The Unique Challenges Of Aerial Robotics

When we think of robotics, the first thing that usually comes to mind for many of us is some sort of industrial arm that’s bolted to the floor, or perhaps a semi-autonomous rover trudging its way across the dusty Martian landscape. While these two environments are about as different as can be, the basic “rules” are pretty much the same. Being on firm ground ground gives the robot a clear understanding of its position and orientation, which greatly simplifies tasks such as avoiding collisions or interacting with nearby objects.

But what happens when that reference point goes away? How does a robot navigate when it’s flying through open space or hovering in mid-air? That’s just one of the problems that fascinates Nick Rehm, who stopped by to host this week’s Aerial Robotics Hack Chat to talk about his passion for flying robots. He’s currently an aerospace engineer at Johns Hopkins Applied Physics Laboratory, where he works on the unique challenges faced by autonomous flying vehicles such as the detection and avoidance of mid-air collisions, as well as the development of vertical take-off and landing (VTOL) systems. But before he had his Master’s in Aerospace Engineering and Rotorcraft, he got started the same way many of us did, by playing around with DIY projects.

In fact, regular Hackaday readers will likely recall seeing some of his impressive builds. His autonomous ekranoplan designed to follow a target using computer vision graced the front page in April. Back in 2020, we took a look at his recreation of SpaceX’s Starship prototype, which used a realistic arrangement of control surfaces and vectored thrust to perform the spacecraft’s signature “Belly Flop” maneuver — albeit with RC motors and propellers instead of rocket engines. But even before that, Nick recalls asking his mother for permission to pull apart a Wii controller so he could use its inertial measurement unit (IMU) in a wooden-framed tricopter he was working on.

Discussing some of these hobby builds leads the Chat towards Nick’s dRehmFlight project, a GPLv3 licensed flight control package that can run on relatively low-cost hardware, namely a Teensy 4.0 microcontroller paired with the GY-521 MPU6050 IMU. The project is designed to let hobbyists easily experiment with VTOL craft, specifically those that transition between vertical and horizontal flight profiles, and has powered the bulk of Nick’s own flying craft.

Moving onto more technical questions, Nick says one of the most difficult aspects when designing an autonomous flying vehicle is getting your constraints nailed down. What he means by that is having a clear goal of what the craft needs to do, and critically, how long it needs to do it. How far does the craft need to be able to fly? How fast? Does it need to loiter at the target location, and if so, for how long? The answers to these questions will largely dictate the form of the final vehicle, and are key to determining if it’s worth implementing the complexity of transitioning from VTOL to fixed-wing horizontal flight.

But according to Nick, the biggest challenge in aerial robotics is onboard state estimation. That is, the ability for the craft to know its position and orientation relative to the ground. While high-performance computers have gotten lighter and sensors have improved, he says there’s still no substitute for having a ground-based tracking system. He mentions that those fancy demonstrations you’ve seen with drones flying in formation and working collaboratively towards a task will almost certainly have an array of motion capture cameras tucked off to the side. This makes for an impressive show, but greatly limits the practical application of these drone swarms.

Nick’s custom Raspberry Pi 4-powered quadcopter lets him test autonomous flight techniques.

So what does the future of aerial robotics look like? Nick says open source projects like ArduPilot and PX4 are still great choices for hobbyists, but sees promise in newer platforms which pair the traditional autopilot with more onboard computing power, such as Auterion’s Skynode. More powerful flight controllers can enable techniques such as simultaneous localization and mapping (SLAM), which uses 3D scans of the environment to help the robot orient itself. He’s also very interested in technologies that enable autonomous flight in GPS-denied environments, which is critical for robotic craft that need to operate indoors or in situations where satellite navigation is unavailable or unreliable. In light of the incredible success of NASA’s Ingenuity helicopter, we imagine these techniques will also play an invaluable role in the future airborne exploration of Mars.

We want to thank Nick for hosting this week’s Aerial Robotics Hack Chat, which turned out to be one of the fastest hours in recent memory. His experience as both an avid hobbyist and a professional in the field provided exactly the sort of insight the Hackaday community looks for, and his gracious offer to keep in touch with several of those who attended the Chat to further discuss their projects speaks to how passionate he is about this topic. We expect to see great things from Nick going forward, and would love to have him join us again in the future to see what he’s been up to.

