RADIOELECTRONIC AND COMPUTER SYSTEMS

Motivation. During nuclear power plant (NPP) monitoring, unmanned aerial vehicles (UAVs) can be used as an affordable and cost-efficient tool to deploy a UAV-enabled wireless network (UEWN) for providing the crisis centre (CrS) needed monitoring data from monitoring stations (MSs) of the automated radiation monitoring system in case of damage of wired networks. However, because of the high electrical power requirement, the normal operation time of a UAV of a multi-rotor type (MUAV) is just 20 to 30 min, limiting the operation time of a UEWN during NPP monitoring missions. The subject matter of the paper is the process of ensuring the persistent operation of a UEWN. The aim of this paper is to develop a queuing theory based approach to scheduling MUAVs for persistent operation of a UEWN during NPP monitoring. The objectives of the paper are: to propose a scheme of deployment of a UEWN to connect a MS with the CrS of Zaporizhzhia (ZNPP) in case of damage of the wired network between the MS and the CrS; to introduce the main parameters characterizing the automatic battery charging station (ABCS) as a multi-channel queuing system; to develop and describe in detail a queuing theory based approach to scheduling MUAVs of the UEWN for persistent NPP monitoring. The following results were obtained. A scheme of deployment of a UEWN, consisting of  LoRaWAN and WiFi segments, to connect a MS with the CrS of ZNPP in case of damage of the wired network between the MS and the CrS was proposed and described. A shift schedule for 3 MUAV fleets to ensure the persistent operation of the UEWN during ZNPP post-accident monitoring missions was built. It was shown that the ABCS can be considered as a multi-channel queuing system, in which two or more channels (battery charge points at the ABCS) are available to handle arriving MUAVs. A queuing theory based approach to scheduling MUAV fleets of the UEWN for persistent NPP monitoring is developed and described in detail. It was evaluated and illustrated by means of plots how the number of occupied channels of the ABCS depends on: 1) the battery charging time for the MUAV at the ABCS, and 2) the flight distance for the MUAV between its location point in the WiFi segment and the ABCS. The next research steps can cover issues regarding to: 1) scheduling MUAV fleets for numerous UEWNs, 2) developing models of a UEWN operation using a LiFi segment for transmission of monitoring data, and 3) developing reliability/survivability models of a UEWN taking into account UAV failures or/and wireless signal interference.

unmanned aerial vehicle; nuclear power plant; shift schedule; multi-channel queuing system; automatic battery charging station; wireless network

Sachenko, A. A., Kochan, V. V., Kharchenko, V. S., Yastrebenetskii, M. A., Fesenko, H. V., Yanovskii, M. E. Sistema posleavariinogo monitoringa AES s ispol'zovaniem bespilotnykh letatel'nykh apparatov: kontseptsiya, printsipy postroeniya [NPP post-accident monitoring system based on unmanned aircraft vehicle: сoncept, design principles]. Yaderna ta radiatsiina bezpeka – Nuclear and Radiation Safety, 2017, vol. 73, no. 1, pp. 24-29.

Fesenko, H., Kharchenko, V., Sachenko, A., Hi-romoto, R., Kochan, V. An Internet of Drone-based multi-version post-severe accident monitoring system: structures and reliability. Dependable IoT for human and industry modeling, architecting, implementation, Denmark, The Netherlands, River Publishers, 2018, pp. 197-217.

Kliushnikov, I. M., Fesenko, H. V., Kharchenko, V. S. Using automated battery replacement stations for the persistent operation of UAV-enabled wireless net-works during NPP post-accident monitoring. Radioel-ektronni i komp"yuterni systemy – Radioelectronic and Computer Systems, 2019, vol. 92, no. 4, pp. 30-38. DOI: 10.32620/reks.2019.4.03.

Fetisov, V., Dmitriyev, O., Neugodnikova, L., Bersenyov, S., Sakayev, I. Continuous monitoring of terrestrial objects by means of duty group of multicop-ters. XX IMEKO World Congress, Busan, Korea, 9-10 Sept. 2012, pp. 85.

Heeseo, C., Park, J., Song, H., Kim, Y., Jeong. H. The IoT based automate landing system of a drone for the round-the-clock surveillance solution. IEEE Interna-tional Conference on Advanced Intelligent Mechatron-ics (AIM), Busan, Korea, 7-11 July, 2015, pp. 1575-1580. DOI: 10.1109/AIM.2015.7222767.

Choi, C. H., Jang, H. J., Lim, S. G., Lim, H. C., Cho, S. H., Gaponov, I. Automatic wireless drone charg-ing station creating essential environment for continu-ous drone operation. IEEE International Conference on Automation and Information Sciences (ICCAIS), Ansan, Korea, 27-29 Oct., 2016, pp. 132-136. DOI: 10.1109/ICCAIS.2016.7822448.

Junaid, A. B., Konoiko, A., Zweiri, Y., Sa-hinkaya, M. N., Seneviratne, L. Autonomous wireless self-charging for multi-rotor unmanned aerial vehicles. Energies, 2017, vol. 10, no. 6. Available at: https://www.mdpi.com/1996-1073/10/6/803. (Accessed 10.01.2020). DOI: 10.3390/en10060803.

Campi, T., Cruciani, S., Feliziani, M. Wireless power transfer technology applied to an autonomous electric UAV with a small secondary coil. Energies, 2018, vol. 11, no. 2. Available at: https://www.mdpi.com/1996-1073/11/2/352. (Accessed 10.01.2020). DOI: 10.3390/en11020352.