SAE 2016 World Congress and Exhibition,
April 2016 · SAE Technical Paper · doi: 10.4271/2016-01-0012
The growing complexity of functionalities in automotive vehicles and their safety-criticality, including timing requirements, demands sound and scalable approaches to deal with the increasing design space. Most often, such complex automotive systems are composed of a set of functions that are characterized by multi-period timing behaviors, e.g., due to environment constraints limiting sensing/acting frequencies, or various worst case execution times of software components.As safety-critical systems must perform the desired behavior within guaranteed time bounds, a valid system configuration is needed including a time-correct schedule that fulfills all timing requirements. This contribution proposes a systematic and correct schedule synthesis of complex multi-rate automotive software systems that ensures precise timing behavior of software components.The proposed synthesis approach - guaranteeing given timing requirements, based on preemptive, time-triggered scheduling - optimizes non-harmonic task sets by minimizing context switches between these tasks. This approach is integrated into the AUTOFOCUS 3 tool-chain, using its models of a software component architecture as well as of a hardware platform, combined with precalculated interrupt sets and a symbolic encoding scheme to synthesize schedules meeting the given multi-rate timing requirements. The approach is demonstrated using an Adaptive Cruise Control System.