Jakob Axelsson

A comparison of fixed-priority and static cyclic scheduling for distributed automotive control applications

This paper compares different scheduling policies applied to distributed systems intended for automotive real-time control applications. We describe the characteristics of systems using fixed priority (FP) and static cyclic (SC) scheduling of processors and bus communication, with combinations ranging from FP bus-FP processors to SC bus-SC processors. FP bus is represented by the Controller Area Network protocol (CAN) and SC bus by a Time Division Multiple Access (TDMA) protocol. We also study the effects of using a global time base. Our main concern is control performance, including input and output jitter and control delay and therefore the response time of a sequence of control tasks and the related communication. For each system configuration we analyze the expected response times of a series of control related tasks (delay) and the temporal variation of the input and output instants (jitter).

Architecture synthesis and partitioning of real-time systems: a comparison of three heuristic search strategies

Studies the problem of automatically selecting a suitable system architecture for implementing a real-time application. Given a library of hardware components, it is shown how an architecture can be synthesized with the goal of fulfilling the real-time constraints stated in the systems specification. In the case where the selected architecture contains several processing units, the specification is partitioned by assigning tasks to these. The use of three heuristic search techniques is investigated: genetic algorithms, simulated annealing and tabu search; and it is described how these can be adapted to the architecture synthesis problem. It is concluded that tabu search is the most promising technique but that simulated annealing is also applicable.

Experience of introducing reference architectures in the development of automotive electronic systems

The requirements on increasing functionality, quality, and, customisation, while reducing cost has lead to the introduction of an architecture centred development process for electronic systems at Volvo Cars. This process enables better control of system integration and achieving non-functional requirements, such as reusability, understandability, etc. The result of the process is a reference architecture that includes strategies for implementing the balanced requirements, architectural views that provide means for reasoning about all the concerns of all stakeholders, and a top-level design of the architecturally significant parts. The reference architecture guides the design of several projects, and thus, cost is optimised accordingly. The main contribution of this paper is that we present experiences from introducing the architecture centred process. The main conclusions are that disseminating and maintaining the reference architecture actually require more resources than developing it. Furthermore, experience shows it is difficult to create an architecture that enables a lot of different variants that is also strategically useable in the long term.

Evolutionary architecting of embedded automotive product lines: An industrial case study

In the automotive industry, embedded systems and software play an increasingly important role in defining the characteristics of the vehicles. Both the vehicles and the embedded systems are designed as product lines, and two distinct architecture processes can be identified. The revolutionary process develops the architecture of a new product line, and focuses on abstract quality attributes and flexibility. The evolutionary process continuously modifies the architecture due to changes, such as additions of new functionality. In this paper, the evolutionary process is investigated through a case study. The study reviews a number of changes to an existing architecture, observing the cause of the change, what quality attributes were considered, and what technical aspects were included. It is also analyzed how the interplay between the two processes can be improved through systematic feedback about what evolution actually takes place.

A Case Study of Issues Related to Automotive E/E System Architecture Development

The use of electronics in vehicles is increasing quickly and the systems are becoming increasingly complex. This makes the engineering of these advanced computer-based systems more and more difficult. In particular, finding a good architecture is a prerequisite for successful design. In this study we investigate key issues related to real-world decisions regarding a cars electrical and electronic system architecture. To extract the key issues an exploratory case study was performed at a car manufacturer. We used semi- formal interviews complemented with a survey to validate the results. The contribution of this paper is twelve issues that reflect the situation at a car manufacturer. Also, possible actions to deal with these issues are provided.

Characteristics of Software Ecosystems for Federated Embedded Systems: A Case Study

Context: Traditionally, Embedded Systems (ES) are tightly linked to physical products, and closed both for communication to the surrounding world and to additions or modifications by third parties. ...

Unified modeling of real-time control systems and their physical environments using UML

Modeling languages that are used to capture the essential properties of embedded real-time computer systems must also allow a description of the systems physical environment. The reason is that the environment is the ultimate source of all requirements on the system, and in particular, real-time constraints are derived from the dynamics of the physical objects under control. However, most modeling languages, including the object-oriented ones, are not well equipped to describe the continuous-time relationships that exist in the real world. This paper shows how the Unified Modeling Language can be extended to include such modeling, thereby improving the design of embedded systems described in the same language. A realistic case study is elaborated to show the practical usefulness of the results.

Correlation between safety assessments in the driver-car interaction design process

With the functional revolution in modern cars, evaluation methods to be used in all phases of driver-car interaction design have gained importance. It is crucial for car manufacturers to discover and solve safety issues early in the interaction design process. A current problem is thus to find a correlation between the formative methods that are used during development and the summative methods that are used when the product has reached the customer. This paper investigates the correlation between efficiency metrics from summative and formative evaluations, where the results of two studies on sound and navigation system tasks are compared. The first, an analysis of the J.D. Power and Associates APEAL survey, consists of answers given by about two thousand customers. The second, an expert evaluation study, was done by six evaluators who assessed the layouts by task completion time, TLX and Nielsen heuristics. The results show a high degree of correlation between the studies in terms of task efficiency, i.e. between customer ratings and task completion time, and customer ratings and TLX. However, no correlation was observed between Nielsen heuristics and customer ratings, task completion time or TLX. The results of the studies introduce a possibility to develop a usability evaluation framework that includes both formative and summative approaches, as the results show a high degree of consistency between the different methodologies. Hence, combining a quantitative approach with the expert evaluation method, such as task completion time, should be more useful for driver-car interaction design.

Quality assurance in software ecosystems

The literature on quality assurance in software ecosystems was reviewed.The resulting six publications were mapped to software lifecycle processes.A research agenda for quality assurance in software ecosystems was derived.A challenge is the cross-organizational interactions needed for quality assurance.Many issues are caused by the user initiated and dynamic system integration. Software ecosystems are becoming a common model for software development in which different actors cooperate around a shared platform. However, it is not clear what the implications are on software quality when moving from a traditional approach to an ecosystem, and this is becoming increasingly important as ecosystems emerge in critical domains such as embedded applications. Therefore, this paper investigates the challenges related to quality assurance in software ecosystems, and identifies what approaches have been proposed in the literature. The research method used is a systematic literature mapping, which however only resulted in a small set of six papers. The literature findings are complemented with a constructive approach where areas are identified that merit further research, resulting in a set of research topics that form a research agenda for quality assurance in software ecosystems. The agenda spans the entire system life-cycle, and focuses on challenges particular to an ecosystem setting, which are mainly the results of the interactions across organizational borders, and the dynamic system integration being controlled by the users.

On the conceptual design of a dynamic component model for reconfigurable AUTOSAR systems

The automotive industry has recently developed the embedded software standard AUTOSAR, which is now being introduced widely in production vehicles. The standard structures the application into reusable components that can be deployed in a specific vehicle using a configuration scheme. However, this configuration takes place at design time, with no provision for dynamically installing components to reconfigure the system. In this paper, we present the conceptual design of a dynamic component model that extends an AUTOSAR based control unit with the possibility to add plug-in components that execute on a virtual machine. This concept is intended to give benefits in terms of much shorter deployment time for new functions, even into vehicles that have already been produced. Further, it creates opportunities for vehicles to take part in federated embedded systems together with other products. It also opens up a market for third-party developers, and fosters open innovation in an ecosystem around the automotive software business.