Bitcraze Forums

Hi,

I am looking to reverse the direction of the motors such that the motors can be mounted upside down, but the chassis remains the same.

From this old post viewtopic.php?p=16079#p16079 Tobias flipped the signs in the powerDistribution function definition.

tobias wrote: ↑Fri Feb 01, 2019 11:07 am I gave it a quick shot and it this worked.

Then since it is now up-side-down I flipped M1.M4 and M2,M3 in power distribution

Code: Select all

void powerDistribution(const control_t *control)
{
...    
    motorPower.m4 = limitThrust(control->thrust - r + p + control->yaw);
    motorPower.m3 = limitThrust(control->thrust - r - p - control->yaw);
    motorPower.m2 =  limitThrust(control->thrust + r - p + control->yaw);
    motorPower.m1 =  limitThrust(control->thrust + r + p - control->yaw);
...

I also tried
This did not work, probably because the problem in this post was also flipping the whole chassis.

NOTE: I can use stock firmware and just reverse polarity of the motors, flip them upside down, then keeping the props facing the same direction. But i would prefer to do it in the firmware than always be flipping the polarity of the plugs.

What about swapping the propellers?

that does get the drone off the ground, but the yaw is uncontrollable. it spins really fast then crashes.

I think you need to flip something in the IMU too

I did a quick test and it actually works pretty well
I flipped the motor mounts up-side down (and flipped the propellers to keep the convex side up) and swapped the A and B propellers.

Since the motors are spinning in the other direction you have to change the sign of the yaw in the power distribution

motorPower.m1 = limitThrust(control->thrust - r + p - control->yaw);
motorPower.m2 = limitThrust(control->thrust - r - p + control->yaw);
motorPower.m3 = limitThrust(control->thrust + r - p - control->yaw);
motorPower.m4 = limitThrust(control->thrust + r + p + control->yaw);

If you put the battery under the CF you move the center of mass down to a better position which makes the platform more stable

This was fun!

Well yes that makes a lot of sense Thanks for that!