Modeling and Analysis of the LatestTime Message Synchronization Policy in ROS

Abstract

Sensor fusion plays a critical role in modern robotics and autonomous systems. In reality, the sensor data destined for the fusion algorithm may have substantially different sampling times. Without proper management, this could lead to poor sensor fusion quality. Robot operating system (ROS) is the most popular robotic software framework, providing essential mechanisms for synchronizing messages to mitigate timing inconsistencies during sensor fusion. Recently, ROS introduced a new LatestTime message synchronization policy. In this article, we formally model the behavior of the LatestTime policy and analyze its worst-case real-time performance. Our investigation uncovers a defect of the LatestTime policy that may cause infinite latency in publishing subsequent outputs. We propose a solution to address this defect and develop safe and tight upper bounds on worst-case real-time performance, in terms of both the maximal temporal inconsistency of its outputs and the incurred latency. Experiments are conducted to evaluate the precision, safety and robustness of our theoretical results.