Closed-loop Production Research Articles

Combinatorial Problems in Multirobot Battery Exchange Systems

This paper addresses combinatorial problems that arise in multirobot battery exchange systems. The multirobot battery exchange system addressed herein is characterized by two types of robots: task robots that provide services at requested locations and delivery robots that deliver charged batteries to task robots when required. Combinatorial problems arising in these systems involve multiple aspects of resource scheduling and path planning that make them more complex than well-known combinatorial problems studied in operations research. We present several heuristic algorithms for solving these combinatorial problems. Our algorithms are inspired by techniques used in artificial intelligence and the design of approximation algorithms. We demonstrate the performance of our algorithms in simulation and analyze how they scale with increasing size of the multirobot system. Note to Practitioners —This paper studies combinatorial problems arising in multirobot systems that intend to sustain themselves using mechanisms for battery exchange. The ideas developed in this paper are broadly applicable to resource delivery and scheduling, closed-loop product supply management, and pickup and delivery problems for transportation. Many of the problems studied in this paper are generalizations of the traveling salesman problem. Simpler variants of these have been studied in operations research with the aim of finding optimal solutions—albeit in exponential time. However, in this paper, we present heuristic algorithms for solving battery exchange problems based on techniques developed in artificial intelligence and the design of approximation algorithms. Our algorithms have polynomial execution times and, therefore, scale very well with increasing size of the system. More expressive variants of battery exchange problems, with a broader class of constraints, must be addressed in the future. In addition, future research should also emphasize decentralized algorithms in order to encourage parallelism and exploit the computing power available on each individual robot.

Industrial clusters and industrial ecology: Building ‘eco-collective efficiency’ in a South Korean cluster

The industrial clusters literature has shaped contemporary thinking on the potential of small firms to become globally competitive through agglomeration gains and collective action. However, clusters often generate negative environmental externalities. The industrial ecology framework suggests that producer agglomerations can spawn closed loop production arrangements that reduce environmental diseconomies. To date there has been little engagement between the industrial cluster and industrial ecology approaches. This paper addresses this critical gap by integrating the industrial cluster and industrial ecology frameworks. It analyses case evidence from the Banwol-Sihwa textiles dyeing cluster in South Korea to show that ‘eco-collective efficiency’ is achievable through cluster-based collective action. This can result in closed loop production and cluster-wide economic and environmental gains. Critical to achieving this is local social embeddedness, cluster-based institutions and the role of coordination powers.

Production routing problems with reverse logistics and remanufacturing

This paper introduces a mixed integer programming model for production routing problems with reverse logistics and remanufacturing, which are closed-loop production routing problems addressed for the first time. A solution method of branch-and-cut guided search algorithm is developed. Computational results from instances adapted from benchmarks of production routing problems show that, the algorithm is more effective when pickup requests are relative high. The problem is also easier to solve when production or transportation costs are lower. The optimal decisions are insensitive to the location of remanufacturing depot whether it is geographically centered or centered with gravity.

Internet of Things - Enabled Visual Analytics for Linked Maintenance and Product Lifecycle Management

When closed loop product lifecycle management was first introduced, much effort focused on establishing ways to communicate data between different lifecycle phase activities. The concept of a smart product, able to communicate its own identity and status, had a key role to play to this end. Such a concept has further matured, benefiting from internet things-enabled product lifecycle management advancements. Product data exchanges can now be brought closer to the point of end use consumption, enabling users to become more proactive actors within the product lifecycle management process. This paper presents a conceptual approach and a pilot implementation of how this can be achieved by superimposing middle of life relevant product information to beginning of life product views, such as a 3D product CAD model. In this way, linked maintenance data and knowledge become visual features of a product design representation, facilitating a user’s understanding of middle-of life concepts, such as occurrence of failure modes. The proposed approach can be particularly useful when dealing with product data streams as a natural visual analytics add-in to closed loop product lifecycle management.

