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
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...
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?
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.)
My question is how straight forward do you think it is to fit a roll stabilized gimbal to any of the above airframes?
Okay. So I have a few questions regarding the APM2 throttle setup. By Default. When there is no APM in the setup. I have to reverse my throttle channel. (Futaba 9C & Turnigy Plush 60A ESC).
The only way I can get Stabilize, Auto, RTL, FBW Throttle to be off on the ground is to reverse the throttle channel (which then makes min throttle on manaual mode actually behave like max throttle!!!!).
This is fine as I don't use manual mode, only stabilize and auto. It's just when the system is initializing in manual mode for a shot period, the throttle spins to Max. Is it okay to reverse the tx's manual throttle default behaviour? seems a tad dangerous?
I have tried various combinations of reversing throttle channel, and reversing APM throttle setting. But nothing seems to cooperate with manual mode.
I had this working last year when i last used APM. But can't for the life of me remember what the settings were! IF anyone is using a similar setup, please let me know how you get around this issue....
Do i simply need to buy a proper ESC...? where a throttle reverse is not necessary in manual mode?
Where did you see that Gatewing has a gimbal? I have an aircraft we use for surveying - called SurVoyeur - check my blog on DIY drones re the A/C. We use Agisoft to process the images. I do not use a gimbal - the camera is a Samsung 22Mpixel with a 21mm Pentax lens, in manual/aperture priority mode. We have so far flown over 6000 hectare , mines, nature reserves, new residential developments etc,and produced fully ortho rectified images, with ground contours down to 8cm. Our (proven) accuracies achievable are 3.5cm horizontal and 4.5cm in Z. Agisoft produces more accurate result if the images include some pitch and roll, ie, oblique images..
We recently processed a gold mine , around 1400 hectare, with the last two parts of the flights in 16m/s winds..The photos were fine - except for the dust on the ground with those winds - left the photos slightly fuzzy..
i agree with Joe-by the way excellent job- oblique photos produce greate point clouds, Also and i know many will hate me for that, flying wings inherently use roll not only to steer but to stabilize, so they move constantly. A tailed fixed wing plaform with a little bit more rudder authority can overcome that.
Dont forget speed and lift, if wings were capable for efficient slow cruise then there would be at least one competition duration glider out there.
"Briefcase" Wings like sensefly sells because they offer compact factor for small LoS surveys, Rtf, less servos-less problems, smaller motors-smaller batterys-less problems, fancy look.
BUT if all your planes surface is wing, think how prone is to zcratces when you land somewere else than the promo video...
My ugly prototype rig has 2m span flies 1hour@29-50km/h, weights 2kg, lands everywere and every time delivers perfects stills with max 5degrees bank angles, i removed the roll stab because it caused more trouble than good.
Sum: zagi style wings are slope fast wings, x5 is ok with only to servos to worry and lots of room, 30min f time is achievable, X8 is huge. If you Still want to built a roll stab, think wisely how you will mount- unmount the camera on the field, search for perfect servos and think codewise(output refresh rate, setup, angles etc) and last but not least Vibes!! You can check the new spoiler code for yaw corrections for wings also.
i have something new running specially for long range mapping! Stay tuned...
leave futabas ch3 Reversed. Boot in manual mode, connect with mplanner, go to radio calibration and check if throtlle works as supposed to (filling the bar from bottom to top), if not go to parameters/ rc channel3 reverse and type -1. Done
Hi Joe, cheers for the valuable advice, I have just had a read through your SurVoyeur blog (I think this is it). The Aircraft looks very good for the task, and it seems a lot of work goes into making the airframe. I like the design, using a V tail, and your mapping areas and spec look very good indeed. The aircraft i've just built has a similar weight @ 4.5kg. but i am not sure it would survive a hard landing. I was considering making a second airframe a lot lighter than the first one. and there is no way i would be able to get it off the ground in the dunes, which is where i will be doing my first proper mapping task.
I'd like to upgrade my camera form the 8 megapixel Ixus80 when i'm happy I have a reliable airframe. Not sure why i thought Gatewing had a gimbal, i must have confused it with another platform.
I'm thinking of at least trying the camera in my streamline 60 inch wing just to see what kind of results i can achieve. Are there any off the shelf airframes you could recommend, i'm also looking at the multiplex fun cub.
Hi James, what airframe would you recommend, I mentioned above possibly the multiplex Funcub. As it is a conventional airframe design. and is also quite strong, and has landing gear so i could sling a gimbal underneath if necessary?
I see your point about landing wings constantly so the bottom is scuffing the ground, I could add a layer of CF to the bottom to prevent damaging the wing on landing?
I'm getting a bit confused on how to move forward with this now, do you think i should pursue designing a new airframe, or buying an off the shelf plane and adding the camera?
from what you have said, should I not bother pursuing using the Skywalker x5 wing?
