This paper investigates a scheduling model for optimal production sequencing in a flexible assembly system. The system features a set of machines working together in the same workspace, with each machine performing a subset of operations. Three constraints are considered: (1) the precedence relation among the operations specified by the assembly tree; (2) working space that limits concurrent operations; and (3) the variation of process time. The objective is to find both a feasible assignment of operations to machines and schedule tasks in order to minimize the completion time for a single product or a batch of products. The assembly process is modeled using timed Petri nets and task scheduling is solved with a dynamic programming algorithm. The method calculates the time required precisely. A detailed case study is discussed to show the effectiveness of the model and algorithm.

Dynamic scheduling in flexible assembly system based on timed Petri nets model

The scheduling literature is extensive, but much of this work is theoretical and does not capture the complexity of real world systems. Capital goods companies produce products with deep and comple...

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A mixed-integer linear programming model for integrated production and preventive maintenance scheduling in the capital goods industry

An event-driven approach with makespan/cost tradeoff analysis for project portfolio scheduling

Product development in the manufacturing industry has been facing unprecedented challenges brought about by ever-changing global and competitive market conditions as well as changing individual customer demands. As manufacturing enterprises become more specialized, they need to communicate and work concurrently on a large volume of product data covering their factories, sub-contractors as well as suppliers. The collaboration and cooperation between enterprises is changing from a supply chain based on material flow to a collaborative product development chain based on task flow. Computer network technologies, especially the Internet, have injected velocity into product development activities and enabled companies to shift their traditionally centralized product development philosophy to networked product development philosophy. This paper introduces a new paradigm called Internet-based collaborative product development chain (ICPDC) to answer the aforementioned needs of current product development. It connects users in geographically different locations to carry out product development activities simultaneously and collaboratively using a series of tools, including product management tools, workflow management tools, and project management tools. Some key aspects of the ICPDC, including its concept, collaboration mechanism, constituents and fashioning principle, are introduced in detail. Furthermore, a framework for the ICPDC based on a Brower/Server is proposed. Finally, a prototype is implemented using web services technology and .Net programming language to demonstrate the feasibility of the structure and the collaborative approach that has been developed.

Internet-based collaborative product development chain for networked product development

In manufacturing enterprise information systems, concurrent design process is one of the focuses of research on design process management. This study proposes a novel process model for concurrent design based on unified modelling language (UML) and polychromatic sets theory. Model primitives and constructs of UML activity diagram, concurrent design activities, and dynamic changes of concurrent design process are described in the polychromatic sets contour matrix. Based on polychromatic sets theory, the model reduction rules and algorithm are proposed. With the feature-based part design and process planning, a UML model of concurrent design process is developed and mapped into polychromatic sets contour matrix model. The dynamic change, model reduction, path search and time consumption of concurrent design process are analysed, and the direction for improving concurrent design process and shortening product development cycle is suggested.

A process model for concurrent design in manufacturing enterprise information systems

This paper presents a methodology for modeling and simulating product development process-based on the extended stochastic high-level evaluation Petri nets (ESHLEP-N). A product development process is composed of many design activities and the ESHLEP-N model can describe some special features of design activity in detail, such as randomness of its duration, uncertainty of its interruption and complexity of design iteration. Therefore, the ESHLEP-N model is employed to simulate a product development process. The initial product development plan obtained by a mathematical method beforehand is taken as the input of the simulation. Then the simulation procedure is proposed, along with four types of rules, i.e. activity-sequencing rules, resource-assigning rules, state-changing rules and the simulation-terminating rule, for scheduling the design activities. An example of the development process of an automobile drive system in concurrent engineering environment is presented to illustrate the method of the ESHLEP-N-based modeling, simulation procedure and scheduling rules. The simulation results show that the simulation procedure and the scheduling rules are effective.

Xiao-Cheng Jiao

Papers

Modeling, scheduling and simulation of product development process by extended stochastic high-level evaluation Petri nets