Shop Floor Control System Research Articles

Process planning interface for a shop floor control architecture for computer-integrated manufacturing

Many researchers have developed ‘standard’ computer-integrated manufacturing architectures in order to reduce the cost associated with software development and maintenance. Since a process plan provides the principal input to a Shop Floor Control System (SFCS), it is necessary to provide the process plan information in a manner suitable for use by the SFCS. However, research in interfacing process planning with different SFCSs has been extremely limited. The reason for this is that proper integration hooks and a generic vision for process plans do not exist. A deterministic description of what process plans are, and how they should be represented is yet to evolve. We describe an information interface between process planning and shop floor control. The functionality, scope, and information content of process plans are discussed in order to provide a clear functional distinction between process and planning and shop floor control. An information architecture for interfacing process plans and SFCSs built. T...

Integrating Scheduling in Logistic Systems for Batch Production

For closing the gap between business-oriented information systems and shop floor control systems in the process industries, industry-specific standard software for production planning and scheduling is needed. The compared results of five case studies in different batch-oriented companies show that there are many requirements in process industries which are not met by today's standard software. The paper summarizes the different problems and needs found in each case study. Common findings are compared and requirements for scheduling systems and their integration into logistic systems are developed.

Shop Floor Control Systems: From Design to Implementation.

Shop Floor Control Systems: From Design to Implementation.

Shop Floor Control Systems: From Design to Implementation

"Shop Floor Control Systems: From Design to Implementation." Journal of the Operational Research Society, 46(8), pp. 1035–1036

The design of a line control system for the modular furniture industry

This paper describes the design and development of a low cost shop floor control system for the modular furniture industry. An architecture in five hierarchical levels has been selected. An overview of the functions performed by line and workstation levels are described, likewise that information system part related with the control system. A detailed discussion about line level is presented and principally the incorporation of a Schedule Manager, based on an expert system. The proposed line level architecture and the software tools used in its implementation give a greater flexibility to the line control system.

A formal functional characterization of shop floor control

Shop-floor control systems for discrete part manufacturing have been widely described by many researchers. These descriptions have led to several proposed frameworks to solve the overall shop floor control problem. Some terms commonly used to describe these frameworks include: centralized control, hierarchical control, heterarchical control, and hybrid control. However, these frameworks have not provided a formal generic vision of shop floor control. Rather, they have concentrated on specific implementations of the problem, or small classes of similar implementations. As a result, the frameworks which have been developed are applicable only to a subset of the problem domain. By contrast, a solution to the general shop floor control problem is highly desirable. It is only after the general shop floor problem is understood that such a general solution can be developed. In response to this need, this paper presents a formal functional characterization of the general shop floor control problem. Key to our functional characterization of the controller is the use of process plans as part of the control. We use a process plan representation model compatible with the ISO TC184/SC4/WG3/P11 proposed standard as part of the control input. The ISO process plan model is converted to a digraph which provide the task representation for control. In this paper, we illustrate how these digraphs provide the essential requirements for input to and for a functional characterization of shop floor control.

Assessing the impact of reducing demand variance through improved planning on the performance of a dual resource constrained job shop

This paper examines the role that both the planning and shop floor control systems play in the operation and performance of a dual resource constrained (DRC) job shop. Using causal analysis, the results show an effective planning system, as it accounts for the largest gain in shop performance. Generating and releasing smoothed schedules (work loads) allows the use of simplified shop floor control procedures such as Order Review/Release (ORR), job dispatching and labour assignment rules without adversely affecting performance. This study uses the results to resolve the current paradox surrounding ORR systems and shows that the ORR rules' performance is strongly dependent on the planning system, and that ORR rules can be considered moderating variables. Further, the study develops a variance control framework that indicates the necessary managerial actions to improve shop performance. This paper demonstrates that the planning system, not the shop floor control system, is the major determinant of shop perfor...

Toward a method for acquiring CIM ontologies

Abstract An important requirement for world-class CIM systems is the ability to capture knowledge from multiple disciplines and store it in a form that facilitates re-use, sharing, and extendibility. Taxonomies and glossaries, in and of themselves, will not fully address this requirement, and will need to be supplemented so as to circumscribe the meanings and logical properties of the terms as precisely as possible. We thus perceive the need for ontologies rather than mere taxonomies. An ontology is a description of the kinds of things, both physical and conceptual, that make up a given domain and the relationships among them as represented by the terminology in that domain. This paper describes a scientific method for acquiring, structuring and maintaining CIM ontologies. An ontology capture method is essential to developing practical CIM ontologies because it facilitates the direct capture of CIM knowledge by practitioners within the manufacturing domain. The proposed ontology capture method includes: (1)A graphical language to support conceptual ontology analysis. (2)A structured text language for detailed ontology characterization (3)A systematic procedure that provides guidelines for effective ontology capture. Finally, the utility of the method is demonstrated by describing how the method is used to develop an ontology of a shop floor control system

