Article on Shrediquette

Paul Escalier from TomsGuide.com just finished his article on my tricopter. It has become a nice story I think :-)

Make Your Own Gadget: From Idea To Reality

Table of contents

1. A Time to Make Something Awesome
2. A Little Bit of Background
3. The Birth of an Idea
4. Taking the Plunge: Buying Some Parts
5. Building the First Prototype
6. Overhaul: Taking the Prototype to a New Level
7. A Few Polishing Touches and a Mini Conversion
8. Future Developments and More Information

Have a look at the article here:
http://www.tomsguide.com/us/tricopter-diy-gadget,review-1552.html

First steps to autonomous outdoor flight...

Some of you might already suspect that I am trying to make my tricopter fly autonomously not only indoors, but also outdoors. I got some parts as a present from watterott.com (GPS & pressure sensor) and I bought an aditional compass sensor. First of all, I had a look at the GPS. It is a 10Hz, 65 channel SUP500F receiver (SUP500F). Results were a bit disappointing:

 I am standing still during logging (~1 minute), with a free view to the sky and no clouds. Next, I tested the pressure sensor (Bosch BMP-085). I was just using some very simple low-pass filters, and results were pretty ok already:

The sensor was moved several times from 0 to 2.5 meters. The compass (HMC6352) also works pretty ok. It delivers very precise heading information, even when the motors are running. But, when the sensor is tilted, there is an error in heading (due to the principle of measuring). There are much more expensive sensors available that can correct for tilt, but that is not really a problem I think: In position hold, the tilt angle will always be pretty low. When doing waypoint navigation, the heading can be read from GPS, hence heading data can be calculated from complementary filtering of gyro/ GPS/ compass if necessary. Here is a extremely boring video of my DLX with pressure sensor and compass active. From second 20 till the end of the video, I am not touching throttle or yaw anymore:

Pressure and compass test on Shrediquette DLX from B. Thielicke on Vimeo.

Finally, I had the opportunity to test a uBlox LEA4 GPS receiver from a friend of mine. On the first picture, I was standing still for ~1 minute, on the second picture I was walking around in several "8's". This GPS receiver seems to be pretty awesome, that's why I instantly ordered one. I am pretty confident that position-hold will work out with this sensor.

GPS, pressure sensor & compass are connected to an extra microcontroller which does all the processing. It sends a small byte array (4 bytes containing throttle, yaw, roll & pitch correction data) to the TriGUIDE via UART. The correction data is forwarded directly to the motors. Like this, modifications on the TriGUIDE firmware are minimal, and processing speed doesn't suffer.