Steam Net Simulation with Real Control System

This master thesis has been conducted for Solvina. Solvina is a firm in Gothenburg, which among other things simulates steam nets for the paper process industry. Doing this Solvina has had to simulate not only the steam net itself, but also to simulate the control system. The purpose of this master thesis was to try to build an interface between the controller and the simulated process so that the simulated steam net could be controlled by the real control system. The process is modelled in Dymola/Modelica. The control system is built in Siemens process control system called Simatic PCS 7 and runs on a PC. The simulated process and the control system run on the same PC and the communication between the process and the control system is a communication between two applications running on the same operative system, which is Windows NT. The two applications communicate with each other by reading from and writing to a common file. The simulated process in Dymola calls a C++ function that reads the control signals from the file and writes the process values to the file, every sampling time. A J++ program communicates with the control system and writes the control signals to the file and reads the process values from the file, every sampling time. The communication is synchronized and the applications access the file using mutual exclusion

Practice of Industrial Control Logic Programming using Library Components

This chapter discusses Programmable Logic Controller (PLC) programming practice, particularly the use of library components, in the automotive industry. A study of program structure and use of library components at two European car manufacturers is presented. The main purpose of the study is to provide understanding of current PLC programming in industry

Organisation and Communication Problems in Automotive Requirements Engineering

Project success in the automotive industry is highly influenced by Requirements Engineering (RE), for which communication and organisation structure play a major role, much due to the scale and distribution of these projects. However, empirical research is scarce on these aspects of automotive RE and warrants closer examination. Therefore, the purpose of this paper is to identify problems or challenges in automotive RE with respect to communication and organisation structure. Using a multiple-case study approach, we collected data via 14 semi-structured interviews at one car manufacturer and one supplier. We tested our findings from the case study with a questionnaire distributed to practitioners in the automotive industry. Our results indicate that it is difficult but increasingly important to establish communication channels outside the fixed organisation structure and that responsibilities are often unclear. Product knowledge during early requirements elicitation and context knowledge later on is lacking. Furthermore, abstraction gaps between requirements on different abstraction levels leads to inconsistencies. For academia, we formulate a concrete agenda for future research. Practitioners can use the findings to broaden their understanding of how the problems manifest and to improve their organisations

On Industrial Automation Software Components

This thesis deals with Programmable Logic Controller (PLC) programs in the manufacturing industry, that is to say programs that coordinate robots and machines. The last years there has been increased competition and shorter life-cycles of many mass-produced products. This places new requirements also on the PLC programs, which must be easily modifiable and quickly made fully operational.One way to make fast and correct modifications of the PLC programs is to reuse as much code as possible. Composing the PLC program from reusable components is a way to accomplish this reuse. Efficient component reuse requires that it is known how the components should be used and what the components guarantee. Hence, these requirements and guarantees must be unambiguously specified. It should also be verified that the implementation of the component indeed fulfils the specification.Testing and simulating the component may be helpful in verifying that the specification is fulfilled. However, in many practical situations it is timeconsuming or even impossible to test or simulate all different cases in which the component can be used. An alternative is to use formal verification. Formal verification of the component means to automatically explore all behaviour of the component, to check whether or not the specification is fulfilled.This thesis investigates how PLC program components can be, and currently are, used in industry. The main result is the definition of Reusable Automation Components (RACs). A component\u27s requirements and properties can be formally specified in the RAC. The specification structure is inspired by a concept called Design by Contract. The specification can be expressed using Ladder Diagrams, a common PLC programming language, augmented with syntax for temporal logic. The augmentation is used to describe the order in time in which the states of the component changes, for instance when outputs should change related to certain inputs. The RAC, including the specification, can be translated into input to a tool for formal verification. Examples show that the RACs may help the users to find errors and inconsistencies within the components, making it easier to do modifications of the code

On Formal Specification and Verification of Function Block Applications in Industrial Control Logic Development

