Showing papers in "Robotics and Computer-integrated Manufacturing in 1985"

Intelligence and cooperation in heterarchic manufacturing systems

Abstract: During the past 30 years, our thinking about complex computer-controlled system has been conditioned by the concepts of hierarchic structures. Recent advances in distributed computing power and open system architectures (particularly local-area networks) have opened the way for heterarchic structures. Based on incomplete and non-algorithmic architecture specifications, these systems will have to exercise a high degree of local intelligence to cope with unforeseen situations. The distribution of information and of decision-making powers requires the development of new architectural tools to achieve cooperation between functions and the emergency transfer of functions. New modes of man-machine synergy and new synthesis methods for such systems are also necessary.

Robot performance measurements using automatic laser tracking techniques

Abstract: This paper describes two laser tracking techniques currently under development at the National Bureau of Standards for robot performance measurements. Tests indicate that the system can be used in real-time to determine the three-dimensional static and dynamic positioning accuracy of a robot end-effector to a few parts in 100,000 (i.e. 12.5–50 μm for a medium to large size robot), and wrist orientations to within 2 sec of arc. Both systems would be simple and compact enough to be considered as a general-purpose portable calibrating tool for robots (or CNC machines), or as an integral part of a robotic system providing real-time position feedback of the end-effector independent of the position and angle feedback of joint members. The ability to dynamically and statistically measure the position of an end-effector to the above accuracy has significant ramifications with regard to meaningful robot performance measurements, and the potential of these systems in other industrial and engineering applications.

Modelling manufacturing systems

Abstract: The traditional approach of extrapolating past experience in order to predict the performance of manufacturing facilities has been found to be quite inadequate for automated manufacturing systems. The need to identify the key factors influencing performance has led to the development of both simulation and analytical models to help in design, operation and control. The basic approaches to the development of such models will be outlined and illustrated with examples pertaining to assembly lines, automatic transfer lines, and flexible manufacturing systems. The value of formal models will be demonstrated by examples of the insights which can be gained through their use. The paper will conclude with a discussion of current research needs in both model development and model application.

Real-time monitoring system of tool breakage using Kalman filtering

Abstract: In this paper, a real-time monitoring system of tool breakage, which measures the cutting torque from the spindle motor current, is described. The system uses an auto-regressive (AR)-model which is adapted for the measured signal using the Kalman filtering technique. The tool breakage is detected by monitoring the residual, that is, the deviation of the observed signal from the estimated value obtained by the AR-model. Additional processing of the residual is introduced to discriminate the signature of tool breakage from the effect caused by the marked change in the cutting condition. To reduce the computation time, the fast calculation algorithm is adopted for estimating the coefficient vector of the AR-model. The monitoring experiment has proven the effectiveness of the system in a milling operation.

The proposed robot software interfaces SRL and IRDATA

Abstract: This paper discusses the research activities on robotics at the Institut fur Informatik III of the Universitat Karlsruhe, Karlsruhe, Federal Republic of Germany. The projects are directed towards the design of user-oriented programming systems and intelligent sensors and controls for industrial robots. The work includes: Development of a high order programming language for assembly robots, simulation of assembly systems, design of a polyprocessor controller for robots, conception of design rules for the integration of robots into CIM systems, development of vision devices and design of multisensor systems for manipulators.

Industrial robot with servo system

Abstract: An industrial robot has a servo system allowing higher-speed robot operation than in conventional robots. The servo system includes a movable arm or arms pivotable about a pivot axis or axes and/or movable along an axis or axes. The servo system includes at least one movable arm pivotal about a vertical axis and associated with a servo motor for angular displacement within a substantially horizontal plane. A servo motor for driving the horizontally pivotable movable arm is mounted on a base frame of the robot. By mounting the servo motor on the base frame, the load on the movable arm can be reduced significantly so as to allow the movable arm to be operated at higher speeds. The servo system includes a controller adapted to control robot operation. The controller is programmed to actuate the working end of the robot arm along a predetermined non-linear trace, in which an acceleration zone is defined inthe vicinity of an initial position of the working end and a deceleration zone is defined in the vicinity of the predetermined working position and a relatively longer constant speed zone is defined between the acceleration zone and the deceleration zone.

Computer-integrated manufacturing as the basis for the factory of the future

Abstract: Today, throughout the world, manufacturing is being subjected to major economic and social pressures which can only be satisfied through major advances in manufacturing productivity and quality. Fortunately, there are also strong technological resources emerging today which have the potential to provide such major advances. These resources derive from the technology which is becoming known as computer-integrated manufacturing (CIM). The technology, taken together with today's long-term economic and social pressures, is clearly shaping the factory of the future. In this paper, the nature and potential of CIM is first defined. It is then evaluated by combining the results of a survey of the CIRP Scientific Technical Committee on Optimization members' estimates with information derived both from recent literature and from the author's personal observations of the development of CIM throughout the world. The resulting appraisal reveals that, although implementation of CIM is still in its infancy, even at this early stage tremendous economic benefits are being reaped from implementation of this technology. In addition, its potential for further benefit, both economic and social, is very large indeed.

