Per Gullander

Overview of simulation tools for computer-aided production engineering

Due to increasing demands on efficiency, quality, and flexibility in manufacturing companies today, it has become very important to structure the development process of manufacturing systems. This process, for example, could be supported by using models, architectures, and simulation tools. The purpose of this paper is to outline the background to simulation in manufacturing engineering and give an overview of simulation software tools used for Computer-Aided Production Engineering. The paper discusses the features that are most important to consider before investing in such tools. A comprehensive overview of commercial simulation software tools is presented and future areas for research and development are discussed.

Towards a Truly Flexible Manufacturing System

Abstract This paper describes the concepts that must be considered in order to achieve a flexible manufacturing system that allows the introduction of new products and new resources without an extensive reprogramming of the control system. In contrast to most other approaches a bottom-up design is attempted. A control software structure based on generic resource models and the basic structure of a resource capability model are presented. A description of how to manufacture the products is also essential. Basic guidelines for a product model are given. Control algorithm aspects are discussed. Operator interface and system dependability are given consideration. Finally, a machining cell, used as a case study, is described.

Generic resource models and a message-passing structure in an FMS controller

This paper presents part of the results from a research project aimed at increasing flexibility and reusability of cell-control software. First to be discussed are the concept of flexibility and the advantages and disadvantages of various types of modular controllers. Then guidelines, generic models that describe the behavior of manufacturing resources, and a message-passing structure are given. The guidelines and the models should be used as the basis to support system developers when implementing modular control software for machining cells. The two main case studies examined to achieve the models are also briefly described.

Comparing quantifiable methods to measure complexity in assembly

In order to measure complexity and stay competitive, manufacturing companies need to be able to quantify production complexity. For this reason, two methods were developed within the context of two concurrent research projects are compared: the Belgian Complexity Calculator, CXC, measures objective complexity and the Swedish Complexity Index, CXI, focuses on subjective complexity, as experienced by operators in the stations. This paper presents a comparative analysis of the two methods by comparing them to seven relevant existing quantitative methods and by examining results from case studies. It is observed that the two methods can be used as a compliment to one another, where CXC can be used for scanning data automatically CXI can be used for in-depth analysis. In addition, the comparison of existing methods provides insight on how to measure complexity depending on need and scope.

Validation of the complexity index method at three manufacturing companies

In order to manage increasing numbers of product variants, tools that can reduce or manage production complexity are vital. The paper describes CompleXity Index (CXI), an index-based method and tool that assess the complexity at an industrial workstation. CXI was validated at three Swedish manufacturing companies investigating how different roles affect the index calculation and if the method measures what was intended. In all three cases, CXI was seen as a useful tool that provided a holistic view of the problems seen at a station. In addition it was indicated that complexity and unbalanced work was connected and that the method could be used to predict problem areas on new stations.

Operator control activities in flexible manufacturing systems

Modern control systems often exhibit problems in switches between automatic and manual system control. One reason for this is the structure of the control system, which is usually not designed for this type of action. This article presents a method for splitting the control system into different control levels. By switching between these control levels, the operator can increase or decrease the number of manual control activities he wishes to perform while still enjoying the support of the control system. The structural advantages of the control levels are demonstrated for two types of operator activity; 1 control flow tracing; and 2 control flow alteration. These two types of operator activity can be used in such situations as when locating an error, introducing a new machine, changing the ordering of products or optimizing the production flow.

Database design for machining cell level product specification

To create a flexible machining cell control system a control algorithm is required that is based on models of products and resources. The scope of this paper is to present the database structure of a model used to describe products. Examples based on a case study of a machining cell are given.

Database Design for Flexible Manufacturing Cells

Abstract One very important aspect when designing modern manufacturing systems is flexibility, such as product flexibility, expansion flexibility and routing flexibility. This paper presents a reference architecture for control systems which has a structure that promotes flexibility. Since a control system is a highly information-intensive system it is very important that the information is stored in a suitable manner. One viable approach is to rely on a database system for the information storage. A database system has inherently a good separation between the structure of a design and the related data. This paper presents the conceptual information design of our generic control system and it is compared with a case study of an existing machining cell.

Exception Handling in a Flexible Cell Control System

Abstract An important aspect of modern manufacturing control systems is flexibility. A complication that must be considered when striving to achieve a completely flexible control system is the occurrence of faults. The structure of the control system must be such that new solutions to new error situations can be easily implemented into the existing structure. This paper presents a reference architecture of a manufacturing control system whose main feature is to provide flexibility. An important part in achieving this flexibility in the control system is the database implementation. The database is described with the help of an Entity Relationship model. The Entity-Relationship model is then extended to deal with error situations using a concept known as exception handling.

Database Design for Machining Cell Resource Models

Abstract To promote flexibility of manufacturing systems a reference architecture, CHAMP, has been developed at Chalmers University of Technology. It uses object oriented principles and a database to model separate parts of a production system. Here, the resource models of the control system and the corresponding parts of the database are explored and described. It is emphasised on the interaction between the internal resource objects, where a generalised handshake protocol is proposed.