The practical possibility of a guaranteed return of budget unmanned aerial vehicles (UAV) to area of the starting point in event of loss radio communication with a video camera or control panel is considered. In this regard, an experimental model of a flying wing with wingspan of 1000 mm and a flight weight of up to 500 g was built, on which a flight controller SPRacingF3 based on the STM32F303 microcontroller with a GPS receiver and a directional video camera was installed to provide FTP flights. Based on INAV firmware, main attention was paid to setting flight modes NAV RTH, NAV FAILSAFE to ensure a guaranteed return. The practical possibility of using GPS Rescue mode for Betaflight firmware to return quadrocopter to a point close in take-off coordinates was also considered. In this regard, an experimental prototype was built with a 250mm frame, but with which OMNIBUSF4V3 flight controller was installed based on STM32F405 microcontroller with a GPS receiver and a heading video camera for FTP flights. During flight tests, it was shown that GPS Rescue mode allows you to return UAV to the launch zone, subject to the settings presented in the work on the assembled quadcopter. When performing GPS Rescue mode, an important condition is the stable connection of GPS receiver with the number of satellites not less than those installed when setting up the firmware. It is established that for the return of UAV of the considered types it is not necessary to use a barometer and magnetometer, functions of which can be performed by GPS receiver.
In this article, the budgetary unmanned aerial vehicles (UAVs) of the rotary type (the hexacopter, the quadcopter) based on flight controllers with ATmega2560, STM32F405 microcontrollers have been developed. A comparison is made of their capabilities, using the most popular firmware developed for them. The firmware was adjusted depending on the sensors, used in the flight controllers. The designed quadcopters, hexacopters are capable of performing the following flight modes. The holding horizontal -uses the gyroscope and the accelerometer. The maintaining a given altitude -uses a barometric sensor. The holding position -GPS receiver is additionally used. The returning to take-off mode and programmed flight along waypoints marked on the map before the UAV launch. A magnetometer is additionally used here. It has been experimentally established, that the hexacopter is more stable in thevflight compared to the quadcopter based on MegapirateNG ver.3.1.5R2 and ArduCopter 3.2.1 firmware. It has been shown, that for large quadcopters with frame sizes larger, than 450mm, INAV firmware is less preferable, than Ardupilot firmware. The built copters can be used for photo and video shooting of terrain with the radius of up to 3.5 km with lithium-ion cells with a capacity of 6000 mAh. They have the flight duration of 15-20 minutes and the average speed of 20 km/h.
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