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

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].

QC 20120221

No abstract

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 interdomain 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.

No abstract

o far there is no common and widely accepted understanding of what mechatronics really is. Many different notions similar to or including mechatronics have been used in various contexts; micromechatronics, optomechatronics, supermechatronics, mecanoinformatics, contromechanics and megatronics are some of these, each coined to put forward a specific aspect or application of mechatronics. Examples of attempts to describe mechatronics include the following. N Mechatronics encompasses the knowledge and the technologies required for the flexible generation of controlled motions [1]. N Mechatronics is the synergistic combination of mechanical and electrical engineering, computer science, and information technology, which includes control systems as well as numerical methods used to design products with built-in intelligence [2]. N Hewit in [3] states: A precise definition of mechatronics is not possible, nor is it particularly desirable, because the field is new and expanding rapidly; too rigid a definition would be constraining and limiting, and that is precisely what is not wanted at present. Mechatronics as an interdisciplinary subject tends to attract contributions from all related fields without really putting forward the opportunities and challenges arising specifically due to the interdisciplinary interactions. An example of this is that many mechatronics conferences have been unfocused and thereby have not attracted the most adequate contributions, which definitely exist. This is a disadvantage in that it hampers the development of mechatronics as an engineering science. Scientific publications in mechatronics, to help in making the subject more focused, are still quite rare. One of the earlier publications is Mechatronics-an International Journal published by Elsevier Science, first published in 1991.

Highly automated road vehicles need the capability of stopping safely in a situation that disrupts continued normal operation, e.g. due to internal system faults. Motion planning for safe stop differs from nominal motion planning, since there is not a specific goal location. Rather, the desired behavior is that the vehicle should reach a stopped state, preferably outside of active lanes. Also, the functionality to stop safely needs to be of high integrity. The first contribution of this paper is to formulate the safe stop problem as a benchmark optimal control problem, which can be solved by dynamic programming. However, this solution method cannot be used in real-time. The second contribution is to develop a real-time safe stop trajectory planning algorithm, based on selection from a precomputed set of trajectories. By exploiting the particular properties of the safe stop problem, the cardinality of the set is decreased, making the algorithm computationally efficient. Furthermore, a monitoring based architecture concept is proposed, that ensures dependability of the safe stop function. Finally, a proof of concept simulation using the proposed architecture and the safe stop trajectory planner is presented.

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.