炼钢-连铸区段天车调度的多目标建模与求解

针对炼钢-连铸区段天车调度问题多机多任务的特点,以天车行驶路程最短、天车间负载时间差异最小、所有吊运任务的总运输时间最短为目标函数,以天车执行任务时受到的时空约束为约束条件,建立了多目标天车调度模型。设计了分区、择车、冲突消解等调度规则以表达天车运行特征。基于调度规则的思想,提出了一种启发式算法对模型进行求解。最后,采用某钢厂钢水接收跨的生产数据进行检验,对比分析模型求解得到的3组调度方案,说明了模型的有效性和可行性,对实际生产过程中的天车调度具有一定的指导意义。     

Constraint Programming Approach to Precast Production Scheduling

Current scheduling practices in precast plants are fairly basic and depend greatly on experience. This may lead to inefficient resource utilization, over-inventory, and/or missing delivery dates. Computer assisted scheduling may therefore be useful in producing better production schedules. This paper shows how constraint programming (CP) can be applied in production scheduling for precast plants. The paper describes a constrained precast scheduling model that incorporates the key constraints and objectives considered by production schedulers. A capacity-based backward-scheduling earliest due date rule and a CP approach are developed to solve the model. The CP approach is computationally efficient, even though it incorporates many problem-derived constraints. The efficiency of the CP approach lies in the fact that the representation (model) is separated from the algorithm (solver). Strategies to improve the performance of the CP approach are identified, and the CP approach is compared against commonly used heuristic rules on an example problem.     

Optimal Repetitive Scheduling Model with Shareable Resource Constraint

An optimal repetitive scheduling model for precast production with the consideration of resource constraints and resource sharing is proposed in this paper. A repetitive schedule, like precast production, needs to take into consideration the impact of limited resources, including equipment (such as cranes, forms, and steaming curing facilities) and skilled labor, on production makespan. Moreover, to economically and effectively utilize these valuable resources (such as cranes and work crews), it is worth taking resource sharing into consideration in precast production. A genetic algorithm-based searching technique is adopted to establish an optimal resource-constrained repetitive precast production scheduling system with the consideration of resource sharing. The system can effectively provide the optimal or near-optimal combination of production durations, resource amounts, and minimum makespan under the constraint of limited resources and with the consideration of resource sharing.     

冶铸轧一体化生产调度方法的探讨

提出了综合采用启发式搜索方法和离散事件仿真方法来解决冶铸轧一体化生产调度问题。启发式搜索方法可以根据工艺约束将用户合同编制成生产计划,而离散事件仿真方法可以评价编制出的生产计划,从而选择较优的调度方案。     

Comparison of Using Mixed-Integer Programming and Genetic Algorithms for Construction Site Facility Layout Planning

The use of modular construction has gained wide acceptance in the industry. For a specific construction facility layout problem such as site precast standardized modular units, it requires the establishment of an on-site precast yard. Arranging the precast facilities within a construction site presents real challenge to site management. This complex task is further augmented with the involvement of several resources and different transport costs. A genetic algorithm (GA) model was developed for the search of a near-optimal layout solution. Another approach using mixed-integer programming (MIP) has been developed to generate optimal facility layout. These two approaches are applied to solve with an example in this paper to demonstrate that the solution quality of MIP outperforms that of GA. Further, another scenario with additional location constraints can also be solved readily by MIP, which, however, if modeled by GA, the solution process would be complicated. The study has highlighted that MIP can perform better than GA in site facility layout problems in which the site facilities and locations can be represented by a set of integer variables.     

钢坯热轧加热炉区生产调度模型与算法

钢坯热轧加热炉区生产调度属于组合优化中的NP-complete问题.本文根据加热炉区生产特点建立了分别以生产能耗最小化和加热质量最优化为主次目标的钢坯加热炉区调度数学模型,将其归结为布尔可满足性问题,构造了采用二进制编码方式的遗传禁忌搜索算法进行求解.基于实际生产数据的模拟优化结果表明,该模型和求解方法充分满足了现场加热炉区生产调度的需求,在满足生产工艺约束的前提下,缩短了生产时间,提高了钢坯入炉温度和加热质量,与传统人工调度方法的结果相比具有更好的节能、高产效果.     

