Friday, February 28, 2014

East Bay Guide to Understanding PID Loops, Part 2

Building on the intuitive model presented in part 1, we take a look at the mathematical model and write a PID control loop based on that model.  Hang in there if you're unfamiliar with the math... it turns out to be pretty straight-forward code in the end!

Like part 1, this is a first take.  I was going to make a second take, but I discovered I had scribbled all over my only nice-looking copy of the PID math.  Your comments are welcome!

The printed formula is from wikipedia.  I tried doing this Khan Academy style with a tablet... wow that's hard to write with, that man is a genius if for no other reason being able to use one of those things!

blogodex = {"toc" : "PID Loops", "idx" : ["tutorials"]};

Things to Try: OSW the OneSheetWing

The ever-awesome Springer made the OSW a while back.

"It's not like we don't have a plethora of wings on the scratchbuilt foamies forum, but, hey, I'm working my way through all the genres in this onesheet madness. For those who may not have seen the OSG or OSB thread, the premise is to make a plane that uses as much of a 20"x30" sheet of dollar store foamboard as possible. So, Here she is the OneSheetWing"

The fuse is just a penthouse to hold the firewall/motor mount and gear out of sight. The pattern on plans is cut out, then the inside v cut and then grooved with top of xacto knife to get it to fold. Glue and tape together. first picture is V1 fuse (was gonna do one on top and one on bottom, but stopped at only the top), but V2 goes together the same.

blogodex = {"index":["Things to Try","OSW","One Sheet Wing"]}

Thursday, February 20, 2014

East Bay Guide to Understanding PID Loops

So here's my take on explaining this topic.  Light on the math, and heavy on the intuitive (I hope!) understanding.

I expect to take another stab at explaining the topic again, and I'm working on plugging in a physics engine to do some real-time simulation.  It's kind of like a game, can you tune the PID loop to lock the copter into position?  (update: it seems that enough people are liking this version that it will stay around for a while.  Sometime or the other I want to learn processing.js, and I'll try an online pid program as my learning project.)

I mention Khan Academy as my inspiration for this, not to imply that it will be anywhere near as good. Anyways, let me know if if this is useful at all or where I've gotten things wrong!

blogodex = {"toc" : "PID Loops", "idx" : ["tutorials"]};

Wednesday, February 19, 2014

Lemon-RX Stabilizer Notes

Lemon-RX has released their DSMX 7 channel stabilizer, and user reports are coming in.  Backwards compatible with DSM2 it's 4.8 grams and $16.30.

Initial reports are good, and I think I'll get one to try out.  Here's some RC Groups notes by jj604:

1) The receiver binds very quickly in DXMX 22mS mode on my DX8.

2) Lemon have screwed up on their Aux2, 7 channel implementation. This is supposed to give you a 7 channel non-stabilised receiver using the bind connector for Aux2 and it does BUT if you have a servo plugged into Aux 2 when you power up the receiver always goes into bind mode! 
I tried it with couple of different servos. It may depend on the servos since the receiver is looking for a connection between signal and ground on the connector and it will be resistance dependent. In practice this is going to be pretty useless.

3) We now know how Aux 1 works. It DOES function as a normal output but also as a switch to turn the stabiliser ON and OFF. Kind of odd. In practice if you use Aux 1 to switch the stabiliser you really only have 5 control channels.

Overall it looks nice. I personally like the separation of stabilisation direction using 3x DIP switches and gain using the 0-100% pots over the Guardian bidirectional pot system. Very logical and easy to sort out. 

On the bench it seemed fairly sensitive but I have not had a chance to flight test it. I would regard this as a 5 channel stabilised receiver with remote On/Off and remote Gain. Very nice combo for many models. 6 control channels is going to require some thinking about in order to use Aux 1 for two separate functions.

I can't see the non-stabilised 7 channel option as being any use at all given the need to connect/disconnect a servo every time you use it.

Lemon-RX officer fmak notes:

I am sorry but we have to use AUX1 so that DX6i owner can use the stabilizer as well. During the stabilizer development it is required to test with DX6i, DX8, DX9 and DX18 so AUX1 is the only option for turning on or off the Gyro. Please let us know for any suggestions or comments. Thanks!


The currently stabilizer will work with DX6i since AUX3 is really an optional "variable gain" control. AUX1 will switch the stabilizer on / off and DX6i will work perfectly OK.

We cannot reserve Aux1 for dual servo aileron (use Y-connector please) because we have to design a stabilizer that also works for DX6i user. I hope this is sufficient as being the entry level, basic stabilizer.

However we are seeing more and more people requesting for flaperon. We will for sure look further into this. Thanks!

There's a good discussion of these points later in the thread.

Johnnymeg reports "It was very simple to get things situated and dialed in. It was very stable and held its heading and altitude very well. The pass through with my inputs was smooth and I didn't have to fight the Rx for control." and provides this video.

Monday, February 17, 2014

Andreas flies his new Skipper up at Tahoe

So Andreas got a HobbyKing Skipper, and has been looking for a chance to fly it off the water.  And what better water to fly off of than the deep blue waters of Lake Tahoe!

Saturday, February 15, 2014

Mobius Action Cam Notes

Here's some notes on the Mobius Action Cam.

LED Status
  • Green: charging
  • Yellow: video mode 1.  solid = standby, blink = recording.
  • Blue: video mode 2.  solid = standby, blink = recording.
  • Red: photo mode or playback mode.  Blink = picture taken.
  • Dump sysconfig.txt by holding mode while powering up.  LED will blink yellow twice when finished.

Good Video Reviews

By RCModelReviews:
By TechMoan

SD Card Formatter

"SD Formatter4.0 is official SD memory card format software.
It formats SD memory cards, SDHC memory cards and SDXC memory cards. Trendy provided the SD Formatter by request from SDA. Number of downloads from SDA web surpasses 2 millions in 2013."

Mac and Windows downloads available.

Thursday, February 13, 2014

Monday, February 10, 2014

Two Flying Boxes!

Ran across these on RCG.  They look like an easy and fun thing to try, and might be an interesting testbed for a stabilization system.