不同工序之间可以无序加工的难题,进而突破现有车间机器使用率低、同类型机器负载不均衡的难点,文中构建了一种面向部分工序无序加工的柔性作业车间等量分批调度模型。首先,基于广泛使用的快速非支配排序遗传算法(NSGA-Ⅱ),提出了一种融合批次、批量和工序排序信息的两段编码结构,采用优先级规则方法获得初始种群,并以最小化完工时间、机器负载均衡率、机器总负荷为优化目标,采用贪心算法求解模型最优值,进而动态构建不同批次的加工路径;然后,对优化目标函数进行排序,再逐步加入非支配排序过程,以解决多个优化目标函数之间难以同时优化的问题,提高求解效率;最后,以某印刷包装企业的木制品加工车间为例,面向现场作业信息,采用仿真手段实现调度过程。结果表明,与优先级调度规则相比,文中所提方法的完工时间平均缩短了6.6%、机器负载均衡方差平均减小了10.7%,文中所提方法的机器负载均衡方差比遗传算法平均减小了53.3%,从而验证了文中方法的可行性,且该方法可以满足印刷包装企业柔性作业车间的高性能调度需求。

基于动态成本卷积的复杂产品批产路径优化问题建模与求解研究

具有复杂工艺路线的装备产品,其生产系统设计的待决策变量之间通常相互耦合、相互影响,对产品最终的批产成本产生着影响,构成了较为复杂的组合优化问题。对此,提出一种基于动态成本卷积的复杂产品批产路径优化模型。该模型考虑了复杂产品工艺路线的各节点均可能存在多种生产设计选项,在各选项对应着不同生产投入和批量效率的情况下,以最终交付产品的批产成本最小化为目标输出生产系统设计和成本卷积路径。同时,建立了混合整数规划模型,并通过对模型中非线性成分实施可控精度线性化,将模型换化为可最优求解的线性模型。最后,针对某连续生产行业设计了小、中、大规模实验算例,验证了所提模型的可行性、合理性和求解效率。

基于最优觅食算法的增材制造中多种类零件分批排样研究

增材制造中多种类零件分批排样存在打印时间成本高和工作台空间利用率低等问题,且需考虑零件高度的影响。分批排样问题包括零件在工作台上放置策略和成型批次分配两个子问题。放置策略涉及成型方向选择、零件碰撞检测和定位策略。基于建立的成型方向准则,利用多边形表示零件投影轮廓,提出基于临界多边形的改进移动碰撞法以确定3种不同形态多边形零件的免碰撞排放范围,提出新的左下定位策略放置零件,新定位策略融合了改进的建设性方法和契合度;提出单机台面积占用最大化策略实现零件成型批次分配。基于上述研究,提出基于最优觅食算法的分批排样算法,算法采用双重编码表达零件放置顺序和旋转角度,以最小化完工时间为目标实现优化分批排样。以案例库零件为对象,与3种对比算法比较,表明所提方法的方案能有效提高增材制造的空间利用率和缩短完工时间。

考虑特性分类批处理负荷可调节能力的数据中心微网灵活性设备分布鲁棒容量配置方法

微网灵活性设备主要用于平抑源荷两侧的波动,其容量配置方法应考虑源荷不确定性的影响,而含数据中心微网的灵活性设备容量配置方法还应进一步考虑数据中心负荷的可调节特性。考虑数据中心批处理负荷的可调节能力和源荷不确定性因素,提出一种灵活性设备容量配置方法。根据负荷特性的不同,将批处理负荷划分为2类以更加准确地量化其可调节能力,一类为带宽时序可变限时可平移负荷,另一类为带宽时序不变可中断平移负荷,对这2类批处理负荷进行详细分析并给出一般性的建模方法;构建数据驱动下的min-max-min两阶段分布鲁棒优化容量配置模型,利用1-范数和∞-范数约束场景概率分布模糊集,采用列和约束生成算法对该模型进行化简求解。对某省数据中心微网进行算例分析,验证了所提方法的有效性。

改进量子位初始映射的综合SWAP优化策略

在嘈杂的中尺度量子时代,传统的初始映射策略忽略了后续操作中可能出现的邻接性的问题。针对这一挑战,综合考虑量子比特间的距离、交互时间和门操作的错误率,设计了一个多因素交互成本函数,并提出综合SWAP优化策略(comprehensive SWAP optimization strategy,CSOS)。该策略包括最佳SWAP选择和基于SWAP的批量更新策略,用于优化量子电路的局部量子位映射。最佳SWAP选择通过对比SWAP操作的效益,选择最佳收益的SWAP门;批量更新策略在映射阶段考虑即将执行的量子操作序列,预先执行批量的SWAP操作。二者综合可以减少整个电路执行过程中的SWAP数量,以最大程度减少映射开销。实验结果显示,CSOS优化方式可以平均减少38.1%的插入SWAP门数量,并降低约12%的硬件门计数开销。

批式流加发酵中的鲁棒脉冲时滞最优控制

本文研究了批式流加发酵中的鲁棒脉冲时滞最优控制问题。首先,提出一个非线性状态依赖的脉冲时滞系统描述批式流加发酵甘油生产1,3-丙二醇(1,3-PD)过程。由于批式流加发酵过程中的动力学参数难以准确估计,本文建立了一个具有连续状态不等式约束的鲁棒脉冲时滞最优控制模型。这里,目标函数为终端时刻1,3-PD浓度及其关于动力学参数的灵敏性的加权和,控制向量为流加发生时甘油的临界浓度及每次流加时甘油的流加体积。然后,通过引入辅助脉冲系统,将该鲁棒最优控制问题转化为等价的标准最优控制问题。进一步,通过约束转换技术,将等价的最优控制问题转化为仅具有盒式约束的罚问题。最后,设计了一种并行差分进化算法求解转化后的罚问题。数值结果表明:当参数受到微小扰动时,尽管牺牲了少量的1,3-PD浓度,但是明显提高了系统的鲁棒性。

双区型仓库订单分批与拣选协同优化研究

针对订单分拣效率低下导致商品出库缓慢的问题,提出一种基于双区型仓库订单分批与拣选的协同优化模型,设计求解模型的CWDP-BSA(clarke-wright and dynamic programming&backtracking search algorithm)协同优化算法。在节约算法中引入快速排序法对订单组合的距离节约值排序,考虑AGV承载量,运用多阶段决策过程最优策略得出状态转移方程求解订单分批模型,确定初始分批方案;并采取多因子选择的回溯搜索算法求解拣选路径模型,以此确定初始拣选方案。再以以上两方案为基础,建立新的基于订单时间窗的订单分批和拣选协同优化模型并求解,进一步优化订单分批和拣选方案。最后通过对比实验得出,平均每批次订单的拣选距离减少了约24.56%,优化后的拣选时间比优化前缩短了约11.4%,在求解不同规模算例时,CWDP-BSA算法的求解结果优于CPLEX软件和其他算法,验证了模型与算法的稳定性和有效性。实验表明,协同优化后的订单分批与物品拣选策略能够有效提升订单出库效率。