HHML: A hierarchical hybrid modeling language for mode-based periodic controllers

In cyber-physical systems, the controllers are widely designed into mode-based periodic modules, which are used to control physical plants. Such a system can be modeled as a hybrid one, i.e., one of the real-time controller programs and interactive continuous plants that obey dynamical laws. In this work, to facilitate the modeling and analysis of periodic hybrid control systems in the field of aerospace and smart cities, a hierarchical hybrid modeling language (HHML) is proposed, which contains a two-hierarchy structure, i.e., mode-hierarchy and module-hierarchy. The former supports modeling a hybrid system at the abstraction level, while the latter is used to describe the behavior of the modules. The operational semantics is investigated for formal analysis, and the translation rules to hybrid automaton are explored for formal verification. A case study is conducted with the lunar lander to demonstrate the effectiveness of the approach.