Tech Tuesday: avionics of the new Avy Aera
Our Tech Tuesday blog series puts our tech team in the spotlight and highlight their contribution to the development of our new Aera drone solution.
Meet our Embedded Systems team
Our Tech Tuesday series continues and this time we put our embedded systems team in the spotlight! They’re responsible for the avionics that go into the aircraft and all the peripherals around it; basically all the electronics that are flight critical for our aircraft and enable integration with the docking station.
We get talking to Dirk, Thierry and Emre who share their process of developing components in-house (and its challenges), what has changed from our previous model and what they are most proud of.
What were you responsible for when designing the avionics of the new aircraft?
Dirk - Embedded Systems Team Lead : We either develop or buy off the-shelf components that go into the aircraft and then we test them, we integrate them, until it’s ready for flight. We work closely with the software and hardware teams to ensure that all components are working properly. I oversee all the designs and systems that we have, thinking of all the activities we need to do aside from design and engineering.
Emre - Embedded Systems Engineer: I design the circuits that have RF features (radio frequency). I write codes for the circuits that have microcontrollers in them and design special circuits, like power circuits, for our motors. There are lots of steps in designing a PCB. First of all we design the schematic and the system topology - we define which radio we should use, which component we should use, then place all these components related to each other.
Thierry - Embedded Systems Engineer: I’m mostly in charge of the propulsion validation, basically all the electronics that are required to properly run the motors. A second part would be battery safety, making sure it charges and discharges correctly. We get useful data from the battery and ensure no dangerous situations can occur.
What have been your main challenges?
Dirk: There is a need for us to deliver working prototypes during the design process so that the other teams (hardware, software) can start testing their system. This takes a lot of time and can be very challenging for us because some devices may not be fully defined yet, nor fully developed, while there is an expectation that they already work.
Thierry: Component shortage has been a very big challenge for us. This means that we either have to design very flexible, or ensure we have enough components to last us the coming production runs which can be challenging.
Emre: The new Aera uses very rare topologies and communication protocols - UAVCAN. This very rare protocol is used everywhere in the aircraft. It’s so new that only a few companies can support this. Our microcontrollers didn’t know anything yet, so we had to teach them how to control the system and had to write the driver ourselves.
We are not just using the technology but we are really making the technology. I spent some time simply understanding the communication to be able to develop the code for our own system. In the current system, we have almost 20 nodes that can communicate with each other via this protocol. This is a huge task for all of us in Embedded Systems as well as Software.
How have we improved the avionics/embedded systems?
Dirk: We took the off-the-shelf component route for our first generation, which helped us get a head start with making aircraft in a short time frame. However, this approach did not meet the standards we were looking for with the newest generation Aera.
“We design almost everything in-house now. Why? Because there are only 2 options online: cheap components made by and for drone hobbyists or extremely expensive components made for military or aviation which are also too big for our system. All the circuits have been redesigned for our specific purposes." - Emre
Thierry, Emre and Dirk sum up the significant upgrades of the new Aera:
Avy brain
All components in the first generation Aera have their own mount integrated into the fuselage with lots of cabling in between the components. This can take quite some time to install. Instead, we put a lot of the standard flight critical components into a single sub assembly - the Avy brain. It includes:
- Full communication suite
- Power management
- Flight computers
- GPS
- Compass
- Airspeed sensors
- External charge management
- FPV camera
“It’s been made more functional, an all-in-one package that just needs to be plugged into a system where you can attach the motors, the battery and then you have a drone.” - Dirk
Redundancy in RF systems
The whole new Aera has been made redundant by making in-house RF systems with very robust communication. In-house R&D allows us to have a lot more control over the hardware we’re using for all our products and ensures seamless integration between them.
Whereas the first generation Aera has redundant communication systems on board, there is still a lot of RF to manage since the antennas are outside the aircraft and not built-in like the new Aera. When LTE starts working, for example, it can get in the way of the GPS because of all the noise it creates, which can result in a jamming effect with the GPS. With the new Aera this is avoided.
The new Aera has:
- 3 different LTE connections
- Direct RC link
- 2 GPS
- SATCOM
- Redundant communication links in the mobile network 4G
- Communication protocol within the whole aircraft
We’ve applied a standardised protocol which reduces the majority of cabling. All the systems have been carefully separated, the radiation has been canalised to the exact correct location and all necessary areas have been cleaned from radio noise.
This protocol is an industry standard protocol that is used in cars and manned aircraft because it is very robust. If a single component fails, the protocol will notice it but won’t cause the aircraft to come down.
