| Popis: |
This paper presents the internal architecture of a Modifiable Off-the-Shelf open-source autopilot. We show starting from a set of functional and hardware requirements why most autopilots use as a core thread a main loop acting as a nonpreemptive static scheduler, reacting to external events, some solicited, some unsolicited (but expected). We explain how the type of bus used to communicate with the sensor impacts the nature of the events received from the sensors (solicited or not). We show that depending on the workload that a main loop iteration has to handle, the execution time of an iteration can be larger than the period, creating potential delays in the attitude correction. Finally, we explore the degrees of freedom that can be used to reduce the impact of these overloads by smoothing the periodic workload. |