Theory, experimental results, and recommended standards regarding the static positioning and orienting precision of industrial robots

Abstract: The terms resolution, repeatability and accuracy are often used to describe the static positioning and orienting precision of industrial robots. Unfortunately, they are not well defined, and values provided for them in robot specification sheets can be misleading. This paper defines these terms precisely, presents theoretical and experimental information regarding robot positioning phenomena, and in the process outlines a structure for treating the subject that may prove to be useful by standards organizations. Fundamental assertions made in the paper are: (1) in order to provide robot figures of merit (FOMs) that are at the same time well defined, meaningful, practically determined, and simple enough to be of value to average robot users, statistical techniques are required, and (2) the most reasonable and cost effective method for generating the performance database from which the FOMs are determined starts with laboratory testing of certain fundamental robot characteristics and then uses computer simulation of robot kinematics to compute performance quantities under various circumtances.

Sensor-based control systems for arc welding robots☆

Abstract: Arc welding is one of the most important areas of application for industrial robots. In most manufacturing situations, uncertainties in dimensions of the part, geometry of the joint, and the welding process itself make the use of sensors essential to maintaining weld quality. In this paper three types of control systems for arc welding robots are described: (1) tracking systems for centering the weld puddle over the joint, (2) weld process controls for maintaining proper seam width and penetration, and (3) supervisory controls for sequencing welding operations. These control functions have been implemented successfully in production using a computer vision sensor integrated into the welding torch. Experimental results are presented demonstrating the capabilities of the system.

Design of an adaptable tool guide for grinding robots

Abstract: A method for surface grinding using a robot with a tool guide mechanism is presented The tool guide is a device to locate accurately the grinding tool and hold it against the work surface in the presence of the large disturbance forces generated in the grinding process The stiffness with which the tool is held is improved significantly and the accuracy of tool positioning is also increased despite the tolerancing errors of workpart dimensions and fixturing The mechanism of the tool guide is analyzed The conditions for the tool guide to locate the tool on the right surface of the workpart and to align the surface automatically are derived On the basis of the analysis a practical tool guide design is discussed Sensors for measuring the work surface orientation and the force applied by the robot arm are described A control scheme for automatically guiding the tool along an unknown surface is then presented

Quasi-static performance of robots

Abstract: Most manufacturers of robotic systems have data sheets where a set of static performance measures are listed. To date, there has been no standardization on how these measures are obtained, what they mean, or what parameters are necessary in quantifying the performance of a robotic system. While some of the parameters currently specified lend themselves quite nicely to one class of systems, these same parameters are meaningless on other classes of systems. A generalized set of performance criteria, not biased towards any particular robotic system, is presented in this paper. Three groups of measures that can be used for quasi-static and dynamic performance analysis of any robot task are defined. These groups are accuracy, repeatability and resolution. For each group, there are a number of subclasses. For each subclass various sensitivities are presented. These include the effects of payload, approach direction and location in the work volume, or any other potential influence. A rather simplistic yet useful analogy of an archer is used to describe the terminology. The relationship of these measures to the ability to satisfactorily develop online and/or offline programs for a robotic system to perform an operation is described. A generic robotic system is presented, the sources of poor performance are identified and some of the more practical techniques to improve the performance of robotic systems are noted. A description of what should be measured and a generalized statistical technique for reducing that data so that all pertinent information is saved while the amount of actual data required is minimized is presented. A concise outline of the experimental procedures used to obtain unbiased robot performance data for determining the various aspects of a robotic systems performance and various forms of summarized performance tabulations are given. These tables of performance information would be beneficial to the quality control of manufacturing robots, for the product design engineer intending to use robots in manufacturing a product (design for manufacturing) and for the manufacturing engineer evaluating the purchase of various robotic systems.

A manufacturing hand

Abstract: In unmanned Flexible Manufacturing Cells, robots can be used for loading machines, inspection activities, and assembly operations. What kind of robotic end-effector should be built for such tasks? The human hand has evolved to be a general purpose manipulator that adapts to the richness of our daily lives but, in doing so, it is not particularly suited to manufacturing operations. Here, we rely heavily on special tools, fixtures, and protective layers. This paper describes the initial development of a hand specifically for manufacturing work. This has involved the manufacture of an instrumented wrist with an adjustable remote center of compliance, and the design of fingers for gripping. Object shapes have also been analysed in order to provide for a stable static grip. Importantly, these studies of the physical aspects of prehension have been matched to tasks. The research has considered a range of industrial operations and specified the level of end-effector control needed. This work is leading to some design guides for robotic end-effectors which, it is hoped, will be of use to industrial designers.

