CompROS: A composable ROS2 based architecture for real-time embedded robotic development

Robot Operating System (ROS) is a de-facto standard robot middleware in many academic and industrial use cases. However, utilizing ROS/ROS2 in safety-critical embedded applications with real-time requirement is challenging because of C1) Non-real-time underlying hardware, C2) No control on the host OS scheduler, C3) Unpredictable dynamic memory allocation, C4) High resource requirement, and C5) Unpredictable execution model for ROS nodes. In this paper, we address these limiting factors by proposing a hardwaresoftware architecture -CompROS- for ROS2 based robotic development in a Multi-Processor System on Chip (MPSoC) platform. The proposed hardware architecture consists of a Hard Real-Time (HRT) RISC-V based subsystem implemented in the Programmable Logic (PL) part of the MPSoC platform, a Soft Real-Time (SRT) ARM-based subsystem in the Processing System (PS) part of the MPSoC platform, and a Non-Real-Time (NRT) PC. While the proposed hardware architecture along with a partitioning layer overcomes the first two limiting factors, the rest are managed by the proposed multi-layer software architecture. We make a bare-metal implementation of XRCE-DDS standard for PL-PS communication, while peer-to-peer PL-PL communication is done through a proposed real-time publish-subscribe approach. The reliable communication for PS-PL communication is done through utilizing C-HEAP protocol. Further, we integrate ROS2 software layers on top of the proposed hardware and software layers. Finally, with respect to C5, we present a real-time execution model of ROS2 nodes by a mapping of ROS2 entities to CompROS entities, which is validated through experimental results. We run ROS2 middleware with an executable size of less than 200 KB on an MPSoC platform.