Sadashiv Adiga

A heuristic rescheduling algorithm for computer-based production scheduling systems

Generation of new production schedules in response to changes that take place on a factory shop-floor is a common requirement in todays complex and flexible manufacturing environment. The current approaches use either a regeneration rescheduling method, which results in unsatisfactory response times or methods that need too much manual intervention for identifying the operations to be changed. We propose a new rescheduling algorithm to address these problems. Our algorithm is based on the construction of a scheduling binary tree and a net change concept adopted from MRP system. It revises schedules by rescheduling only those operations that need to be revised. Our algorithm can be embedded in existing simulation-based scheduling systems or electronic Gantt chart approaches to improve their effectiveness.

Software modelling of manufacturing systems: A case for an object-oriented programming approach

With the recognition of the importance of Computer Integrated Systems (CIM) in improving manufacturing productivity, there is a pressing need for good software modelling approaches to support efficient design and control of manufacturing systems. Software design concepts based on Object-Oriented Programming (OOP) are emerging as powerful techniques for developing large scale software systems. This paper presents important features of object-oriented computing and the relevance of such an approach in modelling and developing software for manufacturing systems.

Object-oriented modeling and implementation of control software for a robotic flexible manufacturing cell

Abstract This paper discusses the development of an object-oriented software for the control of a robotic flexible manufacturing cell (FMC). The control software is based on a formal modeling of the entities involved in a cell and their interactions. An entity-relationship model, message flow diagrams, and state transition models are used to specify the software objects needed to model the operation of an FMC. In an object-oriented approach, the cell controller takes care of coordination and synchronization issues while the individual objects are responsible for their own activities. This approach has numerous advantages over the conventional state transition method where the number of state grows exponentially with the increase in cell components and complexity of control tasks. Implemented in Turbo C++ on an IBM PS/2 computer, the software can accommodate cell configuration changes, such as the number of machines, without reprogramming. Robot dispatching rules that are independent of the cell configuration were developed for handling the simultaneous setups, prevention of order sequence interference and batch break-up situations that are often encountered in FMC control.

Enterprise integration modelling: a review of theory and practice

Abstract A survey of the theory and practice of enterprise integration modelling (EIM) is presented. The emphasis is on the presentation of ideas that are useful for EIM implementations. Clear and concise definitions of the main concepts are presented. These ideas serve as the basis for a discussion of various EIM reference architectures. Important potential research issues and obstacles are identified and a few prototype systems analysed. The paper concludes with guidelines for EIM implementations, and suggestions for modifications to the current approach.

Object-oriented software modeling of a Flexible Manufacturing System

Flexible Manufacturing Systems play an important role in improving our manufacturing productivity. Simulation is emerging as a popular tool in modeling FMS for analyzing its performance in the area of production planning/scheduling. In this paper, we illustrate how to model a Flexible Manufacturing System in the object-oriented paradigm using an example. We present a systemtic approach to the design of object-oriented programming systems based on a combination of data modeling and event analysis techniques.An entity relationship approach is used as the basis for an initial decomposition of the system into objects. The design is refined by an analysis of the events the objects participate in. The design is implemented in Objective-C. Finally, we describe ways in which this model of an FMS can be extended to explore popular research questions in production planning and scheduling.

Measuring manufacturing work group autonomy

The increasing use of autonomous work groups in manufacturing industries has been accompanied by a growing confusion over exactly what group autonomy connotes. Our intent in this paper is to provide clarity to the quantitative measurement of work group autonomy. An examination of classic case studies from the group literature reveals how group autonomy has been conceptualized over time, while highlighting the absence of more modern-day concerns in areas such as equipment maintenance and quality improvement. In attempting to objectively assess the degree of autonomy held by work groups both in the classic studies and in a modern high-technology industry, we find that the existing measurement instrument fails at the latter. A new more finely grained measuring instrument is introduced that covers decisions in the areas of methods, scheduling, task allocation, resource allocation and management, goals, and boundary management. Items on the instrument address topics in performance evaluation, training, equipment maintenance, group membership, and production, among others.

Design and scheduling of flexible assembly lines for printed circuit boards

A particular approach for the design of printed circuit board assembly lines integrated with a scheduling methodology is proposed. The goal of the design and scheduling methodology is to maximize the throughput of the system while keeping work-in-process inventory levels to a minimum. The proposed design is based on the notion that it is easier to control and schedule flow lines than general production lines because for a flow line the scheduling problem is reduced to a sequencing problem. Experimental results of the proposed approach for an electronics manufacturer suggest that by implementing the approach the company can reduce inventory and achieve high throughput levels.

An Object-Oriented Architecture for Knowledge-based Production Scheduling Systems

This paper describes an object-oriented architecture to support decision making in production scheduling environments. An object-oriented world view is used to integrate concepts from discrete event simulation, conventional scheduling logic and artificial intelligence to produce capacity-feasible schedules. The architecture was implemented as a collection of loosely coupled reusable software objects by extending the functionality of software objects from BLOCS/M (Berkeley Library of Objects for Control and Simulation of Manufacturing). Our experience with an industrial prototype is presented.

Object-oriented modeling and simulation of neural networks

The field of neural networks is being investigated by many researchers in order to provide solutions to difficult problems in the area of manufacturing systems. Computer simulation of neural networks is an important part of this investigation. This paper applies concepts from an important trend in software engineering research, namely object-oriented programming, to model neural networks.The design and implementation of a software object library is crucial to obtaining the full benefits of object-oriented programming. In this paper we discuss the design and implementation of a foundation library of software objects for the purpose of simulating and validating different network architectures and learning rules. The library contains objects that implement various types of nodes and learning rules. We discuss the results of our experiments to illustrate the benefits of using an object-oriented approach to modeling neural networks.