Other · Runtime & Infrastructure
4.0 (EVL r58)
Xenomai is an open-source project providing hard real-time capabilities on Linux through a co-kernel (dual-kernel) technique. It historically derived from the RTAI (Real-Time Application Interface) project and is developed by a community in which CNRS and other research institutes play a significant role.
Xenomai 3 (Cobalt series) runs as a small co-kernel alongside the Linux kernel. The RT kernel (Cobalt) takes hardware interrupt priorities and handles real-time tasks directly, treating the standard Linux kernel as an idle task. Real-time applications communicate with Cobalt through the libcobalt library. Cycle latencies are typically 2–10 µs.
Xenomai 4 (EVL series) represents a new approach: instead of a co-kernel it uses the Dovetail interface – a lightweight Linux kernel integration layer introducing out-of-band scheduling without creating a separate co-kernel. EVL is closer in spirit to PREEMPT_RT while maintaining extremely low latencies.
In robotics, Xenomai is particularly used in France (LAAS-CNRS), ROS-Industrial, KUKA manipulators (via Fast Robot Interface), service and research robot control systems. It supports IgH EtherCAT Master as the cycle timer provider.
Real-time operating system with a deterministic scheduler and guaranteed interrupt latency. Typically used in motion control, safety-critical systems, ADAS, and industrial robotics (VxWorks, QNX Neutrino, RT-Linux, Zephyr).
General-purpose or robotics-specialized operating system — Ubuntu, Ubuntu Core, ROS-aware distributions. Provides the platform for middleware, runtime, and robotic applications.
Robot Control denotes the role of software responsible for motion control, command execution, coordination of actuating elements and the direct operational logic of the robot.
The real-time control role describes software responsible for closed control loops executed at a guaranteed, deterministic frequency — typically 1 to 10 kHz for current/torque loops in actuators. Unlike soft real-time, in a hard real-time regime missing a deadline is treated as a system error. Implemented on deterministic kernels (Linux PREEMPT_RT, QNX Neutrino RTOS) or dedicated microcontrollers. Critical for biped balance stability, force control, impedance control and functional safety.
Family of tools providing hard real-time capabilities in Linux and EtherCAT fieldbus communication – the foundation of industrial and robotic low-level control.
KUKA Fast Robot Interface (FRI), LAAS-CNRS systems, research manipulators requiring < 1 ms latency, integration with IgH EtherCAT.
Several hundred active users, mailing list, GitLab, strong presence in European academic environments.
Ubuntu 24.04 LTS 'Noble Numbat' — supported until April 2029. The host for ROS 2 Jazzy.
License family: Strong Copyleft
License family: Weak Copyleft
EVL r58 – Dovetail interface, no co-kernel, arm64 support.
Cobalt LTS – stable branch for production systems.
Introduction of the Cobalt dual-kernel architecture.
