Quadcopter

INTRODUCTION

Drones, also known as unmanned aerial vehicles (UAVs) is an aircraft controlled without a human pilot, but instead operates from a distance under a remote control by a human operator or by on-board computers.

In the past, it was commonly used in military as weapon of war or security application such as surveillance, but recently it was also popularized in popular culture such as sports, photography, movie filming or simply as a hobby.

A drone can have various numbers of rotors, a drone with four rotors is called a Quadcopter. A Quadcopter works based on the two sets of identical fixed pitched propellers; two clock-wise and two counters clock-wise. The control of the vehicle’s motion is achieved by altering the rotation rate of one or more motors, therefore changing its tilt and/or rotation.

FLIGHT MECHANICS

The most important flight mechanics of the Quadcopter are the thrust, yaw, pitch and roll.

The primary function of all the rotors is to provide the thrust which is used to push the Quadcopter into the air and counter the effect of gravity on its body. The yaw is the rotation of the Quadcopter vertical axis. By rotating two opposite rotors at a higher speed than the other two, the induced torque will cause the device to rotate.

The pitch and roll on the Quadcopter are controlled in the same way with different combination of rotors. By increasing the speed of the two rotors at one end of the Quadcopter so that they are running faster than the two rotors at the opposite end, it will cause the faster running end to lift up and the Quadcopter to move in the direction opposite to the lifted rotors.

Depending on the head or front direction, it will determine whether it is the pitch or the roll. If the movement of the quadcopter is along the head such as forward and back, then it is the pitch. If the movement is perpendicular to the head such as it going sideways, from side to side then it is the roll.

FLIGHT CONTROL

The flight mechanics are controlled by the throttle, rudder, aileron and elevator of a radio remote control. Their correlations of their control are as shown below;

Quadcopters are commonly controlled using a radio remote control (RC) which consists of a radio transmitter (Tx) and a receiver (Rx) that will communicate by sending or receiving commands to control the movement and navigation of the quadcopter.

The Tx has two control sticks which controls the throttle, rudder, aileron and elevator. The left control stick focuses on the throttle and rudder. Vertical movement controls the throttle, and horizontal movement controls the rudder. The right control stick focuses on the aileron and elevator, vertical movement controls elevator and horizontal movement controls the aileron.

As a result, these controls manipulate the flight mechanic thus, the movement of the Quadcopter.

qUADCOPTER COMPONENTS

MAIN FLIGHT CONTROLLER (FC)

The brain of all drone and multirotor-copters is the main flight controller. It is a circuit board that gives stabilization with its built-in sensors that detects orientation changes and user command control for maneuvering. This capability is attain by the basic sensor installed on the FC, perhaps the gyroscope and accelerometer.

A gyro measures the rate of rotation/ rotational forces around a particular axis with its three axis gyro stabilization. The units are often in degrees per second, it obtains information on the speed the Quadcopter is rotating around its axis; roll, pitch and yaw. An accelerometer measures acceleration forces to calculate the orientation of a stationary platform relative to the earth’s surface. The unit are normally in gravity (g), the data is used to determine where is up and where is down as It is capable of detecting gravity, hence allowing the Quadcopter to stay stable.

By combining these measurements, the FC will calculate the Quadcopter altitude and the angle it’s flying at to perform the necessary correction to give a smooth flight capability such as flying or hovering perfectly stable and steeper angled turns.

TYPES OF FLYING

There are various selection of FC offered in the market, choosing the suitable FC depending on the kind of flying can produce the best performance. It is important to consider the type of flying will be done before implementing the FC to the Quadcopter. The kind of flying popularized as a hobby can be relevantly categorized into: (i) First Person View (FPV) drone racing/ freestyle flying, (ii) cinematography flying, and (iii) autonomous flying.

FPV drone racing/ freestyle is considered a sport where the pilots built extremely fast and agile drones to fly around a set course as fast as possible using attached camera for vision. It requires a FC that is capable of recovering from very fast roll rate, hold any angle regardless of the steepness, speed and direction it is going, and should be tunable to adjust the flexibility to the user’s preference.