Model for Estimating Evaporation and Transpiration from Row Crops

Accurate estimates of crop evapotranspiration ETc, that quantify the total water used by a crop, are needed to optimize irrigation scheduling for horticultural crops and to minimize water degradation. During early growth, accurate assessments of ETc are difficult in vegetable crops because of high soil evaporation due to frequent irrigation. A model to estimate ETc for vegetable crops, using only daily reference evapotranspiration data as an input parameter, was developed. It calculates crop transpiration and soil evaporation based on ground cover and daily radiation intercepted by the canopy. The model uses a two-stage soil evaporation method adapted to conditions of variable reference evapotranspiration. The model was evaluated against data using measurements from two seasons of lettuce crop, two tomato fields in the same season, and one season of broccoli crop production. Using all of the crop data, the root-mean-square error for measured versus modeled daily ETc was 0.72 mm day?1, indicating that the model works well.     

Investigating the Effectiveness of Certain Priority Rules on Resource Scheduling of Housing Estate Projects

The heuristic method is one of the methods used for the scheduling of resource-constrained projects. This method is commonly used in programming the projects with high number of activities and resources such as construction investments. This paper investigates the effectiveness of three heuristic method priority rules applied in the resource scheduling of ten Turkish housing estate projects which were scheduled according to three preselected priority rules [maximum remaining path length (MRPL), latest finish time (LFT), and minimum slack time (MNSLCK)] in resource-constrained conditions. The performance of each priority rule was evaluated in relation to the duration of the project. The results revealed that MRPL priority reduced the project duration to minimum in six projects, whereas LFT priority yielded the best duration results in three projects and MNSLCK priority in only one project.     

Comparison of Linear Scheduling Model (LSM) and Critical Path Method (CPM)

Due to an increasingly competitive environment, construction companies are becoming more sophisticated, narrowing their focus, and becoming specialists in certain types of construction. This specialization requires more focused scheduling tools that prove to be better for certain type of projects. The critical path method (CPM) is the most utilized scheduling tool in the construction industry. However, for certain types of projects, CPM's usefulness decreases, because it becomes complex and difficult to use and understand. Alternative scheduling tools designed to be used with specific types of projects can prove to be more practical than CPM solutions. This paper provides a comparison of the CPM and a specialized tool, the linear scheduling model, by identifying critical attributes needed by any scheduling tool both at the higher management level and at the project level. Two project examples are scheduled with each method, and differences are discussed. Conclusions support that specialization of scheduling tools could be beneficial for the project manager and the project.     

基于MAS的分布式棒线材轧制在线生产调度系统

针对棒线材生产的不确定性和复杂性,提出了基于多智能体分布式在线生产调度系统（MDOPS）方案,给出了系统总体结构,建立了精轧工序轧制批量调度的数学模型,其中考虑了轧机的维护约束等实际应用约束,采用混合局部搜索的自适应遗传算法进行求解,描述了进化计算、专家系统、启发式规则和人机交互相结合的生产调度计划集成化实现方法,并应用到实际棒线材实时调度中。现场实际运行结果表明,该系统可快速准确收集生产实绩数据,完成生产过程在线监视,编制出符合现场情况、满足工艺要求的高效生产调度计划。     

多目标多约束混合流水车间插单重调度问题研究

研究了多目标多阶段混合流水车间的紧急订单插单重调度问题,综合考虑工件批量、刀具换装时间、运输能力等约束。先以最小化订单完工时间和最小化总运输时间为双目标建立静态初始订单调度模型,再针对紧急订单插单干扰,增加最小化总加工机器偏差值目标,建立三目标重调度优化模型,并分别用NSGA-II算法与融合基于事件驱动的重调度策略和重排插单策略的NSGA-III算法对两个模型进行求解。最后,以某实际船用管类零件生产企业为案例,先对NSGA-II算法和NSGA-III算法的性能进行评估,得到NSGA-II算法更适用于解决双目标优化问题而NSGA-III算法在解决三目标优化问题时表现更优的结论,再将所建模型与所提算法应用于该企业的十组插单案例中,所得优化率接近三分之一,验证了实用性和有效性。      