Online lead time prediction supporting situation-aware production control

Cyber-Physical Production Systems (CPPS) appeared already in recent manufacturing environments, and they are capable of providing detailed data about the products, processes and resources in near real-time. Various analytics techniques are available to exploit such technology related data in decision making, however, these tools typically act in the fields of maintenance and quality. Only a few approaches target production control, while the effectiveness of related processes is of crucial importance from overall performance’s viewpoint. In the paper, a new production data analytics tool is presented, applying machine learning techniques to proactively predict manufacturing lead times to make decisions by implementing a closed-loop production control. The proposed method applies regression techniques, and based on that, it supports job priorization to be utilized in dispatching decisions. The efficiency of the proposed method is analyzed and presented by numerical results of a case study.

Reducing Carbon Emissions in a Closed-Loop Production Routing Problem with Simultaneous Pickups and Deliveries under Carbon Cap-and-Trade

The incorporation of reverse logistics into production routing problems can promote and coordinate the implementation of sustainable development for supply chains. This study aims to incorporate reverse logistics into production routing problems and investigate the reduction of carbon emissions under carbon cap-and-trade. Mixed-integer programming models are proposed for the production routing problem with reverse logistics by considering simultaneous pickups and deliveries in vehicle routing subproblems. To solve this problem, we propose a solution method of a branch-and-cut guided search algorithm based on adaptation of known valid inequalities. Computational results highlight the trade-offs among various performance indicators, including emission levels and operational costs of production, inventory holding, fuel consumption, and drivers.

Optimal design and control of pressure swing adsorption process for N2/CH4 separation

Pressure swing adsorption (PSA) is a very versatile, albeit complex gas separation and purification technology. Due to its complexity and periodic operation, calculation of the optimal PSA system that simultaneously obtains process design and control decision variables is a complicated task. This work presents detailed design and control optimization study of a two-bed, six-step PSA system aimed at heavy component CH4 upgrading. The key optimization objective is to enhance product CH4 recovery while achieving a closed loop product CH4 purity of 75% for separating 68%N2/32%CH4 feed under external disturbances. Traditional sequential and simultaneously design and control approach are employed and compared based on this purpose. The benefits of simultaneous methodology over conventional sequential approach are successfully demonstrated by closed-loop performance results and simulation profiles. The simultaneously design and control methodology has succeeded in synthesizing the optimal PSA cycle which can generate CH4 recovery as high as 97.30%.

Analysis of closed-loop production lines with Bernoulli reliability machines: Theory and application

ABSTRACTIn this article, an iteration approach is introduced to study closed-loop production lines with a constant number of carriers. A Bernoulli machine reliability model is assumed. The closed-loop system is decomposed into multiple small loop lines and further down to two-machine loops, in which the distributions of carriers are derived. Then an iteration procedure is presented to estimate the interactions between the small loops to modify the carrier distributions. Upon convergence, the system production rate can be estimated using these distributions. The convergence of the procedure is proved analytically, and the accuracy of estimation is justified numerically. It is shown that the method has good accuracy and computational efficiency. In addition, a case study at an automotive assembly plant is introduced to illustrate the applicability of the method.

Revenue sharing contract coordination of wind turbine order policy and aftermarket service based on joint effort

PurposeThe purpose of this paper is to discuss how wind farms attract wind turbine manufacturers to get involved in wind turbines’ maintenance service with revenue sharing contract of bundled service under which the background of operation and maintenance (O&M) aftermarket of wind turbine exists. The authors also try to extend the results to the application of product plus service business mode on large-scale equipment O&M service. At present, Chinese wind power industry is suffering from production capacity redundancy. The profit levels for both wind farm and wind turbine manufacturers are relatively low. It is significant for Chinese wind power industry development to coordinate the supply chain of wind power in order to reduce O&M costs and increase revenues.Design/methodology/approachThe present paper discusses product plus aftermarket service contract design on the background of closed-loop product service chain and uncertain equipment demand using revenue sharing contract model.FindingsIf centralized decision making is assumed, the authors find that the wind turbine order increases as the aftermarket service effort level and aftermarket service profit increase; aftermarket service effort level is positively correlative to the service efficiency. On the other hand, if decentralized decision making is assumed, the wind turbine order increases as share of the aftermarket service chain by manufacturer to wind farm increases and share of product supply chain by wind farm to manufacturer decreases. The optimal effort level of wind farm increases as the share of aftermarket service chain increases while the optimal effort level of the manufacturer is a concave function of share of aftermarket service chain if service quality linear correlates with effort level. Meanwhile, the authors find that the revenues of the product supply chain and aftermarket service chain have a concave relationship. This relationship is not affected by the format of relationship between service quality and effort level (linear or exponential).Practical implicationsThe results could potentially be used to provide the wind turbine manufacturer with a greater profit space and satisfy wind farm’s equipment maintenance demand at the same time. It can also guide the practice of revenue sharing in the aftermarket service and manufacturing servitization.Originality/valueIn this model, the authors assumed that both the forward revenue sharing of power generation by wind farm to manufacturer and the backward revenue sharing of maintenance service by the manufacturer to wind farm exist in closed-loop product service chain. Then the authors discussed channel coordination of such cross-revenue sharing contract.

