Using Flying wings for aerial mapping

Hello forum, 

First of all some background...

Having spent a good 2 years playing about with an Skywalker, Ursus and a Canon camera running  CHDK, and designing my own uav, which actually flew recently ,I have come to the conclusion that flying wings may just be the best type of platform for short range aerial mapping tasks to create DEM, DSM models for GIS purposes.

The Skywalker was okay (but quite fragile, and now in pieces!), but I think it is too small to fit a roll gimbal on it. And I've found that if pictures are taken on a slight angle, it is very difficult to use software to tile them up nicely. this is my best effort, but far from perfect. The roads on the right do not line up as the camera must have been on a 45 degree angle when the picture was taken. (click for larger resolution) - It was taken using an ixus80 attached to an URSUS Airframe

3690979741?profile=original

Realizing that I need to use an airframe that can accommodate a stabilized roll gimbal, i started to design and build my own twin boom design. It took 6 months from initial design, to first test flight. It has a wingspan of 2.4m - AUW of 5kg, and a flight duration of around 30 minutes with 2 x 5000mah packs. However it needs a heck of a lot of room to take off and land, something i don't have in the areas i need to take photos. 

Picture of twin boom plane...

3690979788?profile=original

What are peoples experiences with using flying wings for this reason? I have the following types of flying wings, and wondering which one is the best to begin with?

  • jp-si 48" span Zagi
  • Scaled up 60" span jp-si Zagi (hot wire cut by myself)
  • x8 2m wing

I have been using the 60" wing to test the APM2 and 3dr radios. And was using the URSUS (now in pieces after a nasty crash!) as a test platform to practice with the Canon CHDK Kit.

Here's a few pictures of the wing and camera....(click images for larger version.)

3690979799?profile=original3690979812?profile=original

My question is how straight forward do you think it is to fit a roll stabilized gimbal to any of the above airframes?

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Replies

  • Hi Richard!

    I follow your post for a long time. I want to build a UAV for aerial photography and after render DEM models.
    So i see your result with various airplane but always you use free software for building image.
    Have u never tried to build models using a pro service for example dronemapper.com or pix4d?

  • I have been following this thread and have started building my own X-5. I am just about ready to start manual test flights before I run it on the APM. I am new to R/C planes and have a few questions. What servos are you using for the ailerons? How much travel are you getting up and down? I am not sure the servos I got are big/strong enough. They seem to struggle to move the flaps and only a very small amount.

    Thanks,

    Andy

  • Rich

    Regarding your X5 platform, check this out:

    http://www.diydrones.com/forum/topics/arduplane-2-73-released

    This part is what made me think of you:

    "Of these, perhaps the most useful is the ELEVON_OUTPUT option. That makes it possible to setup your transmitter with normal aileron/elevator and get the APM to do a software elevon mixer on output. That gives better control in FBWA mode than the previous elevon options."

    I hope this helps!

    B

  • Does a UBEC interfere with the APM 2.5/GPS/3DR? 

    I'm having CG issues trying to get 2 x 2200mah batteries and the camera balanced. I could solve it all if I could mount the UBEC close to the APM. This is the specific UBEC I am talking about...I'd like to cut away some foam and mount it under the camera embedded in the foam. Pretty much where is in this picture.

    The camera position on the x5 isnt really ideal, as it's not on the CG, I probably should have built it so it balances without the camera, and place the camera on the CG. I'll do that next time!

    3692712201?profile=original

  • Okay then...here's a small update on the x-5 progress. Unfortunately i didn't have time to do any flights or building on the weekend, buying a first house is hard work! 

    I've cut the hole in the bottom of the plane for the camera, and have made a dummy camera of same weight as the Ixus80/sd1100. The Ixus80 is my test camera, and will be swapped out for the sx230  when i'm confident in the planes ability to not crash. The lens is a fairly snug fit, and the foam holds the camera in quite tight, it will not do much for vibration dampening. However because i will be using shutter speeds of 1/1000 minimum I don't think it will cause any vibration blur. I reckon a 3000mah 3s would be ideal. a 2200mah is to light, and 2 x 2200mah are too heavy...But i'm going to go with the two anyway. The CG is about 8mm further forward than it was before. roughly 20mm further than the recommended cg. A bit more reflex should fix that. hmmm

    Some pics.... 

    the underside is quite damaged form skidding across the baked earth...The yellow tape is holding a block of foam in a hole that was gouged out on one of the landings. The white duck tape wrapped around the front of the plane is also a bit creased from a couple of vertical landings.. amazingly besides a slightly crumpled nose, the plane is in pretty good shape. 

    3692709378?profile=original

    3692709517?profile=original

    3692709566?profile=original

  • Guys,
    Remember that WP circle only difines the radius that considers a WP reached not the turning radius. Loiter pertains to turning radius but has no effect on lawnmower mapping Pattern. The APM aims for the WP center and redirects to the next WP when it breaches the WP circle. If the WP circle is to big it will turn earlier and result in more of a jack knife turn around than with a small WP circle where th plane is forced to go straight through the WP before pointing to the next WP center. The only danger in small WP circles is if the aircraft is not tuned well enough or cannot handle wind and results in circling an weaving to reach the WP before continuing on. I think the key is to get a really good tuning set then use the smallest WP circle possible that I'd attainable by your aircraft on first attempt. The last thing is you want to make sure the distance threshold that determines whether or not xtrack gain engages is set to a disance greater than the distance between your lawnmower rows. We've had 15MPH winds every day so tuning has been tough but I'm getting functional performance with the penguin.
    I'll try to capture each of the scenarios we are talking about today and show the results later tonight.
    B
  • Hi Brenden,

    Thank you very much for your perseverance! I have just come back from the field, and achieved much better results. Here is what I did this morning prior to the flight…..

