If It's Worth Ranting About…

A few updates on the Quadcopter

First, a quick note to those who made comments on my blog that got eaten up by moderation. Sorry! That wasn’t suppose to happen! your comments should be up now…

After being nagged for a while, I decided to finally make a new post here.

Most of my recent activity has been with the quadcopter, since it’s about the only thing to do at my new residence at Missouri S & T in Rolla, MO. (Email me for room number if you go to MST and want to visit).

New things:
* Finally caved and bought a GoPro HD Hero. For reasons unknown, I managed to find a MotorSports GoPro on Amazon for only $230, a lot less than all the other packages, which IMO contained far less useful mounting options.

* New frame! Set to be engineered and cut by a buddy of mine over at MST, the new frame should fix the three biggest issues with the old frame by switching to square tubes and new motor mounts.

The GoPro was mounted on the frame by way of sticky pad. I had my doubts about how well this would work, and while it does look horrible, it actually works really well. The camera is cocked over to the left slightly, but until I get the steady cam set up I could care less.

Video quality is generally pretty good, but drops off as a function of available light. The difference between images sampled during low light and light rich environments is amazing.

This is a pretty typical video taken around noon at MST somewhere around the Puck. Recording at 720P @ 60FPS, this is taken directly off the camera and uploaded to youtube. NO post processing or stabilization.

Not bad?

I realize right now that isn’t exactly ultra high quality video, but it is a really decent start. I think things will get much better with the new airframe and the handy cam auto stabilization mount. Compared to the early videos taken with the Kodak Zx3 the GoPro does a majorly better job at all aspects of aerial imaging.

Next week is when I hope to tear down the quadcopter and start fabricating the new frame. Hopefully it won’t be taken out of flying status for too long.

The making of a quadcopter

I felt the need to give the back story to my quadcopter project since my blog was never updated during the actual build process from the time that I received my first box from hobbyking to the time that I made my first flight.

After I received the box of parts, I almost immediately started construction of the quadcopter, however progress was fairly slow for a lot of reasons. For one, there were a lot of little tweaks required on the frame, as well as a lot of other generally time consuming tasks, such as soldering bullet connectors and test fitting components.

Eventually, pieces started to fall into place, and day by day the once bare frame acquired more and more components; first the motors and landing gear, then the ESCs, flight computer mounts and finally, the flight computer itself.

The aircraft was first “test flown” inside at around midnight after several hours of troubleshooting electronics issues. The “flight” only lasted a few seconds, but in that time period, all of the motors began to run rough.

Further inspection reviled that the motors had actually vibrated their lock nuts out, so the outrunner bell was no longer attached to the shaft other than by the force of the magnets and friction. Gary and I eventually took apart all the motors and threadlocked them, but I only ever had more issues with the Turnigy 2217s; all but one of the motor mounts broke, and the vibration issues only got worse.

After a particularly bad incident involving vibration from the motors coupling into the flight sensors, resulting in a sudden flip into the ground, I decided to ditch the Turnigys and buy a set of the more expensive, but presumably higher quality, BP 2217/9s, as well as a new set of 10×4.7″ props.

I ended up having to widen the screw holes on the Lexan motor mounts to get the BP 2217/9s to mount properly, as the Turnigy and BP motor mounts differ by about 1mm in dimensions.

As soon as the new props and motors were mounted, I made my first test flight. No vibrations, or any other issues for that matter.

So, that’s about the full story since my last blog post. Since I made the first flight with the BP motors on Friday, I have put a bit more than an hour of flight time on the aircraft.

Something I also wanted to cover in this blog post was a list of things I was troubled with when building my own quad. These are things that aren’t really documented anywhere, but are quite critical to building a stable quadcopter

Prop sizes and motors
I first attempted to use 12×3.6″ props with the Turnigy 2217-20 motors. I read in the Aeroquad wiki that they recommended 10×4.7″ props for “mid sized quads”, so I assumed that I should probably go a step higher than that. This was not a very good assumption to make. although the quad flew fine on the 12″ props to the naked eye, the quad behaves much nicer on the 10×4.7 props. Two lessons from this:

A) The Turnigy motors should be avoided due to quality control issues (vibration, lack of thread lock, etc), I have had good experiences so far with the BP motors
B) If your quad weights around 2KG, just use 10×4.7″ props, which brings me to my next point…..

Don’t be concerned about the weight of your quad too much
When I was building my quad, I often thought that it was too overweight and that the motors would struggle to lift it (hence, my decision to use the larger props). After I got it flying, I realized that the motors can lift far more than I was giving them credit. I NEVER go any higher than half throttle as the aircraft will shoot up into the sky without hesitation. Around quarter throttle is enough to keep in a nice hover.

ALWAYS use threadlock on screws that touch the motor.
Pretty self explanatory, the motor will generally vibrate out any threaded surfaces attached to it. This was the case with the Turnigy 2217s; the mount mount screws vibrated out actually bending the aluminum motor mount (the screws unwinding from the motor pulled the aluminum mount up, while the other set of aluminum to lexan screws pulled it down) until it broke. By the time I got the BP 2217′s I spent extra time to thread all of the motor mount screws, however I was unable to loosen the lock screws securing the outrunner bell to the shaft, so I simply left them; I figured that if they were tight enough to not loosen under human force, they were tight enough to void the need for threadlock.

As time goes on, I will probably post several updates or other posts on this topic, but I figure this should be enough to cover the sudden burst of images I posted earlier today without any sort of explanation text to go with them.

Quadcopter: Finished, and photos

Quadcopter in a box

After about a 3 hour heatshrink and soldering session with Gary, I now have my quadcopter, albeit in pieces!

