Category Archives: Quadrocopters

AirSim is “live” !

So if you love flying quadrocopters, as I do, then you’ll probably also love flying them in a simulator.  I recently worked on a cool new Simulator with a colleague in Microsoft Research and it was a blast.  The Unreal Game engine is astounding, I love what it can do with rendering reflections, grass blowing in the wind, shadows created by leaves on the trees that also move as the wind blows.  Amazing stuff.

We built the AirSim simulator because we needed a research platform where we could safely test out reinforcement learning algorithms for vision based control of the drone.  Well, obviously we don’t want to have to crash a real drone while it is “learning”, but the problem with existing simulators is they didn’t look real enough.  So we built a new drone simulator using Unreal engine and it works great!

My Lucky Day – Helicopter Restored

It was the first of the month, allowance day, and my son, Sam, had flames pouring out of his pocket, so he bought a Avatar Dragon Fighter GYRO 4CH IR Electric RTF RC Helicopter ZX-Z008 from A week later it arrives, Sam excitedly rips open the box, we charge it up, and 40 minutes later, he starts flying. But in less than 15 minutes, I kid you not, 15 minutes, one motor dies. I can tell it is a motor because it has a sick whining sound and now Sam is devastated. Not to worry, perhaps I can do a repair job and get Sam interested in electronics. So out with the Magnification Lamp and screw drivers. We open it up and see immediately that the shaft of the motor is loose, and has dropped down so that the teeth no longer mesh properly with the gears. We can push it back up into place, and it flies again, but only for a minute until the shaft drops again.

Clearly we have a defective motor. So off we go to the local Hobby shop. We show the person there the problem, and I get the dreaded frown – we all know what it means, “you cheap Dad, how could you buy this junk for your kid, instead of buying a real helicopter from our store”. His eyes even darted over to their expensive selection of helicopters on the wall and back to our broken little toy. He shakes his head, “don’t know what the problem is, could be anything”. I ask if he sells motors that match this machine. He quickly shakes his head again. I could tell he was not going to help me fix this thing. So I have to get more precise with my questioning (which was a skill I picked up in handy class I did at Microsoft once). I ask what is the smallest motor he sells? So off he goes and comes back with this:

And it was $10, ouch, that’s 1/3 the price we paid for the entire helicopter. Oh well, my son is already checking out the $150 helicopters on the wall, so I better give it a shot, so I buy it. The guy behind the counter had that pitiful look on his face, I knew he was thinking “good luck with that sucker!!”. At least they had a motor that looks like it might work. But I knew it was a long shot. I was quietly thinking to myself we probably have a 1 in 10 chance of getting this thing working and I have no idea if I will even be able to get into the thing. You know how cheap toys are made in that “open me once and you’ll never get me back together” kind of way.

But with soldering iron ready to go, I unscrew the outer shell, and a plate covering the gears, fortunately they used tiny little metal screws that will go back together nicely. Lucky strike #1. I pull out the old motor, and find it is a different size from my new one, the new one is smaller. But fortunately, the teeth are the right size (lucky strike #2), so all I have to do is figure out how to get the motor to mount properly and re-solder the wires. But I wire up the new motor and it runs, so the voltages are good. (Lucky strike #3). Next I use electrical tape to get the new motor to fit the mount and a couple of washers to hold it at the right height so the teeth mesh, and button it all back up.

The helicopter doesn’t fly at all. I check the rotors and see they are both spinning in the same direction, so I have the wires reversed. Open it up again, reverse the wires, and we’re good. The helicopter now flies better than it did the first time, it is smooth, easier to control and Sam and I have hours of fun testing our flying skills. Given our luck we both try a “game of life” board game, and indeed it was our lucky day, we both finish the game with over 1 million dollars. And to top it off the weather outside was gorgeous. What a day!