A new FMS architecture based upon networked DSP servo technology

This paper presents a critical evaluation of existing FMS architectures and the academic and industrial design and development strategies used during their formulation. The paper seeks to address the need for, and value of, existing architectures within the industrial arena. More importantly however, this paper puts forward a new two-tier distributed control architecture for FMS based upon new (real-time) networkable DSP servo control methodologies developed by one of the authors for Softronics in Australia. The ramifications of these methodologies are substantial, not only in terms of FMS control, but in the overall simplification of such systems and the development of flexible fixturing devices over the coming decade. This paper also postulates on how new FMS architectures can be developed from such technologies and details why such architectures could be more appropriate to industry needs than those that are currently in existence.     

Pushing a Disk Using Compliance

This paper addresses the problem of maneuvering an object by pushing it through an environment with obstacles. Instead of only pushing the object through open areas, we also allow it to use compliance, e.g., allowing it to slide along obstacle boundaries. Using compliance has a number of advantages: it extends the number of situations in which a manipulation plan can be found, it allows for simpler (i.e., less complicated) paths in many cases, and it often helps solving narrow-passage problems. Here, we present an approach based on rapidly-exploring random trees. Our approach yields paths through the open space, but also exploits the power of compliance.     

Searching for empty convex polygons

A key problem in computational geometry is the identification of subsets of a point set having particular properties. We study this problem for the properties of convexity and emptiness. We show that finding empty triangles is related to the problem of determining pairs of vertices that see each other in a star-shaped polygon. A linear-time algorithm for this problem which is of independent interest yields an optimal algorithm for finding all empty triangles. This result is then extended to an algorithm for finding empty convex r-gons (r> 3) and for determining a largest empty convex subset. Finally, extensions to higher dimensions are mentioned.The first author is pleased to acknowledge support by the National Science Foundation under Grant CCR-8700917. The research of the second author was supported by Amoco Foundation Faculty Development Grant CS 1-6-44862 and by the National Science Foundation under Grant CCR-8714565.     

Maintaining range trees in secondary memory

Summary When storing and maintaining a data structure in secondary memory it is important to partition it into parts such that each query and update passes through a small number of parts. In this way the number of disk accesses and the amount of data transport required can be kept low. In Part I of this paper a number of partition schemes were given for partitioning range trees. In this paper we study lower bounds for partitions. In this way we prove that many of the partitions given in Part I are optimal.Supported by the Netherlands Organization for Scientific Research (NWO)     

Hybrid FMS control architectures based on holonic principles

The escalation in processor technologies and the corresponding reduction in costs have enabled alternative FMS control architectures to be developed without the restrictions of fixed machine controller boundaries. These new architectures can be based upon the use of intelligent servo axes, which are desccribed in this article, as flexible numerical control (FNC). In current parlance, the FNC is a part movement holon within a manufacturing cell. The control architectures that can be derived from the FNC concept are referred to as hybrid architectures and share the emerging attributes of holonics. This article details the problems that arise in the scheduling and control of FMSs in the light of hybrid control architectures. A number of traditional scheduling approaches have been devised to cope with the scheduling of parts to discrete machines, but the problem here is to ascribe the processing (machining) of part features to axis groups. This article documents how two research programs, undertaken at the CIM Centre at Swinburne University of Technology in Hawthorn, Victoria, Australia, have endeavored to address the problem of hybrid architectures and their associated scheduling.     

Learning object-oriented design by creating games

Playing computer games is a popular recreational activity for young people. Creating a state-of-the-art commercial computer game is an incredibly difficult task. Writing a game like Pac-Man from scratch in a modern programming language is still difficult. Fortunately, several currently available tools make game creation easier. These tools can be used to create more complex games, but they offer only limited programming possibilities. Many similar packages exist. One such program is Game Maker, which is a rapid-application development tool. The Game Maker interface uses an object-oriented, event-driven approach. With Game Maker's drag-and-drop techniques, users can create games without writing a single line of code. But the program also includes an interpreted programming language. The program produces stand-alone games that can be distributed freely: a version of Game Maker, itself, is available for free as well.