A design for EoL approach and metrics to favour closed-loop scenarios for products

Recently, environmentally conscious design and extended producer responsibility have become key aspects for companies that need to develop products that are sustainable along their whole life cycle. Design for End of Life (EoL) is a strategy that aims to reduce landfill waste through the implementation of closed-loop product life cycles. It is important to consider disassembly and EoL scenario management as early as the design phase. For these reasons, this paper presents an approach to help designers in the evaluation and subsequent improvement in product EoL performance. The method is based on four innovative EoL indices that compare different EoL scenarios for each product component. In this way, the designer can modify the product structure or the liaisons to maximise the reuse and remanufacture of components as well as material recycling. The presented case studies confirm the validity of the approach in helping designers during the redesign phase of goods and products to reduce the quantity of materials and industrial wastes sent to landfill.

A closed loop production of water insoluble organic acid using bipolar membranes electrodialysis (BMED)

Production of phenylglycine (PG) was achieved by combining a novel bipolar membrane electrodialysis (BMED) with the traditional production process through an in-situ and closed-loop circulation. The H2SO4, produced from Na2SO4 with the BP-C-BP configuration was used to convert the sodium phenylglycine (PGNa) while the alkali produced in base chamber could be used to hydrolysis in the traditional production process of PG. Pure PG crystal was obtained after filtration of the acidified solution when solution pH was kept at 6.9–7.0. The filtrate solution containing Na2SO4 was discharged to the feed solution. As a consequence, a closed loop production was achieved. The effects of current density, flow rate of acid chamber and concentration of Na2SO4 on the performance of BMED were investigated. Results showed that the highest current efficiency could reach 82.7%, the energy consumption could be as low as 1.97kWh/kg for H2SO4 and the yield of PG could reach 94.1%, the energy consumption of PG was 0.69 kWh/kg in the synchronous process in the last step. Naturally, it was not only cost-effective but also environmentally friendly process for the production of water insoluble organic acid using bipolar membrane electrodialysis.

Optimisation of costs and carbon savings in relation to the economic dispatch problem as associated with power system operation

In this paper, the costs and carbon savings in the economic dispatch (ED) problem of the power system operation are optimised. Energy demands and generation are forecast and assimilated using ensemble Kalman filter (EnKF). Optimisation is performed using the ensemble-based closed-loop production optimisation scheme (EnOpt). The real energy parameters of thermal units with green generators (wind farm) are used to test the methodology. The ability of the EnKF to predict, and the robustness of the EnOpt to optimise costs and the resultant carbon emissions are demonstrated. The proposed approach addresses the complexity and diversity of the power system and may be implemented in operational conditions of energy suppliers.

An integrated closed-loop product lifecycle management approach for reverse logistics design

Nowadays, reverse logistics is gaining importance for many companies in different industries. This importance is rooted in the fact that it generates profit and decreases the environmental impacts of products. Even though the decrease of environmental impacts is an indispensable requisite, reverse logistics design is only driven by cost indicators. The main reason behind this high cost is access to environmental information is difficult and is directly linked to data all along the lifecycle of the product. This paper presents a method by which reverse logistics design integrates environmental impacts based on the management of closed-loop product lifecycle. This method is divided into two processes: from beginning of life to end of life and from end of life to beginning of life. The first process integrates product data in order to calculate environmental impacts of the potential reverse logistics networks, whereas the second process selects the most appropriate reverse logistics network before optimising the product based on this particular network. The proposition is illustrated by a case study on a recycled aluminium automotive part.

