Building And Flying A Helicopter With A Virtual Swashplate

June 25, 2020 by Dan Maloney 33 Comments

They say that drummers make the best helicopter pilots, because to master the controls of rotary-wing aircraft, you really need to be able to do something different with each limb and still have all the motions coordinate with each other. The control complexity is due to the mechanical complexity of the swashplate, which translates control inputs into both collective and cyclical changes in the angle of attack of the rotor blades.

As [Tom Stanton] points out in his latest video, a swashplate isn’t always needed. Multicopters dispense with the need for one by differentially controlling four or more motors to provide roll, pitch, and yaw control. But thanks to a doctoral thesis he found, it’s also possible to control a traditional single-rotor helicopter by substituting flexible rotor hinges and precise motor speed control for the swashplate.

You only need to watch the slow-motion videos to see what’s happening: as the motor speed is varied within a single revolution, the tips of the hinged rotor blades lead and lag the main shaft in controlled sections of the cycle. The hinge is angled, which means the angle of attack of each rotor blade changes during each rotation — exactly what the swashplate normally accomplishes. As you can imagine, modulating the speed of a motor within a single revolution when it’s spinning at 3,000 RPM is no mean feat, and [Tom] goes into some detail on that in a follow-up video on his second channel.

It may not replace quadcopters anytime soon, but we really enjoyed the lesson in rotor-wing flight. [Tom] always does a great job of explaining things, whether it’s the Coandă effect or anti-lock brakes for a bike.

Continue reading “Building And Flying A Helicopter With A Virtual Swashplate” →

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

June 17, 2020 by Jenny List 27 Comments

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].

Obstacle Avoidance For Drones, Learned From Mosquitoes

June 17, 2020 by Danie Conradie 10 Comments

Our understanding of the sensory capabilities of animals has a lot of blanks, and often new discoveries serve as inspiration for new technology. Researchers from the University of Leeds and the Royal Veterinary College have found that mosquitos can navigate in complete darkness by detecting the subtle changes in the air flow created when they fly close to obstacles. They then used this knowledge to build a simple but effective sensor for use on drones.

Extremely sensitive receptors at the base of the antennae on mosquitoes’ heads, called the Johnston’s organ, allow them to sense these tiny changes in airflow. Using fluid dynamics simulations based on high speed photography, the researchers found that the largest changes in airflow occur over the mosquito’s head, which means the receptors are in exactly the right place. From their data, scientists predict that mosquitos could possibly detect surfaces at a distance of more than 20 wing lengths. Considering how far 20 arm lengths is for us, that’s pretty impressive. If you can get past the paywall, you can read the full article from the Science journal.

Using their newfound knowledge, the researchers equipped a small drone with probe tubes connected to differential pressure sensors. Using these sensors the drone was able to effectively detect when it got close to the wall or floor, and avoid a collision. The sensors also require very little computational power because it’s only a basic threshold value. Check out the video after the break.

Although this sensing method might not replace ultrasonic or time-of-flight sensors for drones, it does show that there is still a lot we can learn from nature, and that simpler is usually better. We’ve already seen simple insect-inspired navigation for drone swarms, as well as an optical navigation device for humans that works without satellites and only requires a view of the sky. Thanks for the tip [Qes]! Continue reading “Obstacle Avoidance For Drones, Learned From Mosquitoes” →

Combine Broken Drone Propellers For A Second Spin

May 6, 2020 by Danie Conradie 8 Comments

If you’ve ever flown or watched anyone fly a racing drone for any length of time, you know that crashes are just part of the game and propellers are consumables. [Adam] knows this all to well, decided to experiment with combining multiple broken propellers into one with a 3D printed hub.

A damaged propeller will often have one blade with no damage, still attached to the hub. [Adam] trimmed the damaged parts of a few broken props, and set about designing a 3D printed hub to attach the loose blades together. The hubs were designed let the individual blades to move, and folding out as the motors spin up, similar to the props on many photography drones.

Once [Adam] had the fit of the hubs dialed in, he mounted a motor on a piece of wood and put the reborn propellers through their paces. A few hubs failed in the process, which allowed [Adam] to identify weak points and optimise the design. This sort of rapid testing is what 3D printing truly excels at, allowing test multiple designs quickly instead of spending hours in CAD trying to foresee all the possible problems.

He then built a test drone from parts he had lying around and proceeded with careful flight testing. The hubs were thicker than standard propellers so it limited [Adams] motor choices to ones with longer shafts. Flight testing went surprisingly well, with a hub only failing after [Adam] changed the battery from a 3 cell to a 4 cell and started with some aerobatics. Although this shows that the new props are not suitable for the high forces from racing or aerobatics/freestyle flying, they could probably work quite well for smoother cruising flights. The hubs could also be improved by adding steel pins into the 3D printed shafts, and some carefully balancing the assembled props.