Cinematography flying involves aerial photography and filming. This requires a FC with dampened flight characteristic, slow maneuverability control sticks, and easy to control so users don’t have to worry about the technical part of flying. Instead they can push their focus to achieve their perfect shot or the smoothest video possible.

Autonomous flying involves drone automatically taking off, navigating way-point or landing without being manually maneuvered by the user using a radio remote control. This requires a FC that has open-source firmware to allow user’s modification to add or improve features in any way they want using a programming language.

TYPES OF MAIN FLIGHT CONTROLLER

While there are countless brands and types of FC available, only the most popular and frequently used will be mentioned in this report. The FC that works best for FPV drone racing/freestyle flying is the Flyduino KISS Flight controller. Despite not having many features, it is sufficient with its affordable cost, small sized, simple and easy custom firmware used to tune the drone and do what it needs to do, fly. Another alternative is the Lumenier LUX, unlike the Flyduino KISS it offers more features and flexibility. Due to its open-sourced platform and hardware features, the FC can take advantage of all the firmware available to it; they are Cleanflight, Betaflight and Raceflight

The DJI Naza-m v2 is one of the best FC to do cinematography. Its abundant features and function would come helpful to the user as it offers functions such as intelligent-orientation control and return-to-home features. Despite its capabilities and functionalities, the DJI Naza is a proprietary close-source platform meaning it is inflexible and restricted from adding or customizing features as the firmware cannot be tampered or modified with and users have to use it as it is.

In the other hand, an autonomous flying requires a FC with open-source firmware that can caters to the user’s request. The 3DR Pixhawk is such FC; it is designed specifically for autonomous flying because its software and firmware are open-source, and allows customization and modifications to achieve the desired outcome.

DRONE - TELEMETRY CONTROL

Telemetry is a digital two-way data stream, which consist of a transmitter and receiver radio devices. This involves sending and receiving data between a Quadcopter and a laptop which acts as the ground control station. In operating a drone, it provide flight details such as the information of GPS location, latitude, longitude, and flight time of the Quadcopter to the user in real time.

The radio communication between the Quadcopter and RC is also a form of telemetry; however in the UAV world it is not commonly associated together because the RC is considered to only provide control.

To enable telemetry, the telemetry module will connect one onboard the Quadcopter, and one onto the ground station device. There are two frequency bands that drone telemetry uses to avoid collision of one interfering with the other. Those options are 433 MHz and 915 MHz for telemetry. Their difference depends on the country it will be used at, such at 433 MHz is legal in Europe while 915 MHz for the US.

The most frequently used telemetry module is the 3DR Telemetry radio, it’s compatible with the various types of main controller such as the Pixhawk, Arducopter and APM. XBee radios for a DIY telemetry module which can be used so high level instructions could be helpful. The DJI 2.4GHz Bluetooth Datalink is only compatible with DJI products and software, and vice versa; such as the DJI NAZA flight controller and DJI PC Ground station.

GROUND CONTROL STATION

A ground control station (GCS) is commonly a software application, running on a ground-based computer such as a laptop. It communicates with the Quadcopter via telemetry connection and displays flight detail on the Quadcopter to the computer screen, in real-time. Besides displaying flight details, the GCS can also be used to provide direct full flight control over the Quadcopter manually as you would with a RC or autonomously by navigating way-points or using mission planning with MAVLink enabled Quadcopter. By combining a Quadcopter’s camera with telemetry communication, the GCS can monitor and show live video streams captured.

There are various GCS available online for download, the decision to select which GCS depends on the FC compatibility, type of Quadcopter vehicle and user’ preferred computing platform. Most frequently used software applications include, Mission Planner, QGroundControl, UgCS, APM Planner 2.0 and etc. The DJI Naza-M v2 FC can only run on the DJI PC Ground station or UgCS. This is because the software, along with the Naza FC and DJI datalink are all proprietary close-source platforms.