The Hack Chat is a weekly online chat session hosted by leading experts from all corners of the hardware hacking universe. It’s a great way for hackers connect in a fun and informal way, but if you can’t make it live, these overview posts as well as the transcripts posted to make sure you don’t miss out.

[Nick Rehm] explains the workings of a gps-less self guided drone

Autonomous Drone Dodges Obstacles Without GPS

If you’re [Nick Rehm], you want a drone that can plan its own routes even at low altitudes with unplanned obstacles blocking its way. (Video, embedded below.) And or course, you build it from scratch.

Why? Getting a drone that can fly a path and even return home when the battery is low, signal is lost, or on command, is simple enough. Just go to your favorite retailer, search “gps drone” and you can get away for a shockingly low dollar amount. This is possible because GPS receivers have become cheap, small, light, and power efficient. While all of these inexpensive drones can fly a predetermined path, they usually do so by flying over any obstacles rather than around.

[Nick Rehm] has envisioned a quadcopter that can do all of the things a GPS-enabled drone can do, without the use of a GPS receiver. [Nick] makes this possible by using algorithms similar to those used by Google Maps, with data coming from a typical IMU, a camera for Computer Vision, LIDAR for altitude, and an Intel RealSense camera for detection of position and movement. A Raspberry Pi 4 running Robot Operating System runs the autonomous show, and a Teensy takes care of flight control duties.

What we really enjoy about [Nick]’s video is his clear presentation of complex technologies, and a great sense of humor about a project that has consumed untold amounts of time, patience, and duct tape.

We can’t help but wonder if DARPA will allow [Nick] to fly his drone in the Subterranean Challenge such as the one hosted in an unfinished nuclear power plant in 2020.

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Resilient AI Drone Packs It All In Under 250 Grams

When it was first announced that limits would be placed on recreational RC aircraft heavier than 250 grams, many assumed the new rules meant an end to home built quadcopters. But manufacturers rose to the challenge, and started developing incredibly small and lightweight versions of their hardware. Today, building and flying ultra-lightweight quadcopters with first person view (FPV) cameras has become a dedicated hobby onto itself.

But as impressive as those featherweight flyers might be, the CogniFly Project is really pushing what we thought was possible in this weight class. Designed as a platform for experimenting with artificially intelligent drones, this open source quadcopter is packing a Raspberry Pi Zero and Google’s AIY Vision Kit so it can perform computationally complex tasks such as image recognition while airborne. In case any of those experiments take an unexpected turn, it’s also been enclosed in a unique flexible frame that makes it exceptionally resilient to crash damage. As you can see in the video after the break, even after flying directly into a wall, the CogniFly can continue on its way as if nothing ever happened.

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Running A Glider With The PX4 Flight Controller

There are a few open source autopilots available these days for quadcopters and fixed wing aircraft. Two of the most popular are ArduPilot and PX4, however neither is officially capable of working with unpowered aircraft. Despite this, [rctestflight] decided to run some experiments to see just how PX4 would fare when controlling a drone-launched shuttle glider.

The glider is a simple design built from foam board, controlled with two elevons, and fitted with a third servo to handle its release from the tow drone. It’s fitted with a Pixracer autopilot module and a Dragonlink telemetry link to the ground control laptop.

Initial testing was unsuccessful, with the drone ignoring return-to-home commands, and only responding to waypoints. After some further experimentation, performance improved. Testing and tweaking is the name of the game, and while the attempt to fly the glider into the back of the trailer failed, overall the project shows promise.

It’s impressive to see the glider tracing out perfect circles on the map under autopilot control. While it’s not officially supported, [rctestflight]’s work shows that it’s possible to run PX4 on a glider and have some success doing it. Future plans involve weather balloons and high altitude work, and we can’t wait to see the results.

PX4 has been used in a wide variety of projects, and can be used with even quite unusual aircraft. Video after the break.

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Automate The Freight: Medical Deliveries By Drone

Being a cop’s kid leaves you with a lot of vivid memories. My dad was a Connecticut State Trooper for over twenty years, and because of the small size of the state, he was essentially on duty at all times. His cruiser was very much the family vehicle, and like all police vehicles, it was loaded with the tools of the trade. Chief among them was the VHF two-way radio, which I’d listen to during long car rides, hearing troopers dispatched to this accident or calling in that traffic stop.

