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Veröffentlichungen und Vorträge

Im Rahmen meiner Tätigkeit für verschiedene Firmen sind die folgenden Vorträge und Veröffentlichungen entstanden.

2012

2010

2009

2008

2007 und früher

Deterministic Execution Sequence in Component Based Multi-Contributor Powertrain Control Systems

Abstract:
Modern complex control applications, e.g. engine management systems, typically are built using a component based architecture, enabling the reuse of components and allowing to manage the complexity of the application in terms of functional content, size and interfaces. This approach of independently developed components is supported by the concepts available in AUTOSAR and therefore can be expected to gain increasing importance. However, due to the nature of the task of control applications there still is a strong coupling between individual parts of the components resulting in signal chains and consequently in sequencing requirements. The challenge to get such execution sequences implemented correctly is increased, as often the components are delivered by different and external parties. Our approach extends the idea of functional partitioning of the application into the time domain by defining a system of phases with a fixed sequence and a defined content. This allows to design components right from the beginning into this sequencing frame like they are designed today into the component partitioning frame and to define a system sequencing across different suppliers.

Embedded Realtime Software and Systems , Toulouse, Februar 2012

Modeling and Simulation of Embedded Real-Time Multicore Systems

Abstract:
In order to handle the continuously growing functionality in embedded systems, model-based approaches have been established in the development process over the last years. For singlecore architectures, model-based development has increased efficiency of development and software quality. Current trends show that embedded systems will change to multicore architectures within this decade. In this paper, we argue for a work-efficient migration from single- to multicore architectures through a model-based development process. Concerning the modeling of software and hardware components, we propose relevant properties of an architecture description language. Regarding the design phase, we show how simulation technology can be used for schedulability examination supporting engineers for system design decisions. Afterwards we extend the simulation approach by Monte-Carlo parametrization. Finally we evaluate the enhanced approach in a case study, located in the automotive powertrain domain.

Embedded Software Engineering Kongress, Dezember 2010

Effizientes Multicore-Scheduling in Embedded Systemen - Ein simulationsbasierter Ansatz zum Vergleich von Algorithmen für zuverlässige Echtzeitsysteme

Abstract:
Embedded Systeme unterliegen neben den funktionalen Anforderungen besonders nichtfunktionalen Qualitätsanforderungen wie Effizienz, Zuverlässigkeit und Echtzeitfähigkeit. Einprozessorsysteme werden diesbezüglich in hoher Qualität entwickelt; Scheduling-Algorithmen zur Einhaltung aller Echtzeitanforderungen bei maximaler Systemauslastung existieren. Mit steigendem Bedarf an Rechenkapazität können bisherige Konzepte zur Leistungssteigerung jedoch nicht mehr eingesetzt werden – der Umstieg auf Multicore-Systeme erfolgt.
In dieser Arbeit wird ein holistischer simulationsbasierter Ansatz zum Vergleich von Multicore-Scheduling-Algorithmen vorgestellt. Mittels dessen ist es möglich verschiedenartige Algorithmen für Multicore-Systeme zu analysieren. Wir erweitern diesen Ansatz um ein Verfahren zur Untersuchung einer Taskset-Menge deren Task-Eigenschaften stochastisch beschrieben werden. Anschließend werden Kenngrößen vorgestellt, mittels denen Software Design Entscheidungen bzgl. der obigen Qualitätskriterien bewertet werden können. Zum Schluss wird die Anwendung dieses Ansatzes anhand eines Vergleichs der Algorithmen Bin-Packing+EDF und PFAIR PD²-NQ für eine Gruppe von Automotive Powertrain Systemen demonstriert.

Zur Veröffentlichung angenommen von atp international - Automation Technology in Practice

Efficient Scheduling of Reliable Automotive Multi-core Systems with PD² by Weakening ERfair Task System Requirements

Abstract:
Partly Proportionate fair (Partly-Pfair) scheduling, which allows task migration at runtime and assigns each task processing time with regard to its weight, makes it possible to build highly efficient embedded multi-core systems. Due to its non-work-conserving behavior, which might leave the CPU idle even when tasks are ready to execute, tasks finish only shortly before their deadlines are reached. Benefits are lower task jitter, but additional workload, e.g. through interrupts, can lead to deadline violations. In this paper we present a work-conserving extension of Partly-Pfair scheduling, called PERfair scheduling and the algorithm P-ERfair-PD2 which applies Pfair modifications used for Partly-Pfair on the concept of ERfairness and PD² policies. With a simulation based schedulability examination we show for multiple time base (MTB) task sets that P-ERfair- PD² has the same performance as Partly-Pfair-PD². Additionally, we show that P-ERfair-PD² has a much higher robustness against perturbations, and therefore it is well suited for embedded domains, especially for the Automotive domain.

Automotive 2010, Stuttgart, Juni 2010

Partly Proportionate Fair Multiprocessor Scheduling of Heterogeneous Task Systems

Abstract:
Proportionate-fair (Pfair) scheduling, which allows task migration at runtime and assigns each task processing time with regard to its weight is one of the most efficient SMP multiprocessor scheduling algorithm up to now. The tributes for this are tight requirements to the task system. Drawbacks of the algorithm are restrictions to periodic tasks systems and quantized task execution time. Typical embedded real-time do not fulfill this restrictions. In this paper we address these restrictions and present an extended scheduling algorithm, based on Pfair scheduling, with weaker requirements. In a scheduling simulation we evaluate utilization bounds of the extended algorithm.

