Showing papers in "Robotics and Computer-integrated Manufacturing in 1987"

Non-hierarchical control of a flexible manufacturing cell

Abstract: As hierarchically controlled computer-integrated manufacturing systems growthey tend to become complex and their designability, maintainability, expandability and fault tolerance deteriorate. As an alternative, herterarchical control architectures offer prospects of reduced compexity, reduced software development costs, high modularity, high flexibility, and improved fault tolerance. By locating decision making where information originates, global information is reduced to a minimum, scheduling becomes dynamic, machines and parts become “intelligent” entities that cooperatively interact, and the overall system is decomposed into functionally simplified, modular parts. Three flexible machining cell control systems have been constructed at the University of Wisconsin-Madison and are described in this paper: a centralized controller, a hierarchical controller with dynamic scheduling, and a fully distributed heterarchical controller with “intelligent parts”. Comparative results are reported showing that the heterarchical approach possesses a number of advantages including increased fault-tolerance, inherent adaptability and reconfigurability, decreased complexity, and reduced software development cost.

Applying AI in jigs and fixtures design

Abstract: In process planning, the correct selection of fixtures and work holding devices represents an important specification in addition to cutting tool requirements. The arrival at an appropriate fixture design traditionally consists of several phases: careful study of a product specification, retrieval of any existing similar designs, and manual selection of fixture elements based on catalogues and items available in the shop. This procedure depends largely on the knowledge and experience of a tool designer and is both time-consuming and expensive. In addition, manual design procedure does not lend itself readily to computerization. This paper reports the development of fixture design procedure using artificial intelligence. The basic fixture elements are divided into three essential categories: clamping elements, positioning and guiding elements, supporting and base elements. A knowledge-based program structure is used to decide on the appropriate fixture with respect to a particular workpiece specification. The drawing of the elements is then parametrically constructed with an interface program calling standard commands from a drafting package. The elements are assembled interactively to form the final description of the fixture.

An expert system for process planning

Abstract: Fully integrated manufacturing systems, the ultimate goal of today's production engineering research, cannot be realized without automated process planning systems. A knowledge-based expert system incorporating heuristic algorithms as well as analytical and empirical models and which can thus provide a partial replacement for human expertise is the only key to automated process planning. This paper presents an attempt to develop an expert system for automatic process planning using artificial intelligence. In this system, a structural database was incorporated with a knowledgebase for the execution of rules. The programs developed are user-friendly and highly interactive. They allow dialog between the system and the user and require only that the operator answer questions in a familiar workshop language.

Decision support in design and optimization of flexible automated manufacturing and assembly

Abstract: Aide a la decision pour la conception et optimisation des systemes automatises flexibles de fabrication et de montage

An expert system for scheduling in a flexible manufacturing system

Abstract: The use of artificial intelligence techniques has been investigated as a contribution to a solution to the following problems: daily estimated scheduling in a FMS, and real time control of production disturbances. We present our investigation in object oriented languages to represent the relevant information of a scheduling problem, particularly knowledge about constraints and flexibility factors in a shop. We detail the off-line daily scheduling prototype SOJA and the reactive capabilities we are incorporating in it to repair previous schedules with respect to real-time situations. The integration of automatic generation and modification of schedule plans leads us to introduce a coordination level which generates an admissible solution and a local, cooperation level which deals with local modifications of the plan.

Evaluation of FMS: State of the art regarding how to evaluate system flexibility

Abstract: The evaluation of FMS becomes very important in accordance with the advancement of FMS technology. The evaluation method so far employed is the economical justification; however, it should be improved so as to enable the system flexibility to be simultaneously evaluated. Thus, this paper describes the reviewed results on the present trend of system evaluation, putting the main stress on the technology regarding the evaluation of system flexibility.

Knowledge based synthesis system for injection molding

Abstract: Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1985.

Robot simulator in TIPS/Geometric Simulator

Abstract: With the growth of factory automation, the need for off-line robot programming is increasing rapidly. Off-line programming requires a robot simulator. This is the reason for the development of a TIPS/GS (Geometric Simulator), accompanied by a robot simulator. TIPS/GS has been developed as a project in the TIPS Research Association. The goal of this project is to extend the functions and applications of the solid modeler TIPS-1. Four simulators (i.e. the assembly simulator, engineering, NC simulator and robot simulator) have been developed for these extended applications. The robot simulator described in this paper has the following special features: • • When a robot motion is prescribed by the VAL-G language, the result can be seen on a CRT display in several patterns. • • High-speed dynamic display which can almost keep up with real-time movements. • • A shaded as well as wire-frame picture is used for the high-speed display entioned above. • • Supported by the solid modeler, any robot and environment can be used with this system. • • The preparation of a precise interference checker based on an analytical methods. This paper is a report on the development of the robot simulator.

