Extrinsic Motivation: And You Thought Inverted Pendulums Were Hard

An extremely common project for a control systems class is the inverted pendulum. Basically, it’s a robot mounted on a linear rail, a hinge, and a pendulum sticking straight up in the air. Get your algorithms right, and you have a pendulum that seemingly resists the inexorable pull of gravity and a great understanding of how Segways, balancing robots, and quadcopters work.

[zakowy] is taking this to the next level with his entry to The Hackaday Prize. It’s an inverted pendulum with two counter-rotating propellers in a gimballed fan, and the most unstable UAV design we’ve ever seen.

The mechanics of the build consist of a carbon and epoxy frame, with a motor mount that can move in the X and Y axes. This mount holds two brushless motors and is actuated with rather large pitch and roll servos. The electronics consist of the usual suite of sensors found in a quadcopter – gyros, accelerometers, magnetometers, and a barometric altimeter. Everything is controlled by an Arduino Due, getting commands from an RC receiver and sending telemetry back to a computer

[zakowy]’s project didn’t make the cut for the quarterfinalist selection, but he is undeterred. He’s building this strange contraption because he can, not because we’re dangling some great prizes in front of his nose. Right now, [zakowy] is working on a testing rig. This thing will fly, make no mistakes about that.

Videos available below.


SpaceWrencherThis project is an official entry to The Hackaday Prize that sadly didn’t make the quarterfinal selection. It’s still a great project, and worthy of a Hackaday post on its own.

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THP Semifinalist: Autonomous Recharging For Multirotors

Even with visions of quadcopters buzzing around metropolitan areas delivering everything from pizzas to toilet paper fresh in the minds of tech blogospherites, There’s been a comparatively small amount of research into how to support squadrons of quadcopters and other unmanned aerial vehicles. The most likely cause of this is the FAA’s reactionary position towards UAVs. Good thing [Giovanni] is performing all his research for autonomous recharging and docking for multirotors in Australia, then.

The biggest obstacle of autonomous charging of a quadcopter is landing a quad exactly where the charging station is; run of the mill GPS units only have a resolution of about half a meter, and using a GPS solution would require putting GPS on the charging station as well. The solution comes from powerful ARM single board computers – in this case, an Odroid u3 – along with a USB webcam, OpenCV and a Pixhawk autopilot.

Right now [Giovanni] is still working out the kinks on his software system, but he has all the parts and the right tools to get this project up in the air, down, and back up again.


SpaceWrencherThe project featured in this post is a semifinalist in The Hackaday Prize.

Flying A Drone With An Oculus Rift 

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Controlling autonomous vehicles remotely with the use of virtual reality headsets seems like an obvious next step. Already, a few UAV companies have begun experimenting with these types of ideas by integrating Oculus Rift developer kits into their hovering quadcopters and drones. Parrot released a video on their blog showing that they developed a head-tracking system for their Bebop Drone in an effort to bring FPV flights to fruition. It looks like a lot of fun and we want to try one of these out asap!

As for technical specifications, they can be found in the YouTube description of the video embedded below. A quick glance showed that the operating system is based on Android and uses WiFi to connect the handheld tablet to the autonomous vehicle floating above. The range is a whopping 2km, giving plenty of freedom to explore. Moving one’s head swivels the attached camera giving a more immersive flying experience.

This isn’t the first example of FPV drones that we have seen. Previously, we covered an Oculus Rift + Head Tracking setup and another similar integration with a Black Armor Drone. We are bound to see virtual reality equipment used to control drones more and more as developers get their hands on cutting edge hardware like the Oculus developer kit 2 hardware which is currently shipping.

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Axis Glove That Controls A Robot

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This homemade glove and gesture controlled rover was created by [electro18]. It can send temperature, battery level, and object distance to the LCD panel on the wrist. Instead of a typical joystick, this wireless system taps into an embedded accelerometer to maneuver the robot like magic.

The main chassis platform is made of clear acrylic and has additional acrylic strips fixed to the edges for additional strength. A LM35 temperature sensor is wired to the front that monitors the environments that the rover explores. An HC-SR04 Ultrasonic Rangefinder acts as the eyes of the machine. The photodiode is covered with an adaptation of a 6mm heat shrink tube to avoid false readings. Once hooked up and turned on, the robot can be controlled with the futuristic power glove consisting of two parts. An accelerometer strap and a display strap are the biggest parts. The project shows that it is relatively easy to make a system like this. Other items like quadcopters and tiny water boats could be controlled with a similar type of setup.

A video of the axis glove maneuvering the vehicle on a slope can be seen after the break:

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A 3D Printed Brushless Motor

brushlessBuilding electronics with 3D printers is something we see hitting the tip line from time to time, but usually these are printed circuits, not electromechanical parts like motors, solenoids, and relays. [pitrack] thought he could do better than printing out a few blinking LED circuits and designed and built a brushless motor, the same kind you would find on electric model planes and quadcopters.

