UAlberta UASGroup

University of Alberta Unmanned Aircraft Systems Group

The University of Alberta UAS Group is a fledgling team composed of a number of research groups, students and professors at the University of Alberta in Edmonton, Alberta, Canada. The group is based out of the Department of Mechanical Engineering, with members from a variety of other departments, including Earth and Atmospheric Science and Electrical and Computer Engineering. We are currently preparing a small demonstration platform. This UAV platform will be the beginning of an attempt to foster UAS research at our university, and provide an initial starting point for researchers from a variety of disciplines and departments to begin research on unmanned aircraft systems directly (like controls), or, more likely, to investigate payloads and applications (like industrial monitoring).

Current Work

The first platform is Unmanned Aircraft Platform 1, or UAP1.

UAP1

Airframe:

• Type of aircraft: Hobby Lobby Senior Telemaster almost-ready-to-fly model aircraft
  • Modified for bolt-on wing and tail-mounted servos
• Type of engine: 2-stroke 26cc Evolution 26GX with electronic ignition (2S 2500mAh Lipo)
• Dimensions: wing span 2.4 m (94 inches); fuselage 1.6m (64 inches)
• Actuators: Hitec programmable digital servos used throughout

Autopilot Systems:

• Spektrum DX8 system with AR8000 receiver and TM1000 telemetry module for safety pilot situational awareness
• 2S 4000mAh Lipo for servos and autopilot system
• Paparazzi autopilot
  • TWOG v1.0
  • Ublox LEA5H and Sarantel helical antenna
  • Aspirin IMU via I2C
  • Eagle Tree airspeed sensor
  • ATMega168 based PPM encoder
  • SmartFly optical ignition cut-off
• Digi XTend 900MHz radio modems
• Ground Segment:
  • Macbook Pro with OS X 10.6 (running Paparazzi in OS X)

Payload Systems:

• Currently not determined, though initially a GoPro will be mounted onboard

Flight Progress

Currently, we have successfully flown UAP1 in manual and auto1. It took a long time to modify the model, install the autopilot systems and deal with vibration issues from the gas engine.

Vibration (WORK IN PROGRESS)

Vibration can be a major problem in small UAVs. Vibration can come from a variety of sources, but in UAVs the most significant source is rotating machinery, i.e. the primary powerplants in the airframe.

Major Sources of Vibration:

• Main electric motors
• Internal combustion engines
• Unbalanced propellers

Minor Sources of Vibration:

• Flutter or resonance in flight surfaces and airframe
• Actuators or servos for flight or payload control

In general, the main source of thrust will be the primary source of vibration.

• link to vibration background, how to calculate natural frequencies etc, perhaps some modeling discussion

Impacts of Vibration

• airframe fatigue
• wiring connection fatigue (including RF connections)
• lower efficiency
• increased sensor noise, bias (gyros, accelerometers, magnetometers, pressure transducers, etc)
• potential for sensor saturation (gyros, accelerometers in IMU)
• degradation of payload sensor data quality (especially imagery with CMOS sensors, increase in rolling shutter effects, motion blur, shaky video)
• discussion on how to identify vibration problems
• discussion of sensor noise effects, namely on DCM algorithm, give examples with aspirin IMU, add screenshots of logs

Mitigating Effects of Vibration

• mechanical methods, best, helps all parts of airframe
• calculating and testing
• recommended methods and materials
• things to keep an eye out for (resonance on parts)
• software filtering for IMU and other sensors, advantages and disadvantages, explain addition to fw aspirin i2c driver, video shake reduction
• show some samples from vibration testing
• pictures/sketches of mounting methods