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May 08 2012

Arducopter Back in Flight

After a steep learning curve for Arducopter, we have it flying.  Garret left us the Arducopter after graduating, I had never so much as worked with Arducopter before.  Of course I had never worked with Mikrokopters either, but Jonathan was here to teach me everything I need to know about them.  I didn't have that luxury for Arducopter, so progress was a bit slower.

The first thing I did when Istarted working with the ardu was to load new firmware and update to the new mission planner.  Since this was all new software, the Arducopter had to be calibrated from scratch.  After crashes during motor tuning, we had multiple delays while waiting for new parts to come in.

But the Arducopter is flying now, and not a moment too soon.  With summer rapidly approaching and all the orders in, I'm going to start building the Octocopter very soon.  It gives me some assurance that I was able to get the quad Arducopter flying, since the Octocopter also uses Ardupilot.

May 01 2012

New 3DR Radio Telemetry System

http://api.ning.com/files/NC4Rs-RhY6b4ikH5XnjJn9bh*76ndPaxz5IYUQccm2kH9KynI2rt3PDhou4Rt7a56oSW-jaq32tx8avBNPOvuQ__/3DRradiokitdip.jpg

The 3DR radio telemetry system looks very promising!  It is intended to be an improved replacement for xBee radios.  We ordered a set as soon as we heard about them.  With improved performance specs and compatibility with Ardupilot, these radios look like they'll be flying on the next generation of Ecosynth aircraft.

In addition to these radios being specced better than the xBees, we'll be using them with directional antennas (the one on the ground station will point towards the sky; the one on the aircraft will be pointed down towards the earth).  We've always had trouble with xBee communication; even during standard flights the xBees are spotty at best once the kopter is up in the air.  These radios should be a welcome improvement. 

Update: 3DR Radios have come in, and they have been successful in connecting the arducopter to the ground station in the lab.  A flight test will follow soon.

Apr 26 2012

Arducopter Progresses, Octocopter Components Still Arriving

It’s been slow going with the Arducopter, working with it this semester has often seemed like two steps forward and one step back.  However after several stumbling blocks like the Ardupilot board being of the older model now, and  ailing Electronic Speed Controllers:  things are starting to look up!

I was able to update the Arducopter to four brand new ESCs, since one of our big orders just came in (will get to that in a bit).   Earlier we’d had trouble calibrating the Arducopter for flight, it kept wobbling and flipping over.  I feel rather foolish now; the problem was that the ESCs were mismatched!  One had been replaced because it was suspected to be burned out.  I only yesterday realized that of course it would need four identical speed controllers to fly stabile.  Since our Octokopter order of ESCs came in, there were enough spares to outfit the Arducopter for testing.

So a new order did come in!  Our large order from DIYDrones is now in the lab: it included ESCs, propellers, power distribution boards, and Ardupilot boards.  Combined with our previous order from Aeroquad (Mikrokopter OctoXL Frame), we now have most of the components to build an Octokopter, and enough spare parts to build a second one (minus what we’re still waiting on.)  The jDrones order went out yesterday; it was mostly parts that have been out of stock until now.  This order includes the last set of components we’ll need to make a working Octo, the motors.

Things are looking good for the next gen of Ecosynth aircraft; at this point I think that Octokopter work will start as soon as summer research starts, when aircraft moves into the bigger lab.

Apr 10 2012

123D Catch: Realistic Small Area Scanning

One set of software I've come across for forest mapping is 123D Catch.  What it does is takes an orbit of photos taken around a central point and processes out the common points between them, much like Photoscan.  The difference being, 123D Catch is optimized for mapping solid surfaces into a mesh.  What's more, the mesh is photorealistic.  So while the mesh does have a certain margin of error, the photorealistic view of the subject tricks the eye into thinking the 3D representation is a perfect facsimile of the original.

This scanning technique is more applicable on a small scale than a larger one such as Ecosynth pursues, but is useful nonetheless.  The larger the area scanned into 123D, the less accurate the dimensions of the resulting mesh are.  It also only works well on tree trunks and large objects like stones, the software that stitches the mesh together cannot resolve small objects like twiggy tree branches, and they end up as amorphous mixtures of tree and background.  Its uses include keeping a digital record of precious sites or phenomenon before they are disturbed by human intervention.

The following video is a scan of a stand of trees, with surrounding trees and forest included in the background. 

