Scheduling Simulation Model Research Articles

RGV dynamic scheduling model based on kruskal algorithm

In order to solve the problems in traditional processing industry and meet the increasingly urgent demand for product processing performance, intelligent processing has begun to be widely used in industrial production. Today, the Rail Guided Vehicle (RGV) has become one of the main equipment for logistics distribution tasks in intelligent processing systems. [1] It automatically controls the direction and distance of movement according to the command. By planning the dynamic scheduling model of RGV, the output efficiency of industrial production can be greatly improved. Based on the Kruskal algorithm in the greedy algorithm, we design a set of material processing RGV dynamic scheduling simulation model through C++ programming. According to the theory of “local variable optimization and global variable optimization” in the Kruskal algorithm, the shortest path is selected every time the next target of RGV is judged, so that the whole distance traveled is the shortest, wasting shortest time and achieving the highest output.

Operation Flexibility Evaluation and Its Application to Optimal Planning of Bundled Wind-Thermal-Storage Generation System

The growing penetration of wind power in a power system brings great challenges to system operation flexibility. For generation planning in presence of high wind power penetration, it is essential to take the operation flexibility of the system into account. Firstly, this paper developed the system operation flexibility metrics through considering the flexibility contribution of thermal generating units (TGUs) by operational state transition. Secondly, a planning model for the bundled wind-thermal-storage generation system (BWTSGS) that considers the operation flexibility constraints is proposed. The planning model is used to determine the power and energy rating of an energy storage system (ESS) as well as the type and number of TGUs. A daily scheduling simulation model of a BWTSGS is proposed to calculate the operation cost for the planning model and consider the sequential operation characteristics of the BWTSGS. Further, in order to accelerate the computation, a wind power sequential clustering technique based on the discrete Fourier transform (DFT) method is developed for improving the computational efficiency. Case studies have been conducted on a 1000-MW wind farm to demonstrate the validity and effectiveness of the proposed model.

Study on the Hydraulic Characteristics of Cascade Pumping Station on the East Route of South-to-North Water Diversion Project

Aiming at the hydraulic problems existing in the operation of the two lakes in the east route of the South-to-North Water Diversion Project, a one-dimensional hydraulic equation and a pump station performance equation were coupled. Based on the Fortran language, a simulation model for water delivery scheduling of the two-lake cascade pumping stations was developed and combined with the actual measurement from 2013 to 2017. The data has been calibrated for the model, which can simulate the hydraulics of different water transport conditions. Based on the hydraulics method, the hydraulic loss under normal water conveyance conditions between channels was analyzed, calculated and studied. In view of the aquatic problem, Changgou-Denglou section was selected as the research object, and the model was combined based on the measured data. The hydraulic loss under the plugging condition of the aquatic plant was analyzed and calculated and the law was studied. Based on the water balance method, the water loss in the two lakes was analyzed and calculated. The research results can provide reference for the operation of the two lakes in the east route of the South-to-North Water Diversion Project.

Research of Modeling and Simulation for Operation Scheduling Process of Block Stockyard Based on Petri Net

As for the problem of low efficiency and difficulty of the operation of block, a method of modeling and simulation of the operation scheduling process of block stockyard based on Petri net is proposed. Firstly, based on the analysis of the operation scheduling process of block yard, the operation scheduling mode of virtual flow line is presented; Secondly, a virtual flow line model according to the operation scheduling model of block stockyard based on hierarchical-timed Petri net is established and the feasibility of the virtual flow line is proved with the method of invariant; Finally, a block stockyard operation scheduling simulation model based on the digital factory strategy is established and the digital simulation analysis of block yard operation scheduling is carried out. The results show that the mode of virtual flow line operation and the Petri net contribute to improving efficiency of the block stockyard operation scheduling and resources using, the virtual flow line can also avoid the blocking. The effective method and theoretical support are provided in this paper for the block stockyard scheduling.

Optimizing Dosage and Location of Chlorine Injection in Water Supply Networks

Disinfection of the water in the drinking water supply network is usually done by injecting chlorine to the treated water before it is pumped into the network for distribution. However, such an injection process may not be sufficient to ensure that the chlorine residual throughout the network is within the standard limits. Usually, the residual chlorine is reduced as water moves through the pipe network, due mainly to its reaction with a variety of materials in the bulk water and from the pipe wall. Reduction in residual chlorine in the water supply network may lead to degradation of water quality and, thus, poses potential microbial risks to humans. To meet water quality standards, it is recommended to maintain residual chlorine throughout the water supply network within the desirable levels. This paper presents an optimization model based on the hydraulic simulation model (EPANET) and mixed integer linear programming technique for optimal locations and scheduling of booster chlorination in a real water supply network located in Al-Khobar, Saudi Arabia. The results demonstrate better performance with reduced doses of chlorine when booster chlorination is applied to the water distribution network. The findings may assist in reducing chlorine doses, which is likely to reduce human exposure to potentially harmful disinfection by-products in drinking water.