These are the airframes I have, and what i currently think of them for this task...
2.4m twin boom pusher - Too heavy and fragile
Bixler - too small for 1 km2 mapping
jpsi 48" zagi - I could add a gimbal onto this
60" zagi style wing - Big enough to give good flight duration, and I could add a single axis gimbal, at least for roll stab.
x8 - this looks a bit big for the task
My thoughts are the following...
a: try adding the camera to the Standard sized Zagi and do some tests to see if the pics are usable - Leaning towards this option.
b: Try adding a gimbal to the 60" zagi style wing
c: go back to the start and design another airframe from scratch.
d: source another pre-built airframe, like the multiplex funcub
Interested to see what your working on! again, cheers for the advice
Cheers James, form some reason I had it booting straight into Stabilize, and was doing all the calibration when in Stabilize mode, it is now working like perfectly!
If you like Multiplex's rigid foam, then aim for Mentor, more space inside, light weight, VERY robust, and excent flight characteristics for APM and mapping,
Cons : -It can glide for dead stik landing, but u cant say its the best glider out there (30 min max,)
- Tail dragers also have this annoying propeler braking when you have to land on bushes, its the number one selling reason for Skywalkers, ezclones etc to noobs like me :)
-it will take some exacto knife mods for the cam...
-Adding protection to wing, will make it even faster.. and zagis are realy fast for maping
the Skywalker x5 wing, i think its the best of the shelf wing, for your purpose
-Why dont you give Wanes Techpod a chance?? it glides very well, its a pusher, can carry heavy payloads, designed with APM in mind and it has a downward looking camera placement! In a month or so, i will be testing mine!!
-I had great success with Bixler 2! you will need approx 15 passes for, 1km2, with flying alt 100m and your canon for sub 5cm resolution, which translates to 15km total traveled distance. With 36-40kmph cruise speed you can do that with a 2500mah batt! (stock setup)
a: you have the wing and the cam.. go for it,
b: More trouble, but you proved that you can handle it... go
c: Try reading, A LOT! there is a Huge heritage of glider plans with mapping potentials, i am sure, one or two will fit your purpose, you have great design skills, so tranforming a plan to cnc cutted parts will be very easy for you to prototype your ideas. just use the knowlege and the best materials. exotic stuff like carbon and aramid are really arffordable now days. Iam crossing the same path for last 2-3 years and rest assured, every step worth it!
Interested to see what your working on!
imagine that.. less than 2kg, 2h+range, hi-res payloads, bulletproof, waterproof! 200usd range.. all of them inside a backpack...
Cheers James, again, very helpful advice. I'll probably keep the Mentor in mind as a fallback option if I dont have any luck with the X5. They are out of stock everywhere, so in the meantime i will have a mess around with the Zagi style wings and see what kind of quality of photos I can come up with.
I wasn't aware of the techpod, it seems like an FPV plane? I've studied the scematic, and can't see anywhere to mount the Canon?
I do like the idea of using cheap, expendable chinese foamies like the Bixler, I hear mixed reports as to their durability/ Where would you attach the Canon to a Bixler? Hole in wing and looking down?
I have just bought a licence for motorcalc, so I can work out what are the best power systems for my planes. Up until now I have just used whatever motors/props I have had lying around. Except for the Twin, that was chosen using some science! I have always had a tendancy to underpower my planes.
Right then, this is going to be my strategy over the next few weeks...
1. Setup Camera on Zagi - and fly a few sorties, until the X5 is in stock - this should help my get to grips with the APM and the planner, telemetry again, it's been a while since i used it in the field.
2. Buy an X5 when it's in stock, add a static camera mount, see what kind of point clouds / mosiacs I can generate. - Add a lightweight internal gimbal if the plane is too unstable.
3. Failing the above, investigate the techpod.
I'll post updates as to my initial Zagi adventures as and when they happen! My flying field isnt that exciting,
Hopefully there will be enough info in the ground to tile properly...
Slight change of plan, instead of slinging the camera underneath the wing in a polystyrene block, i've decided to remove more of the inside of the plane so I can install everything in a large void inside the wing, the plane will be more streamlined, and will hopefully cover a larger area.
I haven't done any calculations as to flight time etc. But just acquired a motorcalc license, so I should get some flight time estimations soon once i've figured out how to use the interface...
a pic....the camera will be surrounded with foam, and i'll add some rails underneath the plane so the lens doesnt snap off when the plane lands...
Small Update - I've added some thin plywood separators in the equipment bay. Just need to add some foam around the camera. The wiring is much tidier now as well for the APM. Just need to work out how to root the wires from the ESC to the flight pack. Fingers crossed i'll do a first flight with this on the weekend. also, about to hit the buy button on a Hitec Aurora 9 tx. The Futaba 9C screen has finally given up. And the DX6i doesn't have enough channels or switches to be remotely useful!