The paper proposes a novel design technique of cyber-physical systems (CPSs). The system is specified by a Petri net, and further modelled in a hardware description language (HDL) towards final implementation in a programmable device. Contrary to the traditional design methods, the proposed solution is highly focused on the verification aspects. The system is checked three times before the final implementation in hardware. Initially, the Petri-net based specification is formally verified by the application of the model-checking technique. Secondly, software verification of the modelled system is performed. Finally, the hardware verification of the already implemented system is executed. The proposed method is explained by an example of a direct matrix converter (MC) with transistor commutation and space vector modulation (SVM). The main benefits, as well as the limitations, of the proposed solution are discussed and analysed.
In this paper, we study selected aspects of determinism in the control part of a cyber-physical system (CPS) that is specified by a Petri net-based model. In particular, the control interpreted Petri nets (CIPNs) are applied, which are an extension of the ordinary Petri nets, supplemented by signals (related to sensors and actuators) that permit communication with the environment. The notions of weak and strong determinism in a system described by a CIPN are introduced in the paper. The proposed concepts are supported by formal definitions and theorems. Moreover, a novel modelling methodology for a deterministic system specified by a CIPN is proposed. The presented solutions are illustrated by a case study example of a real-life cyber-physical system. Finally, the results of experimental verification of the proposed determinism-based techniques are demonstrated and discussed.
Petri nets are a useful mathematical formalism for specification of manufacturing systems, supported by various analysis and verification methods. The progress made in automating control systems and the widespread use of Industry 4.0 pose a number of challenges to their application, starting from the education at university level and ending with modelling of real case studies. The paper aims to present and analyse the most relevant challenges and opportunities related to the use of Petri nets as a modelling technique of manufacturing systems. The review of the literature is primarily based on the years 2019–2020 to reflect the current state of the art. The newest approaches to deadlock prevention and recovering, but also other important analysis problems and difficulties in modelling real industrial processes are discussed. Trends for the future are also identified.
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