A Petri Net-Based Heuristic Algorithm for Realizability of Target Refining Schedule for Oil Refinery

In discrete manufacturing, a just-in-time schedule is pursued so as to respond better to the market. It is also required in oil refinery. However, the existing techniques for short-term scheduling in oil refinery are based on the push production mode. This paper addresses the short-term scheduling problem for crude oil operations in a pull production way. A target refining schedule resulting from production planning is given as a constraint to make an executable schedule. The system is modeled by a timed hybrid Petri net. This model is structurally simple and can describe the dynamic behavior and all the constraints of the system without any difficulty. Based on the model, an efficient heuristic algorithm is proposed to test the realizability of a target refining schedule. If it is realizable, a feasible short-term schedule realizing it is created. A real-life industrial case study is presented to show the industrial application of the proposed method.     

Modeling and deadlock avoidance of automated manufacturing systems with multiple automated guided vehicles.

An automated manufacturing system (AMS) contains a number of versatile machines (or workstations), buffers, an automated material handling system (MHS), and is computer-controlled. An effective and flexible alternative for implementing MHS is to use automated guided vehicle (AGV) system. The deadlock issue in AMS is very important in its operation and has extensively been studied. The deadlock problems were separately treated for parts in production and transportation and many techniques were developed for each problem. However, such treatment does not take the advantage of the flexibility offered by multiple AGVs. In general, it is intractable to obtain maximally permissive control policy for either problem. Instead, this paper investigates these two problems in an integrated way. First we model an AGV system and part processing processes by resource-oriented Petri nets, respectively. Then the two models are integrated by using macro transitions. Based on the combined model, a novel control policy for deadlock avoidance is proposed. It is shown to be maximally permissive with computational complexity of O (n2) where n is the number of machines in AMS if the complexity for controlling the part transportation by AGVs is not considered. Thus, the complexity of deadlock avoidance for the whole system is bounded by the complexity in controlling the AGV system. An illustrative example shows its application and power.     

Dual-Objective Mixed Integer Linear Program and Memetic Algorithm for an Industrial Group Scheduling Problem

Group scheduling problems have attracted much attention owing to their many practical applications. This work proposes a new bi-objective serial-batch group scheduling problem considering the constraints of sequence-dependent setup time, release time, and due time. It is originated from an important industrial process, i.e., wire rod and bar rolling process in steel production systems. Two objective functions, i.e., the number of late jobs and total setup time, are minimized. A mixed integer linear program is established to describe the problem. To obtain its Pareto solutions, we present a memetic algorithm that integrates a population-based nondominated sorting genetic algorithm II and two single-solution-based improvement methods, i.e., an insertion-based local search and an iterated greedy algorithm. The computational results on extensive industrial data with the scale of a one-week schedule show that the proposed algorithm has great performance in solving the concerned problem and outperforms its peers. Its high accuracy and efficiency imply its great potential to be applied to solve industrial-size group scheduling problems.      

Toward Cloud Computing QoS Architecture: Analysis of Cloud Systems and Cloud Services

Cloud can be defined as a new computing paradigm that provides scalable, on-demand, and virtualized resources for users. In this style of computing, users can access a shared pool of computing resources which are provisioned with minimal management efforts of users. Yet there are some obstacles and concerns about the use of clouds. Guaranteeing quality of service (QoS) by service providers can be regarded as one of the main concerns for companies tending to use it. Service provisioning in clouds is based on service level agreements representing a contract negotiated between users and providers. According to this contract, if a provider cannot satisfy its agreed application requirements, it should pay penalties as compensation. In this paper, we intend to carry out a comprehensive survey on the models proposed in literature with respect to the implementation principles to address the QoS guarantee issue.      

Fuzzy-Petri-net-based disassembly planning considering human factors

Disassembly, as the process of systematic removal of desirable constituent parts from an assembly, is of growing importance due to the increasing environmental and economic pressure. Although disassembly in practice is manual and labor intensive, little attention has been paid to the human intervention in the disassembly process. This paper addresses this deficiency by developing a fuzzy attributed Petri net (FAPN) model to mathematically represent uncertainty in disassembly due to a large amount of human intervention. An algorithm based upon this model is further proposed for optimal disassembly planning with a view to making the technique more applicable to real industry settings. The benefit of the proposed model and algorithm is illustrated through the disassembly of a personal computer (PC) in a prototypical disassembly system.     

An integrated product and process development methodology: Concept formulation

Life cycle engineering, or integrated product and process development (IPPD), is a new trend of research and application in industry and academia. In our previous work, a generic framework was proposed to provide a means for an integrated consideration of the performance optimization issues in a product’s lifetime. Based on this generic framework, this paper proposes and presents an integrated product and process development methodology. Important concepts of the methodology are introduced, and an application procedure is provided to illustrate the systematic application of the methodology to real product and process development. Finally, we provide a brief report of our application of the methodology to personal computer development.