Mar 20 2012

New Jersey Pinelands Fire Research Flight

This past Tuesday (3/6/12) Jonathan and I travelled to New Jersey to conduct wildfire research.

We left Monday evening and drove to the New Jersey Pinelands, where we stayed overnight at the research center.  Our first obstacle was the smoke research payload.  When Jonathan did this smoke research in the past, he had suspended the payload (consisting chiefly of a smoke detector and data logger) on a tether beneath the hexakopter.  The reasoning behind this was that we needed to keep the payload well away from the air disturbance made by the hexa's propellers.  However, the problem with this method is that the hexakopter is unable to self stabilize under a suspended payload, and ends up swinging the payload wildly and eventually crashing.

Jonathan and I did a brief test to confirm that this behavior was still present with the fire payload, it was.  As a solution, we mounted the payload on top of the hexakopter's dome.  A strip of ribbon attached to the top of the payload served to demonstrate that the propellers did not significantly interfere with the airflow though the payload when it was mounted on top.  The hexakopter was perfectly stable with the top mounted payload. 

Tuesday during the wildfire we flew from the research compound which was downwind of the wildfire in the smoke plume.  The hexakopter flew up in 50 meter increments and back down every half hour or so for several hours.  Overall our data collection was a success.  Towards the end we even had the time to mount a camera on top of the payload to take a rather jittery video of the wildfire from the air.

Feb 27 2012

SERC Leaf-off Hexakopter Mission

This past Sunday (2/26/2012) Jonathan, Shelby, and I went to the Smithsonian Environmental Research Center to fly a hexakopter mission during leaf-off.  The image on the left was taken by the camera mounted to "Sally" as it was coming in for a landing.

Since "Raven" still has what we believe is a motor controller issue (contacting Nisarg about this), we brought "Roflkopter and "Sally" to SERC.  Initially "Roflkopter" was designated the primary flight hexakopter, because "Sally" had been noticed as having stripped threads on one of the propeller mounts on top of a motor.  Since the other two holes in the propeller mount were not stripped, we still considered "Sally" flightworthy, just not primary.

Once on site, Shelby and I set up a series of twelve orange contractor buckets along the road through the forest we were surveying.  Jonathan had programmed the rough distribution of them into the dog-tracker GPS to follow when we were setting them out.  Then throughout the rest of the day during flights and other work, we used a handheld GPS tool to determine the precise coordinates of each bucket.  These coordinates will be applied to the buckets in the point cloud representation.

As it turned out, "Roflkopter" was not our best choice for primary hexakopter.  Although it was certainly flightworthy, during flight it bobbed up and down instead of flying in a straight line.  Jonathan believes it is due to the hexakopter's vertical lock setting being miscalibrated or otherwise dysfunctional. 

We decided to fly "Sally" to see if we could collect data from a smooth flight.  After some test flights, we determined that the stripped screw on "Sally's" propeller mount was not going to be an issue this mission, although it will still be replaced.  On "Sally's" first mission, everything seemed to go well but when it returned the camera had run out of battery.  This was odd since the battery we used was most definitely fresh.  The camera did not seem to respond well to new batteries either, so we flagged it for later investigation and switched to a new camera.  Finally, "Sally" flew a successful flight and collected what looks like it will be a complete set of pictures of the forest canopy.

Feb 18 2012

New Undergrads learn the ropes of flying the Hexakopter

Shelby and I are the new mechE undergraduates for the Ecosynth project.  This past week we started learning the ropes to flying the hexakopters.  We started by bringing all three hexacopters to flight-readiness.  "Sally" was already operational, so we used her a s a model for repairing the other two. 

When we started, "Raven" needed new propellers as well as ribbon cables.  "Roflkopter" (I'm very fond of that name) needed its computer reassembled and mounted, as well as new propellers and the arms secured on.  Shelby and I did these repairs with little prior experience, so we were actually a bit surprised when both "Raven" and "Roflkopter" flew successfully.

By the time we finished, none of the three hexacopters were flight-ready any more.  The attached video is actually my one successful landing, the hexakopter controls take a lot of finesse and a lot of practice.  I managed to break a propeller on "Sally" by tipping over on landing, and Shelby managed to break "Roflkopter" 's landing gear with a hard landing.  "Raven" stopped working because of an issue with one of the motor controllers.  We took it back to the lab for analysis, but we called it a day and decided to reconvene next week.

Shelby and I are looking forward to working with these hexakopters and the Ecosynth team.