钢铁企业轧制计划与能源调度协同优化

钢铁企业物质流网络与能量流网络的协同优化是实现钢铁行业高层次系统节能的关键。钢铁企业在不同工况下煤气的富余量以及蒸汽和电力需求量不同,轧制工序(含加热炉)作为电力和煤气消耗大户,轧制计划的改变会影响能量流网络中能源介质的分配和调度。提出了钢铁流程物质流与能量流协同优化方法,在分时电价的条件下,利用启发式规则调度方法对一天内的轧制单元进行合理的排程,然后用线性规划方法以系统运行能源成本最小为目标函数,建立钢铁企业煤气 蒸汽 电力系统不同工况下的耦合优化调度模型。通过LINGO求解出模型的最优解,得到了轧制单元的最优排程以及不同工况下煤气、蒸汽、电力的最优实时生产调度方案,用于指导实际生产。利用S钢厂实际数据进行实例分析,得出的调度方案可实现煤气 蒸汽 电力系统的最优化分配,系统运行的能源成本降低8.54%,验证了模型的有效性。     

基于变邻域搜索的热轧圆钢批量调度多目标优化方法

针对热轧圆钢的批量调度问题,考虑实际生产中工艺规程和交货期对轧制单元连续加工的影响,建立了以最小化设备调整时间、拖期生产惩罚和钢种跳跃惩罚为优化目标的数学模型,并设计了一种嵌入EDD规则的变邻域搜索算法.算法首先结合模型的约束特征,采用约束满足技术生成初始解;根据实际生产需求,将最小化设备调整时间作为主要目标,设计变邻域搜索算法实现目标优化,其中,运用混合算子构造邻域结构和局部搜索,并引入模拟退火接受准则来控制迭代过程中产生的新解;同时,为了最小化拖期惩罚和钢种跳跃惩罚,在求解过程中嵌入了EDD规则以及钢种排序规则.实验结果表明,模型和算法是可行且有效的.     

A Rescheduling Method for Operation Time Delay Disturbance in Steelmaking and Continuous Casting Production Process

 In the steelmaking and continuous casting (SMCC) production process, operation time delay may lead to casting break or processing conflict so that the initial scheduling plan becomes unrealizable. Existing research methods are difficult to guarantee the accuracy of the model and successful application to actual applications. The rescheduling problem in response to operation time delay is firstly analyzed. This is then followed by the establishment of a novel multi-objective nonlinear programming model (MONPM). In specifications, a three-stage rescheduling method is proposed including the batches splitting (BS), forward scheduling method (FSM) and backward scheduling method (BSM). As a result, the real-time application shows that the proposed rescheduling method efficiently ensures the continuous casting and dramatically shortens the redundant waiting time for molten steel in very short rescheduling time.     

炼钢?连铸生产调度的研究进展

针对炼钢?连铸过程的生产调度问题,首先,对生产调度问题的研究方法进行了总结和评述,梳理了各类方法的特点及适用范围;其次,介绍了当前国内外钢厂典型计算机辅助调度系统的一些案例,并讨论分析其特点;最后,在以往研究的基础上,对未来炼钢?连铸过程生产调度问题的研究思路和方法提出了建议,针对静态调度提出了“规则+算法”的研究思路,以国内某特钢厂为例,提出了基于钢厂生产模式优化的调度模型构建方法;针对动态调度提出“多工序协同”的研究思路,提出了基于多智能体的炼钢?连铸过程多工序工艺、质量与调度的协同控制的研究方法。优化高效的建模及求解方法是解决生产调度问题的重要手段之一,旨在改善当前钢厂生产计划编制水平、提高生产计划的可执行性、加强现场实时调控,对实现炼钢?连铸过程稳定化、有序化、连续化运行具有重要意义。      

