A tricopter platform and autopilot using the MBED.

IMU driven by ITG 3200 and ADXL 345

Standard IMU filters with some mods.

First challenges!

IMU unit suffers significant drift. Also no descrintion found on actual putting together of the hardware.

ITG3200 axis X is across the chip Y is longitudinal z is into the chip. ADSL345 axis X is longitudnal, Y across the chip and z in and out.

A general view of the airframe. Structural members are 12 * 5mm hollow carbon fibre box sections. The skid assebly is all carbon glass from a large RC helicopter. 3 motors and meticulously balanced 10*5 props fitted. All the motor wiring put together, 3 motor controllers fitted, direction tested and heatshrunk.


Tail rotor control. using torque control in a 3 rotor system is a pain so I'm using a tilting tail rotor for Yaw control.


I have tested the system with a very large 600g battery pack on board and it lifts off at about 1/3 throttle on the 3 motors so power looks good. The potential to carry a 'useable' load of 300 to 400g looks achievable. That's a really good panasonic HD camera or some other interesting stuff!

On the hardware side a pod to house the Mbed, communications link, battery and other bits would appear to be the next step!

Frame built and motor installation tested. Yaw control via tilting rear rotor. working great.

Now I need to get the IMU unit working.

The drift appeared to be due to setting the filter up incorrectly. Now I have a problem in that aither the yaw axis OR the pitch axis works. I appear to have the X's Y's and polarities mixed up :)

I was thinking of resorting to a bought in IMU to get things going quickly but last night great strides were made in the software so it's looking better now.

4 comments on Tricopter:

15 Feb 2011
23 Dec 2011

Hi Is it the imu ? Or thé items are available standalone ? Best regards

24 Dec 2011

I've switched to using the 9 dof IMU.

The tricopter has now bevome a quadcopter too :)

30 Jul 2015

Now the IMU are under 12 USD for 10 DOF consider fusion algo between gyro and accel in order to lessen drift effect

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