Internal redundancy in future UAV FCCs and the challenge of synchronization

Abstract

As Unmanned Aerial Vehicles (UAVs) describe the recent trend in the avionic industry, they also tend to migrate into the civil airspace. To ensure a safe operation of such systems, even in case of faults, a redundant design of the inherent Flight Control System (FCS), is mandatory. For smaller UAV system, redundancy has not found a widespread use yet, whereas for bigger and more complex systems the redundancy concept is usually implemented by using proprietary hardware solutions. Automotive and industrial Microcontroller Units (MCUs) provide a good basis for the implementation of a new efficient and safe Flight Control Computer (FCC) architecture, which is also able to manage redundancy of the FCS. By using interfaces already provided by the MCUs for the implementation of the redundancy network, the efficiency and integration density can be fairly increased. Thus some guidance is given on how to mitigate MCU related safety concerns and on the implementation of the redundancy network. Also the aspect of achieving a tight synchronization between all nodes within the network is mandatory for every full-time safety critical redundancy system. Thus synchronization is examined in the context of the desired approach, with a strong focus on MCU specific influences and the challenge on how to select a suitable synchronization algorithm. To demonstrate the feasability of the design, an exemplary design is presented which has been implemented for further performance and synchronization measurements.