One very common call was the blood relay — Greenwich Hospital might have had an urgent need for Type B+ blood, but the nearest supply was perhaps at Yale-New Haven Hospital. The State Police would be called, a trooper would pick up the blood in a cooler, drive like hell down I-95, and hand deliver the blood to waiting OR personnel. On a good day, a sufficiently motivated and skilled trooper could cover that 45-mile stretch in about half an hour. On a bad day, the trooper might end up in an accident and in need of blood himself.

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FAA Finalizes Rules For Drones, UAS, And Model Aircraft

The FAA and DOT have finalized their rules for small Unmanned Aircraft Systems (UAS, or drones), and clarified rules for model aircraft. This is the end of a long process the FAA undertook last year that has included a registry system for model aircraft, and input from members of UAS and model aircraft industry including the Academy of Model Aeronautics and 3D Robotics.

Model Aircraft

Since the FAA began drafting the rules for unmanned aircraft systems, it has been necessary to point out the distinction between a UAS and a model aircraft. Thanks to the amazing advances in battery, brushless motor, and flight controller technology over the past decade, the line between a drone and a model aircraft has been fuzzed, and onboard video systems and FPV flying have only blurred the distinction.

The distinction between a UAS and model aircraft  is an important one. Thanks to the FAA Reauthorization Act of 2012, the FAA, “may not promulgate any rule or regulation regarding a model aircraft” under certain conditions. These conditions include aircraft flown strictly for hobby or recreational use, operated in accordance with a community-based set of safety guidelines (read: the safety guidelines set by the Academy of Model Aeronautics), weighs less than 55 pounds, gives way to manned aircraft, and notifies the operator of an airport when flown within five miles of a control tower.

Despite laws enacted by congress, the FAA saw it necessary to create rules and regulations for model aircraft weighing less than 55 pounds, and operated in accordance with a community-based set of safety guidelines. The FAA’s drone registration system doesn’t make sense, and there is at least one pending court case objecting to these rules.

The FAA’s final rules for UAS, drones, and model airplanes change nothing from the regulations made over the past year. If your drone weighs more than 250 grams, you must register it. For model aircraft, and unmanned aircraft systems conducting ‘hobbyist operations’, nothing has changed.

Unmanned Aerial Systems

The finalized rule introduced today concerns only unmanned aircraft systems weighing less than 55 pounds conducting non-hobbyist operations. The person flying the drone must be at least 16 years old and hold a remote pilot certificate with a small UAS rating. This remote pilot certificate may be obtained by passing an aeronautical knowledge test, or by holding a non-student Part 61 pilot certificate (the kind you would get if you’d like to fly a Cessna on the weekends)

What this means

Under the new regulations, nothing for model aircraft has changed. The guys flying foam board planes will still have to deal with a registration system of questionable legality.

For professional drone pilots – those taking aerial pictures, farmers, or pilots contracting their services out to real estate agents – the situation has vastly improved. A pilot’s license is no longer needed for these operations, and these aircraft may be operated in class G airspace without restriction. Drone use for commercial purposes is now possible without a pilot’s license. This is huge for many industries.

These rules do not cover autonomous flight. This is, by far, the greatest shortcoming of the new regulations. The most interesting applications of drones and unmanned aircraft is autonomous flight. With autonomous drones, farmers could monitor their fields. Amazon could deliver beer to your backyard. There are no regulations regarding autonomous flight from the FAA, and any business plans that hinge on pilot-less aircraft will be unrealized in the near term.

DJI Phantoms are now ‘drones’

This is a quick aside, but I must point out the FAA press release was written by someone with one of two possible attributes. Either the author of this press release paid zero attention to detail, or the FAA has a desire to call all unmanned aircraft systems ‘drones’.

The use of the word ‘drone’ in the model aircraft community has been contentious, with quadcopter enthusiasts making a plain distinction between a DJI Phantom and a Predator drone. Drones, some say, have the negative connotation of firing hellfire missiles into wedding parties and killing American citizens in foreign lands without due process, violating the 5th amendment. Others have classified ‘drones’ as having autonomous capability.

This linguistic puzzle has now been solved by the FAA. In several places in this press release, the FAA equates ‘unmanned aircraft systems’ with drones, and even invents the phrase, ‘unmanned aircraft drone’. Language is not defined by commenters on fringe tech blogs, it is defined by common parlance. Now the definition of ‘drone’ is settled: it is an unmanned, non-autonomous, remote-controlled flying machine not flown for hobby or recreational use.