|From:||Prof. Dr.-Ing. Heinrich Warmers|
|Subject:||[Paparazzi-devel] Paparazzi TWOG and Tiny13 tested with low cost IMU|
|Date:||Fri, 23 Jul 2010 22:04:03 +0200|
|User-agent:||Mozilla/5.0 (Windows; U; Windows NT 5.0; de-DE; rv:1.4) Gecko/20030619 Netscape/7.1 (ax)|
Same news for Bremen,
have tested a low cost Sparkfun IMU ( RAZZOR
IMU 6DOF Razor - Ultra-Thin IMU)
The price of the sensors is about 9.9 euro and 6.99 euro in single quantities (lipoly.de). The quality is not as good as the ADXRS610 but we found no significant differences in fly with it since the drift is compensated. For the quadrocopter we use our Klaman-filter (run time is 7.5 ms) and for normal plane we use a filter interdruced by William Premerlani, and Paul Bizard:
Direction Cosine Matrix IMU:Theory, William Premerlani, Paul Bizard,05.17.2009, http://code.google.com/p/gentlenav/downloads/list
The kinematic equations are integrated in a notation of the DCM 50 times per second. To save orthogonality of the DCM for every integration step small adjustments of the matrix elements are applied. For bias and drift error correction a PI feedback controller is used. To estimate the errors the acceleration data and the GPS ground speed is taken into account.
The price of the new sensor set is lower than the old IR system. For the twog the resistors to ground had to be extracted. A low cost system consist of 69$ for the twog (I fetched it for this price currently 125$) 35$ for GPS and 90$ for the IMU. If you can solder the imu self it will cost less than 35 $. You have to short the high pass filter on the rate signal for better performance of the RAZZOR IMU. Currently a paparazzi compatible planar pcb is under development with this sensors (30mm*57mm) with normal servo connectors to fly quadrocopters and normal planes.
need a few weeks to document the work since most of our team members
vacation. We will do this soon as
possible. The changes on the code are marginal.
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