Real-Time Operating System (RTOS)

An operating system that guarantees tasks finish within a set deadline, used for timing-sensitive control.

What defines a real-time operating system is not raw speed but punctuality: through mechanisms such as priority-based preemptive scheduling, it guarantees critical tasks execute within a fixed deadline, with small and predictable timing jitter. A regular desktop Linux is optimized for throughput, and an occasional few milliseconds of delay doesn't matter; but a robot's joint current loop or force-control loop needs to run at a fixed period — 1 kHz or higher — reliably, and missing a cycle can cause jitter or instability. There are two common approaches: running a lightweight RTOS such as FreeRTOS, RT-Thread, or Zephyr on a microcontroller, or using a main controller running Linux patched with PREEMPT_RT, or Xenomai, to get real-time behavior. Higher-level AI policies typically run on a non-real-time system, with low-level control kept on the real-time system, the two communicating over a bus or shared memory.

ExampleThe MCU on a joint driver board runs FreeRTOS to execute the current loop at a fixed period, while the main controller runs a PREEMPT_RT Linux kernel to drive a 1 kHz EtherCAT master.

Also called

RTOS, real-time system

Related

FreeRTOS · RT-Thread · PREEMPT_RT · Xenomai · Hard Real-Time · Jitter (Timing Jitter)

Sources

Real-time operating system - Wikipedia
FreeRTOS