Hibernation

Hi everyone!

While is seems like this project has gone into hybernation, the people behind certainly have not. The flying-machine adventures continue even if the project in itself is finished.

I just want to say here that the project report has been submitted and as soon as it is approved we will upload it to the site so you can comfortably sift through our findings and conclusions in a more scientifically angled format (without having to wade through thousands of my puns).

So, will keep you posted on the report!

//Jens Walker, project manager

Such a poser.

There has been a slight lapse in updates here, since we are now about to finish the project (or rather finish off what we're working on right now for someone else to continue) and we are currently writing our parts for the final report. Since we have run in to quite a few speed bumps along the way, we didn't manage to complete the whole project and produce a complete prototype, however a lot of the grunt work has been done. Hopefully we'll find the right place on the internet to upload all the code so that it'll be of use to someone else. We'll also post the final report here, so if someone's interested they can read it when we're done.

We were actually about to fly it again yesterday, however one of the motor axles broke and we have nowhere enough time to get another one, since the final presentation is monday which marks the official end of this project.

However, Albin has taken our little lovechild to a studio and taken some very flattering pictures, which combined with a few images from in-flight and a 3D-reconstruction made by Alexander makes for some nice presentation material.

Flying against a clear-blue sky.

About to land.

Studio pic 1, simply the copter.

The app started on a phone with the telemetry module next to it.

The copter with it's best friend the controller.

A fused 2D-mapping of an area outside the school.

The same image, but in 3D.

ArchCopter apping!

The Android app has gotten nowhere enough attention here on the blog, so it's about time we correct that! This is what greets you when starting the application:

ArchCopter app splash screen!

Progress has been steady and according to plan and Albin has produced a selling poster view of the app, seen below:

Promotional poster of the application.

What it does is that it takes asks the user to specify a polygon (the corners of the area in question), then it divides it into segments of appropriate width, then sets waypoints such that the whole area is swept.

Apparently the app should be ready for testing soon, and hopefully the copter will be up to the task. 

Testflight again!

So, after Jens cut down the print-time of the hexacopter from about 7 days to 3 with some smart redesigns we where ready to fly again! Since we only have one Raspberry Pi camera and don't want to crash it (yet),  we used a old digital camera and used some duckttape to attach it to our machine. It was a bit bulky and the video isn't that exiting, but it's still a video from mid air!

And here is the flight we where the camera was attached.

The flight after we noticed midair that we had forgot the antenna to the RC-controller. The magic here was that Jens quickly set the hexa to land (it can do that automatically) and somehow it got that command and did the best landing so far.

Me (Anton) and Alexander are working on the case for the RasPi and all the electronics, and hopefully the whole design including camera, gimbal and all the sensors will be easily attached and done in the end of the week.

Stay tuned!

Fatal flaw

Another video of a stable flight. 

Gonna try a backflip next time so that you won't get bored!

So, this is starting to become routine now: We assemble the copter, head out and make one very successful flight. Then we land and try to take off again only to crash. However, this time we had a fairly calm landing, but it broke nonetheless. After further analyzis, we realized that we have a very crucial design flaw regarding the current design of the copter. The small contact area of the crossbar in the lattice work is not enough to sustain the amount of stress we put on it, causing the layers to separate.

Layer separation.

Since it takes about 2½ hours to print one arm, I was not very keen on just reinforcing the bars, so this called for a completely new design, the fourth iteration of the arm.

Arm v4

It is printed in two parts, then rotated around the x and y axis creating a completely symmetric piece. It is also screwed together keeping the layers together, so layer separation should not be an issue with this iteration. Screwed together it forms an I-beam (http://en.wikipedia.org/wiki/I-beam) which is extremely tolerant when it comes to shear and bending loads. On the downside it does not handle torsion very well, but we havn't seen much of that to be honest. One major upside of the new design is that it takes a lot less time to print, one of the reasons being that you can print 4 parts (2 arms) at a time.. These 4 were printed after lunch yesterday:

Four of the new arms!

Since it is very long (18cm) it tends to warp while printing, but another benefit of the design is that since we bolt it together, the individual pieces align and become straight as an arrow!

It took some redesigning of the centerpiece aswell (not something we really wished for since the old one took 5½ hours to print, but since the socket has changed it is a necessity). I decided to make it modular (so that if it breaks, you can just change the parts needing changing) according to the same concept as the arms with two pieces per direction, as follows:

New modular centerpiece arms v3.

And it all comes together as below:

Centerpiece v3 assembled.

That is all from construction for now!

Dummy copter on a stick

The work on determining which speed we should fly at has begun. 

A number of factors must be considered; camera frame-rate, image blurriness. The more images of the same area the better the 3d reconstruction but at the cost of memory and time to compute 3d point cloud. 

Since the copter is waiting replacement parts and some code for the camera we conducted a simple test with the new dummy copter. (Its a smartphone on a stick...)

Plenty of duct tape was used.

By shooting a low res film and walking with the stick raised high to simulate copter flight at approx 3 m over the ground and then checking how the number of feature matches in the images decreased as distance between images increased. 

Since walking with a cameraphone on a stick 3 meters up did not produce as properly oriented and equally spaced pictures as as one would have hoped we should not focus so much attention on the result.

//Alexander.O

Good morning!

I'm glad to report that we are almost back in business, we have now printed all of the parts damaged in the fall, apart from the centerpiece. This has however gone through some changes that hopefully will not impact performance, but has reduced printing time from 8 to 5 hours. We have installed Teamviewer (A remote monitoring software) and a webcam on the computer connected to the 3D-printer, so now we can monitor it from our office. Or lab. Or whatever this should be called.

Screenshot showing the 3D-printing software along with the webcam stream from the computer. Here we recently started printing the centerpiece.

Today we have quite rainy weather here in the north of Sweden, but hopefully it will clear up after lunch when the centerpiece is ready, so that we can get it in the air again.


Emma also tested the reflashed GPS yesterday (We have started using the russian equivalent of GPS, the GLONASS) and is happy to report a mean error of 6m in urban setting. This is to be compared with the 15m that GPS gave. This is of course depending on how many satellites you are able to lock on.

She has also designed and printed a water-resistant case for the GPS module. I must say it is looking rather dashing with its plexi glass roofing!

GPS casing.