Mobile robots, becoming increasingly autonomous, are capable of operating in diverse and unknown environments. This flexibility allows them to fulfill goals independently and adapting their actions dynamically without rigidly predefined control codes. However, their autonomous behavior complicates guaranteeing safety and reliability due to the limited influence of a human operator to accurately supervise and verify each robot’s actions. To ensure autonomous mobile robot’s safety and reliability, which are aspects of dependability, methods are needed both in the planning and execution of missions for autonomous mobile robots. In this article, a twofold approach is presented that ensures fault removal in the context of mission planning and fault prevention during mission execution for autonomous mobile robots. First, the approach consists of a concept based on formal verification applied during the planning phase of missions. Second, the approach consists of a rule-based concept applied during mission execution. A use case applying the approach is presented, discussing how the two concepts complement each other and what contribution they make to certain aspects of dependability.

IEC 60848 GRAFCET is a standardized, graphical specification language for control functions. Because of the semiformal nature of IEC 60848, the details of specifications created with GRAFCET can be interpreted in different ways, possibly leading to faulty implementations. These ambiguities have been partially addressed in existing literature, but solved in different manners. Based on a literature review, this work aims at providing an overview of existing interpretations and, based on that, proposes a comprehensive interpretation algorithm for IEC 60848, which takes all relevant ambiguities from the literature review into account.

The graphical modeling language GRAFCET is used as a formal specification language in industrial control design. This paper proposes a structural analysis that approximates the variable values of GRAFCET to allow verification on specification level. GRAFCET has different elements resulting in concurrent behavior, which in general results in a large state space for analyses like model checking. The proposed analysis approach approximates that state space and takes into consideration the entire set of GRAFCET elements leading to concurrent behavior. The analysis consists of two parts: We present an algorithm analyzing concurrent steps to approximate the step variables and we adapt analysis means from the field of Petri nets to approximate internal and output variables. The proposed approach is evaluated using an industrial-sized example to demonstrate that the analysis is capable of verifying behavioral errors and is not limited by the specification size of practical plants.

Model checking of GRAFCET, an IEC standardized specification language, is typically performed by a translation of GRAFCET into a different (target) formalism. However, analyzing instances of considerable sizes quickly becomes unfeasible due to the state space explosion problem. We propose three techniques to reduce a GRAFCET instance depending on the property to be evaluated, resulting in a smaller state space. These techniques can be employed, even in combination, before transformation into a formalism suitable for model checking.

The graphical modeling language GRAFCET is used as a formal specification language in industrial control design. This paper proposes a static analysis approach based on the control flow of GRAFCET using abstract interpretation to allow verification on specification level. GRAFCET has different elements leading to concurrent behavior, which in general results in a large state space. To get precise results and reduce the state space, we propose an analysis suitable for GRAFCET instances without concurrent behavior. We point out how to check for the absence of concurrency and present a flow-sensitive analysis for these GRAFCET instances. The proposed approach is evaluated on an industrial-sized example.

In the connected world of Industrie 4.0, not only the access to information becomes more and more important, but also secure, standardized, and machine-interpretable communication between assets. The identification of assets forms the basis for all emerging processes, which leads to new requirements. The authors developed a concept to establish the identity of Industrie 4.0 components in decentralized systems by providing a decentralized identity and access management based on distributed ledger technology and integrated this into the concept of the Industrie 4.0 language. The use of decentralized identifiers guarantees more security and reliability for the involved actors in the value chain. Thus, authentication and authorization can be carried out solely between the involved actors without the use of centralized identity providers or certification authorities.