For anyone following this site, here is what I've been up to lately – building a quadcopter based on the Acc_Gyro 5DOF IMU sensor and a 16bit PIC. Although it's still a work in progress I decided to start putting together an article placeholder and build it up as project evolves. It's going to be a long one !
The source code will be Open-Source and will be hosted on Google Code, you can get code for quad copter here:
As usual I like to start with a video demo, it's basically me controlling the tilt of the quad using a RC controller:
This is a PID feedback algorithm and a "Simplified Kalman Filter" as described in my other articles.
First of all there's a a RCGroups thread where I first introduced the project
You'll find some specs there and I will put some material here as well.
Here is Revision 0.1 of schematic (what I started with):
The major parts list is as follows:
MCU: DSPIC33FJ128MC802 (http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en532302)
Motor Drivers: Power N-Channel Mosfets (Many choices -Low Rds(on) and rated for the current , I used IRLR8743 ). Schottky diodes to protect against back-EMF ( I used SS2H10-E3/52T )
Frame , motors propellers: I picked a ready platform that was on sale Dragandfly IV Frame these are actually brushed motors same ones as used in Esky helicopters.
I did some tests on the lift force potential of this frame+motors+props, and was surprise to find out it performed better than some entry-level brushless motors. The lift force of this platform is up to 2.25 lbs. The results of lift-force experiments are compiled in this spreadheet: MotorLiftPower.pdf.
How I measured the lift force ? I didn't have any fancy equipment so I simply fixed the quad in a vise and weighted it it at different throttle levels – the difference in weight gave me the lift power.
For testing just one motor, I used a string attached to the weight:
I built a test rig out of wood for testing the tilt balancing algorithm as you see in the video.
Here are some close-ups of the motor drivers. You'll see the Mosfets and the Schottky diodes, also note the extra solder added to support the high currents that will flow through those traces ( up to 5A per motor !).
Finally here is a view on the top of the board ( notice the PIC , the switching regulator , Acc_Gyro 5DOF IMU and single axes Gyro breakout , from top-left to bottom right).
This is it for now hope to bring you more interesting stuff on this and other projects if time allows !