A low-level control interface for robot manipulators

Abstract: This paper will discuss a possible low-level control interface for a robot manipulator. The first section will present background information describing the capabilities and limitations afforded by the use of interfaces and a proposed system modularization that supports interface specification. The next section presents three possible low-level robot control interfaces within this system. Each will be elaborated on by a specification of the interface information and its use, timing considerations and potential limitations. The paper concludes with a summary discussion and recommendation.

Application of symbolic logic to the design axioms

Abstract: The Design Axions have been advanced as a methodology for use in evaluating designs of products and processes. To date, however, these Axioms have been available only as an informal set of rules. In order for the relationships among these rules to be established definitively, and to facilitate the use of computers for decision-making in design, the Axioms have been expressed here with mathematical precision. This paper investigates the use of symbolic logic for this purpose. The result is that one design rule which was previously believed to be a corollary of the Independence Axiom is actually shown to have the same formal structure. Several other propositions are seen to be derivatives of the Axioms plus some mild assumptions, while still others would require incorporating other laws of nature in addition to the existing Axioms. Another important result of the research is that stating the axioms is symbolic logic suggests how they may be encoded in a logical programming language such as Prolog. An overall architecture for an axiomatics expert system is therefore presented.

The value of multiple independent robot arms

Abstract: When multiple independent robot arms attempt to perform concurrent operations at the same work cell, spatial interference imposes limits on the degree of parallelism that can be achieved. It is shown that as the number of independent arms approaches infinity, the degree of parallelism is bounded. Mathematical limiting values are derived for the extent of parallelism for two cases of an idealized simplistic application. The main value of these results is to demonstrate that under conditions of spatial contention, there is little merit in having more than two independent arms at a work cell. Designing the work cell to reduce contention increases the value of multiple independent arms.

Robotics software systems

Abstract: A robotics software “system” is defined here as one which allows robot users to program robot tasks in terms of key states of the task, instead of manipulator motions. It consists of two subsystems: a language system and a planning system. The language system involves the design of syntax and semantics of a robot programming language whereas the planning system determines specific manipulator movements for a given task defined in a task-level language. This paper describes the major components of a robotics software system and reviews principal research findings in the related aspects including programming languages, manipulator and world modelings, motion planning, and graphic simulation. Underlying research issues are addressed at the end.

On-line scheduling for adaptive control machine tools in FMS

Abstract: Adaptive control is available to adjust the operating speed of machine tools in FMS according to the condition of production, but it changes the time of each operation and disturbs the previously determined schedule. In this paper, on-line scheduling which changes the schedule according to the change of operating times is proposed. It is verified by computer simulation that on-line scheduling using SLACK, EDD, or the Look Ahead heuristic rule is available. The Look Ahead rule is the best for decreasing the lateness of due dates. Algorithms to change the adaptive control mode between optimization for cost performance and that for productivity according to the condition of the schedule are proposed, and their validity is verified by computer simulation.

Robot planning system

Abstract: The paper discusses the development of a computer-aided robot planning system. The proposed methodical procedure is based on the steps of “Manufacturing Systems Analysis, Determination of Basic Data, Documentation of Information, System Layout Planning and Evaluation, Decision on Economic Feasibility, Final Detailing of the Planned System and Planning of the Systems Installation”, which are described in detail. Further software modules, corresponding to the phases in the planning procedure, as well as the data flow requirements, are presented.

Experiences and further development of the FFS (free-form shapes) CAD/CAM system

Abstract: The FFS (Free-Form Shapes) is a minicomputer-based turnkey CAD/CAM system. By means of it a wide range of free-form engineering components can be designed and manufactured. The latest version of the FFS was released in 1982 and since that time it has been tested and utilized in the production of industrial parts. After presenting the basic structure of the system some practical problems of its application are discussed in detail, such as incorporating conventional geometric items into free-form geometry, cross-sectional design, limited use of three-sided patches, pocketing of free-form parts and machinability tests.

A fast algorithm for high accuracy gauging using computer vision

Abstract: A vision-based inspection system capable of measuring convex-profile cylindrical objects has been developed Both vertical and horizontal measurements are possible as well as cross-sectional reconstructions A new algorithm has been developed that minimizes the number of camera views needed to obtain accurate reconstructions This increases the speed of the analysis procedure A production version of the inspection system has been installed in a forging plant; for this application camera lenses and other equipment dimensions give a measurement accuracy of ±10 mm on length and ±15 m 2 on cross-sectional area

AML as a plant floor language

Abstract: End users would benefit from a standard plant floor language able to control robots, NC tools, and a broad variety of other manufacturing and test equipment. AML, A Manufacturing Language, is now portable, with implementations running on a variety of IBM and non-IBM computers. We have experimented with AML enhancements, including multi-tasking, linkages to other computer languages, and data type and operator extensibility. In addition, we have studied issues of AML compilation and its use as a unified language for CAD/CAM. AML has been used experimentally to run non-IBM robots. It is suitable for controlling NC machine tools. Based on the requirements for a general purpose plant floor language, AML is emerging as a strong candidate for a potential standard in industrial automation.

