Eine modulare Steuerungsarchitektur für Industrieroboter

Abstract

Most of a robot controller's functionality is determined by its system software. Developing this software demands an unduly high proportion of the total development costs. This and the fact that control systems for industrial robots are still more or less closed systems motivated the research for new ideas and concepts required for a modular controller architecture. The basic idea behind the new concept is the development of a flexible, easily extendible software architecture for an industrial robot system. The architecture would be based on a modular and as far as possible hardware-independent structure. The system could thus be easily adapted to particular tasks with minimal technological effort and at little cost. Quite like a modular hardware system, a predefined software structure is filled up with the software modules required by the specific application, resulting in an individually tailored controller software which may easily be maintained and adapted to changing requirements just by replacing a few specific modules. Based on this idea a new controller architecture designed for general industrial applications and consisting of seven layers is developed which - analogous to a typical enterprise hierarchy - extends from off-line programming to the operative level and represents a holistic robot control system. In this way a software architecture designed for industrial robot controllers, for the first time, has been developed beyond its current field-level operational capabilities to handle global operational and control functions of robot based manufacturing systems. Under the new architecture the specific functions of each layer are analyzed and grouped into reusable modules with specified interfaces, and also a special communication and synchronization mechanism is developed to match the modular architecture. To demonstrate the interaction of the individual layers, the internal and external information flows are discussed and different layout configurations compared. The tactical-control-unit responsible for planning and executing the robot's motions is used to verify the proposed architecture in detail. Beginning with the development and comparison of different methods of describing robot trajectories, all essential path elements and their data structures are classified before the execution of a robot motion is analyzed in detail. For this reason an extendible geometric profile generator is presented, which does not only support commonly used interpolation methods, but also generates steady path transitions between any trajectories including segments not adjacent to one another. Spline functions and symmetrical and asymmetrical speed profiles, specially developed for this purpose, make it possible to generate continuous, unimpeded, geometrically and velocity controlled robot motions. Finally, a sensor based, dynamically adjustable environment model is introduced.