ИСТИНА

The results of the first stage of work on the creation of an air data system, which is an inte- gral part of the UAV onboard measuring unit for determining the parameters of the atmosphere, are presented. Such systems have become one of the most important tools for environmental monitoring in the last decade [1-3]. The air data system (ADS) consists of an 8-hole probe and a pressure sensor unit. It allows you to determine the vector of airspeed, dynamic head and static pressure along the trajectory of the UAV [4, 5]. The processing of ADS data and an inertial measurement unit data makes it pos- sible to determine the speed and direction of the wind along the UAV's trajectory. At the first stage of work, a prototype of an 8-channel probe was developed and manufac- tured (Fig. 1,a). Probe diameter - 10 mm, length - 200 mm. There are 7 pressure holes with a diameter of 0.8 mm were made on the hemispherical head: one central and 6 lateral ones with an equal step along the roll angle of 60°. Pressure ports for measuring static pressure are made at a distance of 8 diameters from the probe head. The pressure sensors unit includes six differential pressure transducers to measure pressure differences between the central and lateral ports and two absolute pressure transducers to meas- ure static pressure and total pressure in the center hole. Interrogation and control is carried out by a microcontroller, which allows recording data to an SD card and transmitting it via the RS- 485 interface to the on-board measuring complex. The methods of calibration and measurements, the results of calibration in the T-503 NSTU wind tunnel and flight tests as part of the Tsimlyanin flying laboratory based on a small- sized aircraft-type UAV of a hybrid scheme are discussed (Fig. 1,b). The latter means that the takeoff and landing of the UAV is carried out vertically, like a helicopter. ab Fig. 1. 8-hole pressure probe (a) and unmanned aerial vehicle “Tsymlyanin” during test flights in Tsym- lyansk in August 2020 (b). Fig. 2. Flight data. a - comparison of the flight altitude based on static pressure, total and dynamic pressure and GPS; b - indicated air speed and its components relative to the 8-hole probe axes. The analysis of the flight test results showed the system operability, which is confirmed by the adequate registration of the measured parameters at all stages of the flight. As an example, in Fig. 2,a a comparison between barometric altitude and GPS altitude is shown. The static pressure for determining the barometric altitude was found in two ways: (a) directly from the static pressure channel reading; (b) as the difference between the total pressure and the dynamic head, determined from the pressure measurements on the hemispherical part of the probe. Figure 2,b presents data on airspeed and calculated components of the velocity vector on the body axis. The work was performed using the equipment of the Center for Collective Use “Mechan- ics” of the ITAM SB RAS, the engineering center “Industrial Aerodynamics” of the NSTU. The development of the Tsimlyanin UAV and its tests were carried out with the support of the Rus- sian Science Foundation grant No. 18-77-10072. REFERENCES 1. Langelaan J.W., Alley N., Neidhoefer J. Wind field estimation for small unmanned aerial vehicles // Journal of Guidance, Control, and Dynamics. 2011. Vol. 34, No. 4. P. 1016–1030. 2. Elston J., Argrow B., Stachura M., Weibel D., Lawrence D., Pope D. Overview of small fixed-wing unmanned aircraft for meteorological sampling // Journal of Atmospheric and Oceanic Technology. 2015. Vol. 32, No. 1. P. 97–115. 3. Calmer R., Roberts G.C., Preissler J., Sanchez K.J., Derrien S., O’Dowd C. Vertical wind velocity measure- ments using a five-hole probe with remotely piloted aircraft to study aerosol-cloud interactions // Atmospheric Meas- urement Techniques. 2018. Vol. 11, No. 5. P. 2583–2599. 4. Shevchenko A.M., Berezin D.R., Puzirev L.N., Tarasov A.Z., Kharitonov A.M., Shmakov A.S. Multi-hole pressure probes to air data system for subsonic small-scale air vehicles // Proc. of 18 Int. Conf. on the Methods of Aerophys. Research (ICMAR 2016): AIP Conference Proceedings. 2016. Vol. 1770, Art. 30005. 9 p. doi.org/10.1063/1.4963947 5. Shevchenko A.M., Shmakov A.S. Multi-hole pressure probes to wind tunnel experiments and air data systems // Proc. of 25 Conf. on High-Energy Processes in Condensed Matter (HEPCM 2017): AIP Conference Proceedings. 2017. Vol. 1893, Art. 030088. 6 p. doi.org/10.1063/1.5007546