Sandglass-type product specification management method for supporting modular design of semiconductor manufacturing equipment

The product life cycle for semiconductor manufacturing facilities has been significantly reduced as a result of the technological advancement of the semiconductor manufacturing process and the expansion of its demand. To ensure long-term market competitiveness under this environment, many companies attempt to convert their systems into mass customization production systems. In general, the specification management for semiconductor manufacturing equipment has adopted the method of making the bill of materials structure of the existing equipment into a new one based on the same physical structure and then customizing it according to a customer’s demands in the detail design phase. However, this method results in longer lead times and difficulties maintaining data consistency due to frequent design changes in connection with various derived products. We suggest a sandglass-type product specification management method to efficiently reflect varying and versatile requirements in product development and shorten the design lead time. In addition, we propose a method to support the modular design of semiconductor manufacturing equipment by classifying the standard specifications for a final product into product component and part component specifications. Finally, we develop a closed-loop product specification management system called NEXUS using our method, and apply this system to semiconductor manufacturing processes.

Linear Activity Analysis of Production for Closed-Loop Businesses—Case Study of a Hungarian Apple Juice Factory

In the context of closed-loop and integrated production systems Koopmans linear activity analysis of production provides a relevant method for decision makers. The benefit of the method is to consider alternative production technologies at a time and model multiple material flows (inputs and outputs, including waste/pollutants) as well. In this paper Koopmans theory is proposed for modeling the reduction of waste in closed loop production processes. The method of linear activity analysis provides flexibility to measure the amount of waste by setting limiting constraints justifying the purpose of the model. Based on these features the method can be used in the future for modeling Blue Economy type of businesses. The case study of a Hungarian apple juice factory compares the conventional/linear and the new/closed loop production model. Result in GAMS software yields notable outcomes for the closed-loop apple juice factory showing not only the reduction of waste and by-products, but the expansion of new value-added products and jobs at a profitable level.

Adaptation of the Product Structure-based Integrated Life cycle Analysis (PSILA) technique for carbon footprint modelling and analysis of closed-loop production systems

In a previous work, the Product Structure-based Integrated Life cycle Analysis (PSILA) technique was developed to conduct cost modelling and analysis of closed-loop production systems. In this paper, we expand the utility of this technique into carbon footprint (CFP) modelling and analysis of closed-loop production systems – enabling companies to make informed decisions on whether to adopt closed-loop production based not only on economic but also environmental performance. A description of the PSILA technique applied for carbon footprint modelling and analysis is explained, followed by a case study of closed-loop production of a flat-panel display (FPD) monitor to validate the technique. We verified the CFP result simulated by the model built through the PSILA technique, or PSILA-CFP model in short, against the result generated by a model built through the conventional Life Cycle Assessment (LCA) method. A benchmarking analysis was then conducted to compare the closed-loop production system against the linear production system. Through this analysis, we demonstrated how the CFP result can be broken down based on the product structure, thus enabling us to granularise the result and trace the impact of implementing a closed-loop production system to the individual modules, components and materials that are recovered, reutilised or treated in the system. The results were able to show that the implementation of the closed-loop production system for the FPD monitor can potentially result in an overall CFP reduction of 39.91 million kg CO2e, of which 90.03% is contributed by the closed-loop recycling of ABS. The other significant contributors of CFP reduction are from the closed-loop material recycling of the aluminium, which accounts for 8.13 million kg CO2e or 20.37% of the total CFP reduction. A sensitivity analysis was also carried out to investigate the effects of data uncertainties, which may invalidate assumptions made in the case study. In summary, we have successfully adapted the PSILA technique so as to provide decision support in the form of analytical insights on how a closed-loop production system will perform in terms of carbon footprint, why it performs this way and what to look out for if the decision is made to implement such a system.