Evaluation of SIMDualKC Using Lysimetric Data for Estimating Daily Evapotranspiration of (Coriandrum Sativum L. (

The SIMDualKc model is an irrigation scheduling simulation model that uses dual crop coefficient method for estimating ETc by computing two separate soil water balances in daily time-step, one for the soil evaporation layer from which Ke is computed, and the other one for the entire root zone to compute the actual Kcb adjusted to the soil moisture conditions. In this study, lysimetric measurements of evapotranspiration rates relative to (Coriandrum sativum L.) during 2 years were used for model calibration and validation. Kcb values for coriandrum were found as 0.21 for the initial, 1.12 for the mid-season and 0.79 at harvesting period. Model results have shown a good agreement between the actual daily evapotranspiration predicted by the model and the ones resulting in water balance calculation on drainable lysimeters, and root mean square errors of estimates (RMSE) of about 1.64 mm and 1.53 mm for the calibration and validation, respectively.The modeling efficiency EF and the index of agreement dIA were equal to 0.8 and 0.93, respectively, thus indicating good performance of modeling with SIMDualKc. Model estimates of evaporation (E) for validation and calibration years displayed an average of 181 mm, representing 25% of ETc. In conclusion, results show that the model is appropriate to simulate the daily evapotranspiration adopting the dual Kc approach for coriandrum in west regions of Iran.

A production scheduling simulation model for improving production efficiency

AbstractA real manufacturing system of an electronic company was mimicked by using a simulation model. The effects of dispatching rules and resources allocations on performance measures were explored. The results indicated that the dispatching rules of shortest processing time (SPT) and earliest due date are superior to the current rule of first in first out adopted by the company. A new combined rule, the smallest quotient of dividing shortest remaining processing time (SRPT) by SPT (SRPT/SPT_Min), has been proposed and demonstrated the best performance on mean tardiness time under the current resources situation. The results also showed that using fewer resources can increase their utilization, but it increases the risk of delivery tardiness as well, which in turn will damage the organization’s reputation in the long run. Some suggestions for future work were presented.

Dual crop coefficient modelling applied to the winter wheat–summer maize crop sequence in North China Plain: Basal crop coefficients and soil evaporation component

The dual crop coefficient (Kc) approach to estimate crop evapotranspiration (ETc) separately considers soil evaporation (E) and plant transpiration (T) by computing a soil evaporation coefficient (Ke) and a basal crop coefficient (Kcb), respectively, with Kc=Ke+Kcb. This approach may be more precise than the single Kc approach particularly when the crops incompletely cover the ground. The SIMDualKc model, which is adopted in this study, is an irrigation scheduling simulation model that uses a daily time-step for performing two separate soil water balances, one for the soil evaporation layer from which Ke is computed, and the other for the entire root zone, thus allowing to compute the actual Kcb adjusted to the soil moisture conditions (Kcbadj). The standard Kcb is corrected to the climate, crop density and height. Two years of field experimental data relative to winter wheat and summer maize were used for model calibration and validation using soil water content data observed with time-domain reflectometry (TDR) in a silt loam soil. Field data also include E measured with microlysimeters placed along the crop rows. The calibration procedure consisted in adjusting the basal crop coefficients, the soil evaporation parameters used to compute Ke, and the soil water depletion fraction for no stress (p) to achieve the best fit of the observed soil water content data. The calibrated Kcb values for winter wheat were 0.25 for the initial and the soil frozen period, 1.15 for the mid-season and 0.30 at harvesting. For the summer maize, the initial, mid season and end season Kcb were respectively 0.2, 1.10 and 0.45. Model results have shown a good agreement between model predictions and field observations of the soil water content of both crops, with root mean square errors of estimates (RMSE) of about 0.01m3m−3 for both the calibration and validation. The modelling efficiency EF and the index of agreement dIA were larger than 0.96 and 0.99, respectively, thus indicating good performance of modelling with SIMDualKc. Model estimates of E using Ritchie's approach were compared with microlysimeter data; for winter wheat a RMSE=0.37mmd−1 was obtained, while for maize RMSE of 0.45 and 0.49mmd−1 were obtained for both years of observations. Results for soil evaporation allow confirming the appropriateness of using Ritchie's model to estimate soil evaporation of a cropped soil. E averaged 124mm for wheat, representing 29% of ETc, and 146mm for summer maize, i.e. 41% of ETc. In conclusion, results show that the model is appropriate to simulate the soil water balance adopting the dual Kc approach and may be further used to develop improved irrigation schedules for the winter wheat–summer maize crop sequence in North China.

