Ground Control Station - UAV

**Note** If you want to get straight to the building process, skip sections with (*)

Introduction *

Nowadays, UAVs are much more popular than before because of the lower cost of systems and the wide range of applications where you can use them. Many high tech companies are even getting involved in that field like Amazon with their Prime Air delivery drone.

Élikos Polytechnique Montréal is a student club that helps students interested in that field of engineering to extend their knowledge of those available unmanned systems. Hobbyist communities already started to improve custom flight controllers and it is now possible to find multiple solutions for open flight control software like PX4 and ArduPilot.

Ground Control Station (GCS)... Why? My laptop can do all the work! *

This is exactly the first question that I had to deal with when I brought the idea to improve the effectiveness of our flight sequence by adding a complete control system. We were using mostly laptops but I always found that solution to be temporary considering that it requires a bit of knowledge to set up some softwares like Mission Planner (ArduPilot) or QGroundControl (PX4). It was complicated to get everyone to use the same settings and it was too much time-consuming for those who were just interested in flying a drone to test something they've built. So I thought that getting everyone to use the same computer attached to the Ground Control Station would be a great improvement.

GCS's features - What I wanted to improve? *

Élikos participated in few competitions over the years like the IARC (International Aerial Robotics Competition) and the SUAS (Student Unmanned Aerial System) competition. Both of those contests brought challenges that we had to find solutions for. Last year, it was required to fly a UAV over a solar panel out of the line of sight to detect with cameras those that were damaged (using IR). We went with a typical solution using analog video-feed to help a pilot to navigate to the solar panel location. Many issues came out at this moment:

• The screen was way too small for this purpose.
• Analog systems are reliable and simple but the video quality isn't great and it's hard to analyze anything captured by it.
• We had no data communication system implemented so we couldn't analyze data in real-time during the flight.

Let's dive in

I'll divide this project as follow:

• Mechanical
• Electrical (AC and DC)
• Software and Network

Mechanical part:

The GCS needed to be portable so I went with Nanuk case model 945 which we already had at the time.

Next step, I designed 3 main components to fit inside: the backplate, the cover bottom plate, and the cover top plate.

With the drawings, I contacted a company to make the cuts using a laser. It is quite cheap to manufacture nowadays. Material: SS-304 and aluminum 6061.

Having all the parts in my hands (electrical and mechanical components), I started the assembly:

• Hole size used for this build: 1/8"
• Use #6 self-tapping screws with washers to fix the DIN rails and the wire ducts

Then come the tagging and the wiring of all the components. I decided to tag every wire in my system to quickly be able to find any connections using the electrical schematics. If you don't use AutoCAD Electrical which provides a feature to tag wires, I suggest that you simply follow your own system and start from 100 to 1XX. Don't forget to put the number at each end of your wire.

I used a Dymo Rhino label printer for this process but any label printer would work too.

The final result at the moment looks like that:

Electrical part:

The system can be divided into two sub-categories: AC and DC. The DC circuit will use a 6S Lithium-Polymer battery to act as a backup power supply when we use the GCS outdoor. This part of the project still requires more testing since it needs some battery management features. The electrical schematics already include that part of the design.

I used AutoCAD Electrical to create the schematics so it may not be as clear for everyone depending on experience but in a nutshell, follow these simple guidelines:

• 2 sources : 120VAC and 6S Lipo Battery (6 cells * 4.2V max/cell = 25.2V)
• Get one AC/DC for 120VAC to 24 VDC
• Use a Battery Management System (BMS) to protect Lipo from over-discharge and overcurrent. *Use common Lipo charger to charge the battery.
• Use an SPDT switch between 24VDC (coming from AC/DC and 25.2V Lipo)
• Use two DC/DC (24V/12V, 24V/5V or 12-24/5V, etc..)
• Get some protection for overcurrent and short circuit using fuses or circuit breakers (C or D type). *Rule of thumb: 1.25*Current consumption = current rating
• PoE ethernet switches are quite expensive so I used passive PoE cables instead. To do so simply remove the jack connector and plug it to your 24V system. *Important note* Verify the tolerance of your equipment when using DC voltage from a Lipo battery because the voltage varies a bit. With Ubiquiti equipment, tolerance is generally in the range of +/- 10%.
• Take a look at my Bill of Materials (BOM) for more details on the components.