On the Exact Inter-departure, Inter-start, and Cycle Time Distribution of Closed Queueing Networks Subject to Blocking

This paper presents a method to determine the exact inter-departure, inter-start and cycle time distribution of closed queueing networks that can be modeled as Continuous-Time Markov Chains with finite state space. The method is based on extending the state space to determine the transitions that lead to a departure or to an arrival of a part on a station. Once these transitions are identified and represented in an indicator matrix, a first passage time analysis is utilized to determine the exact distributions of the inter-departure, inter-start, and cycle time. In order to demonstrate the methodology, we consider closed-loop production lines with phase-type service time distributions and finite buffers. We discuss the methodology to automatically generate the state space and to obtain the transition rate matrices for the considered distributions. We use the proposed method to analyze the effects of the system parameters on the inter-departure, inter-start time, and cycle time distributions numerically for various cases. The proposed methodology allows the exact analysis of the inter-departure, inter-start, and cycle time distributions of a wide range of production systems with phase-type servers that can be modeled as Continuous-Time Markov Chains in a unified way.

Numerical model of the Habanero geothermal reservoir, Australia

A TOUGH2 reservoir model has been developed for the Habanero enhanced geothermal system (EGS), located in the Cooper Basin, Australia. The reservoir, interpreted to be the sub-horizontal Habanero fault, was defined by the extent of the stimulated seismic cloud. A 1D natural state model was used first to calibrate the rock thermal properties, heat generation and the heat flux at the base of the model. The temperature distribution was matched against measured down-hole data from well Habanero 1. A 3D model was then developed with 9 horizontal layers and aligned along an impermeable eastern boundary fault. Gravity potentially plays an important role so the model was tilted to the west-south-west. Since the fine 72,000 cell model only extends to 20km2 whilst the reservoir rock (Innamincka Granite) extends to over ∼1000km2, Dirichlet boundary condition (large block volumes) was used for the sides with closed boundaries at the top and bottom. These large cells simulate the extension of the reservoir beyond the limited dimensions of the basic model. The permeability of the stimulated and mud damaged zones was calibrated using stable closed-loop (doublet) production and injection history data. The porosity was calibrated by simulating the two tracer tests carried out at Habanero. In preparing future production forecasts, four different well layouts were considered: staggered line drive (SLD); inverted 4-spot, regular 5-spot and east-west SLD. For each scenario, closed-loop circulation at 25, 35 and 45kg/s per well was modeled for a production period of 20 years. The well patterns were stretched to about the maximum well separation available within the existing seismic cloud, as well as hypothetical seismic clouds. For a larger-scale development plan the best outcome was chosen by balancing short-term temperature against long-term extensibility. The results within the existing seismic cloud indicate the 4-spot layout as the most optimum. The best temperature performance is obtained from an extended seismic cloud when using an east-west SLD.

Improvement of the evaluation of closed-loop production systems with unreliable machines and finite buffers

A closed-loop production system, or loop, is a system in which a constant amount of material flows through a single fixed cycle of workstations and storage buffers. Manufacturing processes that utilize pallets or fixtures can be viewed as loops. Control policies such as CONWIP and Kanban create conceptual loops. Gershwin and Werner (2007) developed a decomposition algorithm that accurately evaluates Buzacott type closed-loop systems of any size. However there are cases where the evaluated production rate, as a function of some system parameter, is discontinuous. Such a discontinuity may give misleading results for loop system design and optimization method. We present two modifications that improve the algorithm of Gershwin and Werner (2007). Two new special types of two-machine one-buffer building blocks are developed for the decomposition, and analytical solutions for them are found. Numerical experiments are provided to show the improvement of the evaluation accuracy as compared with the existing algorithm. The discontinuity in production rate is greatly diminished with these modifications.

Allocation solutions for secondary material production and end of life recovery: Proposals for product policy initiatives

This paper aims at analysing how secondary materials production and end of life recovery processes are modelled in life cycle-based environmental assessment methods in order to discuss their suitability in product policy-support contexts, with a focus on Sustainable Consumption and Production (SCP) policies. The equations prescribed in three published, widely recognised standards are evaluated. In addition, more recent modelling approaches that have been adopted in the context of two EU product policy initiatives (the Product Environmental Footprint (PEF) and the Resource Efficiency Assessment of Products (REAPro)) are similarly analysed. All of the methods are scrutinised against eight criteria which we deem to be important in product policy-support contexts, including comprehensiveness, accommodation of open-loop and closed-loop product systems, and consideration of recyclability/recoverability rates, to name a few. Based on this analysis, it is suggested that the PEF and REAPro modelling approaches appear to be better suited for use in product policy-support contexts than do the currently widely endorsed methods that we considered.