In every brushless DC motor, there are a few common parts: the rotor has a few powerful magnets embedded in it, a stators with coils of wire, and the an enclosure to keep everything together. [pitrack] printed all these parts off on his Makerbot, winding each of the three coils with about 400 turns of 26 AWG magnet wire. Also embedded in the stator are a trio of hall effect sensors to make the control via an Arduino and an L6234 motor driver easy.

For his next trick, [pitrack] is going to test the efficiency of the motor and attempt to optimize it. In the long term, it should be possible to parameterize the design of one of these printed motors, effectively allowing anyone to type in the torque and Kv rating of a desired motor, plug that into an equation, and have a motor design come out the other end.
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Congress Destroys A Hobby, FAA Gets The Blame

As ordered by the US Congress, the FAA is gearing up to set forth a standard for commercial UAVs, Unmanned Aerial Systems, and commercial drones operating in America’s airspace. While they’ve been dragging their feet, and the laws and rules for these commercial drones probably won’t be ready by 2015, that doesn’t mean the FAA can’t figure out what the rules are for model aircraft in the meantime.

This week, the FAA released its interpretation (PDF) of what model aircraft operators can and can’t do, and the news isn’t good: FPV flights with quadcopters and model airplanes are now effectively banned, an entire industry centered around manufacturing and selling FPV equipment and autopilots will be highly regulated, and a great YouTube channel could soon be breaking the law.

The FAA’s interpretation of what model aircraft can and cannot do, and to a larger extent, what model aircraft are comes from the FAA Modernization And Reform Act Of 2012 (PDF). While this law states the, “…Federal Aviation Administration may
not promulgate any rule or regulation regarding a model aircraft…” it defines model aircraft as, “an unmanned aircraft that is capable of sustained flight in the atmosphere; flown within visual line of sight of the person operating the aircraft; and flown for hobby or recreational purposes.” The FAA has concluded that anything not meeting this definition, for example, a remote controlled airplane with an FPV setup, or a camera, video Tx and Rx, and video goggles, is therefore not a model aircraft, and falls under the regulatory authority of the FAA.

In addition, the FAA spent a great deal of verbiage defining what, “hobby or recreational purposes” in regards to model aircraft are. A cited example of a realtor using a model aircraft to take videos of a property they are selling is listed as not a hobby or recreation, as is a farmer using a model aircraft to see if crops need water. Interestingly, receiving money for demonstrating aerobatics with a model aircraft is also not allowed under the proposed FAA guidelines, a rule that when broadly interpreted could mean uploading a video of yourself flying a model plane, uploading that to YouTube, and clicking the ‘monetize’ button could soon be against the law. This means the awesome folks at Flite Test could soon be out of a job.

The AMA, the Academy Of Model Aeronautics, and traditionally the organization that sets the ‘community-based set of safety guidelines’ referred to in every law dealing with model aircraft, are not happy with the FAA’s proposed rules (PDF). However, their objection is a breathless emotional appeal calls the proposed rules a, “a strict regulatory approach to the operation of model aircraft in the hands of our youth and elderly members.” Other than offering comments per the FAA rulemaking process there are, unfortunately, no possible legal objections to the proposed FAA rules, simply because the FAA is doing exactly what congress told them to do.

The FAA is simply interpreting the Modernization And Reform Act Of 2012 as any person would: FPV goggles interfere with the line of sight of an aircraft, thus anyone flying something via FPV goggles falls under the regulatory authority of the FAA. Flying over the horizon is obviously not line of sight, and therefore not a model aircraft. Flying a model aircraft for money is not a hobby or recreation, and if you’re surprised about this, you simply aren’t familiar with FAA rules about money, work, and person-sized aircraft.

While the proposed FAA rules are not yet in effect, and the FAA is seeking public comment on these rules, if passed there will, unfortunately, exactly two ways to fix this. The first is with a change in federal law to redefine what a model aircraft is. Here’s how to find your congresscritter, with the usual rules applying: campaign donations are better than in-person visits which are better than letters which are better than phone calls which are better than emails. They’ll also look up if you have voted in the last few elections.

If passed, the only other way these rules will align with the privileges model aircraft enthusiasts have enjoyed for decades is through a court ruling. The lawsuit objecting to these rules will most likely be filed by the AMA, and if these rules pass, a donation or membership wouldn’t be a bad idea.

The Ultimate Tiny Altimeter

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While traditionally a project geared more toward the model rocket crowd, a lot of people are flying quadcopters these days, and knowing the altitude your RC aircraft reached is a nice thing to know. [Will] came up with a very nice, very small, and very lightweight altimeter that’s perfect for strapping to microquads, their bigger brothers, and of course model rockets. As a nice bonus, it also looks really cool with an exceedingly retro HP bubble display.

The components used in this tiny altimeter include a MEMS altitude and pressure sensor, HP bubble display featuring four seven-segment LEDs, an Arduino Pro Mini, and a tiny 40 mAh LiPo capable of powering the whole contraption for hours.

In the video below, [Will] shows off the functions of his altimeter, sending it aloft on a quadcopter to about 100 ft. There are settings for displaying the minimum, maximum, and delta altitudes, all accessed with a single button.

While it’s not the most feature packed altimeter out there, it’s still much better than commercial offerings available for the model rocket crowd.

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