Our team, the Funky Shiitake Mushrooms created a dual-envelope hybrid airship as a platform for aerial robotics.
It is equipped with a wireless camera, a LiPo battery, three speed controllers (ESCs), a 2.4GHz radio, and four motors and propellers (two on the vertical axis, two on the horizontal axis). The frame was made out of carbon fiber and lashed together with cotton string and cyanoacrylate, in the simple yet strong shape of a rhombus. We ran another carbon fiber rod down on the long diagonal for the electronics, and added several additional rods. Each horizontal propeller had their own ESC allowing for the blimp to be tank-driven and making it possible for the hybrid airship to turn while positionally stationary.
Our device is highly maneuverable, able to switch from flying backwards to forwards with ease, and the horizontal ESCs enable the hybrid airship to turn in place, making a full 360-degree turn in 2 seconds.
The first version of our device was designed to deliver a payload in last year's Tech Challenge (www.techchallenge.thetech.org), which simulated delivering instrumentation to take readings from an active volcano. We then modified our device for Robogames (www.robogames.net) for surveillance, using an LED array, a security camera that worked in the visible and infrared spectrums, and a wireless intercom.
When the scenario for the 2009 Tech Challenge came out in August 2008, our team immediately began brainstorming. The problem was to place ping-pong balls to the top of a 8-foot tall model volcano, simulating real-life payload deliveries of sensor equipment and other scientific equipment. We soon narrowed our designs down to several airborne vehicles. The decision to make a hybrid airship was a long process; we narrowed our list of designs down after striking out other designs like helicopters and off-the-shelf blimps.
The idea of an easily built, inexpensive aircraft accessible to anyone inspired us to do research into hybrid airships. We saw the hybrid airship as an alternative to conventional airplanes and rotorcraft (i.e. helicopters) because of its combination of stability and maneuverability – it’s nearly impossible to break, safe to use indoors and around people, and thus promising as a platform for mobile robotics. In addition, it does not need a runway like an airplane, nor is it as difficult to operate and maintain as a helicopter.
Who will enjoy this the most?
The cost of our device was around $500, including the cost of several refills of helium. That is around the cost of an off-the-shelf model helicopter outfitted with camera, sensors, and gyroscopes, and compared to a helicopter, our device is much easier to pilot, has longer operating times, and has lower-cost consumables (heli blades are $10 a set, and you'd be amazed how fast you can go through them...).
We can envision a low-cost version of our device using around $250 of materials, using a bare minimum of carbon fiber and the most basic RC radio system, and a more common blimp envelope.
Because of the affordability, ease of use, and versatilility of the hybrid airship as a platform, we imagine that people would find our design to be useful if they were looking for a robust airborne aircraft more stable than a helicopter and less expensive to build than many other standard aircraft devices.
We designed our hybrid airship from scratch, calculating the weight of the device and the lift provided by helium and propellers, and making diagrams of the placement of electronics in relation to the device’s center of mass. And when everything seemed to go together, we got to work. Rough prototyping started in November 2008, and we had a functional device by mid-April of 2009.
Our propeller and motor mount.
A prototype of our drop mechanism. The receiver pictured here ended up attached to the other side of the frame. This was during our first round of prototyping so resourceful (and messy) use of commonplace materials was inevitable.
Rebecca (the girl on the left) ran the vertical propellers for altitude. Eric (not pictured) manned the horizontal propellers. Catherine is on the right. In this photo, we're practicing in our school's auditorium
We also brought the device around school and demonstrated it to some of our teachers and staff. Here is a picture of a demo we gave in our advisor's room. We even have the camera operating and a video feed on the projector.
Once TechChallenge was finished, we worked on modifying the blimp for Robogames. That's Raymond working with the blimp's electronics. ESCs are in the center of the frame. Receivers are attached to the back where Raymond's left hand is.
For more information, see our website, which also has a blog about the design and construction process that we went through this year.
Our hybrid airship carried approximately 200g for Tech Challenge, and 100g for Robogames. With batteries, motors, and propellers designed to create more thrust, we can modify our device to carry a larger payload, like a digital camera or GPS module.
We are currently working on a second hybrid airship; we have the frame and mylar envelopes.
One of our plans for the new airship is to integrate a microcontroller to give it autonomous capability. For example, the SunSPOT controller (http://www.sunspotworld.com/) includes its own wireless radio, accelerometers, and gyroscopes; if we redesigned our control system around it, we could replace the RC radio with a computer-controlled system that would allow the airship to maintain a steady position, navigate from waypoint to waypoint, and steady itself in light winds. We also plan to integrate reversible ESCs to the verticle controls and add a fail-safe, which would consist of a mechanism to cut the spine of colorful helium balloons loose.
Below is the video. We had limited space to demonstrate our device. Had we had more room our blimp could fly faster and higher. And there's a certain elegance to it when it's in full power.