MultiWiiCopter Build Log
Posted 22 July 2011 - 02:55 PM
I ignored all the MultiWiiCopter fuss until a few weeks ago. I was considering going to a larger quad and started looking around for frames and control boards. I would have gone with a MikroKopter kit but cost is still a bit steep. Being a DiY fellow, I began to digest the MultiWiiCopter discussions. From what I can tell, I'm definitely late to the party, but I think this was a good thing. That is because there are now plenty of online resources to help out. Here is a starting point:
So here I am to tell about my experience. More to the point, today I had my first hover with it. So I think it is a good time to show some works in progress. For sure, I should write about it before I forget the fun details.
Before I start, please realize that my design choices (frame selection, motors, props, tasty snacks & beverages, and so on) were just personal picks. Some project choices involved dart boards and coin tosses. So please don't think that my parts list is anything special. There's a million ways to build this monster and so be prepared to read the endless discussions in the links shown above. Then build what YOU want. That's the beauty of DiY.
First, here's a photo of the new model, compared to the Gaui 330X-S I've been flying the last few months. The new WiiCopter is definitely bigger!
Posted 22 July 2011 - 03:22 PM
But then I found this video, which from the comments on YouTube, appears to have alienated some Italian engineers. But, its tongue-in-cheek discussion instantly helped me understand the mindset of the Arduino world.
Things to know:
* Arduino is named after a bar in Italy where the developers hung out. Or so they say.
* A "sketch" is nothing more than a source code file.
* All Arduino code is written in the C language.
* The C source code files are named with a .pde extension instead of the .c that the world outside Arduino would normally use.
* The Arduino experience includes an IDE application that allows you to compile and upload the code into any Arduino board.
* "Shields" are nothing more than add-on boards sold by a growing cottage industry made up of Arduino engineers and hackers.
Posted 22 July 2011 - 03:34 PM
You will find that there are dozens of choices out there, with prices starting at about $20 USD. Hoverthing's X-8 frame was the winning selection (it has the look of a scaled-up version of my Gaui 330X-S). I had them customize a black kit with two red arms. I also added some extra double-tab mounting plates. Total was $117 USD to my door.
Here's a catalog photo of the stock kit (from the retailer's web site):
Catalog page: http://www.hoverthin...&products_id=31
The kit is very high quality (a delight to build) and they had very friendly customer support.
Here's an early build photo that shows the front mounted red arms and the double-tab plates on the center hub:
They are certainly not needed, but some hobbyking.com shock absorbers are mounted on the legs.
Spring Shocks, A2016T32781/16173, 2 pair x $4
I purchased motors and ESC's from HobbyPartz.com:
Exceed RC Rocket 1050KV Brushless motors, $14 X 4.
Volcano 30A ESC's, $14 x 4.
Props are from Maxx Products, maxxprodrc.com:
EPP1045 10X4.5 contra-rotating sets, $5 x 2.
The model's AUW is 52oz with a 3S 4000mAH pack. The weight does not include any camera gear or other goodies.
Posted 22 July 2011 - 04:24 PM
Arduino Pro Mini 328 - 5V/16MHz, $19. (http://www.sparkfun.com/products/9218)
FTDI Basic Breakout - 5V (USB/Serial adapter), $15.
To help avoid a wiring rats nest, a naked Paris V3.0 shield board was purchased from www.multiwiicopter.com (one of many sources for MulitWiiCopter shields and parts).
I came within a mouse click away from ordering the Wii game controller items that are needed for the basic build. But a flash of insanity overcame me and I decided to create a custom 10DOF IMU sensor board. I spent a couple weeks buried in Altium Designer working on the custom hardware. Once the PCB layout was finalized, the custom board and components were ordered. A few weeks later the IMU-X (not a fancy name, I admit) was assembled and working. The reward for all the extra effort was a small (37 x 20 mm) sensor board. The IMU-X sensor board has the following features:
- BMA180 3-axis Accelerometer Sensor
- HMC5883L 3-axis Magnetometer Compass Sensor
- ITG3200 3-axis Gyro Sensor
- BMP085 Digital Pressure Sensor (for altitude hold)
- MPU-6000 3-Axis Accelerometer / Gyro Sensor (not used, for future)
- On-board 5V to 3.3V logic conversion, voltage regulator, and LC supply filter
And despite adding more work to the endless list of things to do, I also created a custom Arduino "I/O Expander" board that would allow me to add some special functions to my Quad. The expander board is 45 x 38 mm. It contains four high current FET switches (to control four strings of LED's). Custom code inserted in the Sketch file provides several lighting sequences that are triggered by the flight mode states. Last night at 2AM I fired it up for the first time and it looks awesome. I'll post a video soon.
Posted 22 July 2011 - 04:40 PM
The buzzer feature adds a second audio alert to the MultiWiiCopter. There's some custom code involved to control it.
The input port can be used to read configuration jumpers. I'm using one of the inputs with a micro sized push button switch.
This pushbutton switch turned out to be a very good idea. Some new code was integrated in MultiWii's V1.8 release to do some new functions:
(1) If pressed at power up the four ESC's throttle points are automatically calibrated. I love this feature.