Protection:

• Put a least one circuit breaker or a fuse after each AC/DC or DC/DC converter to respect the maximum current output of your modules.
• You should do the same before each important device like the PC, the monitor or the radio modem.

Power distribution:

24VDC:

• PoE passive cables (power Ubiquiti Equipment)
• DC/DC converters (5V and 12V)

12VDC:

• Monitor
• PC (Intel NUC7i7BNH)
• Fans (1X exhaust and 1X intake)

5VDC:

• RFD900 (radio modem)
• **Raspberry Pi if you prefer it over a regular PC

Notes DC part:

• The battery management system is quite important to implement in the system to protect the battery from over-discharge. A great and simple solution is to use a Lipo battery tester which we can remove the buzzer to trigger a relay that disconnects the battery from the circuit. DIY Perks has a nice tutorial for that.
• Finally, simply connect the output of your BMS to your SPDT switch. This switch chooses the voltage from the AC/DC converter or the DC from the battery. (Still work in progress)

Software and network:

To replace the previous system which was using analog communication, I went with Ubiquiti equipment to implement a Wi-Fi communication between the GCS and the UAV instead. The product line-up used in this project is called airMAX. More specifically, I used two Bullet AC for more portability but any airMAX products work with each other. LiteBeam and Bullet AC is also a good combination for a better range.

With sponsorship from DeplotDepot, I was able to easily get all the Ubiquiti equipment so special thanks for that. The last thing that is not shown in this diagram is the access point. I went with the Ubiquiti AC Pro that connects to an ethernet switch in the GCS. This feature allows anyone to remotely connect to the GCS and get all the data provided by the Wi-Fi communication. I went with an Intel NUC7i7BNH inside the GCS instead of the Raspberry Pi to get all the software working on a single computer powerfull enough to analyze data.

Ubiquiti equipment is quite straight forward to work with. These are the guidelines that the software team followed :

How to set up a Bullet AC and a LiteBeam AC Gen2 (or another Bullet AC) with a bridge

1) Power up the Bullet and let it broadcast its SSID

2) When you see the SSID "Bullet (...)", connect to it using a laptop

3) Make sure to set up a static IP address for the laptop on the connected wifi connection. (I used 192.168.1.21 since 192.168.1.20 is the Bullet's IP. Mask is 255.255.255.0 and gateway is 192.168.1.1)

4) Now that you have a static address, you can communicate in the network created by the Bullet. Open a web browser and type the Bullet's address (192.168.1.20) in the address bar.

5) Follow the instructions to create an Admin account. If you don't have the instructions and you have a login page instead, you need to reset the Bullet (or LiteBeam), reboot it and do step #4 again.

6) Now you should be able to connect to the Bullet's admin panel. Go to the settings section on the left.

7) Go to the network tab.

8) Make sure the mode is in "Access Point PtP" (by default it's "Station PtP")

9) Set the Bullet's IP address as 192.168.1.2 (by default it's 192.168.1.20) and save changes. This is necessary since the other Bullet (or LiteBeam) will have a default IP of 192.168.1.20 and they won't be able to communicate.

10) Now you can connect your laptop, or any device through the Ethernet connection and the device will be part of the network.

Pairing with the LiteBeam

11) Power-up the LiteBeam and do the same steps as the Bullet to set it up. Make sure to keep the IP address 192.168.1.20 (a.k.a don't do step #9) and keep the network mode as "Station PtP" (a.k.a don't do step #8)

12) The Bullet and LiteBeam should automatically connect to each other. For any device that you want to add to the network, either from the Bullet side or the LiteBeam side, make sure to set a static IP address (mask is 255.255.255.0 and gateway is 192.168.1.1) that hasn't been used by any other device in the network. Optionally, you can try to set up a DHCP server or make the Bullet and LiteBeam use IPV6.

13) You should now have a functional network that you can use as a LAN.

Credits:

Big thanks to the software team of Elikos for making the last part of this project possible with the set up of the network. Finally, I would like to thank Elikos' sponsors for investing in our student club which leads to an incredible learning experience for designing projects from scratch.