Mashchak A. Models for risk assessment of unmanned aerial vehicle radiosystem.

In this work were solved a scientific and applied task of increasing the degree of risk assessment adequacy of reliability components models of unmanned aerial vehicles (UAV) computing-navigational onboard system. This task is solved by reasoned reliability improving of the most critical in terms of safety UAV computing-navigational subsystem modules and subsystems. Solving this problem was based on developing of a methodology for quantitative determining the risk index of computer and navigation subsystem of UAV computing-navigational onboard system. Namely this risk index is a minimal cut sets which are determined without fault tree building. Proposed methodology allows to meet the challenges of exploitation risk level reducing of UAV computing-navigational system in the design phase stage of UAV development. This is achieved by assessing the exploitation risk of UAV modules different variants and configuration options with taking into account the cost of its realization. For the methodology of assessing the exploitation risk level of UAV computing-navigational system were developed a reliability computing subsystem model and navigation subsystem model. These subsystems are the main part of UAV radio system. Models are developed with a high detailed representation of the critical fail state. This high detailed representation of the critical fail state gives opportunity to determine the faults of separate modules which causes to fail of whole UAV computing-navigational system. Also the algorithm and prototype software tool is developed. This software tool is based on the proposed methodology for assessing the exploitation risk level of UAV computing-navigational system. Software tool automates the processes of obtaining quantitative risk index. Obtained quantitative risk index takes into account: subsystems fault-tolerant configurations; hardware failures; software failures; affiliation of certain failure to two or more minimal cut sets; reliability of satellite navigation systems signal receiver; reliability of operator commands receiver. Also to visualize the causes and consequences of fails the proposed software tool allows to build in automated mode the fault tree which is based on obtained minimal cut sets. Based on developed algorithm and models is made a possibility to make a quick model rebuild for risk assessment.