|
UAV PROJECT |
|
|
|
Other Sites |
|
Interactive |
|
|
The following sensors will be
used:
- IMU: Rotomotion
6-DOF
- GPS: Garmin
eTtrex
- Pressure sensors: one absolute and one differential pressure
transducer
- Infrared sensors: 6 FMA
thermopiles with built-in amplifiers
- Radio reciever: 7 channel Tower Hobbies FM
The sensor setup is designed to give a simple method for attitude control and navigation, but also to provide enough information for developing a good linear model of the airplane.
The IMU and the Atmel controller have been assembled and packaged. Some pictures are shown below. Thw Atmel controller setup was designed by Rotomotion. It takes in the measurements from three gyros, three accelerometers, and the PWM receiver signal. It outputs these over a serial link to the Flashlite computer. The controller also drives 8 servos, either in a manual control mode, or as directed by the Flashlite.
The Tower Hobbies servo has been modified to supply the multiplexed PWM signal to the battery plug terminal. This allows the controller board to power it and read the PWM using a standard servo lead. The modification is transparent from the outside, and the receiver can still be used normally, if needed.
The pressure sensor used for altitude determination is amplified and temperature compensated for operation between 0 and 15 psia. Its outputs were scaled and shifted to allow the Flashlite to accurately measure pressures in the range of 7.5 to 15 psia. A test circuit and the finished board are shown below. The differential sensor which will be used to estimate airspeed has not yet arrived. It has a range of 0-0.3 psi, and will be amplified with an instrumentation amplifier.
The FMA thermopiles are just the sensors FMA uses for their Co-Pilot system. They have built in amplifiers. In this project, 6 of them will be used to estimate the pitch and bank attitude of the airplane. The extra two sensors allow inflight calibration and an extended attitude sensing range.
The Garmin Etrex will provide 1Hz position and velocity in the navigation frame. Its main limitation is the 1 second lag in its outputs. For this reason, it will be used primarily for navigation. As a backup, it can be used to supplement the pitot-static system.
|
6-DOF IMU sensor set.
Altitude reference pressure sensor board.
Finished IMU package.
Finished IMU package showing serial interface, power connection, and PWM signal input lead.
Garmin Etrex to be used as the onboard GPS.
4 of the 6 FMA thermopiles.
Thermopile sensors from a different angle.
Tower Hobbies 7-Channel FM receiver modified to output the multiplexed PWM signal to the Rotomotion controller board.
Test Circuit for the altitude sensor setup.
|
"Sense what?"
Copyright © 1998-2004 Weed Wacker Aviation. All rights reserved.
