Model-based Control of a Handling System with SysML

For programming controllers in industrial automation systems languages based on IEC 61131 represent the state-of-the-art. However, these languages have limited capabilities for describing multi-disciplinary aspects. Model-based approaches that have successfully been applied to software engineering projects also provide a promising alternative for the engineering of automated manufacturing systems. The integration of model-based approaches into conventional control architectures still represents a challenge. Using a handling system for unloading parts from a pallet as an example this paper demonstrates and evaluates a practical approach for developing control logic based on a SysML model. The approach consists of three steps: First, the behavior of the system components (e.g. grippers, axes) are described in an interdisciplinary way, representing the internal state as well as an IEC 61131 compliant signaling interface. The second step is to develop agents that implement the actual logic and are able to control the virtual components using the implemented interface. In the last step, during commissioning of the real system, the virtual components are replaced by a module syncing the signals of the virtual agents interface with a PLC providing the same interface for the real system, effectively having the real system now being controlled by virtual agents.