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Field inspection process of the cellular network infrastructures is an important step during Radio Network Optimization. It allows the collection of all physical data of needed relays to efficiently optimize the network performances. The human-based performed inspection is initiated after the raise of a set of issues. The initiated operation is intended to resolve the cited issues as the errors in physical parameters extraction of relays, human safety issues as burns and falls, etc. This work revolves around an assembly and configuration of quadrotor drones in telecommunication relays inspections because of their easiest construction and their rapidly services. The user of the realized UAV can control and initiate the operation so intuitive thanks to its graphic control interface.
Higher School in Applied Sciences Tlemcen, Algeria
Walid Yassine Medjati
Airbus Operations GmbH, Germany
*Address all correspondence to: h.megnafi@essa-tlemcen.dz
1. Introduction
Radio network optimization is one of the main steps to improve the performance of telecommunications cellular networks after deployment and commissioning to solve various problems in order to implement an activity with maximum efficiency and offer a better quality of communication to subscribers [1, 2]. Many operations of radio optimization could be optimized and facilitated with the introduction of drone exploitation as the audit process of cellular networks relays that is used by humans which causes a lot of problems such as taking a lot of time, subject to human error and lacks rapid response in the event of a disaster [3]. Drones also known as unmanned aerial vehicles (UAVs), without human crew on board, and are rather controlled by a person in the field or autonomously via a computer program; the development of drones has led to a change in architecture and operating concepts through the evolution of their features and capabilities [4]. there are so many types of drones that we can easily find in the world and all these drones are working for different applications, the military operations was among the first most common applications of drone technology, because it helps to easily control problems related to surveillance [5], but that does not mean that UAV applications are limited to the military world but also serve a large part of the economy with advanced mechanisms and impressive capabilities [6], Drones are now working in all fields where humanity operates, for example, used to deliver blood or medical supplies to African countries [7], we can find them also in the agriculture industry [8], personal transportation, Journalism, architectural photography [9], engineering applications [10], Commercial Applications [11] as well as in the world of internet [12]. Currently drones are operating in many fields and, with constant technological advances, these machines will be even more robust and useful [13]. This paper describes a telecommunication’s assets inspection process based on the use of autonomous UAVs and human supervised ones capable of overcoming issues related to the human-based classical inspection. Thus, we made a comparative study of both classical and UAV based inspection processes.
The paper is structured as follows: In the second section, we present the concept of quadrotor UAVs. In the third section (section 3), we present the frame design and building of UAVs. In the fourth section we defines the different standard components of quadrotor UAV and its characteristics. In the fifth section, we present the quadrotor assembling methodology. In the sixth section, we present an automated inspection process based on quadrotor UAV. In the seventh section, we present the obtained results validated by the comparative study with the classical inspection process. In the last section, we discuss further perspectives of the process development.
The quadrotor consists of a main body having four centrally connected arms and four brushless motors attached to each end of the arm. Four rotors are attached to each engine whose rotation of the propellers/rotors is controlled by radio control. All of these motors are connected to controllers to control the speed of each individual motor. These controllers are connected together in parallel with the power distribution board. Further, a battery is used as the power source. The assembly diagram of the quadcopter drone is shown in Figure 1 [14].
Figure 1.
UAV assembly diagram [13].
The motor distribution is powered by a battery. In this way, the board evenly distributes power to the four electronically controlled drives, eventually reaching each motor. The accelerometer measures the angle of the quadrotor on the X, Y and Z axes and adjusts and stabilizes the revolutions per minute (RPM) of each motor [14, 15].
The following paragraph describes the components we have selected to make this drone.
The first approach to designing the frame is to mount each arm at a central intersection to provide convenient mounting points and good support for each frame component [16]. The two arms are mounted vertically in the center and fixed by two boards. These boards are the basic support for flight controllers, batteries and distribution boards. Motors are attached to the ends of each arm [14]. The components used to assemble a quadrotor drone are described below.
3.1 Quadrotor SK450 frame
The frame is made of durable fiberglass and the arms are made of light nylon polyamide, with a height of 450 mm and 80 mm.
3.2 Carbon fiber propellers 12 in
Propellers are used to generate aerodynamic thrust. The first pair of propellers rotates clockwise (pusher) and the other pair rotates counterclockwise (puller) [17]. The thrust generated by propellers depends on the density of the air and the speed of the propeller, its diameter, the shape and surface of the blade and its pitch.
