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Oct 19 2018

How the Drone Works: Principle and Core System

Introduction

        It's cool to watch the drone fly freely in the air every time when someone else has the remote control in their hand. But do you know how the drone works?

Article Core

Introduce the Drone

Purpose

Analyse Principle and Core System of Drone

Article Name

How the Drone Works:Principle and Core System

Category

Electronic Component

Application

Multiple Fields

Keywords

Drone,UAV,Flight Management and Control System,MCU

Catalogs

The Drone

Concept

Application

Composition

The Flight Control System

Concept

Flight control system component module

Function

The Main Control Module MCU

Concept

The Working Principle of the Drone

MCU Mission


The Drone

1.Concept

        Unmanned aerial vehicle (UAV), also called drone, is an unmanned aircraft operated by radio remote control equipment and its own program control device, or operated by the onboard computer completely or intermittently.

2.Application

        Drones are not only widely used in areas of aerial photography, agriculture, plant protection, miniature selfie, express transportation, disaster rescue and wildlife observation, but also used to themapping, surveillance of infectious diseases, and so on.

3.Composition

        A drone consists of an airframe, a flight control system, a data link system, a launch recovery system, and a power supply system. The flight management and control system, which is equivalent to the "heart" part of the drone system, has an important impact on the stability, data reliability, accuracy and real-time performance of the drone, and is decisive for its flight performance.

the drone


Core of the Drone: the Flight Management and Control System

1.Concept

        The flight control system is the core control device of the drone, which is equivalent to the brain. Whether or not the flight control system installed is also an important indicator to distinguish the drone and general aviation model.

        After the early remote control flight, its navigation and control mode has developed into autonomous flight and intelligent flight. The change of navigation mode requires higher accuracy of flight control computer, and the increase of the mission complexity requires high computer power. Miniaturization not only places high demands on the power consumption and volume of flight control computers, but requires small size and good mobility. High precision requires not only high computer control precision, but also the ability to run complex control algorithms.

2.Flight control system component module

        The flight control system collects the flight state data measured by each sensor in real time, and receives the control commands and data transmitted by the radio monitoring and control terminal from the communication channel of the ground monitoring and control station. After calculation, the control command is output to the executing mechanism to realize controlling the UAV of various flight modes and realize managing and controlling the mission equipment; simultaneously transmit the status data of the drone and the operational status parameters of the engine, onboard power supply system and mission equipment to the onboard radio data terminal in real time, and then sent back to the ground monitoring station via the radio downlink channel.

        According to the function, the hardware of the flight control system includes: a main control module, a signal conditioning and interface module, a data acquisition module, and a servo drive module. 

the drone

3.Function

        The various modules are combined to form a flight control system, and its core is main control module, which combined with other modules to meet the function requirements of flight control and flight management of a series of small drones with only needs to modify the software and simply modify the peripheral circuit. It can thus achieve reducing system development costs by multiple models use one developed system. The main functions of the system are as follows:

(1) High-precision acquisition of multi-channel analog signals, includes gyro signal, heading signal, rudder angle signal, engine speed, cylinder temperature signal, dynamic and static pressure sensor signal, power supply voltage signal. Due to the accuracy of the CPU's own A/D and the limited number of channels, an additional data acquisition circuit is used, whose chip-select and control signals are generated by the decoding circuit in the EPLD.

(2) Output signal state.The output switching signal, analog signal and PWM pulse signal can be adapted to the control requirements of different actuators, such as steering gear, aileron steering gear, up-down steering gear, air passage and throttle steering gear, etc.

(3) Multiple channel communication. Communication with onboard data terminals, GPS signals, digital sensors, and related task devices is realized by using a plurality of communication channels. Since the serial port configured by the CPU's own SCI channel cannot meet the system requirements, the design uses multiple serial port expansion chips 28C94 to expand 8 serial ports.


Core of the Flight Control System: the Main Control Module MCU

1.Concept

        MCU (Microcontroller Unit) is to properly reduce the frequency and specifications of the central processing unit, and to integrate the peripheral interfaces such as memory, counter, USB, A/D conversion, UART, PLC, DMA , and even LCD driver circuits on a single chip, forming a chip-level computer for different combinations of different applications. MCU is important in the flight system of the drone. MCU plays an important role in the flight system.

2.The working principle of the drone

        To achieve controllable/autonomous flight, the drone mainly needs to complete attitude control, shooting/measuring, information storage/transmission, and environmental awareness (for anti-collision). A starting point of the automatic control principle is the closed-loop feedback control, that is, after the input adjustment is applied, the change of the control amount is measured and feedback is adjusted to input until the control amount reaches the target value. For example, a track is set for the drone, and the flight position is measured in real time during the flight to deviate from the track, and the corresponding yaw correction is performed. Environmental awareness is the use of various sensors (optical cameras, ultrasound, etc.) to detect obstacles on the trajectory of the drone, such as buildings, bridges, etc., and to make maneuver circumvention.

        The drone moves vertically and uses the rotor to advance and stop. The relative nature of the force means that when the rotor pushes the air, the air also pushes the rotor back. This is the basic principle that the drone can go up and down. Furthermore, the faster the rotor rotates, the greater the lift, and vice versa. To turn the drone to the right, the angular velocity of the rotor 1 needs to be reduced. Although the lack of thrust from the rotor 1 can cause the drone to change the direction of motion, the upward force is not equal to the downward gravity at the same time, so the drone drops.

        The drone is symmetrical, it also applies to lateral movement. Each side of the four-wheeled drone can be the front side, so how to move forward explains how to move backwards or to the sides.

3.UAV MCU mission

MCU

        The role of flight control system in the drone is equivalent to the driver's role in manned aircraft. We believe that the flight control system is the most important core technologies in the drone. The flight control system generally includes three parts: the sensor, the onboard computer and the servo actuating device. The functions mainly include the three types of unmanned aircraft attitude stabilization and control, drone mission equipment management and emergency control.

        In addition to MCU, the drone also needs gyroscopes, accelerometers, geomagnetic induction, air pressure sensors, ultrasonic sensors, optical flow sensors, GPS modules, etc. to cooperate with each other to finish the flight. The IMU senses the attitude of the aircraft in the air and sends the data to the master processor MCU. The master processor MCU will control the stable operation of the aircraft through the flight algorithm according to the instructions of the user operation and the IMU data.

        Because of the large amount of data that needs to be calculated and the need for very real-time control, the performance of the MCU also determines whether the aircraft can fly stably and flexibly.



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