Drone Porteur

Introduction

Our project is titled 'Carrier Drone,' a project that aims to make the necessary modifications to the DJI Matrice 300 to allow it to carry smaller drones, such as the DJI Mini 3 or the DJI Tello Edu, underneath it. A rewriting of the project was done during the initial reports, and can be presented as follows: The objective is to have the Matrice 300 take off with several smaller drones like the Tello Edu. To achieve this, we need to design a cradle/basket attached to the Matrice 300 on which we can attach the smaller drones. Once the takeoff is complete, we must be able to initiate an in-flight release of the small drones from the Matrice 300, without interrupting its flight. Once released, the Tello Edu drones begin their flight, engage in a predefined mission, and start their landing. We can list a couple milestones here :

• First is studying the drones APIs in order to effectively control and move the drones.
• We then need to make the different parts and PCBs to assemble them for the basket and the drone.
• After designing and check the PCBs are functional, making all everything communicate with eachother was essential.
• Once all the previous steps were completed, we then could start making functional takeoffs, drone realeses and landings.

This project was part of our final evaluation during the second semester of the Master 2 ASPIC program. This graduation project revolved around two main courses: MOCPI and PFE. The first course focused on the various aspects of organization within the work industry, including making code readable and clean, dividing tasks among group members, and so on—essentially, the project's format. The second course, in contrast, focused on the project's content. For this course, we needed to hold meetings with the client, implement the desired functionalities, and, most importantly, demonstrate results.

A FULL REPORT FOR THE PROJECT IS AVAILABLE HERE

Development

Electronic Parts

Regarding the equipment needed, this equipment would need to control up to four servo motors controlling the grabbing system on the basket. Therefore, we decided to use two main electronic components: a Pi Pico RP2040 and a Pi Zero 2W. First, we'd need the Pi Zero 2W to provide a visual interface for displaying results, offer good support for potential users, and provide effective feedback during operation. This module will be used for WiFi communication between the carrying basket and the drones loaded onto it. However, we encountered a problem: the Pi Zero cannot control the grabbing system because it lacks the ability to send PWM signals to control the servos. Consequently, we realized we needed a second module capable of communicating with them. This module is the Pi Pico RP2040, mounted on the basket. This simple module was sufficient for controlling the servos, and it communicates with the Pi Zero via Serial.

During the project, we decided to design our own PCBs in order to not have a handmade circuit with wires everywhere mounted on the Matrice300. All the design were made on the software KICAD and the different attemps and designs were ordered on the website JLBPCB. the components are soldered using 'reflow soldering' techniques. This involves heating the entire PCB according to a temperature curve to control the melting of the tin and flux. The components are placed in their positions before the tin melts and correctly reposition themselves as the tin melts. The PCB is then cooled according to a curve to prevent subjecting the tin, PCB, and components to sudden temperature changes. Electronic components are very sensitive to temperature variations, and failure to adhere to the temperature curves specified by the manufacturers can lead to unpredictable behavior. The PCB is cleaned, and through-hole technology (THT) components and connectors are soldered. See above an exemple of our PCB once finished.

3D Parts Designing

Several different parts had to be designed for the project to function. Over the weeks, we explored various approaches for creating the carrying basket, the grabbing system, and the drone adapters. All of these designs were created using Fusion 360 software and 3D printed at home with FDM printers and PLA+ filament.

Drones implementation

The core of the project is the usage of drones. One drone will have the carrier role and the other one the carried role.

• The first drone used was the DJI Matrice300, which will have the carrier role. This drone will be controlled manually by a pilot as it carries the other smaller drone and the carrying basket.
• The second drone we'll mention is the DJI Mini3, the first carried drone we worked on. After some research and work, we quickly realised that the recent DJI APIs didn't support this drone, and everything available online was in "testing". We still managed to design an Android application mimicing the control joysticks, and retrieve and video stream from the drone. The work on this drone was then dropped.
• Lastly, the carried drone we kept for the project was the DJI Tello Edu. A much simpler drone to work on, firstly because less recent means more documentation online, and we could work on it with Python, which was impossible with the Mini3. We managed to make available API work, and fully control the Tello Edu.

Results and Demonstration

All the objectives for the project were completed and the client was very satisfied with the work. We managed to fully control the DJI Tello Edu, design all the needed parts and components for the Matrice300 and its carrying basket, as well as making complete demonstrations of the work. See below a demonstration video of the result :