A Multi-Agent Simulation Model for Water Resources Allocation and Scheduling

The South-to-North Water Diversion Eastern Route Project of China is a complex large scale system. It is important of constructing a modelling and simulation for this type of system. This paper proposes a modelling and simulation technique for large scale water project based on Agent calculation and complex adaptive system (CAS). The simulation experiment system, about multi-Agents of water resources in East CAS management features is conducted using SWARM. We demonstrate also the interaction within all kinds of objects and the behaviour of system evolvement in the course of water resources allocation and scheduling. The simulation results show the proposed simulation model effective.

A Simulation Model for Spatial Scheduling of Dynamic Block Assembly in Shipbuilding

Accurately predicting the required spatial resource for aggregate block assembly in shipyard production is difficult due to the following reasons: 1) lack of optimal block on-jig configuration and 2) the dynamic and stochastic nature of production system. Consequently, managerial objectives are seldom achieved without effective production planning and control. In this study, a look-ahead scheduling mechanism with an application of discrete-event simulation is proposed to solve the dynamic spatial scheduling problem. A systematic simulation-based framework is suggested for validating schedules generated at high-level planning together with a heuristic-based optimizer for improving spatial resource utilization. Through imitation of the dynamic spatial operation under various priority rules, statistical analysis of resultant performance can be conducted to select the best performing control policy. A case study with computational experiments is performed and results are reported. Issues relevant to system implementation are highlighted as well.

Design of Simulation Model for Production Scheduling in Flexible Manufacturing Systems

The complex interaction and the high costs of modern manufacturing systems make it necessary to evaluate their use performance. Production scheduling problem is one of the key problems of research of manufacturing systems since with a proper scheduling, the utilization of resources is optimized and orders are produced on time which improves the shop performance and associated cost benefits. However the complexity of modern production systems makes the use of analytical tools more difficult. Thus a computer simulation model of the existing computer integrated manufacturing system based on the control logic that describes the operation of the system is developed to test the performance of different scheduling rules with respect to mean flow time, machine efficiency and total run time as performance measures. According to the results of experiments, the model agrees with the real system.

Hierarchical mine production scheduling using discrete-event simulation

Mine planning involves different levels of decision-making depending on the time horizon under consideration. The main goal of this study is to develop a discrete-event simulation model to link long-term predictive mine plans with short-term production schedules in the presence of uncertainty. We have developed, verified and validated a discrete-event simulation model for open pit production scheduling using the SLAM simulation language. The simulation model takes into consideration constraints and uncertainties associated with mining and processing capacities, crusher availability, stockpiling strategy and blending requirements. Application of the simulation model is presented by an iron ore open pit mine case study.

Research on Modeling and Simulation of Scheduling with Tool Failure in FMS

Failure in FMS includes two aspects: equipment breakdown and tool failure of which should be considered in an excellent FMS scheduling system. Most of past scheduling researches have only discussed the former and the analysis of the latter rarely seen in relevant papers. The scheduling system without tool failure processing seems to be not coincident to the actually production in which tool breakdowns are very common. This paper gives a dynamic scheduling simulation model with concern of the two kind failure using Object-Oriented technology and Colored Petri Net (OOCPN). Rescheduling strategy of tool failure is proposed and the simulation analysis is given which shows that our model and principle are effective and adaptable to actual case.

Irrigation scheduling strategies for cotton to cope with water scarcity in the Fergana Valley, Central Asia

The Central Asian countries face high water scarcity due to aridity and desertification but excess water is often applied to the main irrigated crops. This over-irrigation contributes to aggravate water scarcity problems. Improved water saving irrigation is therefore required, mainly through appropriate irrigation scheduling. To provide for it, after being previously calibrated and validated for cotton in the Fergana region, the irrigation scheduling simulation model ISAREG was explored to simulate improved irrigation scheduling alternatives. Results show that using the present irrigation scheduling a large part of the applied water, averaging 20%, percolates out of the root zone. Several irrigation strategies were analyzed, including full irrigation and various levels of deficit irrigation. The analysis focused a three-year period when experiments for calibration and validation of the model were carried out, and a longer period of 33 years that provided for an analysis considering the probabilities of the demand for irrigation water. The first concerned a wet period while the second includes a variety of climatic demand conditions that provided for analyzing alternative schedules for average, high and very high climatic demand. Results have shown the importance of the groundwater contribution, mainly when deficit irrigation is applied. Analyzing several deficit irrigation strategies through the respective potential water saving, relative yield losses, water productivity and economic water productivity, it could be concluded that relative mild deficits may be adopted. Contrarily, the adoption of high water deficit that produce high water savings would lead to yield losses that may be economically not acceptable.

