System and integration tests for continuous integration of virtualized control applications using service virtualization (SITVIS)

• Applicant: Dr.-Ing. Armin Lechler
• Subject Area: Production Automation and Assembly Technology
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 569217200

The transformation of industrial production technology from rigid, hierarchical systems to flexible and adaptable systems is the subject of current research. The paradigm shift is to be achieved through software-defined manufacturing (SDM). For the implementation of SDM, a separation between infrastructure and functionality is necessary. In order to decouple infrastructure and functionality as far as possible and enable more flexible use of resources, virtualized programmable logic controllers (vPLCs) are used instead of classic hardware controllers, which are rigidly coupled to the machine via a fieldbus. The execution time of the control code of the vPLC depends on the available computing resources (e.g. CPU, RAM, bandwidth, network). Control applications have strict real-time requirements, which is why, in addition to the correctness of the result, the time at which it is available must also be checked. The decoupling of application and infrastructure enables continuous adjustments to the production functionality. In information technology (IT), the concept of continuous integration and deployment (CI/CD) is used to adapt software. In preliminary work, it was evaluated that the use of CI/CD for virtualized real-time applications is not yet possible because the tests in the integration phase cannot emulate the time behavior of the applications for the production system. This means that system tests, which are used by today's hardware-in-the-loop (HiL) simulations in automation technology, are not sufficient for virtualized real-time applications. In HiL simulation, the inputs and outputs of the controller are linked to the configured test setup. The simulation sends signals to the controller, which returns values that in turn influence the simulation in order to test the software. HiL simulation can be used to simulate the behavior of the system when executing the control software, but not the behavior of compute resources. The method is meaningful for hardware controllers, but not for virtualized controllers, because the machine behaviour depends on the controller and the behaviour of the controller depends on the computing resources of the test system. The project description emphasizes that it is necessary to emulate the behavior of the production system on the staging system in order to reliably test virtualized real-time applications and thus enable the implementation of CI/CD for automation applications. To this end, emulation methods for implementing service virtualization as an abstraction layer will first be considered and evaluated. Methodologies for the realization of integration and system tests will then be developed, which will be validated by integrating them into the real-time orchestration of the institute's SDM demonstrator.

• DFG Programme: Research Grants
• Co-Investigator: Professor Dr.-Ing. Alexander Verl