Software aspects of PLC´s application in robotic workcells

The subject of control system design is usually approached from two distinct perspectives: development of general principles such as mathematically or experimentally derived theory, and case studies which describe instances of specific applications in practice. This paper fills the gap between these two approaches for a particular topic, application of PLCs to robotic workcells. Specifically, the subject of interest is organization of PLC program. Robotic workcells are custom built. Despite that, it is possible to discern common physical features and operating characteristics among robotic workcells. As a good design practice, these common traits are used, on an individual device or axis of motion basis, to generate typical portion of code. Similarly, on equipment, workcell or global level, typical organization of code is developed with a standardized program format, order and naming conventions. A library of code segments can be developed for specific sensors, actuators, axis of motion arrangements, robot and workcell configurations. This library can then be used for mix and match software development without sacrificing flexibility to customize or refine programs. Since the structure of the code is standardized and known ahead, the benefits of this approach extend beyond the code development stage to the program debugging and the life of product maintenance and repair troubleshooting of equipment.