3.3 Turnigy multistar 980 Kv motor
The engine has a significant impact not only on flight time, but also on the payload the vehicle can carry. It is imperative to use the same engine throughout the same vehicle, as if pair of engine were of the same brand and model. Also, from the same production, their speeds may be slightly different and it is the air traffic controller who takes care of this [17].
3.4 Electronic speed controller (QBrain ESC)
The electronic speed controller (ESC) controls the speed and direction of the motor by inputting signals from the flight controller. The ESC must handle the maximum current drawn by the motor.
3.5 Pixhawk flight controller
The flight controller is a Pixhawk Mini programmable autopilot microcontroller manufactured by 3dr with enhanced sensors (accelerometer, gyroscope, etc.) that provide excellent flight stability and navigation to specific GPS coordinates.
3.6 Radio remote control turnigy 9X
The radio control receiver sends a wireless input to the vehicle and uses at least four channels connected to the following to control the movement of all vehicles.
Pitch (controls the vehicle to forward/backward motion).
Roll (moving the vehicle left and right).
Yaw (clockwise or counter-clockwise rotation).
3.7 2200 mAh lithium battery
The batteries are lightweight and offer high capacity with high discharge rates. Battery capacity is measured in ampere-hours (Ah), and the larger the capacity, the longer the flight time [18].
Assembling a quadrotor requires several steps, from assembling the chassis and the electronic components, to calibrating and finalizing the vehicle. Before explaining, we will present the tools used for assembly. This part describes the interconnection of electronic components and the assembly of the chassis without electronic components [17].
4.1 Connection and wiring of components electronic
Assembling a quadrotor requires several steps, from assembling the chassis and components, to calibrating and finalizing the vehicle. Before explaining, we will present the tools used for assembly. This part describes the interconnection of electronic components and the assembly of the chassis without electronic components as is shown in Figure 2 [17].
Figure 2.
The wiring diagram of electronic components of quadrotor.
4.2 The assembly frame alone
To assemble the vehicle frame, we follow the steps below:
Assemble the four arms with the main board using screws.
Mount the skids at the end of each arm.
Mount the motors plates at the end of each arm.
Mount the upper board.
4.3 Complete assembly with electronic components
This part describes the complete assembly of the sk450 quadrotor frame, including the assembly of the flight controller and electronic wiring.
4.3.1 Motors mounting
The motors are mounted in the correct order at the ends of each arm using a motor plate. The rotation of the motor changes according to the choice of user and gives the vehicle certain movements (Take off, landing, Throttle, yaw, pitch, roll, etc.).
4.3.2 ESC mounting
The ESC is mounted on the main board and wired to each motor in the correct order. Signal input is sent from the flight controller to the ESC, which adjusts motor speed. The ESC assembly is shown in the Figure 3.
Figure 3.
ESC assembly.
4.3.3 The power module mounting
As shown in Figure 4, the power module with four outputs is fixed on the central plate with cable clamp and connected to the electronic flight controller (ESC).
Figure 4.
Mounting of the power module.
4.3.4 The flight controller mounting
After assembling the chassis upper board, we will use the mounting foams to securely attach the Pixhawk Mini to the chassis center of gravity of the vehicle frame. These foams act as vibration dampeners that allow the flight controls to operate properly. The flight controller should also point to the front of the vehicle. Figure 5 shows the Pixhawk mini flight controller mounting:
Figure 5.
Pixhawk mini flight controller mounting.
4.3.5 Wiring the flight controller to the power module
With 6 pin cable. We connect the flight controller to the power module in order to power it when connected to the battery.
4.3.6 The GPS module and radio telemetry mounting
As shown in Figure 6, the GPS module is mounted and oriented at the front of the vehicle. Then, assemble the wireless telemetry and communicate wirelessly with the vehicle
Figure 6.
Assembly of GPS module and radio telemetry.
4.4 Base station installation/configuration
We used Q Ground Control in order to control the vehicle and configure the electronics. This helps you visually change and configure the required settings. It is open source software, and you can even modify your code to your specific needs. You can also change the lighting mode of UAV (property), such as how it responds to input, low and fast stabilization. The Q Ground Control station is also used to plan missions and provide specific navigation paths based on GPS coordinates.
4.4.1 PX4 firmware implementation
We launch the program Q Ground Control after downloading and installing it on computer by selecting “Firmware” on the sidebar, and then we connect the flight controller to the computer via a USB cable.
After downloading and installing the QGroundControl program on computer. Firstly, we select “Firmware” from the sidebar. Then, we connect the flight controller to the computer using a USB cable and start the QGroundControl program.
