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System und Dessen Grundlagen / System and its Fundamentals

Ziele und Ergebnisse des Projektes „Sehr fortgeschrittene Handhabungssysteme“

Das mit Mitteln des BMFT durchgeführte Vorhaben “Sehr fortgeschrittene Handhabungssysteme” hatte eine Laufzeit vom 01.08.1977 bis zum 31.12.82. Es wurde am Fraunhofer-Institut für Informations- und Datenverarbeitung (IITB), Karlsruhe, in Zusammenarbeit mit dem Fraunhofer-Institut für Produktionstechnik und Automatisierung (IPA), Stuttgart, durchgeführt.
Das Vorhaben ist gegliedert in eine erste Phase bis 15.04.1979 und eine zweitePhase bis Mitte 1981. In einer dritten Phase bis Ende 1982 wurde ein industrieller Einsatzfall vorbereitet. Die beiden letzten Phasen liefen in Abstimmung mit den Arbeiten der Arbeitsgemeinschaft Handhabungssysteme.
Im Rahmen des Projektes wurden einerseits neue Verfahren zur Regelung, Steuerung und Programmierung, andererseits optische und taktile Sensoren für Industrieroboter entwickelt,die die Voraussetzung bilden für die Erschließung neuer und anspruchsvoller Einsatzgebiete für Industrieroboter der dritten Generation. Die Verfahren wurden auf Mehrrechner-Mikroprozessorsystemen implementiert und zusammen mit den Sensoren an an einigen prototypischen Einsatzfällen — Greifen von ungeordneten Teilen von einem schnell laufenden Band, Fräsen von komplex geformten Edelstahl-Gußteilen mit einem Roboter — demonstriert.
P.-J. Becker, M. Syrbe

Steuerung und Regelung / Control

Einsatz regelungstechnischer Verfahren für typische Roboteranwendungen

The paper gives a survey of closed-loop control algorithms developed in the course of the project “very advanced industrial robots”. In line with the original objectives, a modular system of efficient algorithms has been obtained, which can be adapted with low effort to a wide manifold of existing and future manipulation problems, robot configurations and hardware components (servo and sensor systems). The basic approach to the design of a joint control algorithm which is tailored for a special manipulation problem will be provided by the inverse system principle. Because it warrants both the joint decoupling and a global system linearization, the option is obtained of introducing a controller separately for each joint which optimally tatisfies special performance requirements (e. g. time optimality, no overshoot) and hardware conditions. The efficiency of the developed algorithms for typical classes of manipulation problems will be demonstrated by investigations and practical case studies carried through at the Fraunhofer-Institute IITB.
H.-B. Kuntze, W. Patzelt

Regelungsalgorithmen für Industrieroboter — eine Übersicht

The objectives of this review are to summarize and to evaluate the present state of knowledge concerning control algorithms for industrial robots (IR). In the past 15 years, there has been a confluance of research on this field and excellent results of general interest have been produced. However the wide practical application of the results is rather poor. One reason for the gap between research and industrial practice seems to be the lack of information as regards existing control concepts and corresponding areas of industrial applications. It is the aim of this survey paper to contribute to the efforts of closing this gap. Main subjects of investigation are models and closed-loop algorithms for positional and force control of IR. Other important topics such as dialog systems, command languages or sensor hardware can only marginally be discussed.
H.-B. Kuntze

Fortgeschrittene Gerätestruktur und Programmierung von Robotersteuerungen und -regelungen

A robot control system has to manage several tasks. In the first part of this paper these tasks are conceptually devided into eight classes. The robot control system has to satisfy all the requirements of these eight classes. However the complexity of the various tasks depends on the robot configuration and on the application. Therefore its necessary to develop a modular robot control system. In the second part of this paper such a modular multi-microprocessor-system is described. Not only hardware modularity is required but a modular software system is indispensable to adapt a robot control system to special applications. High-level languages support the software modularity.
At IITB a modular robot control system has been realized using PEARL (Process and Experiment Automation Realtime Language) as high-level programming language exclusively. Finaly this paper reports on the results, which could be reached using this robot control system milling hard-metal surfaces.
K.-H. Meisel

Verfahren zur Steigerung der Zuverlässigkeit und Sicherheit von Industrierobotern

The operation of industrial robots implies some risks because malfuntions in the control system can cause self destruction of the robot mechanics or unexpected obstacles in the robot environment can provoke a collision. These risks can be met in two fundamentally different ways: by the introduction of fault-tolerant or robust system structures and by the application of collision avoiding control algorithms. Compared to the large number of publications on various aspects of robot control (e. g. positioning, decoupling etc.) the security and reliability problems are rather neglected. Therefore, the aim of this paper is to give a short but comprehensive survey on synthesis principles and usage possibilities and to provide first experimental and simulation results.
H.-B. Kuntze, W. Schill

Bildschirmorientierte Programmierung von IR

The use of colour video system for the control and supervision of complex industrial plants is now a well established technology. Even operators with small knowledge in information science are thus able to program these systems. In this paper we report on the possibilities of using such colour video systems as aids for the programming of industrial robots.
P.-J. Becker, K.-H. Meisel

Sensoren / Sensors

Leistungsfähigkeit und Grenzen optischer Verfahren zur externen Positionsvermessung von Handhabungssystemen