A simulation study of automated guided vehicle dispatching

Abstract: This paper reports a simulation study to investigate the relative performance of five automated guided vehicle (AGV) dispatching rules. The study found that distance-based rules are most effective while AGV attribute-based rules are least effective. Both AGV speed and the number of AGVs in use are factors critically affecting the performance of a flexible manufacturing system. This paper demonstrates that computer simulation is a viable tool for assisting FMS design and evaluation.

Flexible manufacturing cells and systems with computer intelligence

Abstract: When in 1983 the first flexible manufacturing cells with computer control and a fully automatic supply of tools were presented at the EMO in Paris, a lot of people had not yet recognized that this introduced a trend-setting development (Fig. 1). In the meantime, this cell concept is generally viewed as the most expedient way to get into flexible automation for the boring, drilling and milling of prismatic workpieces. There are already several such computer-controlled manufacturing systems in practical use, and a large number are planned for the immediate future. This company alone, which the author is part of, has built more than 50 systems of different sizes but with the same basic design. Most of the users are medium-size plants whose main objective is to reduce production costs and achieve higher conversion flexibility.

Dynamic routing in reentrant flexible manufacturing systems

Abstract: Consider a flexible manufacturing system (FMS), with several parallel production lines. Each line is statistically balanced. Due to process time and yield variations, some workstations may be temporarily starved of parts during the FMS operation, while others may have too many. The purpose of the dynamic routing algorithm described here is to achieve real-time load balancing in a stochastic processing environment and thus to increase the performance of the system in throughput, workload balance and reduced work-in-process queues. We formulate the problem and develop an optimal stationary policy (for two lines that have a material handling transport between them) based on the input buffer state of each station.

CIM: Competitive edge in manufacturing

Abstract: The factory of the future will be formed by a new generation of mechanical technology, computer-based information systems and electronic process controls. Innovations in information technology provide the chief impetus for new kinds of corporate-wide integrated information systems. Existing islands of automation will be integrated to form an organizational structure which will avoid the current production bottlenecks. CIM systems will significantly influence productivity and flexibility and thus will be the main determinant of profitability and competitive edge.

Representation of FMS with Petri Net graph and its application to simulation of system operation

Abstract: This paper describes a newly developed software program with its simulation results for a machining shop of FMS (Flexible Manufacturing Systems), which has features of discreteness and concurrency. To overcome these difficulties, we adopted an event-driven structure for a program by employing a Petri Net graph to depict all operational states and transitions. The simulation program outputs necessary and sufficient results of this discrete and concurrent system in a short execution time by a popular computer of a sequential machine.

Knowledge engineering within integrated process planning systems

Abstract: The use of knowledge-based systems in the product development process will support the process planner as well as the designer. The process planner needs real expert consultance and for the designer manufacturing information must be available during the design process. This paper outlines some recent work in the development of a knowledge-based drilling operation planning system at IPK, Berlin.

Applicability of expert systems to flexible manufacturing

Abstract: The following report will discuss the applicability and impact of knowledge-based systems in flexible manufacturing using the Integrated Manufacturing and Assembly System at the Machine Tool Laboratory (WZL), Technical University of Aachen, as a potential application case.

Descriptive methods for computer-integrated manufacturing and assembly

Abstract: Modeling techniques are used to study and analyze the structure and the dynamic behavior of computer-integrated manufacturing and assembly systems, both during the planning and the operational stages This paper discusses the requirements to be fulfilled by descriptive means for such modeling purposes Different modeling approaches, various classifications and examples of other approaches are also discussed

EXMAS—Knowledge based system for maintenance of complex mechanical systems

Abstract: EXMAS is a Knowledge Based System for Integrated System Maintenance Complex Mechanical System (EXMAS being an abbreviation for: Expert Maintenance System) It is part of a complex DESIGNER expert system, which is currently under development at the Department for Production Engineering Department of the Faculty of Mechanical Engineering in Belgrade The theoretical approach for the DESIGNER expert system is the theory of automata applying artificial intelligence tools The knowledge block is introduced as a structure of the man-machine cybernetic entity Basic engineering activities in the integrated system of maintenance are: computer aided design for maintenance, computer aided maintenance technology design, and computer aided maintenance planning and control This paper gives several parts of this expert system

AI tools for intelligent manufacturing

Abstract: Conventional software tools are inappropriate for the representation of several important features of engineering knowledge. This paper outlines these features and discusses the applicability of several Artificial Intelligence techniques.