4.4.2 Frame selection
The airframe tab displays a multi-frames configuration that can be handled by the autopilot. We select the appropriate chassis configuration. After confirming your selection, the flight controller will restart.
4.4.3 Sensors calibration
The embedded IMU (inertial measurement unit) includes a gyroscope, compass, and accelerometer that must be calibrated to the flight controller can stabilize its flight. Adjust the sensor by manually moving the vehicle in the specified direction.
4.4.4 Radio calibration
After turning on the transmitter, select the appropriate mode and start moving the joystick in the specified direction. We can monitor the transmitter channel, in order to assign a specific channel to a specific input, and use the Q Ground Control software to perform wireless calibration.
4.4.5 Flight modes selection
In flight mode, we can perform autopilot assisted flights and also manual. We configure the receiver to control the following principal flight modes:
Stabilized: when the sticks are released, the vehicle flight difficulty and stabilizes itself automatically
Altitude: Takeoff and landing are controlled at maximum speed.
Position: When you release the joystick, the quadcopter stops and stays in a stationary position.
4.4.6 Flight
When flying a drone, you should first check the following conditions:
Choose the right environment: Drone test flights will initially be conducted in two different environments: indoors (controlled environment) and outdoors (real environment). However, drone test flights are subject to weather conditions (wind, rain, etc.) which may affect the handling of the drone.
Neighborhood: To set the path and flight plan of UAV, we must take note of the dwellings, objects, trees, surrounding apartments, objects, trees, and streets. However, avoid flying near or in front of the airport.
Flight mode study: Various modes and settings can affect the ability to control flight and drones. Before flying, you need to configure the drone according to the environment you choose.
Battery check: Make sure the battery is properly charged to avoid an emergency landing.
After following the predefined steps of the quadrotor assembling and Configuration, The released quadrotor who wears a 4K camera to inspect the transmission part of telecommunication networks is shown in the Figure 7.
5. Automated telecommunication relay inspection process
In order to solve the issues related to the human-based inspection process, we designed a new process by introducing a new technique based on the use of autonomous UAVs capable of overcoming the issues faced during such operations. Introducing such a process allows the evaluation of telecommunications relays (NodB) physical state and improves the inspection operation by tackling its major problems such as safety, cost and efficiency. To illustrate our new process we built a quadrotor UAV which provides the needed agility and stability during the flight ensuring a reliable gathering of image/video data.
5.1 Description of the new inspection process
The UAV allows us to gather a set of high quality images and videos from where the physical parameters of all the infrastructure are extracted as (Azimuth, Tilt, Height, Antenna type, etc.) in a short time frame and by eliminating the human intervention. This process will be divided into the following steps:
Site access: Only one operator is needed to complete the inspection operation. The technician will plan the autonomous flight (route, altitude, coordinate, etc.) without the need to take any safety cautions in case of difficult site accessibility.
Flight planning: The technician uses the QGroundControl interface in which he inputs the set of informations needed for the autonomous flight of the UAV including the inspection route. The interface will provide a set of flight data and logs during the flight (Battery autonomy, speed, flight mode, etc.).
Pre-flight checks: Before launching the flight, the UAV operator must go through a list of verifications on the vehicle to ensure its safety and airworthiness for the success of the operation.
Flight: The operator arms the motors and launches the vehicle take off using the assistance of the radio controller. The vehicle will then follow the designated route to inspect the infrastructure by approaching it. The vehicle is equipped with a 4K camera mounted on the front of the frame and will record images continuously during the whole operation.
End of the operation: The vehicle will automatically come back to the initial take-off point keeping a constant flight altitude and will then initiate the landing.
5.2 The automated inspection process scenario
Figure 8 describes the designed automated inspection scenario.
Figure 8.
The automated inspection process scenario.
In the 1st segment, the UAV is recording images of the feeder cables state from bottom to top. In the 2nd segment, the vehicle is measuring the height of the antenna and its azimuth, and will then capture 360° panoramic images of the area surrounding the tower. The measurement of the height and azimuth is made using the embedded sensors (GPS, Compass, Accel/Gyro, etc.). In the 3rd segment, the UAV captures a side view of the antenna to measure the tilts and define the type of the antenna. In the 4th segment, a global view of the infrastructure is captured. After completing this, the vehicle initiates the landing.