聚合分期算法在露天矿中长期生产计划编制中的应用

露天矿中长期生产计划是在最终境界的基础上确定矿块的开采顺序,以获得最大的总净现值。采用整数规划的方法来求解露天矿生产计划编制问题（OPSP）时,由于实际矿山最终境界内矿块个数太多,构建整数规划模型需要大量的二进制变量,超出了现有求解器的能力,使得问题无法求解。针对这一问题提出矿块聚合和分期求解相结合的启发式算法：将空间上n3个相邻矿块聚合,然后通过启发式方法,分期次逐渐求解、逐步迭代、更新模型,以减少模型变量和约束。利用VC++编程并调用CPLEX求解器实现该算法,应用于某铜矿,实现了长期计划的自动编制。结果表明：该算法能够显著减少用整数规划法求解OPSP时的变量个数,成百倍地提高解算效率,在较短的解算时间之内得到较优的结果,解决了OPSP因变量规模太大而无法求解的问题,并且能够较好地应用于各种规模矿山的实际生产计划编制工作。     

Predicting quadriceps muscle activity during gait with an automatic rule determination method

It has been suggested that control using a skill-based expert system can be applicable to gait restoration. Rule-based systems have several advantages for this application: they generate a fast response (they are not computationally intensive) and they are easy to comprehend and implement. A major problem with using such systems is the inability of users to determine its rules. In this study, an automatic method for obtaining the production rules from a set of examples is described. The rule base was automatically induced from a model which used external sensor signals as inputs and electromyogram (EMG) patterns as outputs. The method is based on the minimization of entropy. A production rule estimated the muscle activity pattern using the sensor information. The algorithm was tested using data recorded from six able-bodied individuals during ground level walking, with and without ankle-foot orthoses. The data showed that gait variability will increase in able-bodied subjects when the motion of ankle joints is restricted, thus, providing a good test for generalization. The experimental results illustrate performance of the production rule that estimates quadriceps muscle group activity pattern for ground level walking in able-bodied subjects.     

Process Model Perspectives on Management and Engineering Procedures in the Precast/Prestressed Concrete Industry

The preparation of detailed models of information and process flow by 14 member companies of the North American Precast Concrete Software Consortium has provided a unique window into the current management, engineering design, and production operations in this industry. The modeling was performed using the authors’ Georgia Tech Process for Product Modeling tool, within the framework of the consortium’s effort to develop a precast concrete product model and to specify new integrated three dimensional modeling software. The paper opens with a comparative economic review of precast construction internationally and in North America, which reveals that the market share of precast construction in North American is relatively low. The models are analyzed and aspects of the underlying management procedures that they reveal are discussed, such as types of contracting arrangements, cost estimating, design outsourcing, engineering design communication, mold design, product diversity, and quality control. The results highlight aspects of precast management processes that may be re-engineered through appropriate application of information technology.     

Irrigation Scheduling. II: Heuristics Approach

A sequential irrigation schedule that honors user demands of duration and minimizes earliness and tardiness is interpreted as a single-machine schedule with earliness and tardiness costs and a common deadline (or fixed interval). A heuristic solution is presented for this irrigation scheduling problem. Four models are presented to reflect the different methods in which an irrigation system at the tertiary unit level may be operated, the first model permits jobs to be noncontiguous, i.e., idle time between jobs is permitted, whereas the others permit contiguous jobs only. The heuristic is tested extensively and the solution quality is compared with either an optimum solution from an integer program or the best available solution obtained from an integer program within allocated computation time. The heuristic is computationally efficient for all models presented, however for schedules with noncontiguous jobs, or where idle time is inserted before and after a contiguous set of jobs, solution quality deteriorates. The work brings the science of single scheduling from operations research into irrigation scheduling and suggests areas for further development.     

特殊钢厂炼钢-连铸调度模型

针对特殊钢厂的炼钢-连铸调度问题,建立了多目标调度模型.在模型求解过程中,对静态调度策略和动态调度策略进行了探讨.在静态调度部分,结合炼钢厂运行原则,并根据炼钢炉和连铸机作业周期的不同对应关系,对生产模式进行了分类,给出了相应的求解方法.在动态调度部分,给出了基于规则的动态调度策略以及具体的时间调整方法.最后,根据某转炉特殊钢厂的实际生产状况,在三台连铸机同时生产的情形下,对三个浇次的调度计划进行了仿真计算.通过与实际生产数据的比较,表明所采用方法的有效性.