The design of a capacity requirements planning system for flexible manufacturing systems

Abstract The operating and manufacturing characteristics of a flexible manufacturing system (FMS) mean that a traditional planning procedure of material requirements planning (MRP) and capacity requirements planning (CRP) cannot be followed. Thus the planning works between the master production schedule and the shop-floor control (SFC) systems are analysed and reassigned to the MRP, CRP and SFC systems. A CRP system designed for FMS is presented in this paper. It determines the requested capacities by carrying out part type selection, batch size determination and process plan selection, and by estimting tool slot requests. If there is insufficient capacity, the CRP system calculates the overtime hours required to complete the production of demand quantity for a specified part type.

Intelligent workstation controller for computer-integrated manufacturing: Problems and models

A shop floor control system (SFCS), an integrated part of computer-integrated manufacturing, oversees the production required to fill orders. To effectively control these activities, it is necessary to define a control architecture and functional perspective of how a SFCS operates. In this paper, a hierarchical SFCS (shop, workstation, equipment) is adopted. The paper presents the problems and models necessary to develop an intelligent workstation controller (IWC) at the middle level of a SFCS. The IWC is responsible for selecting a specific process routing, allocating resources, scheduling and coordinating activities across the equipment, monitoring the progress of activities, detecting and recovering from errors, and preparing reports. The IWC fulfills this responsibility using three functions—planning, scheduling, and execution. Requirements for the development of the IWC are to create a process plan representation model, specify the evolution of a process plan from the shop down to the equipment, and define all of the functions to be integrated into an intelligent controller. A deadlock detection and resolution model is also presented to maintain the system in a deadlock-free state. Finally, the IWC software is created to demonstrate the architectural linkages with other controllers. As a result, the development of the IWC will save cost and time in developing control software for automated manufacturing systems.

Production control for just-in-time tool-and-die manufacturing

Abstract The strategy to implement production control varies in different types of manufacturing systems. We address the issue of production control in unit-based manufacturing systems where the production batch size of the final product is one or two, the product is custom designed and is made up of numerous individual components with similar process routeings lor special machine tools, turbines, boilers, tool-and-die, injection moulding equipment, custom fabrication, etc. We have developed algorithms to generate master production schedules in this particular domain of manufacturing systems using the concept of workgroups. We show how a Kanban-based JIT shopfloor control and purchasing system can be implemented in such systems in tandem with an inventory management system by utilizing the concept of demand lists. We also propose a model for practical implementation of production control in this domain. The methodology is illustrated at a tool-and-die plant where a CIM software is used to apply the JIT-ba...

Order Control by a Hierarchical, Self-Organizing Computer System

Job processing on the typical shop floor is normally influenced by technical or organizational dependent disturbances. Due to growing efforts to meet the customers' demands with respect to short notice changes to orders (product variants and delivery dates), MRP-systems and subordinate shop floor control systems such as scheduling systems have to deal with these disturbances. This forms the basis for a new approach to order control systems implementing cascaded control loops starting with customers' orders and regarding the aspects of real-time rescheduling, process plan alternatives as well as simulating the impacts on future machining and delivery shop order sequences. Reactions to disturbances are offered by a knowledge-based module. This paper describes a concept to help solve the problems encountered by the subcontractor. This concept is based upon a hierarchically organized distributed computer network enabled to reorganize itself in case of a computer or interface failure.

Conceptual design of a shop floor control system from IDEF0

An approach for designing a shop floor control system is proposed in this paper. In this approach, the IDEF 0 model, Biemans' model, and the Phillips' CAM model are three major technologies used for determining the control request, control classification, and the control allocation. This approach has further been applied to propose a real shop floor control system in Taiwan, whose discussion is presented at the end.

Information system architecture for heterarchial control of large FMSs

In this paper we investigate the design of a distributed information management system for heterarchical (decentralized) shopfloor control in large Flexible Manufacturing Systems (FMS). We characterize the complexity of information management in automated manufacturing, and study the interaction between the shopfloor control system and the information management system. We describe protocols for a heterarchical control scheme, and identify the information content of messages that are transmitted between autonomous manufacturing system entities under this control paradigm. On the basis of the proposed shopfloor control protocols and the information requirements at each type of manufacturing system entity, we develop an information system architecture that is capable of supporting heterarchical shopfloor control in large FMSs.

