Computational Delay in Vehicles and Its Effect on Real Time Scheduling

Present research into critical embedded control systems tends to focus on the computational elements and largely ignore the link between the computational and physical elements. This link is very important since the computational capability of the computer can greatly affect the performance and dynamics of the system it controls. The control computer is in the feedback loop of control systems and contributes to feedback delay in addition to already existing mechanical delays. While mechanical delays are compensated in control design, variable computational delays cause system to underperform in its intended physical behavior and impose a cost in terms of fuel or time. For this reason, the scheduler in a real-time operating systems should not focus only on the task deadlines, but also on efficient scheduling which minimizes the effect of computational delay on the controlled plant. The proposed work provides a systematic framework to manage and evaluate the implications of computational delay in vehicles. The work also includes cost sensitive real-time control task scheduling heuristics and Dynamic Voltage Scaling (DVS) for better energy/thermal control. We show through simulations that our heuristic achieves a significant improvement in cost over the traditional real-time scheduling algorithm Earliest Deadline First (EDF) and show that it can adjust according to energy constraints imposed on the system