Automated generation of PLC code for implementing mode-based control algorithms in buildings

In practice, manual planning and implementation of control function logic in building automation and control systems (BACS) is a source of failure. Textual descriptions of control functions are often not standardized and inaccurate. Therefore, they may result in misunderstandings in the following implementation process. The increasing complexity of building energy systems makes the problem even worse. Regarding this problem, we have introduced the MODI method in previous work. The MODI method enables a systematic development of mode-based control algorithms and utilizes signal-interpreted Petri nets as a formalized description method to avoid ambiguity in the description of control algorithms. However, the implementation of the mode-based control algorithms in BACS remains unclear. Manual programming of the algorithms is in practice time-consuming and error-prone. In this paper, we introduce a software-assisted framework to support the implementation of mode-based control algorithms in programmable logic controllers (PLCs) by generating PLC code automatically. In a case study, we apply the framework to implement a mode-based control strategy for an air handling unit and test the strategy in a simulation. In future work, a digital data source and exchange method across the planning and the construction processes of BACS will be considered as a data input of this framework to further facilitate the generation of PLC code.