Table of Contents

1. System Overview
2. Basic Build and eCalc Statistics
3. Physical Assembly
   • Flight Controller
   • ESC
   • Raspberry Pi
4. Firmware
   • Flight Controller - ArduPilot/Kakute H7
   • ESC
   • Raspberry Pi
5. Raspberry Pi Antenna Setup
   • Pi ssh setup
   • Pi UART setup
   • Pi Connection Example
   • Pi button setup
6. Calibration/Tuning
   • []

1. System Overview

This system was created to create a foundation for more advanced Computer Science and Mechanical Engineering projects. Goals for this project were:

Presise Control - We have a very small indoor flight space so presicsion/safety was important

Controlled Environment - We wanted the system be simple, but also very accurate, in order for users to be confident there is very little noise or inconsitancey in the system.

Computer Based Control - Lastly wanted control of system to be encapsulated in easy to use code library, allowing begginner proggrammers to use the system without low level knowlegde of communication or flight control.

Ultimately, with these contraints in mind, we decided to create a Motion Capture Drone system.

This system is comprised of three main components:

Drone: Custom built, running ArduCopter firmware, with Raspberry Pi (Using Pymavlink library)

Ground Control Computer: Running Python (Using Pymavlink library) + Motive (Optitrack Software)

Motion Capture System: 6 Cameras connected to ethernet switch (Connected to Ground Control Computer)

This system leverages the existing functionality of ArduCopter Firmware, and Mavlink Communication Protocal. Meaning this system can be immediately be used with ArduCopter UAV's or could be easily adapted to work with any UAV that utilized Mavlink Communication.

2. Basic Build and eCalc Statistics

First we need to build our drones! To confirm the performance of our proposed custom drone build, we use Ecalc Software. Ecalc takes in information about your custom drone, and predicts metrics such as Thrust:Weight and flight time

Basic Drone parts include, Frame, ESC, Motors, Props, and Batteries. Ecalc will also take into account the power draw of any drone components like Flight controller, FPV camera, and antenna. To begin we will make an Excel file with all of proposed parts, with summed weights, and power draws (not including motors)...

Note the totaled weights and power draw. Power draw does NOT include motors.

Next step is to input this information into Ecalc ...

Note we are using "Including Drive" as our weight option. This is because we have chosen all parts and know the actual weight. The other options beside "include drive" will asume your total weight doesn't include particular components and try to add those weights for you. In this case we can ignore the warning related to total weight, because the estimated weight that ecalc thinks this build should weigh is more than our actual parts. But since we went to the trouble of finding the actual total weight of our drone, we can ignore this.

Take aways:

In order for our drone to be safely fly, Load, Current, Est. Temp, and Thrust-weight all have to be in the green. If these metrics are in yellow and red, drone my not be able to fly, or prone to damage itself.

Flight time and Specific Thrust can be in Yellow or Red. Since we are going for an indoor drone with reasonably long flight time, our specific thrust is in the yellow. This is okay because specific thrust relates how effienctly our drone is turning wattage into thrust, and does not relate ablitly to drone to fly or possibly overheat.

With this ecalc calculation we can confirm our drone will operate correctly with this combination of parts.

3. Physical Assembly

Flight Controller

For our flight controller we are using Kakute h7 mini 1.3s. Compatible with Ardupilot Firmware.

For wiring with PI, we are using Pi only as antenna, so we much make four connections, 5v, Ground, Tx (transmit pin), and Rx (recieve pin).

For Wiring FPV Camera, our model has it's own antenna, so we only need 5v and GND

Raspberry Pi

Additionally, we added a button to the raspberry pi in order to properly turn off pi (Pi must be turned off before battery is unplugged, otherwise pi does not shut down correctly).

Electronic Speed Controller (ESC)

Flight controller comes with 6 pin JST connector, but our ESC has a different pin mapping, so the connector has been repinned as such:

ESC motor connections in general do not matter, motor will be able to move no matter how the three pins are connected to ESC. The only difference it makes is the direction the motor spins, which you are able to switch in ESC firmware if desired. However for ease of use, we decided to use pin connectors between motor and esc for easy direction swapping...

In addition to motors, a XT30 connector is soldered onto power connections of ESC this connects direclty to 1100mah 2s High Voltage Lipo Battery.

4. Firmware

Flight Controller - ArduPilot/Kakute H7

For our flight controller, we decided to use ArduCopter firmware. Exact version is included in Firmware folder. Or you can download latest version here: https://firmware.ardupilot.org/Copter/

STM32Cube Programmer and ArduCopter ISO

Installation guide follows general ArduCopter installation available here: https://ardupilot.org/copter/docs/common-loading-firmware-onto-chibios-only-boards.html

In Short the steps are:

1. Download arducopter_with_bl.hex (from repo, or latest from: https://firmware.ardupilot.org/Copter/), we want "with_bl" because your esc is using running BLHeli_s...

