Sungsik Park

CORBA-based integration framework for distributed shop floor control

Distributed shop floor control is likely to become a key component of 21st century manufacturing technology. The interest in distributed control arises from the promise of increased flexibility, reliability, and tolerance to the uncertainty that exists in the shop floor environment. However, the communicational complexities involved in the integration of distributed equipment controllers have long hindered the development of distributed systems. The present paper proposes a COBRA-based integration framework for the efficient and effective development of distributed shop floor control systems (SFCS). The framework integrates the data and methods common to the distributed controllers into services and provides the mechanism for each controller to access the services via CORBA. The use of CORBA as a middleware provides the basis for simple and well-defined interfaces between service servers and distributed equipment controllers located on heterogeneous platforms. A systematic implementation procedure is also included in the framework to allow easy implementation of the defined services and each controller. A prototype system is presented to validate the proposed integration framework. The proposed framework will enable system developers to efficiently and effectively implement distributed SFCSs.

Adaptive and dynamic process planning using neural networks

Although feature-based process planning plays a vital role in automating and integrating design and manufacturing for efficient production, its off-line properties prevent the shop floor controller from rapidly coping with dynamic shop floor status such as unexpected production errors and rush orders. This paper proposes a conceptual framework of the adaptive and dynamic process planning system that can rapidly and dynamically generate the needed process plans based on shop floor status. In particular, the generic schemes for constructing dynamic planning models are suggested. The dynamic planning models are constructed as neural network forms, and then embedded into each process feature in the process plan. The shop floor controller will execute them to determine machine, cutting tools, cutting parameters, tool paths and NC codes just before the associated process feature is machined. The dynamic nature of process planning enables the shop floor controller to increase flexibility and efficiency in unexpected situations.

Integrated development of nonlinear process planning and simulation-based shop floor control

Although several methods of simulation-based SFC have been suggested for the SFCS, this research only paid attention to the generation of a target simulation code and could not be fully integrated with the SFCS. Hence, this paper focuses on the conceptual architecture for the rapid and adaptive realization of a simulation-based SFCS for a discrete part manufacturing system. The developed simulation-based SFCS can process non-linear process plans. To this end, the new simulator engine must be developed. It advances the simulation clock and drives the simulation-based SFCS by investigating the information contents specified in the process and resource models.

A combined process/resource model for shop floor simulation

The paper describes process and resource modeling capabilities of PRISM (process and resource model-based intelligent simulator). The former allows users to model nonlinear process plans that contain all possible routings through the processes in the shop, decision-making rules associated with those routings, and precedence relationships among the processes in those routings. The latter allows users to define all of the properties of shop floor resources and decision rules associated with those resources.

Petri-net-based rapid development of a task execution module of equipment controller for distributed shop floor control

Abstract Although many conceptual structures for shop floor control have been proposed, their implementation methodologies have not been satisfactorily achieved yet due to the cost and time required for developing new control software and modifying the existing software. This paper suggests a Petri-net-based tool to rapidly develop a task execution module in the equipment controller for distributed shop floor control. To develop a task execution module, the users have only to build an extended Petri-net model to represent information on how to control the equipment device. The C++ code of the task execution module for intra-activities is then automatically generated from the developed model and plugged into the equipment controller. A prototype task execution module exemplifies that an equipment controller can be constructed or modified easily by adding/deleting several modules in the proposed framework. Consequently, the proposed tool will help the distributed shop floor control system adaptively evolve according to various control environments.