Cotton irrigation scheduling in central Asia: model calibration and validation with consideration of groundwater contribution

AbstractThe calibration and validation of the irrigation scheduling simulation model ISAREG for Central Asian conditions were performed using cotton field observations in the Hunger Steppe over the period 1983–87, and in the Fergana Valley for 2001–03. The calibration referred to the crop coefficients and the soil water depletion factor for no stress. Groundwater contribution was considered in computations adopting a set of parametric equations used in ISAREG. Calibration and validation were performed by comparing the observed and simulated soil water content during each crop season. Various indicators of goodness of fit were used to assess model validation. For the Hunger Steppe, the validation also included the comparison of model‐computed and field‐measured crop evapotranspiration, which was performed with the energy balance method. Results obtained show a good agreement between field observations and model predictions, thus allowing use of the ISAREG model to generate and assess alternative irrigation schedules aimed at improved water use in Central Asia. Copyright © 2008 John Wiley & Sons, Ltd.

Irrigation scheduling for furrow-irrigated maize under climate uncertainties in the Thrace plain, Bulgaria

Climate change creates uncertainties for irrigation management. To cope with them, simulations were performed for the present and scenario-built weather conditions that include a pessimistic scenario of precipitation decrease in the next 25 years. In a former study, the irrigation scheduling simulation model ISAREG was calibrated for two maize varieties: the water stress-resistant hybrid Kn-2L-611 and the water stress-sensitive hybrid H708. Both are subjects of this study, which compares four irrigation scheduling alternatives: (1) refilling the soil reservoir and adopting a management-allowed depletion fraction (MAD) of 0.47; (2) refilling the soil reservoir and adopting MAD=0.33; (3) partially refilling the soil reservoir and adopting MAD=0.47; and (4) crop without irrigation. For the very dry year and the present climate all alternative irrigation schedules behave similarly but for the average year, alternatives 1 and 3, allowing a larger soil water depletion with MAD=0.47, require less water than the alternative with MAD=0.33. However, analysis of impact on yields using simulations relative to every year during 1970–1992 shows that alternative 2 leads to less impact on yields. The results of simulations were compared with irrigation schedules presently advised in the region and show that the latter do not fully cover crop requirements in dry seasons, when some yield decrease occurs. Simulations for the pessimistic scenario show that all three irrigation scheduling alternatives can easily accommodate the foreseen changes mainly by selecting suitable irrigation dates. The results of simulations do not allow selecting one among the three alternatives as the best irrigation scheduling strategy but are useful for later building an information system for farmers using actual weather data. Relative to the rainfed crop, the results indicate that yield impacts highly increase for the pessimistic scenario, particularly for the water stress-sensitive hybrid H708. The results indicate that vulnerability to climate change is higher for non-irrigated crops and that coping with possible rainfall decreases requires adopting less sensitive crop varieties, including when deficit irrigation would be applied for water saving.

Modelling and multicriteria analysis of water saving scenarios for an irrigation district in the upper Yellow River Basin

Water saving in irrigation is a main issue in the Yellow River basin. This paper refers to a field and modelling study performed in the Huinong Irrigation District, a very large surface irrigation system in Ningxia, upper Yellow River basin, intended to assess water saving and improved water use issues. The decision support system SEDAM was purposefully developed to evaluate alternative scenarios of improvements of farm and off-farm irrigation canal systems. It includes a demand and delivery simulation tool and adopts multicriteria analysis. Simulation is performed at various scales, starting at the distributor and then successively at the sub-branch, branch and sector scales. It uses a database built from random generation of system characteristics at these scales, and based on field surveys. Demand is built from exploring interactively the irrigation scheduling simulation model ISAREG and the surface irrigation models SRFR and SIRMOD, which were previously parameterized. The first is used to generate improved irrigation schedules and the second to define improved basin irrigation scenarios. In addition, a simple paddy irrigation tool is used to simulate replacing the current deep flooding method by shallow water irrigation. Water delivery scenarios are built to match those of demand including several improved procedures that aim at controlling runoff and seepage. Results indicate that progressively adopting farm and delivery system improvements leads to reduced canal seepage and runoff, which is essential to an effective functioning of the drainage system, in addition to control diversions into the Huinong canal. Water savings amount to more than 50% of actual water use. However, results referring to the economic criteria, particularly to the farm gross margin, reveal that more stringent improvements have low impacts, i.e. the respective utilities increase little when scenarios require higher investments. The described application shows that adopting a DSS simulation model and multicriteria analysis is appropriate to assess water use improvements in large irrigation systems and that it is advantageous to perform the analysis of related impacts by combining economic and environmental criteria. The importance of adopting improved delivery systems is also evidenced.

