Martin Törngren

Timing problems in real-time control systems

The paper formulates and discusses timing problems in real-time systems from the sampled data point of view. Different ways to eliminate the effects of communication delays are considered.

Fundamentals of Implementing Real-Time Control Applicationsin Distributed Computer Systems

Automatic control applications are real-time systems which pose stringent requirements on precisely time-triggered synchronized actions and constant end-to-end delays in feedback loops which often constitute multi-rate systems. Motivated by the apparent gap between computer science and automatic control theory, a set of requirements for real-time implementation of control applications is given. A real-time behavioral model for control applications is then presented and exemplified. Important sources and characteristics of time-variations in distributed computer systems are investigated. This illuminates key execution strategies to ensure the required timing behavior. Implications on design and implementation and directions for further work are discussed.

SaveCCM - a component model for safety-critical real-time systems

Component-based development has proven effective in many engineering domains, and several general component technologies are available. Most of these are focused on providing an efficient software-engineering process. However for the majority of embedded systems, run-time efficiency and prediction of system behaviour are as important as process efficiency. This calls for specialized technologies. There is even a need for further specialized technologies adapted to different types of embedded systems, due to the heterogeneity of the domain and the close relation between the software and the often very application specific system. This work presents the SaveCCM component model, intended for embedded control applications in vehicular systems. SaveCCM is a simple model in which flexibility is limited to facilitate analysis of real-time and dependability. We present and motivate the model, and provide examples of its use.

Vehicle Applications of Controller Area Network

The Controller Area Network (CAN) is a serial bus communications protocol developed by Bosch in the early 1980s. It defines a standard for efficient and reliable communication between sensor, actuator, controller, and other nodes in real-time applications. CAN is the de facto standard in a large variety of networked embedded control systems. The early CAN development was mainly supported by the vehicle industry: CAN is found in a variety of passenger cars, trucks, boats, spacecraft, and other types of vehicles. The protocol is also widely used today in industrial automation and other areas of networked embedded control, with applications in diverse products such as production machinery, medical equipment, building automation, weaving machines, and wheelchairs.The purpose of this chapter is to give an introduction to CAN and some of its vehicle applications. The outline is as follows. Section 2 describes the CAN protocol, including its message formats and error handling. The section is concluded by a brief history of CAN. Examples of vehicle application architectures based on CAN are given in Section 3. A few specific control loops closed over CAN buses are discussed in Section 4. The paper is concluded with some perspectives in Section 5, where current research issues such as x-by-wire and standardized software architectures are considered. The examples are described in more detail in [14]. A detailed description of CAN is given in the textbook [6]. Another good resource for further information is the homepage of the organization CAN-in-Automation (CiA) [3]. The use of CAN as a basis for distributed control systems is discussed in [13].

Guidelines for a graduate curriculum on embedded software and systems

The design of embedded real-time systems requires skills from multiple specific disciplines, including, but not limited to, control, computer science, and electronics. This often involves experts from differing backgrounds, who do not recognize that they address similar, if not identical, issues from complementary angles. Design methodologies are lacking in rigor and discipline so that demonstrating correctness of an embedded design, if at all possible, is a very expensive proposition that may delay significantly the introduction of a critical product. While the economic importance of embedded systems is widely acknowledged, academia has not paid enough attention to the education of a community of high-quality embedded system designers, an obvious difficulty being the need of interdisciplinarity in a period where specialization has been the target of most education systems. This paper presents the reflections that took place in the European Network of Excellence Artist leading us to propose principles and structured contents for building curricula on embedded software and systems.

Tool Integration beyond Wasserman

The typical development environment today consists of many specialized development tools, which are partially integrated, forming a complex tool landscape with partial integration. Traditional appr ...

Cyber-physical system design contracts

This paper introduces design contracts between control and embedded software engineers for building Cyber-Physical Systems (CPS). CPS design involves a variety of disciplines mastered by teams of engineers with diverse backgrounds. Many system properties influence the design in more than one discipline. The lack of clearly defined interfaces between disciplines burdens the interaction and collaboration. We show how design contracts can facilitate interaction between 2 groups: control and software engineers. A design contract is an agreement on certain properties of the system. Every party specifies requirements and assumptions on the system and the environment. This contract is the central point of inter-domain communication and negotiation. Designs can evolve independently if all parties agree to a contract or designs can be modified iteratively in negotiation processes. The main challenge lies in the definition of a concise but sufficient contract. We discuss design contracts that specify timing and functionality, two important properties control and software engineers have to agree upon. Various design approaches have been established and implemented successfully to address timing and functionality. We formulate those approaches as design contracts and propose guidelines on how to choose, derive and employ them. Modeling and simulation support for the design contracts is discussed using an illustrative example.

What is embedded systems and how should it be taught?---results from a didactic analysis

This paper provides an analysis of embedded systems education using a didactic approach. Didactics is a field of educational studies mostly referring to research aimed at investigating whats unique with a particular subject and how this subject ought to be taught. From the analysis we conclude that embedded systems has a thematic identity and a functional legitimacy. This implies that the subject would benefit from being taught with an exemplifying selection and using an interactive communication, meaning that the education should move from teaching “something of everything” toward “everything of something.” The interactive communication aims at adapting the education toward the individual student, which is feasible if using educational methods inspired by project-organized and problem-based learning. This educational setting is also advantageous as it prepares the students for a future career as embedded system engineers. The conclusions drawn from the analysis correlate with our own experiences from education in mechatronics as well as with a recently published study of 21 companies in Sweden dealing with industrial software engineering.

The science and education of mechatronics engineering

We try to get to the heart of multidisciplinary engineering, of which mechatronics is an excellent example, and point out how the integration of disciplines leads to new degrees of freedom in design and corresponding research directions that otherwise would not have been investigated. This is the major contribution achieved by a multidisciplinary approach to engineering science; it leads to a new important research field and at the same time helps to push research in related fields into new fruitful directions. We point to a number of areas that have benefited from the interdisciplinary perspective and a focus on interactions between disciplines including: engineering curriculum; mechatronics research; control of nonlinear mechanical systems; real time control systems modelling; and time varying control systems.

Modelling Support for Design of Safety-Critical Automotive Embedded Systems

This paper describes and demonstrates an approach that promises to bridge the gap between model-based systems engineering and the safety process of automotive embedded systems. The basis for this is the integration of safety analysis techniques, a method for developing and managing Safety Cases, and a systematic approach to model-based engineering --- the EAST-ADL2 architecture description language. Three areas are highlighted: (1) System model development on different levels of abstraction. This enables fulfilling many requirements on software development as specified by ISO-CD-26262; (2) Safety Case development in close connection to the system model; (3) Analysis of mal-functional behaviour that may cause hazards, by modelling of errors and error propagation in a (complex and hierarchical) system model.