One Wheel Is All We Need To Roll Into Better Multirotor Efficiency

Multirotor aircraft enjoy many intrinsic advantages, but as machines that fight gravity with brute force, energy efficiency is not considered among them. In the interest of stretching range, several air-ground hybrid designs have been explored. Flying cars, basically, to run on the ground when it isn’t strictly necessary to be airborne. But they all share the same challenge: components that make a car work well on the ground are range-sapping dead weight while in the air. [Youming Qin et al.] explored cutting that dead weight as much as possible and came up with Hybrid Aerial-Ground Locomotion with a Single Passive Wheel.

As the paper’s title made clear, they went full minimalist with this design. Gone are the driveshaft, brakes, steering, even other wheels. All that remained is a single unpowered wheel bolted to the bottom of their dual-rotor flying machine. Minimizing the impact on flight characteristics is great, but how would that work on the ground? As a tradeoff, these rotors have to keep spinning even while in “ground mode”. They are responsible for keeping the machine upright, and they also have to handle tasks like steering. These and other control algorithm problems had to be sorted out before evaluating whether such a compromised ground vehicle is worth the trouble.

Happily, the result is a resounding “yes”. Even though the rotors have to continue running to do different jobs while on the ground, that was still far less effort than hovering in the air. Power consumption measurements indicate savings of up to 77%, and there are a lot of potential venues for tuning still awaiting future exploration. Among them is to better understand interaction with ground effect, which is something we’ve seen enable novel designs. This isn’t exactly the flying car we were promised, but its development will still be interesting to watch among all the other neat ideas under development to keep multirotors in the air longer.

[IROS 2020 Presentation video (duration 10:49) requires no-cost registration, available until at least Nov. 25th 2020. Forty-two second summary embedded below]

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Quadcopter With Tensegrity Shell Takes A Beating And Gets Back Up

Many of us have become familiar with the distinctive sound of multirotor toys, a sound frequently punctuated by sharp sounds of crashes. We’d then have to pick it up and repair any damage before flying fun can resume. This is fine for a toy, but autonomous fliers will need to shake it off and get back to work without human intervention. [Zha et al.] of UC Berkeley’s HiPeRLab have invented a resilient design to do so.

We’ve seen increased durability from flexible frames, but that left the propellers largely exposed. Protective bumpers and cages are not new, either, but this icosahedron (twenty sided) tensegrity structure is far more durable than the norm. Tests verified it can survive impact with a concrete wall at speed of 6.5 meters per second. Tensegrity is a lot of fun to play with, letting us build intuition-defying structures and here tensegrity elements dissipate impact energy, preventing damage to fragile components like propellers and electronics.

But surviving an impact and falling to the ground in one piece is not enough. For independent operation, it needs to be able to get itself back in the air. Fortunately the brains of this quadcopter has been taught the geometry of an icosahedron. Starting from the face it landed on, it can autonomously devise a plan to flip itself upright by applying bursts of power to select propeller motors. Rotating itself face by face, working its way to an upright orientation for takeoff, at which point it is back in business.

We have a long way to go before autonomous drone robots can operate safely and reliably. Right now the easy answer is to fly slowly, but that also drastically cuts into efficiency and effectiveness. Having flying robots that are resilient against flying mistakes at speed, and can also recover from those mistakes, will be very useful in exploration of aerial autonomy.

[IROS 2020 Presentation video (duration 14:16) requires free registration, available until at least Nov. 25th 2020. One-minute summary embedded below]

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Hackaday Podcast 080: Trucks On A Wire, Seeing Sounds, Flightless Drone, And TEA Laser Strike

Hackaday editors Elliot Williams and Mike Szczys flip through the index of great hacks. This week we learn of a co-existence attack on WiFi and Bluetooth radios called Spectra. The craftsmanship in a pneumatic drone is so awesome we don’t care that it doesn’t fly. Building a powerful TEA laser is partly a lesson in capacitor design. And join us in geeking out at the prospect of big rigs getting their juice from miles of overhead wires.

Take a look at the links below if you want to follow along, and as always, tell us what you think about this episode in the comments!

Direct download (~65 MB)

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Justice For The Gatwick Two: The Final Chapter In The British Drone Panic Saga

At the end of 2018, a spate of drone sightings caused the temporary closure of London Gatwick Airport, and set in train a chain of events that were simultaneously baffling and comedic as the authorities struggled to keep up with both events and the ever widening gap in their knowledge of the subject.

One of the more inept actions of the Sussex Police was to respond by arresting the first local drone enthusiast they could find on Facebook, locking up a local couple for 36 hours and creating a media frenzy by announcing the apprehension of the villains before shamefacedly releasing them without charge.

In a final twist to the sorry saga, the couple have sued the force for wrongful arrest and false imprisonment, for which the cops have had to make a £200,000 ($250,117) payout including legal fees.