2. Download and Install STM32CUBEProgrammer software: https://www.st.com/en/development-tools/stm32cubeprog.html

3. While holding down Kakute H7 mini's DFU button, connect to PC via USB

4. "USB Configuration" hit the refresh button, the port should change from "No DFU detected" to "USB#" # being any number. Hit connect.

Then device information should display at bottom of USB configuration window.

5. Now click the "open file" tab, and select the previously downloaded "arducopter_with_bl.hex"

6. Lastly, hit download...

After this arducopter will install on flight controller and you can disconnect when you are done...

Electronic Speed Controller (ESC)

Our esc comes with blheli_s, meaning we will use BLHeliSuite to configure esc settings NOT BLheliSuite32. In our setup the only purpose of using BLHeliSuite is to reverse the direction of motors, without rewiring them. You may not need to use this configuration software you don't need to swap directions without rewiring...

BLHeliSuite

1. Download and Launch BLHeliSuite, available here: https://www.mediafire.com/folder/dx6kfaasyo24l/BLHeliSuite

2. Power Flight controller and Esc via battery (FC and ESC are connected via the modified 8-pin JST connector referenced in hardware setup for FC).

3. Once stack is powered by battery, plug flight controller into computer via USB.

4. In BLHeliSuite, click "Select ATMEL/SILABS Interface" drop down, and select "SILABS BLHeli Bootloader (cleanflight)" or the yellow "E".

5. Now, in com window, select COM port that FC is currenlty connected under, Hit "connect", then hit "read setup"

Now you should be connected to ESC settings, and have the ability to modify ESC settings per motor. You can modify a single motor or muiltiple at same time by selecting motor numbers:

Then you can reversed motor direction for selected motors:

Raspberry Pi

We are using Raspberry Pi Zero 2 W, so we need to flash a Pi OS on an SD card. You can follow official documentation here: https://www.raspberrypi.com/documentation/computers/getting-started.html

Or follow the simplified steps below.

Raspbian Image Flasher

1. Download and Install Rasbien Pi Imager: https://www.raspberrypi.com/software/
2. Start application, and plug in SD Card that Pi OS will be flashed on.
3. Click "Choose Device"

4. Choose the Pi we are using, in this case Rasberry Pi Zero 2 W

5. For the OS, since we have now need for Desktop GUI, we are opting to use "PI OS Lite" (no desktop env). To do this hit "Choose OS"

6. Select "Other" options

7. Select "PI OS Lite (64 bit)

8. Now we must edit advanced settings, so Pi will automatically connect to a wifi network of our choosing. This is needed because we will be directly SSH into Pi. Select "Next" then seleect "edit settings". OR just click CTR + SHIFT + X on windows and linux.

9. Fill in all General settings. Hostname, Usernane, and Password will define how pi appears on local network and how to log into it (You will want to remember the username and password you set in "Set Username and Password" section). Configuration of wireless LAN is where you should put your network information (In our case the name and password to our wireless network).

10. Next in the "Services" tab, make sure that SSH is enabled.

11. Lastly save all edited settings, (You don't need to change antything in "Options" Tab). Then confirm flashing of SD Card, then Wait for Rasbien to flash OS. SD Card should be good to plug into Pi once done!

5. Raspberry Pi Antenna Setup

The setup of Mavlink communication (Drone control) from ground computer through raspberry pi to flight controller follows the basic steps laid out in this guide: https://ardupilot.org/dev/docs/raspberry-pi-via-mavlink.html Simplified steps for our use case are below...

Flight Controller Params

First we must change some parameters on our Ardupilot Firmware, if you haven't arealdy installed the ardupilot firmware refer to Flight Controller in "Firmware" Section of documentation.

We will be ajusting settings using Mission Planner ground control software built for ardupilot, this guide assumes basic knowlege of mission planner, and how to change paremeters.

If you haven't used mission planner before it's strongly recommned to skim through the documentation, here are some useful links:

Overview: https://ardupilot.org/dev/docs/raspberry-pi-via-mavlink.html

Installation steps: https://ardupilot.org/planner/docs/mission-planner-installation.html

Basics of Connecting: https://ardupilot.org/planner/docs/common-connect-mission-planner-autopilot.html

1. Connect FC directly to PC via USB C, then connect to FC with Mission Planner.

2. Select "Config" Tab, then "Full Parameter List"

3. Change Serial2_protocal to 2 or mavlink 2. "Serial2" in our case are the RX and TX pins on our Kakute H7 mini Flight controller, we are telling the firmware to expect "Mavlink 2" communication protocal on those pins.

4. Set Serial2_baud to 57600 (Note offical documentation recommends 921600, in our case we got the system working useing 57600)

5. Save Params and disconnect.

Flight contoller is ready to recieve and trasnmit mavlink messages on RX and TX pins that Pi is connectd to.

Pi ssh setup

To configure Raspberry Pi we opted to SSH into Pi's command line over network. Since during the Pi's OS flasing, we uploaded the settings for Pi to connect automatically to our wifi network. We simply need to find the assigned IP address our local network has given our PI.