Embedded Realtime Software and Systems , Toulouse, Mai 2010

Quirks and Challenges in the Design and Verification of Efficient, High-Load Real-Time Software Systems

Abstract:
Existing concepts for ensuring the correctness of the timing behavior of real-time systems are often based on schedulability analysis methods using exact proofs. Due to the complexity of the scheduling problem, today typically worst case approximations are used to judge the reliability of the timing behavior in software systems. In industrial practice, however, this leads to large safety margins in the design of products which are commercially unacceptable in many application domains. For such highly-efficient systems, schedulability analysis methods that are too pessimistic are of limited benefit. As a consequence, penetration of real-time analysis is suboptimal in the industrial software development, which possibly leads to insufficient quality of the developed products. Therefore, new approaches are needed to support the design and validation of high-load real-time systems with an average CPU load of 90% or above to improve the situation.

Embedded Realtime Software and Systems , Toulouse, Mai 2010

Partitionierungs-Scheduling von heterogenen Tasksystemen auf Multiprozessoren in Automotive Steuergeräten

Abstract:
Diese Arbeit befasst sich mit der statischen Aufteilung von heterogenen Tasksystemen auf SMP Multiprozessoren im Automotive Powertrain Bereich. Eine Besonderheit dieser Systeme ist eine Kombination aus kooperativer und preemptiver Verarbeitung von zeitgesteuerten und ereignisgesteuerten Tasks. Da die Aufteilung von Tasks ein Problem mit NP-Schwere ist, verwenden wir hierfür Partitionierungsheuristiken. Zur Validierung der Heuristiken präsentieren wir einen neuartigen Ansatz zur Echtzeitanalyse, basierend auf einer Multiprozessor- Schedulingsimulation.

Embedded Software Engineering Kongress, Dezember 2009

Application Specific Performance Indicators for Quantitative Evaluation of the Timing Behavior for Embedded Real-Time Systems

Abstract:
In the design and development of embedded real-time systems the aspect of timing behavior plays a central role. Especially, the evaluation of different scheduling approaches, algorithms and configurations is one of the elementary preconditions for creating not only reliable but also efficient systems - a key for success in industrial mass production. This is becoming even more important as multicore systems are more and more penetrating the world of embedded systems together with the large (and growing) variety of scheduling policies available for such systems.
In this work simple mathematical concepts are used to define performance indicators allowing to quantify the benefit of different solutions of the scheduling challenge for a given application. As a sample application some aspects of analyzing the dynamic behavior of an combustion engine management system for the automotive domain are shown.
However, the described approach is flexible in order to support the specific optimization needs arising from the timing requirements defined by the application domain and can be used with simulation data as well as target system measurements.

DATE Conference 2009, Nizza

Alternative C++ Object Representation for Embedded Systems

Abstract:
In specific domains for embedded devices, like the automotive domain, a strong cost pressure exists that requires highly optimized solutions. Due to environmental and other constraints, RAM is costly and scarce, while typically much more Flash-ROM is available (e.g. 1.5 MB of Flash-ROM vs. 56 kB of SRAM). In order to optimize RAM consumption, as many as possible of the constant values must be stored in Flash-ROM.
However, when using C++ as implementation language, its internal object representation prohibits such kind of optimization. A C++ object always resides completely either in RAM or in ROM, giving away a high optimization potential.
The paper describes requirements for objects under such specific constraints, identifies drawbacks of the C++ language and discusses different approaches that improve the usability and resource consumption of C++ in the embedded domain.

To be published.

A Model-Based Development Method for Device Drivers

Abstract:
The present contribution deals with the experiences of introducing a modelbased software development method for device driver families used in electronic control units in the automotive domain (e.g. engine management systems). Besides the technical experiences with UML, SysML and the corresponding tools for requirements, modeling and code generation we will discuss the key benefits as well as the crucial factors for success.

Paper published at the Automotive Software Engineering Day (ASE) within the 38th annual conference of the Gesellschaft für Informatik (GI).

An application-based EDF scheduler for OSEK/VDX

Abstract:
Earliest deadline first scheduling performs processor utilization up to 100 percent and improved robustness in overload situations. However, most automotive applications are running under static priority policy. Because of this, the standard operating system in the automotive industry, OSEK/VDX, just supports priority scheduling. This paper describes an EDF scheduler plug-in for OSEK/VDX. The plug-in provides EDF scheduling without changes to the operating system by delaying task activations.
The add-on was tested for an engine management system developed by SiemensVDO. Results of this experiment are presented and discussed, showing that the EDF scheduling techniques can improve the system in aspects of robustness and resource utilization.

DATE Conference 2008

Simulation von dynamischen Systemen im Automotive Bereich

Motorsteuergeräte aus dem Automobilbereich stellen hohe Anforderungen an die Echtzeitfähigkeit. Eine effektive, quasi-gleichzeitige Verarbeitung verschiedener Funktionalitäten kann nur durch ein optimiertes Scheduling erreicht werden.

Sowohl die Optimierung wie auch die Validierung der dynamischen Architektur wird unter anderem mit Simulationen durchgeführt. Dabei wird das Tool ChronSim der Fa. Inchron verwendet.

Eine der durchgeführten Simulationen wurde von der Fa. Inchron auf dem KFZ-Entwicklerforum 2007 vorgestellt:

5. Artisan User Conference D.A.CH in Lindau (2006)

Vorlesung Betriebssysteme an der Hochschule Regensburg (2004)