The envelope is 9 meters long and 2.2 meters in diameter when inflated. It is composed of two layers, an outer envelope of ripstop Nylon and an inner PVC bladder. The outer envelope is sturdy and weatherproof, and protects the inner envelope from puncture. The strong envelope contains velcro mounts and anchors for the four fins, gondola, control cables, and banners along the sides of the blimp. Valves at the nose and tail allow the inner bladder to be filled with helium—for payload reasons our ballonet has been removed. (The ballonet is an airtight bag which allows the density of the blimp to be adjusted by adding or releasing air.) The envelope weighs approximately 15 kilograms.
The two 23cc engines are mounted port and starboard on a rotating shaft that passes through the gondola, allowing them to rotate 180 degrees. Each Zenoah G-23 engine is rated at 2 horsepower at 10,000 RPM, and they can drive the blimp in winds of up to 10 mph. We use tri-bladed, wooden Zinger propellers with a diameter of 13 inches and a blade pitch of 10 degrees. (3 blade 13-10 props.) They typically achieve 7000 RPM. The 2-liter fuel capacity enables the blimp to stay aloft for about 45 minutes. The motor mount shaft has been re-machined with thicker, higher quality aluminum to increase its strength and reliability as well as its serviceability.
The control surfaces consist of two vertical fins and two horizontal elevators mounted at the rear of the blimp with Velcro and cable. The fins have been redesigned from stock to provide more surface area and a wider range of motion from the stock fin designs. Our new direct-drive fin system increases fin complexity somewhat but avoids the small range of motion problems and slow response that manifested in the stock fins. In fact, our new design is so much more efficient that we can flap the fins like bird wings over a full 180 degrees of rotation! The only drawback is an increase in servo wear, but given the current price of servos this has not shown to be a problem. The fins are currently constructed out of balsa wood and polymer outer coating, but an investigation into using Hexalite, carbon fiber, and other advanced materials is underway.
Sensor Array and Electronics
Our current sensor array consists of GPS, gyroscope, dual video cameras, and servo control system. We have the ability of logging and displaying GPS position data, temperature, heading, altitude, local time, and velocity information as well as provide this data to any process that needs it running on our custom Blimp control layer. All the sensors connect to the onboard laptop via USB, FireWire (IEEE 1394), or serial connections.
Communication with the onboard computer takes place over a wireless LAN. Using a standard 802.11b network, with 802.11a on the horizon, we can stream video and data from the blimp back down to the ground as well as control all the hardware and software on the blimp in real time. The LAN allows the blimp to interface easily with other computers on the ground, and our remote procedure call architecture makes full advantage of the connection to fully distribute blimp processing workload.
As the software is being stabilized, radio control is the primary communications method for the blimp. This control, which shipped with the blimp, does not interface with the computer, but allows direct operator control of engine throttles, engine pitch, and fin servos.
Peripherals and Payload
One of the blimp's most useful aspects is the ability to carry a wide variety of computer peripherals for data collection. Current testing has focused on the use of a moveable web camera and a digital video camera to provide streaming video to the ground via the computer and wireless LAN. This data has a multitude of uses. Such images can provide useful feedback to control algorithms, improving the stabilization of the blimp. Aerial photography could also be used both for short-term activities, such as filming sports events and Commencement, and for long-term projects, such as mapping and GIS activities.
The Blimp is being used as the development platform for ROCI - The Remote Operations and Control Interface. This system is designed for universal control of robots and fleets of robots. Utilizing Web Services and SOAP, ROCI is written to the .NET platform.
ROCI is currently on version 2.0 - it provides a fully distributed computing platform which makes programming the distributed system completely transparent. Your code can be injected into any node in the network, running in a viral and distributed fashion. For more information contact Vito