End-To-End Timing Analysis in ROS2

Abstract

Modern autonomous vehicle platforms feature many interacting components and sensors, which add to the system complexity and affect their performance. A key aspect for such platforms are end-to-end timing guarantees, which are required for safe and predictable behavior in every situation. One widely used tool to develop such autonomous systems is the Robot Operating System 2 (ROS2), which allows creating robot applications composed of several components that communicate with each other to form complex systems. Furthermore, it guarantees real-time constraints and provides reliable timing behavior using a custom scheduler design that manages the execution of all components. These components and their data propagation form multiple cause-effect chains that can be analyzed to determine two key metrics: maximum reaction time (which is the maximum time for the system to react to an external input) and maximum data age (which equals the maximum time between sampling and the output of the system being based on that sample). However, an end-to-end analysis for cause-effect chains in ROS2 systems has not been provided yet. In this paper, we provide a theoretical upper bound for the end-to-end timing of a ROS2 system on a single electronic control unit (ECU). Additionally, we show how to simulate a ROS2 system to get a lower bound for the timing analysis and introduce an online end-to-end timing measurement method for existing ROS2 systems. We evaluate our methods with a basic autonomous navigation system and determine the timing behavior for different components and sensor configurations.