Assembly begins tomorrow, after I pick up a few things I left at Gary’s house.

March 2011 Update

I haven’t really written anything here in a really long time, so I figured I might give a bit of an update to what I am currently working on…

RWAR: Still going, messing with the autopilot for the most part and getting to test every once in a while when the weather is nice. I said before that I would be at the Sparkfun AVC, but I had another conflicting engagement which, unfortunately is over the same few days. That’s OK though, I still enjoy playing around with it in a non-competition environment.

Quadcopter: Woohoo, parts from Hobbyking will get in tomorrow!, the marathon soldering session with Gary on Tuesday afternoon to get the airframes and power distro system ready.

NETMF: Not doing very many projects I can talk about. GHI was nice enough to send me a bunch of devboards, and I have been playing with the FEZ Rhino OEM kit extensively. I also plan to see about doing a sort of bike computer a bit later on as the weather gets better.

Another project I finished was a PPM decoder based on Ward and Blake Ramsdell’s *duino FPGA shield using a Netduino+ for USB joystick emulation. The short and skinny is that I can plug my DX6i into the FPGA, then plug the FPGA/N+ into my computer and have my transmitter show up as a 4 axis, 2 button joystick in windows. If you have any interest in the sourcecode for the N+ or the bitstream for the FPGA please send me an email at the address on my contact page.

IMU: You might notice the new tab on the nav bar on top of this page for the Cortex IMU project, by Yonghan Ching and myself. Yonghan completed the electrical/PCB design and I will be developing the cross compensation firmware for the onboard Cortex M0. Please see the tab for more details, plus an opportunity to own your very own!

Entconnect: I’ll be at Entconnect 2011 later on this month. Probably be talking about NETMF or something.

I quite like my quadcopter

A few weeks ago, I got really into the idea of having my own quadcopter after seeing some of FPV-Leif’s videos on Vimeo.

I kept to myself about this for a little while, then one day I started talking to my friend Gary Liming about it and discovered he was wanting to do a quadcopter project of his own.

Since then, we have been working rather rapidly through the design process. I am doing all of the software/electronics engineering, while Gary is doing the airframe design, since he has a CNC to cut parts on.

We have decided to name our Aeroquad derivative “ESPCopter”, the “ESP” being for “Expensive Spinning Platform”. The main objective is to get a stable flying platform that can be used for aerial photography.

For right now, I don’t have anything much to take pictures of, but I will start blogging about this project regularly.

Progress so far:
Flight computer: Purchased ($250+) and completed (Me)
Frame: Most parts purchased ($??), Pending (Gary) (First rev parts may be cut next week)
Motors, ESCs, battery, power bus: Pending (Me)

RWAR: RAIN!

The past few days have basically been solid rain, so I have naturally lost a lot of testing time for RWAR.

So far, I am still working the north turn issue mentioned in my last post, but I am replacing a massive portion of the heading-hold autopilot, so I am hoping that fixes it by complete replacement.

In the mean time, I need RWAR to be stable and confirmed working before I make any major changes, IE, the new body. Now that the holidays are over, except to have the new autopilot architecture running within the next few days.

RWAR: “No blog update since Halloween?”

I took a little break from RWAR over that last few weeks due to GPS problems.

Those issues have since been resolved, and RWAR is operation again, so I thought I might write up a new post.

Today was mainly spent on repairing RWAR and verifying sanity of the new Skytraq powered GPS.

I finished installing the new GPS last night, but when I connected the battery and hit the master switch…… Nothing. After a quick look around, I found the issue: the power harness was broken at the point where it splits off from the main power lines to the ESC.

After soldering a new connector on, I hit the master switch and……. Nothing. Again.

After a bit more troubleshooting, I found out that the issue lie somewhere in the switch assembly, but it was unclear as to whether it was actually in the switch or in the connection to the switch. I decided to remove the problem entirely and solder in a new switch. So for the second time, I hit the master switch…. All green lights

I managed to get one final run in before sunset, and although the new GPS made RWAR more accurate, there is still an issue when RWAR takes the first northern tun on the route. All navigation up to that point is perfect, but as soon as it passes the most southern waypoint to head north, navigation goes haywire and the truck will go way off course to the left.

It’s unclear where the issue is coming from, so I’m just going to scale the route down to a single southern waypoint followed by a single northern waypoint. RWAR will depart heading south, hit the southern most waypoint and then (hopefully) turn on course to the northern waypoint. If I can’t replicate the issue that way, I guess I’ll have to step through code and see where I went wrong.

A fairly new development is that RWAR has a new electronics tray! Built by my friend Gary Liming, the tray looks to improve on the flimsy RC truck body I can currently using. I was hoping to get the tray replaced today and get some nice pictures, but I ended up spending all my time repairing RWAR, so tray installation will probably happen tomorrow, after I do more testing on the north-turn issue.

RWAR: .3 miles of navigation

I reached a bit of a milestone with RWAR today. For the first time, RWAR was actually able to navigate itself all of the way up my block by itself.

The only issues that I am currently working are GPS related. The code works flawlessly, but the GPS has problems getting an initial fix. Once it does, it tends to be pretty stable, but until then RWAR is liable stray off course. This issue should be solved by getting a new GPS, probably a SUP500 from Sparkfun.

RWAR: Navigation system DONE

I have been somewhat absent on the blog lately, mostly because I have been busy finishing RWAR’s navigation system.

The heading hold autopilot was completed about a week ago, and the GPS integration was completed about 3 days after.

Today, RWAR navigated between two points for the first time, then 3 points (depart, destination, back to departure point).

I’ll post a more complete write up later, but for now I figured I’d give a very quick status update