Dr. Henrik Lipskoch

Abstract
Today, batteries serve as a power supply for almost every electronic device which people carry around or install in locations that have no access to the mains. The longer a battery powered system can operate without need for recharge or battery replacement, the more will maintenance cost and the number of faults due to insufficient power supply decrease. This work considers multiple independent software tasks that are assigned to the same processor.
The tasks are supposed to have hard deadlines and are to be scheduled earliest deadline first (EDF). Energy consumption is optimised using processor voltage and frequency scaling, per task or per task set, and processor shutdown, periodically or task-dependent. An event-stream based hard real-time test ensures the feasibility of the solutions, and it provides low computational complexity for the optimisation problem. Optimal configurations in the sense of a long operating life are determined with the help of a battery model which is developed in this work. The model is evaluated with measurements on real batteries. A positive effect of pulsed discharge was falsified for pulses in the range of 50 μs to 10 ms. Based on the results, a battery model is derived which is as simple as the Peukert-formula and which provides an error of less than 7% for the battery samples which were used in the experiments.


Keywords
battery operating life, hard real-time, earliest deadline first, event streams, energy savings, voltage scaling, frequency scaling, processor shutdown, low-power modes, battery model, pulsed discharge Batterienutzungsdauer, Echtzeitsysteme, Ereignisströme, Batteriemodell, gepulste Entladung.


Author
Henrik Lipskoch studied mathematics and computer science at the Carl von Ossietzky University Oldenburg and Linköping University, Sweden. From 2005 to 2008 he was holding a scholarship of the research training group "TrustSoft" funded by the Deutsche Forschungsgemeinschaft (DFG). In 2010 he received his doctorate from the University Oldenburg with this work. Today, he is working as a software developer and in his spare time, he is doing research in the field of embedded real-time systems.
The work presented in this book targets the problem of maximising the operating time of a battery powered embedded computer-system that is subject to real-time constraints. Though a computer-science topic, the content also touches mathematical modelling, electrical engineering, and electrochemistry.

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