84 T he role of a real-time operating system (RTOS) is becoming increasingly critical for unmanned systems, and for a number of reasons. As developers want to reduce the size, weight and power (SWaP) of a system design, so they are moving away from using a single processor core to multiple cores. An RTOS helps manage the complex software running on those cores. The complexity of autonomous designs, with their millions of lines of software code, also increases the risk of bugs and security breaches. An RTOS provides a secure baseline for the operation of a system, simplifying the certification for the safety and security processes. Adding machine learning (ML) alongside deterministic control systems is also boosted by using an RTOS for separation. As a result, there is a wide range of commercial RTOS systems available, as well as open source versions and developers implementing their own designs. This leads into considering the programming language and tools used to build the system for any type of unmanned platform, from aircraft and ground vehicles to sea-going vessels. Heart of an RTOS An RTOS is essentially a scheduler. It ensures that a processing task can be performed on a processor core in a certain amount of time to give determinism to the system control software. Different techniques can be used, from a simple ‘round robin’ that has a series of regular time slots where tasks can be executed, to a system that prioritises the tasks and allocates a time for the Nick Flaherty explains why real-time operating systems are growing in importance and how the different types can be used Behind the lines October/November 2020 | Unmanned Systems Technology