(2) If pressed while the motors are running the model is immediately disarmed. This saved me today during one of my hover tests; During the test flight I had dialed-in too much rudder and aileron trim, which messed up the remote motor disarm function. So I carefully reached under the spinning props and pressed the button to kill the motors. If I would have needed to unplug the 4000mAH 3S LiPO I think I would be missing some finger tips right about now.
(3) If pressed while the model is disarmed (Tx sticks at low throttle/neutral) the ACC sensor is calibrated.
Posted 22 July 2011 - 05:17 PM
Speaking of setting the PID parameters, the provided application program is very nice. It has a realtime 3-D stick model so you can confirm that all sensors are working (and with correct orientation). The PID values are changed in the program's provided data fields (via mouse driving sliders) and a single mouse click updates all the new parameters via the USB connection (Bluetooth connectivity is possible too). It's useful software based tools like this that help the rest of us achieve our DiY dreams!
Posted 22 July 2011 - 11:32 PM
Im still surprised the wii gyros are up to the job.
Posted 23 July 2011 - 09:00 PM
I spent about an hour today playing with the PID parameters. I made some progress and it is hovering much better. It is still a bit loose feeling so I will continue experimenting with the values.
I tried to make a video of the I/O Expander board's LED lighting control feature. It was too dark and my Aiptek camcorder didn't do well. So I'll try again.
Edited by Mr.RC-Cam, 24 July 2011 - 06:58 PM.
deleted worthless video.
Posted 24 July 2011 - 08:51 PM
Posted 24 July 2011 - 10:56 PM
Posted 25 July 2011 - 08:40 AM
I'm still working on the PID's. At this point hover stability is very similar to a traditional R/C model heli. I need to dumb it down a lot more for my lowly stick skills.
Seems to hover just fine, is it easy to recover to level from extream manovers?
At the moment, with my latest PID parameters, it is definitely more difficult to control than my Gaui Quad. For sure, I'm not ready to try anything more aggressive than basic hovering. Hopefully that changes with more practice or better PID's:)
Posted 26 July 2011 - 08:08 PM
is it easy to recover to level from extreme maneuvers?
With the stability feature (ACC) turned on the quad will quickly transition from a steep attitude, back to level, when the sticks are released. It is very similar to what you experience with a FYE-20A stabilizer. There are times where I feel the mulitwiicopter does a better job than the FY-20A (but it could just be due to the larger model). But for sure, it works as well as the FY-20A. The big difference is that you have much more control over how the multiwii behaves. The PID parameters you choose will define the model's behavior.
I haven't tried fast forward flight yet since I haven't had time to fly at a large enough field. So in the meantime I have moved on to setting up the compass and altitude sensors. I've tried several PID values on the compass and I cannot tell if it is actually doing anything. The sensor works fine in the GUI, but in flight the model does not appear to have any better tail holding with the compass turned on than without. So I'll continue hammering on it.
The altitude hold feature is working, but the elevation varies a lot (at least ±10 feet). I recall reading there will be improvements to the barometer code on the next sketch release.
Despite the steep learning curve and some bugs, it is a very cool quad project. I'm quite happy with it.
Posted 26 July 2011 - 09:51 PM
There are so many quad controllers about now its hard to know which way to go, a nice neat unit like the FY90Q that supports PID adjustments would be the best but I dont see one
Posted 26 July 2011 - 10:05 PM
Posted 27 July 2011 - 09:12 AM
I wont rush out and buy it though, not until I can get the FY90Q working a bit better. Maybe the wii copter is a better bet Im not sure yet.
Posted 27 July 2011 - 11:12 PM
Posted 27 July 2011 - 11:18 PM
Today I was trying to resolve my wiicopter's altitude hold and compass issues. During a test flight the model did a sudden flip and face planted into the ground. Quite an unexpected and horrific thing to see! Anyway, it was caused by a bad motor bullet connector (the factory did a bad solder job). So I'm grounded while the little fellow is mended (nothing serious). Plus I need to bleach some underwear.
Posted 28 July 2011 - 10:53 AM
Posted 28 July 2011 - 11:39 AM
good you found the fault and didnt go off looking for something more technical.
I feel very fortunate. There have been several reports of mysterious flip involved crashes with the WiiCopter. Some victims suspect the code. But fortunately my flip was just a brainless broken solder joint on a motor. The flip was quite amazing. The quad went from "here" to "there" in about a microsecond; It was all over before I could even comprehend what had happened.
The poor thing was patched up and back in the air this morning. I'm happy to report that the compass feature is now working. The reward is a very steady Yaw hold -- totally amazing.
Last on the list is to solve the altitude hold problem. At the moment it is working but it's not very precise. I've posted on the WiiCopter forum to see if the experts there can offer a solution.
I discovered an interesting issue with the altitude baro sensor that I have not seen reported by the WiiCopter gang. Like many baro sensors, the IC die inside the BMP085 is photoelectric. That is to say, any light exposure on the vent hole will cause a bias change in the sensor data. I could see this on my workbench with a small incandescent flashlight pointed towards the sensor's hole. While aiming the flashlight at it the PC application's GUI would easily push the Altitude graphing off the chart and raise the reported numeric data. My sensor is exposed to sunlight when I fly so I installed some dark rubber foam over the vent hole and the light exposure effect has gone away.This didn't solve my immediate problem, but I expect it will provide better baro performance when I get things working right.