Algorithmic representation of work cells and task description for off-line programming

Abstract: Representation algorithmique d'une cellule de travail et description des tâches en vue de la programmation hors ligne

Functions required for advanced flexible manufacturing systems

Abstract: This paper describes the concept and functions of multilevel supervisory systems aimed at a more efficient operation of advanced flexible manufacturing systems. A supervisory system consists of a control system, an adaptation system, a process monitoring system and a machine failure diagnosis system. Thus supervisory system assure the control of machining accuracy, the detection of human errors and tool breakage, and the identification of machine failures. This paper presents some successful results of the implementation of these subsystems.

Impact of Automation on Process Control Decision-Making

Abstract: This paper investigates changes in the process control of a vehicle assembly plant which had been modernized from a principally manual procedure to one that uses programmable automation extensively. Process control is defined as the information flow and decision-making required to perform basic process operations. We investigate the effects of implementing a computer-integrated production system on the amount and types of process control decision-making and on the distribution of process control decision-making between humans and machines. After automation, the emphasis on decisions regarding product quality specifications increased and the emphasis on decisions related to flexibility in handling a variety of product options decreased. Decisions concerning product quality specifications, as well as timing and synchronization of tasks, were usually performed by automated equipment, while decisions relating to the flexibility of the process remained, to a large extent, under manual control. Whereas humans made nearly 75% of the decisions required to assemble and weld a vehicle body in the principally manual system, humans made fewer than 10% of similar decisions in the automated system.

Robust adaptive axis control of manipulator

Abstract: A robust adaptive control scheme is presented in this paper for the control of the independent axes of a manipulator which have uncertainties in parameters and disturbances. The robustness is achieved by applying the Model Reference Adaptive Approach in order to obtain the adaptive laws which do not require the exact knowledge of parameters or payloads and disturbances. Both the second and third order model axes powered by a DC motor are taken into account. Results of digital simulation show that the rotation of the controlled axis follows exactly that of the desired model in spite of the wide range of changes in parameters and payloads.

An integrated approach to CAD/CAPP/CAM based on Cell-Constructed-geometric-Model (CCM)

Abstract: Approche integrale pour les systemes de conception, ordonnancement et fabrication assistes par ordinateur. Utilisation d'un modele geometrique construit a partir d'une cellule elementaire

Robot system integration into computer-integrated manufacturing

Abstract: Industrial robotics has proved to be a key technology for flexible automation in manufacturing and assembly. The prime emphasis for future research will concern the integration of robots into computer-integrated manufacturing (CIM) systems. In this paper a research project on the “Operational Control of Robot System Integration into CIM” will be presented. The main components of this project are the development of a computer-aided planning system and the establishment of an offline programming system for robots. The interrelationship between these two areas will be discussed as well.

Robot applications supported by CAD simulation

Abstract: Employing a CAD simulation system to assist with the processing of robotics projects enables the detection of many problems at a significantly earlier stage than previously, i.e. before the start of production and assembly. The first section of this paper explains the requirements to be met by the simulation system. A description of the system employed at KUKA follows. Finally, a report is given of practical applications of the simulation system which have been carried out within the company.

Safety in robotic installations

Abstract: The rapid growth of the robotic industry has made it imperative to consider more seriously the safety aspects of robotic installations. Some work has been initiated recently in this area; a standard proposed by the Robotic Industries Association is a step in the right direction. This paper is based on an investigation of the state of the art in robotic safety, and contains an analysis of the sources of accidents, and the accident-prone operational phases of robotic installations. It forms the groundwork (literature survey) of a research project at the University of Windsor to develop a hardware/software-based safety system. It is suggested that both the robot manufacturer and the user should regard robotic safety as an important consideration.

A model-based vision system for industrial parts using a small computer

Abstract: A model-based vision system has been successfully implemented in a small computer environment. This approach uses a basic solid modeling system to develop three-dimensional models of mechanical parts. From those models, two-dimensional projections are taken for every stable state of the object, with many orientations around the object's vertical axis for each stable state. These two-dimensional projections are treated as synthetic binary images, from which a variety of features may be measured and extracted. A similar procedure is used for a binary image of an object from a real scene, and features are also extracted for that image. A simple matching procedures uses the model-based feature sets to determine the real object's stable state position and orientation. This paper describes the system in detail and shows examples of its use.

Application of expert systems to process control

Abstract: This paper describes the EXTASE system, an expert system for alarm processing in the vacuum distillation tower of a refinery. The system is able to find the cause(s) of an active alarm as well as the dependencies between alarms that were originated by the same disturbance in the process. Starting with an analysis of the operato's activity while performing information synthesis tasks, a computer model is abstracted. This model is based on a very simple hypothesis-driven search strategy. The search relies on causal relationship called “couplings” which encode the operator's basic knowledge about the behavior of the process. This approach allows the system to account for possible sensor failure in the diagnosis of process alarms.