Continue reading “Combine Broken Drone Propellers For A Second Spin” →

A Hackable Drone Without All The Wiring

May 2, 2020 by Danie Conradie 13 Comments

Drones have come a long way in the past decade, and a lot of the pioneering work that made them mainstream was done by individual hackers and small teams. This often involves cobbling together components into flying crow’s nests of wiring. To streamline things a bit for hackers, the team at Luminous Bees are working on Ardubee, a small 3″ drone designed from the ground up for hacking.

The Ardubee is built around a single PCB that also acts as the frame of the drone. Onboard is an STM32F427 microcontroller, IMU, barometer and compass, ESCs, ESP8266 for telemetry, and a downward-facing range finder. It’s ready to connect to an SBUS RC receiver and a range of pluggable modules are in development to expand the drone’s capabilities. It’s designed to run the open-source Ardupilot software, which we’ve seen in so many DIY autonomous vehicles. Power is provided by a single 18650, which will probably limit higher speed maneuverability a bit but should be fine for the slower precision flight that such a drone is likely to be used for.

The team already has a swarm of larger 5″ drones that they developed for light shows. In the process they developed their own Ultrawide-band indoor positioning system, which will also be available for the Ardubee. They hope to launch a Kickstarter campaign soon and are asking for input from the community, so they can know what features need to be prioritized. We look forward to seeing where this project goes!

Autonomous vehicles are a popular topic around here for air, land, and water, and we have no doubt there will be many more.

Thanks for the tip [Andreas]!

Giant Scale RC A350 Airliner Using Carbon Fibre And 3D Printing

April 29, 2020 by Danie Conradie 16 Comments

Large scale RC aircraft are pleasure to see on the ground and in the air, but putting in the months of effort required to build them requires special dedication. Especially since there is a real possibility it could end up in pieces on the ground at some point. [Ramy RC] is one of those dedicated craftsman, and he has a thing for RC airliners. His latest project is a large Airbus A350, and the painstaking build process is something to behold.

The outer skin of the aircraft is mostly carbon fibre, with wood internal framing to keep everything rigid. The fuselage and winglets are moulded using 3D printed moulds. These were printed in pieces on a large format 3D printer, and painstakingly glued together and prepared to give a perfect surface finish. The wing surfaces are moulded in flat section and then glued onto the frames. [Ramy RC]’s attention to detail is excellent, making all the control surfaces close as possible to the real thing, and retractable landing gear with servo actuated hatches. Thrust comes from a pair of powerful EDF motors, housed in carbon fibre nacelles.

This project has been in the works for almost 5 months so far and it looks spectacular. We’re looking forward to the first flight, and will be holding thumbs that is remains in one piece for a long time. See the video after the break for final assembly of this beast.

For the next step up from RC aircraft, you can always build your own full size aircraft in your basement. If you have very very deep pockets, get yourself a private hangar/workshop and build a turbine powered bush plane.

Thanks for the tip [tayken]! Continue reading “Giant Scale RC A350 Airliner Using Carbon Fibre And 3D Printing” →

A DIY Functional F-35 Is No Simple Task

April 27, 2020 by Danie Conradie 19 Comments

The advent of affordable gear for radio-controlled aircraft has made the hobby extremely accessible, but also made it possible to build some very complex flying machines on a budget, especially when combined with 3D printing. [Joel Vlashof] really likes VTOL fighter aircraft and is in the process of building a fully functional radio-controlled F-35B.

The F-35 series of aircraft is one of the most expensive defence project to date. The VTOL capable “B” variant is a complex machine, with total of 19 doors on the outside of the aircraft for weapons, landing gear and thrusters. The thruster on the tail can pivot 90° down for VTOL operations, using an interesting 3-bearing swivel mechanism.

[Joel] wants his model to be as close as possible to the real thing, and has integrated all these features into his build. Thrust is provided by two EDF motors, the pivoting nozzle is 3D printed and actuated by three set of small DC motors, and all 5 doors for VTOL are actuated by a single servo in the nose via a series of linkages. For tilt control, air from the main fan is channeled to the wing-tips and controlled by servo-actuated valves. A flight controller intended for use on a multi-rotor is used to help keep the plane stable while hovering. One iteration of this plane bit the dust during development, but [Joel] has done successful test flights for both hover and conventional horizontal flight. The really tricky part will be transitioning between flight modes, and [Joel] hopes to achieve that in the near future.

The real Lockheed Martin F-35 Lightning II project is controversial because of repeated budget overruns and time delays, but the engineering challenges solved in the project are themselves fascinating. The logistics of keeping these complex machines in the air are daunting, and a while back we saw Marine ground crew 3D print components that they were having trouble procuring through normal channels.

Continue reading “A DIY Functional F-35 Is No Simple Task” →