Research On Real-time And Fault-tolerance For Flight Control Software

Flight control system is one of the key subsystems of UAV, in charge of UAV flight control andtask execution. The onboard flight control software (FSW) is an important part of UAV control system,which requires not only correct function but also real-time and high reliability. Traditional design offlight control software is often more concerned about how to implement function. The performance ofsoftware relies more on developers’ experience and finial software testing. With the expanding scaleand increasing complexity of FSW, software non-functional attributes such as real-time andfault-tolerance are having greater and greater effects on the software overall performance. On thefoundation of realizing software functional modules, design ideas and methods of real-time systemsand fault-tolerant systems are applied in software development, in order to improve real-timeperformance and fault-tolerant ability.Firstly, the requirements analysis based on FSW characteristics are implemented. The thesisdescribes principles of development, introduces operating environment, designs software overallarchitecture and interior communications strategy. The functional modules are also designed anddeveloped.Then, real-time design methods of FSW are studied, on the foundation of analyzing executiontime of task and task characteristics, period and priority of the FSW tasks are designed. And thestrategy based on priority inheritance is used to solve the problems of critical resource competitionand allocation.After that, fault-tolerant design methods of FSW are studied, software fault-tolerant schemebased on CPU utilization is designed to monitor task execution time and deal with abnormity. Controlrecovery strategy is used to improve adaptability of FSW after abnormal reset. Data fault tolerancemechanisms are applied to ensure that the data in the software is safe and reliable.Finally, in the semi-physical simulation environment, simulation of real-time and fault-tolerantdesign is completed. The results of simulation reply that: the FSW is fully functional, which meetsreal-time and fault-tolerant requirements. The FSW meets the design requirements.