Developing a control system for an automated manufacturing system is a challenging task. In addition to controlling and coordinating the machines and robots used in the production, the safety of the operators must be assured. The control system should also be easily modifiable and quickly made fully operational, to reduce down-time and ramp-up-time of the manufacturing system. To handle these challenges, Programmable Logic Controllers (PLCs) and a set of standard programming languages are typically used. Many industrial practitioners also use standardized programming structure and they reuse code in form of function blocks between and within different programming projects. Although the PLC programming is well standardized, there is no established standard for the specifications. The function blocks are typically documented informally, for instance using natural language and pictures, or not specified at all. Unambiguous specifications of function blocks would not only promote efficient reuse and facilitate verification, but are fundamental for the part handling safety. International safety standards emphasize the importance of specifying and verifying safety-related software.This thesis proposes the Reusable Automation Component (RAC) framework for formal, mathematical specification and verification of function blocks. The RAC formal specification removes ambiguity and enables automated and exhaustive off-line verification using model checking. Developing formal specifications is typically a tough task for PLC programmers and maintainers and this thesis therefore proposes methods and a language for assisting the specification development. The main contributions of the thesis are the proposed specification assistance and industrial studies on PLC programming and function block specifications.A prototype RAC tool has been implemented in which the function blocks can be specified and then verified using a model checking tool. Several industrial examples show that the RAC framework may help the users to find errors and inconsistencies within the function blocks, and to confirm that the expected safety properties are fulfilled

On Formal Specification and Verification of Function Block Applications in Industrial Control Logic Development

Developing a control system for an automated manufacturing system is a challenging task. In addition to controlling and coordinating the machines and robots used in the production, the safety of the operators must be assured. The control system should also be easily modifiable and quickly made fully operational, to reduce down-time and ramp-up-time of the manufacturing system. To handle these challenges, Programmable Logic Controllers (PLCs) and a set of standard programming languages are typically used. Many industrial practitioners also use standardized programming structure and they reuse code in form of function blocks between and within different programming projects. Although the PLC programming is well standardized, there is no established standard for the specifications. The function blocks are typically documented informally, for instance using natural language and pictures, or not specified at all. Unambiguous specifications of function blocks would not only promote efficient reuse and facilitate verification, but are fundamental for the part handling safety. International safety standards emphasize the importance of specifying and verifying safety-related software.This thesis proposes the Reusable Automation Component (RAC) framework for formal, mathematical specification and verification of function blocks. The RAC formal specification removes ambiguity and enables automated and exhaustive off-line verification using model checking. Developing formal specifications is typically a tough task for PLC programmers and maintainers and this thesis therefore proposes methods and a language for assisting the specification development. The main contributions of the thesis are the proposed specification assistance and industrial studies on PLC programming and function block specifications.A prototype RAC tool has been implemented in which the function blocks can be specified and then verified using a model checking tool. Several industrial examples show that the RAC framework may help the users to find errors and inconsistencies within the function blocks, and to confirm that the expected safety properties are fulfilled

A Study of Industrial Logic Control Programming Using Library Components

In this paper a study of logic control programming practices and use of library components at two European car manufacturers, is presented. The research provides results important to consider for researchers and PLC vendors when developing frameworks for control program generation, to cope with new requirements of flexible manufacturing systems. The main observations are: the programs, written mainly in Ladder Diagrams and Sequential Function Charts, frequently reuse pre-developed function blocks; it is important that the control programs can be understood and used for trouble-shooting by the operators; and finally, the code handles, besides automatic control, also safety and supervision, human machine interface, product data, communication etc., the code for automatic control is a minor part of the total code

A Study of Industrial Logic Control Programming Using Library Components

In this paper a study of logic control programming practices and use of library components at two European car manufacturers, is presented. The research provides results important to consider for researchers and PLC vendors when developing frameworks for control program generation, to cope with new requirements of flexible manufacturing systems. The main observations are: the programs, written mainly in Ladder Diagrams and Sequential Function Charts, frequently reuse pre-developed function blocks; it is important that the control programs can be understood and used for trouble-shooting by the operators; and finally, the code handles, besides automatic control, also safety and supervision, human machine interface, product data, communication etc., the code for automatic control is a minor part of the total code

Formal Specification and Verification of Components for Industrial Logic Control Programming

Component based approaches to develop industrial logic control programs promise to shorten development and modification times, and to lessen programming errors. However, to get these benefits it is important that components verified to work properly are reused. This work proposes using Reusable Automation Components (RACs), which contain not only the implementation but also a formal specification defining the correct use and behaviour of the component. This specification uses temporal logic to describe relations over time. The specification is helpful both for users of the components and for developers since the complete RAC including the specification can be translated into input to a tool for formal verification, to determine whether the specification is fulfilled or not. This paper shows how the RAC can be both implemented and specified using the common IEC 61131 standard and Ladder Diagrams. An industrial example is presented, specified and formally verified. It shows that RACs may help the developers to find errors and inconsistencies within the components, making it easier to do modifications of the code