Model-Driven Development of Control Applications: On Modeling Tools, Simulations and Safety

Control systems are required in various industrial applications varying from individual machines to manufacturing plants and enterprises. Software applications have an important role as an implementation technology in such systems, which can be based on Distributed Control System (DCS) or Programmable Control System (PLC) platforms, for example. Control applications are computer programs that, with control system hardware, perform control tasks. Control applications are efficient and flexible by nature; however, their development is a complex task that requires the collaboration of experts and information from various domains of expertise.This thesis studies the use of Model-Driven Development (MDD) techniques in control application development. MDD is a software development methodology in which models are used as primary engineering artefacts and processed with both manual work and automated model transformations. The objective of the thesis is to explore whether or not control application development can benefit from MDD and selected technologies enabled by it. The research methodology followed in the thesis is the constructive approach of design science.To answer the research questions, tools are developed for modeling and developing control applications using UML Automation Profile (UML AP) in a model-driven development process. The modeling approach is developed based on open source tools on Eclipse platform. In the approach, modeling concepts are kept extendable. Models can be processed with model transformation techniques that plug in to the tool. The approach takes into account domain requirements related to, for example, re-use of design. According to assessment of industrial applicability of the approach and tools as part of it, they could be used for developing industrial DCS based control applications.Simulation approaches that can be used in conjunction to model-driven development of control applications are presented and compared. Development of a model-in-the-loop simulation support is rationalized to enable the use of simulations early while taking into account the special characteristics of the domain. A simulator integration is developed that transforms UML AP control application models to Modelica Modeling Language (ModelicaML) models, thus enabling closed-loop simulations with ModelicaML models of plants to be controlled. The simulation approach is applied successfully in simulations of machinery applications and process industry processes.Model-driven development of safety applications, which are parts of safety systems, would require taking into account safety standard requirements related to modeling techniques and documentation, for example. Related to this aspect, the thesis focuses on extending the information content of models with aspects that are required for safety applications. The modeling of hazards and their associated risks is supported with fault tree notation. The risk and hazard information is integrated into the development process in order to improve traceability. Automated functions enable generating documentation and performing consistency checks related to the use of standard solutions, for example. When applicable, techniques and notations, such as logic diagrams, have been chosen so that they are intuitive to developers but also comply with recommendations of safety standards

Designing Functional Safety Systems: A Pattern Language Approach

Human beings, at least most of us, want to feel and be safe. This is one of the fundamental needs of an organism. However, several of the processes and machines used in current societies introduce hazards that could and can harm us causing unnecessary pain and financial losses. Still, our modern societies need these processes and machines to operate so we cannot really be without them. Fortunately, there are ways to reduce risks introduced by systems around us to a tolerable level.This thesis considers the design and development of safety-related systems and safetyrelated parts of control systems referred to as functional safety systems. These systems implement safety functions that reduce risks introduced by machines, processes, and other systems. That is, the functions affect the system under control so that the likelihood of occurrence or severity of consequences are reduced.The design and development of safety systems is typically regulated by laws and standards. This increases the cost of safety system development and therefore eventually also the product in which it is incorporated. However, from a manufacturer viewpoint, safety in all its forms is also a potential asset for the companies developing, producing, and selling the systems. An increase in efficiency to develop and design safety systems offers the potential for a larger margin or increased sales due to the reduced price.One way to support design and development efficiency is to apply good design methods and solutions in form of design patterns. In this thesis, a design pattern language for the development and design of functional safety systems is introduced. The purpose of the language is to support the designers in their task to design and implement safety functions in machines and processes. The language considers various aspects of the development and design of safety systems starting from the initial phases of hazard and risk analysis, followed by the selection of the hazard and risk reduction methods, and concluding with the hardware and software structure, functionality, and design principles considerations. Finally, a functional safety system may, and often does, co-exist and co-operate with a control system. Therefore, a part of the pattern language takes this aspect into account.To compile the design pattern language and the included patterns a design science research approach complemented with grounded theory approach is applied The data to identify the patterns is collected from literature, personal experience, interviews, and discussions with industry representatives and people engaged with the design or use of systems including safety systems or functionality. Like the patterns have evolved during the research, so has the approach to identify, document, and process the patterns