Master's Thesis Arno Eggert
Modelling of a HiL test bed for simulative operations with a virtual PLC Name
The institute of energy efficient buildings and indoor climate possesses a Hardware-in-the-Loop (HiL) test bedwhich majorly constitutes a climate chamber and a hydraulic system. This test bed is used to investigate house-internal energy components under real environmental circumstances. To automatize the operations the test bed incorporates a programmable logic controller (PLC). Since the software periphery of the PLC and the test bed underlie a successive developmental process, the test bed control and its related simulations models are continuously adapted. The resulting consequences for the test bench can be only examined and analysed by using the physical test bed which is the focus of the current work. To construct a virtual copy of the existing test bed its physical properties are used. This copy, including the particular sub-systems of the test bed, is modelled in Dymola with the help of existing databases, resulting in a real-time capable simulationmodel. Consequently, this simulation model is coupled with the virtual test bed controller in the TwinCAT 3 runtime. If the Hardware PLC is exchanged with the virtual PLC, it emerges a Software-in-the-Loop (SiL) system that can support the developmental process as a software tool at the real test bed. Additionally, current advancements of the communicator strive a successful exchange of variables trough the ADS-protocol. Therefore, the given investigations focus on the implications of the datatype conversion of continuous in discrete variables for the real-time capability of the simulation model.However, it has been shown that under some circumstances real-time capability is disrupted when intertwining the virtual test bed with the virtual control. This paper addresses this issue by associating the real-time capability with an algebraic loop and the cycle time of the virtual PLC. By developing appropriate interfaces between the communicator and the virtual sub-systems the algebraic loop can be removed. Lastly, the virtual and the physical test bed are compared. Based on the paper at hand it is possible to link complex and virtuell PLCs with an appropriate model in Dymola and to analyse and test them in real-time. In the future elementary structures in the programming of a PLC can be developed without a hardware periphery and the created test bed model can be used as a tool to construe a HiL-3 test bed.