A robust adaptive scheduler for an intelligent workstation controller

A shop floor control system (SFCS) consisting of three hierarchical control levels (shop, workstation, and equipment) is described. Each controller plans, schedules, and executes the activities necessary to process an order. An intelligent workstation controller (IWC), which is a part of the SFCS, is described in detail. The 1WC receives information such as part type and quantity, part routeing specifications, and process plans from the shop level controller and coordinates production activities. The IWC performs three main functions—planning, scheduling, and execution in real-time in order to ensure completion of jobs assigned by the shop controller. The focus of this paper is to develop a robust adaptive scheduler to support the IWC which fits within the functional SFCS architecture. The objectives of this paper are: (1) to develop a neural network model that generates several part dispatching strategies based on workstation status; (2) to develop a mutti-pass simulator that evaluates the generated stra...

Communication and control in small batch part manufacturing

This paper reports on the development of a real-time control network as an integrated part of a shop floor control system for small batch part manufacturing. The shop floor control system is called the production control system (PCS). The PCS aims at an improved control of small batch part manufacturing systems, enabling both a more flexible use of resources and a decrease in the economical batch size. For this, the PCS integrates various control functions such as scheduling, dispatching, workstation control and monitoring, whilst being connected on-line to the production equipment on the shop floor. The PCS can be applied irrespective of the level of automation on the shop floor. The control network is an essential part of the PCS, as it provides a real-time connection between the different modules (computers) of the PCS, which are geographically distributed over the shop floor. An overview of the requirements of such a control network is given. The description of the design includes the services developed, the protocols used and the physical layout of the network. A prototype of the PCS, including the control network, has been installed and tested in a pilot plant. The control network has proven that it can supply a manufacturing environment, consisting of equipment from different vendors with different levels of automation, with a reliable, low cost, real-time communication facility.

A review of: “Shop Floor Control Systems.” By A. BAUER, R. BOWDEN, J. BROWNE, J. DUGGAN and G. LYONS (London, Chapman and Hall, 1991) [Pp. xx + 344] Price £35·00.

A review of: “<i>Shop Floor Control Systems.</i>” By A. BAUER, R. BOWDEN, J. BROWNE, J. DUGGAN and G. LYONS (London, Chapman and Hall, 1991) [Pp. xx + 344] Price £35·00.

DESIGN OF A KNOWLEDGE-BASED ON-LINE SIMULATION SYSTEM TO CONTROL A MANUFACTURING SHOP FLOOR

In this paper, the design principles of a new knowledge-based on-line simulation (KBOLS) architecture for the purpose of integrating the supervisory decision making process with a shop floor control system is discussed. The requirements for implementing the KBOLS architecture in a computer integrated manufacturing environment are presented. The special features of the KBOLS architecture include a knowledge-based controller capable of interacting with the shop floor and a manufacturing simulator, a shared blackboard data structure for knowledge bases, and a learning module. The KBOLS architecture is implemented in a flexible manufacturing system for analyzing interruptions due to machine breakdowns and rush orders.

Production-Monitoring Integration in Planning and Control of FMS

Running of flexible manufacturing systems (FMS) has pointed out an acute requirement of the production-monitoring function (PM). The system presented in this paper integrates the PM function into the FMS control and management all within a global architecture. Indeed the decisional system is assumed to be hierarchical. A new cooperation protocol among the various levels is modeled by means of an interpreted colored Petri net (ICPN) thanks to a sensitivity range concept associated with each level. The shop floor control coordination is also ensured by an ICPN. Finally, in order to link both the decisional and the shop floor control systems, every component of the whole system is regarded as an object and the objects communicate via messages (objected-oriented design). Daemons allow the system consistency and some of them are defined thanks to the sensitivity range notion. Using ICPN and object-oriented models together has many advantages, especially simulation possibility (including the decision system), homogeneity and extensibility.

A Benefits Study of Ergonomically Designed Chairs with Direct Labour Employees

Focuses on measuring changes in productivity related to ergonomic improvements. Although most ergonomic studies focus on health benefits, describes a project which used a “real‐time shopfloor control system” to collect objective data to determine what effect, if any, the use of ergonomically designed chairs have on the productivity of apparel‐manufacturing employees. Subjective (interview) and objective data were collected in two apparel plants over a period of several months. Both “before” and “after” data were analysed to discover if fatigue or other factors related to productivity were changed.