    1. Re-Calibrate the TX and test FBW-A – for some reason it is still only banking at 30 degrees left and right, not sure why, it could be due to the elevon mixing.
    2. Updated Mission planner from 1.2.36 to 1.2.45, which enabled me to download the logs for yesterdays and today’s flights.
    3. Removed the pitch and roll trim used for manual control on launch. Added a bit of mechanical up trim. Then re-levelled the plane using manual level

    I then looked at my local weather to get the wind direction (Southerly), and planned the flight in APM Planner. Fortunately 90 degree lines were all I needed to get some nice up wind climbing switch backs. By default, missionplanner puts first way point bottom left, and then bottom right, then starts going up, this wouldn’t have worked as the turns would have been with the wind, then I discovered you can reverse waypoints so the first waypoint is top left. So theoretically I could plan the flight lines in any direction ensuring the plane is always doing up wind turns and crosswind legs (I had also previously been flying legs into the wind, and against the wind thinking this was best practice!).

    From what you said regarding that the flight lines were as good as can be expected without xtrack, I turned the default cross track values on today.

    I then hand launched the x5 and begun the flight!!!

    3692689902?profile=original

    The results were much better than yesterday, screenshot from the on board APM Log, much smoother than the .tlog kml. Has anyone managed to do better than the below, or is this as good as it gets?

    3692689923?profile=original

    Now, what I don’t understand is why I can’t seem to go about this the right way by completing the FBW-A tests first – I have left the default PID settings In place and not changed anything. I did do a fair bit of flying around in FBW-A today just to document how the plane behaves. I have attached a nice small log file with a simple mission, and a simple fbw-a path showing turns, and pitch up and pitch down. My only thoughts are that FBW-A tuning is for completely unconvensional airframes that can’t fly nicely with the standard PIDs.

    All in all, this is much better, and definitely something I can build upon. Next steps…

    Add camera, add a proper hatch closing mechanism, add motor cover (for flying in rain), fix catapult, reinforce bottom of plane as it’s ruined from landing on hard soil!

    One final question, the telemetry was awful as shown here – below is a screenshot of the telemetry data received from the flight shown above, as you can see there are large periods of a few hundred meters where no telemetry is being received at all – are people using the standard telemetry settings and achieving good results?

    I’m using the 3DR 433mhz UK regulated settings, and they are awful!!!

    3692689788?profile=original

    Onwards and upwards….!

    2013-04-21 15-05 15.log

  • I Have Panthom 1.5 from Hk, But Not Fly Yet,

  • FBW-A tuning...Non Success... help!!

    FBW-A - clarifications

    Hi, I have a few questions on the tuning process. We spent an extensive amount of time at the field today trying to tune the plane to pass the FBW-A test. I have soe questions around FBW-A.

    1. The Max bank angle is 45 degres in the PID settings. Why does the UAV not acheive the max banking angle in FBW?
    The Only way to acheive 45 degree bank on FBW-A is to set max banking angle to 60 degrees in the PID settings, however on RTL the plane banks much too much and loses height rapidly.
    What is supposed to happen in FBW-A when the stick id fully pushed to the left? It seems to do constant cirlces at 30 degrees, and never gets to 40 degrees. It rolls into the turn quickly.

    This is the same for pitch, max pitch angle was set to 15 degrees, but when pulling back on the stick, the plane would only climb at 10 degrees. Is this normal FBW-A behaviour?

    Having got to the point where the plane rolls to a max bank and pitch angle, quickly without bouncing, we moved onto testing Auto mode.

    Auto mode - clarifications

    We setup square waypoints (wind was less than 3m/s) about 200 meters apart. Set cross track gain to 0.

    Here are the results....

    3692688485?profile=original

    Shouldn't it be doing something similar to the below following the red line?

    we tried increasing Nav Roll P (with cross track on 0), but this did not help. The Plane kept doing large snakes between waypoints, but didn't stay on the line when we added the default 100.000 cross track amount.

    We also kept entry angle at 30 degrees.

    3692688566?profile=original

    Based on the results, I have some questions around how waypoints work....

    Mission planning, is it best to plan photo runs cross wind, or with and against the wind?

    Waypoint radius - Purpose of the radius? Can it be disbaled so autopilot heads for center of waypoint, then make turn for next waypoint.

    Home point - UAV doesn't use home point set in software, it circles over the point where the waypoint files were uploaded/where the APM was turned on. I can manually move Home, but the APM ignores this move.

    On FBW-A the plane turns quite gently when full left stick is applied, however with the same PID values, on auto mode, the plane turns much more aggresively. Shouldnt they both turn with the same bank angle and radius??

    Any help to identify why I cant tune the airframe would be greatly appreciated! 

    Rich

    If anyone could look at the .tlog attached at the FBW-A tests, that would be great!

  • Moderator

    @ richard

    I have been following this with you guys, Brenden is doing this right and I think a good write up to demonstrate this process could be included in the WIKI somewhere.

    some info for you

    yes, you can update the PID's in flight, no reset. BUT do it a small step at a time!!

    regarding the reflex in the wing

    All flying wings need drag for stability. The drag is usually produced by wing twist (fixed) or Reflex (adjustable) if you reduce the reflex the drag will reduce and the plane will go faster! this might not be what you need. remember that the flying wing is still one of the most effiecent aircraft to fly, consider how fast you want to land as well.

    It is better find a GC that gives you good,smooth manual control and then find the correct reflex by trimming, once you have the correct reflex then reset the pushrod lengths to make this your RC neutral control position so your trims are at zero.

    If you have a lot of reflex then you will need a forward CG, You can reduce the reflex as log as you move the GC rearward, dont try to eliminate the reflex completly or you will have a tiger by the tail.

    No flying for me this weekend 70mph winds forecast. Grrrrrrr

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