Features of integrated model-based co-modelling and co-simulation technology

Given the considerable ongoing research interest in collaborative multidisciplinary modelling and co-simulation, it is worth considering the features of model-based techniques and tools that deliver benefits to cyber-physical systems developers. The European project “Integrated Tool Chain for Model-based Design of Cyber-Physical Systems” (INTO-CPS) has developed a well-founded tool chain for CPS design, based on the Functional Mock-up Interface standard, and supported by methodological guidance. The focus of the project has been on the delivery of a sound foundation, an open chain of compatible and usable tools, and a set of accessible guidelines that help users adapt the technology to their development needs

An Experimental Scrutiny of Visual Design Modelling: VCL up against UML+OCL

The graphical nature of prominent modelling notations, such as the standards UML and SysML, enables them to tap into the cognitive benefits of diagrams. However, these notations hardly exploit the cognitive potential of diagrams and are only partially graphical with invariants and operations being expressed textually. The Visual Contract Language (VCL) aims at improving visual modelling; it tries to (a) maximise diagrammatic cognitive effectiveness, (b) increase visual expressivity, and (c) level of rigour and formality. It is an alternative to UML that does largely pictorially what is traditionally done textually. The paper presents the results of a controlled experiment carried out four times in different academic settings and involving 43 participants, which compares VCL against UML and OCL and whose goal is to provide insight on benefits and limitations of visual modelling. The paper's hypotheses are evaluated using a crossover design with the following tasks: (i) modelling of state space, invariants and operations, (ii) comprehension of modelled problem, (iii) detection of model defects and (iv) comprehension of a given model. Although visual approaches have been used and advocated for decades, this is the first empirical investigation looking into the effects of graphical expression of invariants and operations on modelling and model usage tasks. Results suggest VCL benefits in defect detection, model comprehension, and modelling of operations, providing some empirical evidence on the benefits of graphical software design

Safety assurance of an industrial robotic control system using hardware/software co-verification

As a general trend in industrial robotics, an increasing number of safety functions are being developed or re-engineered to be handled in software rather than by physical hardware such as safety relays or interlock circuits. This trend reinforces the importance of supplementing traditional, input-based testing and quality procedures which are widely used in industry today, with formal verification and model-checking methods. To this end, this paper focuses on a representative safety-critical system in an ABB industrial paint robot, namely the High-Voltage electrostatic Control system (HVC). The practical convergence of the high-voltage produced by the HVC, essential for safe operation, is formally verified using a novel and general co-verification framework where hardware and software models are related via platform mappings. This approach enables the pragmatic combination of highly diverse and specialised tools. The paper's main contribution includes details on how hardware abstraction and verification results can be transferred between tools in order to verify system-level safety properties. It is noteworthy that the HVC application considered in this paper has a rather generic form of a feedback controller. Hence, the co-verification framework and experiences reported here are also highly relevant for any cyber-physical system tracking a setpoint reference

Digital Twin for Hybrid Installations

The product development and lifecycle management is constantly affected by digitalization. The same trend has been also observed in the simulation technology. The system simulation has evolved from applications with limited and specific use cases to more standardized and multi-disciplinary tools. The “Digital Twin” concept is the most recent advancement in this field where its definition is beyond a simulator. The concept arose from the “Industry 4.0” development and it can be described as a bi-directional communication between physical products data and their digital representation in the entire product lifecycle. A hybrid power module consists of components such as an engine, a gearbox, the generator sets, the batteries, and technologies for efficiently exploiting the mechanical energy form the engine and the electrical energy from the batteries. The modular product development necessitates adoption of systems engineering approaches and principles in order to handle the product lifecycle management appropriately. Handling the product lifecycle management for the hybrid power modules encompasses the integration of disengaged elements, data, and stakeholders throughout the product development. In order to address the abovementioned problem, model-based systems engineering approach incorporates available tools and technologies. A product lifecycle management platform and tools in hand like web services and functional mock-up interface justify the development of a digital twin application. This application must be able to reveal the adoption of system of systems view for hybrid power module development. This can be achieved by creating a reference system model and continuously enriching it with the product lifecycle data. To begin with the implementation of a digital twin application, systems engineering theories are studied, a software development lifecycle is chosen, prototypes of the application, and development technologies are selected. Lastly, the application is programmed and deployed. The digital twin application is embedded inside a product lifecycle management platform and exploits other resources and data alongside. The application is a simplified implementation of the “V” lifecycle model in systems engineering and achieves objectives like task-centered product development, value co-creation in business processes, product data management, simulation-based, and requirements validation among others

Checking SysML Models for Co-simulation

Cyber-physical systems (CPSs) are often treated modularly to tackle both complexity and heterogeneity; and their validation may be done modularly by co-simulation: the coupling of the individual subsystem simulations. This modular approach underlies the FMI standard. This paper presents an approach to verify both healthiness and well-formedness of an architectural design, expressed using a profile of SysML, as a prelude to FMI co-simulation. This checks the conformity of component connectors and the absence of algebraic loops, necessary for co-simulation convergence. Verification of these properties involves theorem proving and model-checking using: Fragmenta, a formal theory for representing typed visual models, with its mechanisation in the Isabelle/HOL proof assistant, and the CSP process algebra and its FDR3 model-checker. The paper’s contributions lie in: a SysML profile for architectural modelling supporting multi-modelling and co-simulation; our approach to check the adequacy of a SysML model for co-simulation using theorem proving and model-checking; our verification and transformation workbench for typed visual models based on Fragmenta and Isabelle; an approach to detect algebraic loops using CSP and FDR3; and a comparison of approaches to the detection of algebraic loops