Integrated simulation application design for short-term production scheduling

This paper focuses on the development of an integrated short-term production scheduling simulation model for a complex manufacturing operation. The decision making tool has a front-end user data interface built with Microsoft Access and Visual Basic for Applications software. The model assists production planners to make informed decisions on how best to schedule simultaneously two lanes of daily or weekly production on a unique plastic parts manufacturing line. The advantages and disadvantages (model weaknesses) of using the simulation model, especially as a scheduling tool, are discussed. In this particular application, we find that the advantages far outweigh the disadvantages.

Model Validation, Crop Coefficients and Yield Response Factors for Maize Irrigation Scheduling based on Long-term Experiments

This paper reports on using independent historic datasets relative to 19 years (1972–1990) experiments with maize for the calibration, validation and further testing of the irrigation scheduling simulation model ISAREG, and to derive appropriate crop parameters. The experiments concern diverse irrigation and rainfed treatments in a Vertisol at Pustren experimental site (Stara Zagora). The calibration of the model consists of deriving crop coefficients Kc and depletion fractions for no stress relative to the main crop growth stages, thus adapted to local climate and soil conditions, through searching the minimal differences between observed and model-simulated soil water content. The calibration was performed using data for 1976, while data for 1987 was used for validation. The resulting average errors of the estimate (AEE) for the soil water content are respectively 0·012 and 0·023 cm3 cm−3, thus indicating appropriate model parameterisation. The accuracy of the calibrated model was tested against experimental long-term data (1972–1990) from all irrigation and rainfed treatments by comparing the computed versus observed seasonal evapotranspiration. Results show a regression slope b close to the 1:1 line and a relatively small value for AEE, 49·75 mm season−1, which is less than 10% of the average crop evapotranspiration observed. The yield response factor Ky was also derived from the observed data sets for the two hybrid varieties used, resulting in a value for Ky of 1·0 for the hybrid Kn606 adopted during the first decade and a value of 1·5 for the hybrid H708 used during the second one. A statistical test was also performed to compare the model predicted versus observed relative yield decrease due to water stress for both varieties yielding a regression slope b of 0·952 and an error AEE of 0·048 for the hybrid Kn606 and b of 0·958 and AEE of 0·067 for the H708, which show that model predictions are appropriate. The results obtained support model use for developing water saving and environmentally oriented irrigation practices in the Trace region, South Bulgaria.

Modelling for Improved Irrigation Water Management in a Temperate Region of Northern Spain

This study refers to a region with temperate climate due to Atlantic influence and variable rainfall during the spring–summer season. Surface irrigation is traditionally practiced in this region, but this system is being progressively replaced by sprinkler irrigation. To assess the irrigation requirements and to select the most appropriate irrigation management practices, an irrigation scheduling simulation model was used after calibration/validation. Several alternative schedules were generated and evaluated according to impacts on yields and on percolation of excess applied water referring to each soil type and to conditions of very low, average, high and very high demand. Irrigation requirements under very low and very high demand conditions vary largely, in the range 124–358 mm for silage maize and 34–275 mm for grass pasture. Schedules refer to different soil water thresholds, and fixed (40 mm) and variable net irrigation depths, which range form 30 to 54 mm. Moreover, the different schedules were studied according to differences in the soil water-holding capacities of four soil types present in the area. In addition, the irrigation schedule previously proposed for supporting modernisation was evaluated. It showed an even worse performance in relation to those produced in this study. It was observed that, when sprinkler systems are well designed to produce high distribution uniformity, several alternative sprinkler schedules that minimise yield losses due to crop stress and percolation can be implemented. Findings suggest that a schedule with a constant application depth of 40 mm is best for immediate implementation, while a schedule with variable irrigation depths could be adopted when supported by a geographic information system and more sophisticated advisory facilities.