Simulating Preemptive Scheduling with Timing-aware Blocks in Simulink
Andreas Naderlinger
Department of Computer Sciences, University of Salzburg.
andreas.naderlinger@cs.uni-salzburg.at
ABSTRACT
This paper introduces an extension of the modeling and simulation environment MATLAB/Simulink. It enables control and system engineers to consider software execution times, as well as the effects of scheduling and preemption inside software-in-the-loop (SIL) simulations. To this end, we present the concept of a Simulink block whose execution lasts for a finite amount of simulation time. During this time, the simulation engine continues to update the plant or other blocks with outputs that have already been calculated by the block. Execution time information is assumed to be known (or based on some random distribution). Source-level annotating the control software with target specific timing information enables a finegrained and even a control-flow dependent simulation of the block. We outline the required synchronization with the simulation engine of Simulink. This timing-aware block consumes simulation time in the same sense as a task consumes CPU time on a target. We describe a mechanism to execute a set of such blocks with (potentially cyclic) data dependencies with a static priority scheduler inside Simulink, including support for preemption. The presented approach permits a development process, where a typical time invariant and platform agnostic model is incrementally transformed into a platform-specific one that makes the simulation more realistic.
