Tuning

I flew the second tuning/test flight with the APM today. It’s been a beautifully calm, sunny day but the bank holiday meant that there were too many dog walkers and errant dogs present to do too much testing.

I flew in FBW-A mode to test out some new pitch and roll PID settings and the aircraft performed much better. FBW-A mode is amazing and makes the flying of the aircraft so much easier.

The screenshots below are from KMZ exports from the logs of the aircraft flying in a few different flight modes.

Loiter mode. 3 laps were flown. APM does a good job of keeping altitude and I don’t see any GPS wander. I tried some rudder input that’s where you can see the tightening of the circle.

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FBW-A. A few FBW-A logs. You can see how APM smooths out the flight nicely. image

The whole flight

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First flight with the APM complete

I’ve finally got around to testing out Ardupilot on a live flight. It was much too windy for a test flight and so was short and untidy. I’m now waiting for a calm day to get it tuned.

There was some bad “porpoising” when I switched to auto. The pitch P value needs to be reduced though this is going to be time consuming with just myself at the field. I really only tested the APM on manual and stabilise mode so the plan for next time is to switch stabilise over to FWB-A and start to tune the pitch P value to remove the porpoising.

Once I have the APM tuned I will start flying some planned missons with the camera on board.

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APM has arrived

A package containing an APM plus a GPS module and 433 Mhz telemetry arrived today. I’ve tested it a little and have the telemetry working. It’s exciting stuff.

I imagine that I am going to be spending a lot of time working out how this all works before I get anywhere near putting it in a plane.

 

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APM

I’ve completed the build of the Bixler 2 and integrated a Canon IXUS 220 HS into the airframe.

The camera is using CHDK with the excellent KAP_UAV script to take sequential photographs.

I made what I would consider a successful test flight today with the camera but no autopilot on board. An image from the 3D render of the photo montage can be seen in the previous post. This evening I have taken the next step and purchased an APM plus telemetry and GPS to take me to the next step.

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The first test run. Without an autopilot so the photos taken are a little all over the place. Still, the software has done a great job of stitching it all together.

The first test run. Without an autopilot so the photos taken are a little all over the place. Still, the software has done a great job of stitching it all together.

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Hatches

Progress is still slow whilst I wait for the HobbyKing order of a new motor and mount to arrive. I have however fitted the elevator and rudder servos  well as assembling the wing and adding some hatches beneath the wing.

Waiting for orders from HobbyKing to arrive can be very frustrating!

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Slow progress

This second build is taking much longer than the first. I’m planning the layout of all the components so the plane will be future proof and allow the various electronic components to be moved around the fuselage to counterbalance a camera and autopilot in the future.

I have removed a few of the bulkheads from the centre of the fuselage and will add a door to the side of the fuselage. This needs to be done carefully to avoid compromising the structural integrity of the fuselage.

I have also mounted the elevator and rudder servos in the rear of the fuselage near the control surfaces. This should also help in the counter balancing of a camera in the nose.

I have a few more components on order from HobbyKing, most importantly a larger motor, propeller and motor mount to carry the extra weight of a camera and APM. Until these arrive in a week or so the build is on hold.

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A great TED video about ecological surveying from an aircraft. Imaging spectrometers are talked about, they are used foot identifying species and chemical composition. These might be very useful for UAS work.

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The trap of over engineering

Radio control modellers have a tendency to over engineer their models. I’ve seen this a lot in the past and people can often be adding nearly 500 grams in weight with their various modifications of tape, coverings, backup systems and carbon fibre rods. Individually these things may not weight much but they add up and you can end up in a loop of strengthening to compensate for the weight you added when strengthening. I’ve seen some ridiculously over engineered Bixlers whilst trawling various forums and blog posts.

I’m aware that the Bixler will need strengthening and modifying for my UAV project however I need to strengthen things enough to stop the wings folding mid air, but I still want a nice flying model than can cope with low speed flying conditions without stalling.

The Bixler really isn’t meant as a heavy lifter and I can imagine it losing a lot of its flight characteristics if overloaded. I try to keep as close to the KISS principle as possible.

I’ve noted some of the various projects to strengthen the Bixler for FPV/UAV purposes in my research document 

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