1. Power PI (with micro USB). Then, in our local network settings, Locate your routers "Dynamic Host Configuration Protocal Client Table" or "DHCP Cliets List" (This step may vary depending on router and firewall settings on wifi network...) In our case the IP address asigned to our drone is XXX.XXX.X.101, (Note I've put X placeholder in for security, the IP address will be all numbers). Also keep note of our Ground Control Computer in this case "Jayden's Laptop" with IP of XXX.XXX.X.106.

2. Open Powershell or equivilant. Type "ssh [email protected]" XXX.XXX.X.XXX being the IP of the Pi we observed earlier.

3. If connecting to Pi for first time (Or Ip has been reset for any reason), type "yes" for saving device.

4. You will then be prompted to type in a password. *NOTE: the username (in this case robotics) and password for PI are set when Flashing OS onto SD card, you should have them written down or saved somewhere. Refer to Section "Firmware" subsection "Rasberry PI" step #8 if you are confused...

If you've done everything correctly you should be SSH'd into PI, and able operate PI via command line interface

Pi UART Setup

1. Now that you are ssh'd into pi, we need to open up UART pin to allow for mavlink communication to take place. In rasberry pi cmd line, type "sudo raspi-config"

2. You should open the raspberry pi's configuration menu, from here select "Interfacing Options"

3.. Now select "P6 Serial"

4. When prompted, select no to “Would you like a login shell to be accessible over serial?”.

5. When prompted, select yes to “Would you like the serial port hardware to be enabled?”.

6. Reboot the Raspberry Pi when you are done.

The Raspberry Pi’s serial port will now be usable on /dev/serial0.

Pi MAVProxy Relay

Now we need to install mavproxy, both on our Pi and our Computer... the official documentation is here: https://ardupilot.org/mavproxy/docs/getting_started/download_and_installation.html#mavproxy-downloadinstalllinux Simplified steps are:

1. SSH into Pi
2. Type use this code to install mavproxy (Install all dependencies! It may take 5-10 minutes)

sudo apt-get install python3-dev python3-opencv python3-wxgtk4.0 python3-pip python3-matplotlib python3-lxml python3-pygame
pip3 install PyYAML mavproxy --user
echo 'export PATH="$PATH:$HOME/.local/bin"' >> ~/.bashrc

For Windows MavProxy install use this installer (visit official documentation if this link is deptricated): https://firmware.ardupilot.org/Tools/MAVProxy/

Pi Connection Examples

Now that Mavproxy has been installed, we are ready to use Rasberry Pi as "antenna" to control/calibrate our drone!

Example 1, Cmd line control directly from PI SSH Terminal In this example we will ssh into pi and run MavProxy to connect it to flight controller. And control our drone by typing commands directly into Pi terminal over network

1. Power drone via charged battery (we don't need any wired connections to FC or Pi!)
2. Pi should power on automatically (if everything is wired correctly), SSH into pi
3. Run this code

 mavproxy.py --master=/dev/serial0 --baudrate 57600

It's important to note with in this example, Mavproxy is only being used as communication between the Pi and FC on the drone. We are using network (ssh) to type commands direclty to PI's terminal (running mavproxy). Ultimately, we want to establish mavlink communication across the network as well, to all allow other programs that use the Mavproxy communication protocal to talk directly to drone over network. see example 2.

Example 2, Using Mavproxy as "relay" In this example we will now run mavproxy, and specify a local IP address for to relay it's mavlink connection to...

1. Access the IP address of your PI and Computer you desire to control drone from. In our case the unique identifiers of our IP addresses are Pi = .101 Computer = .106

2. SSH into PI, and run this command

Note the master is the same as the first example "/dev/serial0" this is the RX and TX uart connection to FC, the new startup argument out is the destination IP address that you with to relay our communication to. In our case the IP ending in .106

3. Open another PowerShell terminal on your computer, now simpley run mavproxy, no need to specify master or out

Congragulations we've acheived mavproxy communciation over wifi, if mavproxy connected correctly you should see the same cmd line interface for drone control that we saw when were direcly connectd over SSH. The only differnce now is that we have a Mavproxy is being used over network, not just between Pi and FC.

What does this mean?

Now that our pi is relaying our mavproxy connection to our computer's IP address. We can now connect with ardupilots "Mission Planner" Ground control software, but instead of using USB C wired connection. We can connect direcly to drone over wifi network. Which means we can now do all our conrol, calibration, and parameter changing wirelessly over the wifi network!

Example 3, connecting to drone with mission planner over network

1. SSH into pi
2. Run Mavproxy code with XXX.XXX.X.XXX being the IP of your computer
3. Open Mission Planner, and in connection tab select "UDP", Baudrate of "57600" and port number of 14550

Now we are connected wirelessly with Mission planner!

Pi Button Setup

Flight Controller Configuration

Motor, Frame, Propeller, and Battery

Failsafes and Warnings

Calibration