Phoenix Project Design
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Design and Systems Overview
The Phoenix Project design is a unique combination of complex subsystems fully integrated into an operational autonomous flight platform. The main vehicle used for transporting all the components essential for autonomous flight is the Bergen Industrial Twin R/C helicopter. The Bergen Twin weighs 18 pounds and is capable of carrying a 27 pound payload. The new turbine helicopter wheighs approximately the same, but can carry significantly more payload.
Propulsion: New this year, the helicopter is now powered by a miniature turbine engine manufactured by Wren and installed by Bergen on the standard industrial airframe. The team's second airframe is currently at Bergen's shop in Michigan being overhauled after ground resonance ripped the rotor shaft in half this summer. While the propulsion systems have very different control curves and characteristics, the differences should only affect control constants in the software, and not the actual control algorithms.
Ground Station: Developed extensively last year, the ground station is designed to allow monitoring and control of the onboard computer while the helicopter is flying, via a wireless data connection. The ground station runs on the Linux operating system and has all the power necessary to run computer equipment at a flying field. Future uses of the ground station may include image processing necessary to complete level 2 of the competition.
Network Connections: Reliable communication at least 1.5 km from the ground station is necessary for the competition. The existing communications network uses both directed and omni-directional antennas, with off-the-shelf wireless router components, to establish this link. Flight data, telemetry, and images will be transmitted from the helicopter.
Positioning System: A high-quality global position system (GPS) receiver mounted on the helicopter, augmented by an additional transmitter at the ground station, will give the absolute position of the helicopter at all times. It is necessary for the navigation software to determine the flight path to reach competition waypoints.
In-flight Computer: This is the primary control system in the helicopter, as it handles communications and integrates data available from the other components. It is expected that the computer will handle navigation internally, while exposing a monitor interface to the ground station. This was a primary focus of the previous electrical team, and should see good service this year.
Servo Controller: The base helicopter is designed for remote control. It implements all the standard servo functions (throttle, collective, pitch, roll, and yaw) in the standard way. To use this existing infrastructure, a servo controller board has been developed to translate servo position commands (from the flight computer) to a code the servo understands. It is possible to switch individual servo channels from remote control to autonomous control, making it easier to debug the flight control system.
Internal Navigation: While the GPS unit provides (relatively) slow and absolute updates on the helicopter’s latitude, longitude, and elevation, a second unit provides very fast relative changes. Called the internal navigation system (INS) or the attitude/heading reference system (AHRS), it consists of sensors that provide the computer with acceleration, velocity, and position measurements in 6 degrees of freedom. This information can be used to maintain stable flight, adjusting for variable wind forces on the helicopter.