We have presented and detailed the assembly and configuration process of the UAV and its components. Then, we considered a telecommunication relay inspection operation established by the human being by implementing the technique of using a quadrotor drone. These operations are carried out in order to protect the conditions of activities in order to regulate the operation and management of communication provided by telecommunication operators. Generally, these inspections require climbing and a visual inspection of the structure. Each structural element is checked and verified [19]. The structures examined are usually steel masts, steel and concrete towers, satellite dishes, sector antennas and rooftop telecommunication structures [20, 21], etc.
These inspections are entirely manual, a costly activity for infrastructure companies and cause problems for operators and users, and these inspections are time-consuming. For this and thanks to integrating tools such as 4K cameras, measurement sensors, etc. We have developed an on-site audit technology using a quadrotor drone, capable of inspecting any telecommunications site. These technologies provide detailed measurement and monitoring of the status and operation of critical equipment. However, when the condition of the infrastructure is closely and continuously monitored, the risk due to faulty equipment can be significantly reduced.
The quadrotor was developed to perform checks in hard-to-reach areas and altitudes to troubleshoot any issues. Some of these problems include telecommunication errors, burns and incorrect physical parameters, falls due to climbing the antenna, etc. It is in this context that we have introduced an audit intervention for different heights of telecommunication towers. An inspection operation was triggered for a 20 m high tower, carried out by the radio team of phone operator Mobilis – ALGERIA. During this operation, the aerialist recorded all the necessary time of various measurements of the physical parameters of the relay, namely the tilts, azimuths, heights, type of aerials, etc. Likewise, we considered the same tower, but this time based on a quadrotor drone. As soon as the drone completes its mission, the results obtained are evaluated using a comparative table describing the execution time of the two previous operations as indicated in Table 1.
Tower inspection steps
Human-based inspection tower (minutes)
UAV inspection tower (minutes)
Checking the feeders and tower climbing
8
2
Determination of tower altitude
5
/
Taking photos of the type of antenna and orientation.
1
1
Measurement of the GPS points and azimuth
2
/
Measurement of antenna tilt
1
1
General site photo
1
1
Tower descending
5
1
Total time
20
6
Table 1.
The execution time of the 20 m tower.
The table details the duration of each step of the inspection process carried out with human support or using a quadrotor drone on a 20 m high tower. The human execution time in the “up turn and check feeders” step is much longer than the time it takes to be executed by the quadrotor drone, similar to the “down turn” step. Tower height determination, GPS (global positioning system) and azimuth points are measured when the drone takes over the camera orientation and begins to determine the antenna type, so this does not doesn’t take too long. The high sensitivity of the GPS & Compass sensor integrated into the drone allows more precise measurements than the traditional compasses used by the aerialist. The drone inspection time is 6 minutes, while the total time of all human inspection steps is 20 minutes. This means that the drone will save more time and avoid risks that may occur during this process.
The radio team has two towers of 40 and 70 m, to check whether the height can influence the execution time of all the UAV inspection stages or not. We have started a second measurement mission to be carried out. The balances obtained are compared with a histogram showing the execution time of the two operations, as shown in Figure 9.
Figure 9.
Comparative histogram of the inspection execution time for each tower.
Comparing the two operations, we can see that the 20m tower measured by the antenna operator takes 20 minutes, and the 70m tower takes 45 minutes, and regarding the operation performed by the drone, the 20m tower m took six minutes while that of 70 m is 14 minutes. We notice, at all tower heights, the duration of the UAV-based inspection operation is shorter than the traditional one. It means, the inspection carried out by the drone gives precision of the measurements, reliability of the information obtained and to save more time in such missions.
The quadrotor drone offers such inspections and thanks to its stability, rapid deployment, a wide angle of view, precision in the physical parameters measured, precious time saving and high quality panoramic images in real-time. In addition to that, all problems that may arise during such operations (burns, human error, falls, etc.) have been eliminated.
This study first showed the purpose of the drone and its possible uses. Next, I explained the concept of the quadrotor drone and the chassis assembly and its electronic components. Next, we introduced the configuration and assembly method of the quadrotor drone. We chose this type of drone because of its stability, superior battery life, reliability, running efficiency and long flight time compared to other types of drones.
Therefore, the future application area of precision quadrotor drones will integrate different sensors for precise measurements, providing different possibilities for the continuation of this project. Integrating machine learning algorithms to make it completely autonomous for more complex communication operations.
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Written By
Hicham Megnafi and Walid Yassine Medjati
Submitted: 22 February 2022Reviewed: 04 March 2022Published: 21 December 2022
Open access peer-reviewed chapter