Propulsion
In the previous generation, we put block waves on the motor to drive it which can deliver high performance but isn’t the most efficient. It creates a lot of electronic noise, which can degrade GPS performance, antenna performance and RC link. This causes LTE connection to be weaker and lowers the positioning of the aircraft.
We’ve moved to a field oriented control drive algorithm on the motor, which is basically a sine wave that we put on the motor. This is a lot more efficient, generates a lot less heat compared to a regular ESC (Electronic Speed Controller) driving the motor. This results in higher performance, more efficiency and it also plays nicely with the rest of the system.
The whole propulsion setup is a huge upgrade. The margin of amount of thrust we can deliver means the propulsions setup doesn’t work as hard when the aircraft is in a basic hover flight because all components are used way below their maximum ratings. This makes the aircraft more efficient, perform better and last longer in the same mission.
Battery
A big difference in the new Aera is that we revised the whole propulsion system setup and went for a bigger battery with a higher voltage, which also meant that we needed to look into the safety of our battery.
The new aircraft has extra battery telemetry, protection and control logic, allowing for onboard charging. This will be extremely useful with autonomous missions. For example, when users need to place a blood bag and deploy the drone, they won’t need to handle the battery but simply connect it with a cable, making the operation manageable for everyone, even without a technical skill set.
Precision landing capability
The new GPS implementation integrated into the new Aera allows us to precisely land on the Avy Dock. The GPS in the Dock is able to communicate with the drone to compensate for any atmospheric disturbances between the satellites and the aircraft, allowing us to be precise to the cm. Electronically speaking, having this capability is a very big improvement. To compare, the first generation Aera lands within a 5m radius of a desired location so this is something that we literally improved more than 100x!
What makes the new Aera so special and what are you most proud of?
Emre: Our RF systems are a really nice improvement. Sometimes it’s like magic - you cannot see it, you cannot touch the radiation patterns, you cannot change anything until you test it. When it works, it’s the best feeling.
Dirk: The way we assemble the aircraft (in-house) has improved a lot with this new aircraft, making production scalable. Most components now go into sub assemblies that are produced outside of the aircraft, which reduces the time we need to spend on the physical airframe before it’s ready for flight.
Thierry: The development of the electronics has been a huge win for us, aside from just the avionics that go in the aircraft.
We’re also developing external parts for integration with the docking station, testing jigs and charging solutions. We’re really expanding our electronic development beyond the aircraft and putting the building blocks in place for our drone response network.
Thanks to our Embedded Systems team for sharing their insights - what a ride it’s been!
Don’t miss out on the next and last edition of our Tech Tuesday series diving into the software of our new solution. We’ll be talking to our Software & Controls team who will shed light about their role in developing the software of the new Aera and the integrations made with our docking station. They share the challenges that come with developing software that enables autonomous missions for our drone response network.
Glossary
Avionics: a sub-category of electronics. It is basically the electronics that go into an aircraft. The main distinction is that it requires a very specific quality of design and manufacturing. Every small component like a resistor or connector on the PCB is flight critical. Redundancy, big safety margins and extensive testing are critical.
Component: a part or element of a larger whole, of the aircraft. For example: capacitors, resistors, microcontrollers etc.
Driver: a driver is a part of the software that translates the high level commands into low-level commands to specific components. ‘Flash a green light’ might become ‘send 74 69 6E 79 2E 63 63 2F 77 6D 6F 6E 75 7A on the CANbus’.
ESCs: electronic speed controllers send power to the electric motors. A signal from the flight controller causes the ESC to raise or lower the voltage to the motor as required, thus changing the speed of the propeller. They’re the interface between the motors and the flight controller.
Microcontroller: an integrated circuit that contains a microprocessor along with memory and associated circuits and that controls some or all of the functions of a system. It allows the system to interface with a wide variety of sensors like ultrasonic or infrared range sensors, GPS, temperature sensors or radio communications.
PCB: a Printed Circuit Board is a piece of fibreglass with 2 or more layers of copper all to which components are soldered such as resistors, capacitors, microcontrollers and connectors. This is essential for ensuring consistency, performance and reliability of flight critical parts.
RF: an RF sensor works by passively listening to the radio frequency spectrums in which drones communicate with their controller. It sends data from a computer or microcontroller wirelessly to the aircraft using an RF transmitter/receiver (or two-way transceiver). GPS and our 4G connection are also RF systems.
RC: Radio Controller allows the drone pilot to directly control the drone using radio signals.
UAVCAN: Uncomplicated Application-level Vehicular Computing and Networking is a lightweight protocol designed for reliable intra-vehicle communications using various communications transports, targeting various network types in subsequent revisions.