Structural properties in kinematics of robots, articulated mechanisms and prosthetic arms

Abstract: Kinematics of spatial manipulating systems can be deeply understood and effectively solved introducing structural considerations. The concept of kinematic equation of motion and its canonical form, introduced by the authors, is further developed using moving coordinates and the components of the “absolute” and generalized coordinates vectors are discussed in detail. The results obtained are based on standard matrix transformations and can be applied to CAD of manipulating systems for industrial robots, articulated mechanisms and prosthetic arms.

Use of coherence analysis for the evaluation and adjustment of robot gear performance

Abstract: Previous work by our group has demonstrated that it is possible to use the robot joint excitation technique and coherence analysis function to adjust robot joint gears for maximum robot precision. A robot joint gear box equipped with gear adjustment mechanism was instrumented so that the gap between the teeth of a pair of gears (backlash) could be measured. The translational and rotational components of robot link motion were decoupled using multiple sensors so that the relationship between the coherence analysis function of each type of motion and gear backlash could be investigated. The sensitivity of the adjustment technique to various input signals and sensor positions was also examined. Results show that coherence analysis can be used as a measurement technique to determine the precision with which the robot joint link responds to control signal input.

Robot language from the standpoint of FA system development—An outline of FA-BASIC

Abstract: A new unified FA (Factory Automation) language has been developed. The language is suited for robot control, vision system control and programmable controller (PC) control and enables a unified means for programming. The language is called FA-BASIC and has common functions such as expression, control structure and input/output statement based on BASIC language. FA-BASIC is composed of three subsystems: FA-BASIC/R for robot control, FA-BASIC/V for vision system control and FA-BASIC/C for PCs. Many languages have been developed up to now, but most of them were aimed at single purposes. These single purpose languages were too limited when developing an integrated FA system, because several languages and different program-making methods must be mastered. Using FA-BASIC, programming with mutual interconnections between robots, PCs and vision devices is done by the one common method. In this paper, the basic design concept and functions of FA-BASIC will be presented, along with the features of FA-BASIC/R and on outline of a robot control system using a standard mechanism-independent intermediate language and standard fundamental modules. Also, for easy programming, an off-line programming system with graphical aids and a menu-selection method which require no special effort to master will be introduced as the only present-day universal robot programming method.

EIA project 1393: A high level communications standard

Abstract: This paper describes, at a functional level, the communications standard (P 1393) being developed by the Electronic Industries Association (EIA) N/C committee. The relationship of P 1393 to the Open Systems Interconnect (OSI) seven layer model developed by the International Organization for Standardization (ISO) is also described. P 1393 defines a user level format and protocol for bidirectional transfer of digitally encoded messages in a manufacturing environment. As such, it defines a comprehensive language for high-level communications to programmable devices on the plant floor, including numerical control machines, programmable controllers and robots. It is intended to support not only existing needs in a manufacturing environment, but to be systematically expandable to accomodate future requirements as well, so that the automatic machine shop, and eventually the automatic factory, can evolve.

The two-track society

Abstract: The rapid growth of high-technology industries is one of the most important economic trends in recent years. Yet there has been a tendency, among journalists, public policy analysts, government officials and others, to overstate the nature of the changes which are taking place. We are not witnessing “the end of the industrial age” nor are basic industries about to be replaced by high-technology industries. For at least the next decade, basic industries will continue to be important sources of employment and output. More importantly, they will serve as markets for high tech goods and services as they modernize their operations. The future will see a two-track economy which is built on both high-tech and basic industry.

Computer numerical control for assuring the machining accuracy of contour milling

Abstract: In this paper, a software technology for improving the machining accuracy in contour milling is discussed, in which the continuous path control is thoroughly investigated from the viewpoint of system synthesis, and the computer numerical control is effectively used. It is shown that the proposed “real-time cutter path rectification” offers an effective means to overcome the serious problem of the thermal deformation of workpieces. In this case, it is necessary to take many factors into consideration; the diversity of shapes, the change of cutting conditions, the unstable thermal situation, and so on. Therefore, the adaptive control is applied to compensate the thermal displacement of the contour during the cutting process. Relating to this subject, the effective cutter radius, which depends on cutter wear, is also evaluated in real-time operation; and the cutter diameter compensation is included in the “cutter path rectification”. In order to assure the machining accuracy, a new approach to contour measurement is proposed, in which the continuous path control by CNC system is used. It is certified through some experiments that the method proposed in this paper is useful to realize the flexible automation with high machining accuracy.