We reported extensively on the events surrounding the case 18 months ago, and then on a follow-up event at London Heathrow airport. The mass media at the time were full of the official line that drone hobbyists must be at fault, but then as now we were more interested in seeing some hard evidence. As we said then: Show us the drone.

So how has the new drone law progressed, since it was decided that Something Must Be Done? Enthusiasts have continued as before, and the multirotor community is as technically creative as ever. We were fortunate enough to host the Lets Drone Out podcast at MK Makerspace back in those halcyon days before the pandemic and see the state of the art in sub-250g craft, and with those and commercial offerings such as the DJI Mavic Mini all requiring no registration there is increasingly little need for an enthusiast to purchase a larger machine. The boost to the British drone industry we were promised has instead been a boost for the Chinese industry as we predicted, and of course we’re still waiting for the public inquiry into the whole mess. Something tells us Hell will freeze over first.

If you’d like the whole backstory in a convenient and entertaining video format, can we direct you to this talk at CCCamp 2019.

Thanks [Stuart Rogers] for the tip.

Keystone Kops header image: Mack Sennett Studios [Public domain].

Flying Batteries For Drones

Power is the bane of drone pilots. You’d like to fly longer which means a bigger battery. But a bigger battery will weigh more which leads to less flight time. You have to strike a balance and for most consumer drones that balance is about 20 minutes of flight time, more or less. Researchers at Berkeley have a different idea: don’t use a bigger battery, but simply replace the battery in flight.

The idea isn’t completely new. After all, many planes refuel in flight — a technically sophisticated operation, but it occurs every day. The scheme here is to have a primary battery and a secondary battery. When the secondary battery is low, the drone ejects it while running on the primary battery. Another secondary battery flies to the drone and docks with it becoming the new main power source.

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Gatwick Drone Incident: Police Still Clueless

Quietly released and speedily buried by Parliamentary wrangles over Brexit is the news that Sussex Police have exhausted all lines of inquiry  into the widely publicised drone sighting reports that caused London’s Gatwick Airport to be closed for several days last December. The county’s rozzers have ruled out 96 ‘people of interest’ and combed through 129 separate reports of drone activity, but admit that they are no closer to feeling any miscreant collars. There is no mention of either their claims at the time to have found drone wreckage, their earlier admissions that sightings might have been of police drones, or even that there might have been no drone involved at all.

Regular readers will know that we have reported extensively the sorry saga of official reactions to drone incidents, because we believe that major failings in reporting and investigation will accumulate to have an adverse effect on those many people in our community who fly multi-rotors. In today’s BBC report for example there is the assertion that 109 of the drone sightings came from “‘credible witnesses’ including a pilot and airport police” which while it sounds reassuring is we believe a dangerous route to follow because it implies that the quality of evidence is less important than its source. It is crucial to understand that multi-rotors are still a technology with which the vast majority of the population are still unfamiliar, and simply because a witness is a police officer or a pilot does not make them a drone expert whose evidence is above scrutiny.

Whichever stand you take on the drone sightings at Gatwick and in other places it is clear that Sussex Police do not emerge from this smelling of roses and that their investigation has been chaotic and inept from the start. We believe that there should be a public inquiry into the whole mess, so that those embarrassing parts of it which they and other agencies are so anxious to quietly forget can be subjected to scrutiny. We do not however expect this to happen any time soon.

Keystone Kops header image: Mack Sennett Studios [Public domain].

Aussies Find The True Meaning Of Drone Flight

Ah, stereotypes. Once they’ve solidified it’s surprisingly hard to shake them. When non-Australians think of a generic Aussie then, the chances are that a Crocodile Dundee type of character will spring to mind — a ‘Strine-speaking outdoorsman with a beer in hand. This group of Aussies aren’t helping the case, with a video posted by Australian drone retailer UAVme and featured by ABC News where a large multirotor lifts a guy in a lawn chair, beer in hand, over a lake to do some fishing.

Antics aside, having enough capacity to lift a person is pretty impressive. The drone in question appears to be a large hexacopter frame with rotors both below and above the boom, achieving an unusual dodecacopter configuration.

Of course we’re entertained by the sight, who wouldn’t envy them a spin under a drone in the relative safety of an environment where an unscheduled landing merely means getting wet? It seems Austrailia’s Civil Aviation Safety Authority isn’t quite so happy though, as ABC reports the usual chorus of condemnation. Entertainingly though it’s unclear whether or not our plucky adventurer — named as [Sam Foreman] — has in fact broken any laws given that he’s not flown in restricted airspace, over people or habitation, or above the legal altitude.

This isn’t the first such story we’ve brought you from Down Under, back in 2016 an Aussie landed in hot water for picking up a Bunnings sausage in a bun with his drone.

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