USING FLIGHT CONTROL SYSTEMS IN UNMANNED AERIAL VEHICLES

ABSTRACT

The control system, as shown in the article, provides the supplied parameters of the transition process. A built-in gyroscope, accelerometer, compass, and barometer are all included in the flight controller. On board the unmanned aerial vehicle, a flight controller (polyotny controller) such as the Pixhawk-4 is utilized as a flight controller. Without the direct involvement of the pilot-operator in the management of the aircraft, automated systems provide complete automation of particular stages of the flight.

АННОТАЦИЯ

Система управления, как показано в статье, обеспечивает заданные параметры процесса перехода. Встроенные гироскоп, акселерометр, компас и барометр входят в состав полетного контроллера. На борту беспилотного летательного аппарата в качестве полетного контроллера используется контроллер полета (полиотный контроллер), например, Pixhawk-4. Без непосредственного участия пилота-оператора в управлении летательным аппаратом автоматизированные системы обеспечивают полную автоматизацию отдельных этапов полета.

Keywords: UAV, Pixhawk-4, accelerometer, compass, barometer.

Ключевые слова: БПЛА, Pixhawk-4, акселерометр, компас, барометр.

INTRODUCTION. Aerodynamic forces and moments occur during the control of the movement of unmanned aerial vehicles (UAVs). As the regulating factors for the control of the aircraft, the angles of inclination (roll), torsion, danger (risk) and traction (thrust) of the engine are used, which allow to influence its movement.

UAVs as a control object involves a complex dynamic system due to the large number of interrelated parameters and the complex interactions between them. Complex movements are often divided into the simplest types:

• angular movements and center of gravity movements;
• longitudinal and lateral movement.

The governing bodies that make up management actions can be divided into two groups:

- longitudinal control body, which provides movement in the longitudinal plane;

- lateral motion control, which provides the necessary characteristic of changes in the angles of rotation, displacement and rotation in the lateral plane.

Such a division of controls is conditional, which can be attributed to flight modes in which controls interact with other actions. At the same time, such an approach allows to highlight the main functions of certain bodies and management channels and to independently solve tasks of relatively simple and practical importance.

Four control channels are needed to ensure full automation of flight control:

- engine control channel (thrust);

- channel (pitch) control channel along the transverse axis;

- control channel for longitudinal rotation (roll);

- channel to control the rotation along the vertical axis (risk).

The engine control channel regulates the movement according to the set flight program. The following three control channels provide the desired angular position of the apparatus in space. Information about the movement of the unmanned aerial vehicle, i.e. the commands generated in the steering wheel, aeronautics and engine control support that provide the specified flight control, comes to the appropriate channels. Sustainable flight management is not possible without creating an acceptable quality automatic control system. The aircraft control system serves to ensure flight along a given trajectory by generating the required aerodynamic forces and moments on the wing and aerodynamic surfaces [10].

MAIN PART. Control systems can be of three types - manual, semi-automatic and automatic. In a manual control system, the pilot-operator assesses the situation, ensures that control pulses are generated, and uses the control levers to turn the steering wheel while holding them in the desired position via the control panel. In the semi-automatic system, the pilot-operator control signals are modified and amplified using various automatic control devices and amplifiers, ensuring optimal stability and control characteristics of the aircraft. Automated systems provide full automation of individual stages of the flight without the direct involvement of the pilot-operator in the control of the aircraft.

In the automatic system, in the process of adjusting the control of the flight angle of the aircraft, the input of the regulator receives the desired values of the angle or altitude, and the variables at the output of the regulator change the angles of the elements, pitch, roll and risk channels.

Requirements to the management system:

- minimum transition time;

- lack of readjustment (aperiodic process).

The control system must provide the given parameters of the transition process. Controllers include a built-in gyroscope, accelerometer, compass and barometer built into the flight controller. A flight controller (polyotny controller) such as Pixhawk-4 is used as a flight controller on board the unmanned aerial vehicle. The PX4 is a new advanced Autopilot system built on the design of an open source database and developed by 3D Robotics. Key advantages include a fast-powered 32-bit processor and sensors from renowned STMicroelectronics, as well as the Real-Time NuttX operating system, which provides excellent performance, flexibility and reliability in managing any standalone device.

The advantage of Pixhawk-4 boards is the presence of internal multi-stream information processing, completely new features of Autopilot, such as Lua-scripting programming language for flight tasks (missions) and actions, the PX4 driver's adjustable capability ensures time efficiency in all processes. The Pixhawk-4 core module can be expanded with additional features such as digital air speed sensor, support for external multi-colored LED indicators, external compass and more. All external devices are automatically detected and adjusted. The Ublox NEO - M8N GPS module in conjunction with a compass provides information about the drone's geographic location and is additionally used as a sensor to monitor its flight altitude.

This module also includes a compass, as it is used directly on the drone. The advantage of the external compass over the flight controller is that it reduces the effect of vibrations generated by the operation of the engines and at the same time increases the accuracy of direction (course) maintenance. The Ublox NEO - M8N GPS module has higher accuracy (up to 0.6 meters) than previous versions of the module, as well as lower power consumption. Suitable for accurate and stable flights on maps in aircraft. NEO - M8N is characterized by fast search of signals, high-precision location and functionality.

The NEO - M8N GPS module uses the original M8N chips. It has a built-in compass. Updated location information has been improved to 10 GHz. The GPS module supports the detection of the location of various satellite systems, for example, the GLONASS satellite navigation system of Europe, Japan, China, including Russia. The support of so many different satellite systems ensures high accuracy of the drone’s position in space. Engines are one of the main propulsion vehicles on board the drone.

With a heavier drone, lower-kilovolt and larger-blade motors should be chosen, which will create more torque, i.e., more power to lift the drone structure. Engines should be selected primarily with a cooler so that they can run as little as possible (overheating) and stable in hot weather, as well as select engines depending on the weight of the aircraft structure.

CONCLUSION. Drones and all UAVs use three-phase DC motors without collectors (brushless). When choosing them, it is necessary to pay attention to their nominal, ie the number of revolutions in volts (KV), first of all, when choosing engines, they should be selected as soon as possible not to wear out (overheating) and coolant in hot weather, as well as the weight of the engine drone design must be selected. A heavier drone has a smaller KV and a larger engine size should be selected, which generates a larger current, i.e. more power is generated to lift the drone’s design. It is also important to pay particular attention to multi-rotor aircraft engines, as there is a difference between these engines and engines designed for unmanned aerial vehicles.

The engine speed controller has a small control board that increases or decreases the number of revolutions in the engine by receiving a signal (wide pulse modulation) from the flight controller.

The engine switches off in 1 microsecond, in 1.5 microseconds, the engine runs at 50% and the pulse width at 2 microseconds with a maximum rotation of the engine runs at full power. Controllers, like engines, should be selected primarily based on the type of drone; there is a big difference between aircraft type and multi-rotor type. The operating frequency is at least 600 Hz  in multi-rotor controllers and 400 Hz  in aircraft controllers.

Another important criterion in the selection of the controller (regulator) is the wind power station - WPS (the device does not take into account the battery), ie there is no additional power supply. Due to the built-in power supply in the speed regulator, it creates additional interference in the control signals generated on this board, which leads to distortion of the control signal. It is recommended to use a ferrite ring for such reduction in the built-in WPS on the speed regulator board. There is also a large synchronization in the operation of multi-rotor speed regulators, and it is possible to correct them.

In addition to the criteria listed above, the controllers are selected based on the maximum current value consumed by the motor.

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