K. Desoyer

Flexible Robots - A Survey

Abstract Industrial robots and handling devices will be of great importance in future. Today robots are used for various purposes in different industries. Main disadvantages of the robots used today are the very heavy construction, the relatively slow speed and the “unintelligence”. Therefore the next generation of robots will be more “intelligent”. Such robots have to be equipped with external sensors giving them additional information about their surroundings. In addition these robots will be faster and therefore they have to be lightweight constructions. The last two features will lead to socalled “flexible” robots which are very complicated to describe mathematically and to control The paper starts with a short description of the main parts of an industrial robot. After some general considerations on the construction of lightweight robots, some methods for the mechanical modelling of flexible robot structures are discussed and compared. Based on these various models for the dynamic behavior an overview of possible control methods and strategies is given

Comparison of Digital Control Algorithms for Industrial Robots

Abstract Today most of the industrial robots applied in practice are controlled by means of conventional, linear control algorithms which are implemented in the control computer. The development of faster, weight weight robots yields to additional control problems. For this new generation of robots advanced digital control algorithms are necessary and have to be available in the nearest future. The model for the dynamic behavior is those of a nonlinear, timevarying, multivariable system. Such models are too complicated for the development of control algorithms. Further difficulties arise from the choice of optimal algorithms as well as parameters. A powerful tool for solving these problems is simulation. Therefore, a sufficient accurate model of an industrial robot with simple kinematic structure including the drives and gears was implemented at the analogue part of a hybrid computer system. Various digital control algorithms with the same structure but of different order have been simulated at the digital part. The resulting paths were plotted and offered the possibility to compare these.

Simplified Models for Robot Control

Abstract The differential equations describing the dynamic behaviour of a robotic arm lncluding drives and gears are strongly coupled and highly nonlinear especially in case of an articulated arm. In order to allow the application of the well developed theory and control synthesis procedures for linear systems, a low order, coupled, linear and autonomous model is derived by linearization and order reduction which is - at least for nowadays stiff robots equipped with powerful drives - accurate enough for controller design and - if necessary - path prediction. The suggested procedure is simple and allows to estimate the influence of coupling terms as well as an easy updating of the model and/or controller parameters according to the actual working area

Modelling of Flexible Robots — An Introduction

Abstract This survey gives a short introduction to the today robot structure and problems of motion control and some remarks for future aspects of lightweight, high performance robots, that will include parts with non negligible flexibilities. How the modelling of this time variant elastic deformations, a substantial part of any control strategy, can principally be done is shown based on the recent literature. The quasistatic method uses substitutive springs to describe the elastic deformations at special locations. For the dynamic behaviour of vibrating flexible links FE-methods, a vibration mode or shape functions approach or other combined methods may be applied. The characteristics of the FE-methods are their advantage of a realistic modelling of complex shaped links but with the drow back of high evaluation time. The vibration mode methods need a special knowledge to select the right set of functions but lead to short evaluation time. Combined methods are also based on a fracturizing of the deformable elements into smaller units, whose elastic properties can be described more easily. The modelling of the elastic properties and an adequate control will be an essential basis for a future time and energy efficient robot performance.

CAD in Robot Control Education

Abstract The authors have been teaching since 5 years fundamentals of Industrial Robots and Handling Devices for students of Mechanical Engineering, Electrical Engineering as well as Applied Mathematics and Computer Sciences. These fundamentals include mechanics, model building, simulation and control. For the practical education mainly in laboratory courses two personal computers, a little hydraulic driven robot and a hybrid computer system for simulations is available. At a lower level the students solve the kinematic and kinetic equations with the personal computer for different structures of robots. The hybrid computer system is applied for simulations of the controlled robot. The hydraulic driven robot can be controlled by means of a control box with pushbuttons for movements (e.g. up/down, rotate and grip and for start/stop). Another programming possibility for robot movements consists by using a special language which is different for each robot. Both possibilities are little efficient for education at a higher level. Therefore the control box of our robot is replaced by a personal computer for advanced studies. For all laboratory experiments the necessary software packages are written in dialoge form like a CAD system.

Hinweise für den Benützer

Die Aufgabensammlung ist in drei Teile gegliedert: Angaben, Losungen und eine Zusammenstellung der fur die Losung der Aufgaben wesentlichen Grundlagen.

Einführung in die Statik

Die Kraft \( \vec{F} \) (force) ist eine gerichtete Grose (ein Vektor), graphisch darstellbar durch einen Pfeil (Lange entspricht dem Betrag der Kraft). Die Krafteinheit im internationalen Einheitensystem ist das Newton (N), mit dem Kilogramm (kg) als zugehoriger Masseneinheit:

COMPARISON OF DIGITAL CONTROL ALGORITHMS FOR INDUSTRIAL ROBOTS

1N=1kg.m/{{s}^{2}}