In an working place equipped with an industrial robot, the knowledge of the exact position of the hand of the robot and of the parts that are handled, is of crucial importance. Consequently, there must be provided facilities for external measurement. In a (hypothetical) working place, several tasks of this kind are demonstrated (Fig. 1):
The whole place is monitored for safeguarding. One type of workpiece is fed by an conveyor belt, its position is measured, then it is taken by the robot and assembled with a second part. Before assembling, the position of the part relative to the gripper is determined. After assembling, the parts are machined by the robot. The assembly is then placed on a pallet, the position of which must be measured.
Some of these measurements may be done by the internal references of the robot, but with heavy loads, high dynamics, temperature effects etc., external referencing is necessary.
Optical methods are discussed to accomplish the different needs of these measuring tasks. It is shown, which errors may occur and how to avoid them.
The tasks are classified according to the measuring accuracy and the range which is needed, and to the complexity of the measuring scene (Fig. 4). The complexity of a scene depends on the content of the scene. The safeguarding scene e. g. is highly complex, because there are unknown objects to be expected.
The complexity of the scene determines, how sophisticated the sensor must be. The accuracy and the range determine the selection of the optics. The measuring tasks shown above are discussed in these terms. Examples for implementations are given.
Georg Zimmermann

Externe 3D-Messung an Industrierobotern durch Laser-Triangulation

So far there exists no satisfactory way for the exact measurement of the three-dimensional movements of industrial robots. For testing robots and for accurate handling and machining tasks the usual indirect measurement by the angular positions of the motors is insufficient because of elasticity and backlash in the mechanics of the robots.
In this paper we describe alaser-optical system which measures on-line the position of the robot hand to 10−4 in three-dimensional space in kartesian coordinates by triangulation: Two laser beams follow automatically a special corner cube mounted on the robot. The efforts for setting up the system are kept low by a semiautomatic calibration procedure.
H. Bolle, H.-J. Rösler

Arbeitsraumüberwachung beim Industrieroboter durch automatische Bildverarbeitung

The operation of industrial robots poses various risks for equipment and personnel within the workroom. This paper shows how an automatic visual surveillance system could be used to prevent collisions between man and machine. The system is based on detection, recognition, and tracking of moving objects and persons from images of the workroom taken by a fixed TV-camera. While motion and current position of the robot is obtained by extracting characteristic features of the robot from each image frame,persons intruding into the workroom are detected by comparing the gray values of consecutive frames. Any change can be caused by illumination, actual motion, electronic noise, or technical insufficiencies. A decision is obtained only from considering regional characteristics. Therefore the image is divided into square regions of,e.g., 8×8 pixels. Change classification then is performed by evaluating statistics of consecutive gray values within each of the regions. Since an illumination change leads to constant log-quotients within a region (the geometry is assumed to be fixed), this case is decided for by a rating of their calculated variance. Additional parameters are employed to counter noise and camera effects. Finally the square regions are labelled as no change,change due to illumination, change due to motion, or uncertain (i.e. statistical base is insufficient.). All regions indicating motion are used for a rough segmentation. A trajectory of the intruding person is established as soon as the picture border is trespassed, and cleared when leaving the field of view. The system has been simulated successfully in software.
Uwe L. Haass

Erweiterung der Einsatzmöglichkeiten von Industrierobotern durch Sensoren und taktile Greifer/Sensorsysteme

The number of industrial robots applied in the area of assembly is yet very small — in opposite to other production areas. One reason for this is, that industrial robots do not yet have the sensitive abilities required for the assembly process and the control of assembly operations. One of the objectives of the research work at the Fraunhofer-Institute for Manufacturing Engineering and Automation (IPA), Stuttgart, was therefore to solve the problems of joining by means of tactile sensors and visual control. The solutions which were found and which will be applied for industrial robots in the future are described in this report.
E. Abele, D. Haaf, J. Spingler, M. C. Wanner, U. Schmidt

Anwendungen / Application

Aufgabenspezifische Probleme und Lösungen beim Einsatz eines Industrieroboters zum Bearbeiten komplexer Gußstahl-Oberflächen

The paper investigates the future extent of technological competition between advanced industrial robots (IR) and machine-tools. New control methods for IR have shown that the performance limits of IR which in contrary to machine-tools are highly elastic are far from being reached. By further development of control methods the IR will be opened to machine-tool applications, too. Some exemplified specific problems and approaches to solutions are shown by use of an application, the machinig of cast metal pieces.
P.-J. Becker

Anwendungs- und steuerungsangepaßtes Einlernen, Abspeichern und Berechnen von Fräsbahnen

In this paper a method for teaching, recording and on-line computing of continuous cutting trajectories for a computer controlled industrial robot (IR) used as cutting machine tool is presented. Like the algorithms for digital closed-loop control and coordinate transformation, the algorithm of cutting trajectory calculation has been formulated in the real-time programming language PEARL and implemented on a microcomputer. The proposed concept differs from the other well known methods used for conventional CNC-controlled machine tools in several points. It requires comparably low processing speed and memory capacity. Both the teaching of the measured points on the pattern workpiece and the interpolation of the continuous cutting trajectory are performed on a single microcomputer. The trajectory calculation is done online i.e. after each interpolation step the cutting tool carried in the IR hand is newly positioned. The feasibility and good performance quality of the presented alternative method has been confirmed by experimental investigations using a fast rotating hard metal alloy cutting tool.
M. Salaba, W. Schill
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