Autonomous flight p2.

To the right, the flight plan of my latest UAV flight. I programmed the UAV to fly in a pattern across the local field where I fly. A manual take-off used, then switching to waypoint (auto) mode. The UAV returned to launch nicely, hovering at 15m until manual take over and landing.

I couldn’t properly attach my normal point and shoot for photos or video during the flight so I’m looking into buying a GoPro like camera for this purpose.

Autonomous flight p1.

Here is a small map of a waypoint mission I flew two days ago. Although giving control to the autopilot does give you some sweaty palms the ardupilot performed wonderfully. I’m rather sad I neglected my work on the UAV so long. Part of it was having limited access to a nice and safe area to fly over. I’m now closer to a tram stop that takes me out of town so flying is more convenient and less of a hassle. More experimenting, especially with flying gridded layouts will follow.

Loitering away

[caption id=”” align=”alignright” width=”350”] arducopter, old config.. updated pictures will follow[/caption]

I got my arducopter up and running the past week. I updated to the latest firmware (3.0.1). Previously I had to fight wires to calibrate the multicopter during the compass calibration dance. But I found out that you can do most of the setup of the arducopter over the XBee telemetry, so I don’t get tangled anymore. Having calibrated my compass properly and compensating for compass drift due to motor and ESC interference (compassmot values down to 5%!) I get really good GPS hold / loiter performance. During rather windy conditions my multicopter wouldn’t drift outside a 2x2m box. During calm wind conditions this was a square meter box at most. Rather impressive performance for a budget quadcopter. Next up, flying some way point missions.

Cellulose extraction – first trials

[caption id=”” align=”alignright” width=”320”] NaOH treatment of wood samples[/caption]

This week I started with a first -trial- cellulose extraction for my wood core stable isotope experiment. I have one plate to test the routine and look for possible flaws in the setup before ordering the final batch - money permitting. The setup has been running for a two days now. The picture in this posts shows the small wood samples submerged in NaOH to remove all resins, tannins etc. In a next step you add a strong acid to eat away the lignin and leave the cellulose behind.

The procedure is done in a hot water bath (60°C). I noticed that a lot of water evaporated, or more than I was used too when learning the procedure at GFZ Potsdam last October. Even with a small lid on it the water level decreased at a significant rate, with the possibility of not heating the reagents at the end of a treatment. After some thinking I found to culprit to be the laminary flow system on overdrive. Evaporation depends on the temperature of the water and the air, the evaporative surface area but also the velocity of the air mass above the surface. Given that all other parameters did not deviate significantly from the setup in Potsdam the more draughty laminary flow system in Ghent was an easy find. Opening the hood a bit more so the velocity of the air moving over the heated setup was less reduced the evaporation to within workable values. Covering the tray with a lid would reduce evaporation even further. Covering the water surface itself as with swimming pools, limiting the surface area from which you could evaporate water, would allow me to limit the refills after treatments even further. More on this later…

 

 

New paper in Nature Communications

The Nature Communications paper that was recently accepted and on which I contributed can be downloaded from the Nature website! (http://www.nature.com/ncomms/2013/130805/ncomms3269/full/ncomms3269.html). Congrats to all co-authors on pushing this along.

Another paper with Simon Lewis as lead author was also recently published. They used some of the our data to quantify above ground biomass for 260 plots across tropical africa (http://rstb.royalsocietypublishing.org/content/368/1625/20120295.short).

Pagination


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