Instability: motor speeds bouncing up and down.

[jjbunn]

I'm having a lot of beginner's difficulty getting my quad in the air. I'm using the latest software and configurator, with a 1.7 shield having gyros and accelerometer. I've calibrated everything except the TowerPro ESCs ... those I initialised directly, outside the configurator.

Since I don't fancy holding the quad while doing the pre-flight checks, I put it on a takeoff platform, arm it, and stand back.

The symptoms of my problems are this:

1) At low throttle settings, with the quad flat on the platform, the front and right motors are spinning, but the left and rear aren't. If I tickle the throttle up, then the left and rear will fire up and continue even when I back off the throttle.

2) As I increase the throttle, the quad starts to lift equally on the front and right motors. By trimming the yaw, pitch and roll controls on the transmitter, I can get the front and right to settle down.

3) At this point, if I tickle the throttle upwards, the quad starts to rotate anti-clockwise on the platform. By adjusting the yaw trim I can almost stop that motion.

4) At this point, all the motors are spinning evenly, and the quad is sort of jiggling around looking as if it's waiting for just a little more throttle to get airborne. However, if I give it more throttle it invariably flips over (as if the front/right motors get disproportionally more power).

Another experiment I did was to look at the configurator's "Vehicle Status" display while I held the quad down on a table with one hand and varied the throttle with the other. The motor speeds were bouncing up and down until I used at least 1/2 throttle, then they became stable, with 1 and 3 being much higher than 2 and 4 ... this corresponds to Front and Rear being much higher than Right and Left, I believe (so not consistent with what I saw in 2) above).

The configuration is a "+", motors are TowerPro 2410, the props are APC 9x3/8 pullers on the Left/Right motors and APC 8x6 pushers on the Front/Rear motors (which rotate clockwise, looking from on top, I believe). The AUW is 2lbs 13oz (1.3kg). The battery is a 2560mAh Turnigy. Motor to motor distance is 29".

Any suggestions and advice most welcome. I suspect that I may have a screwed up software configuration.

Thanks!
Julian

[jjbunn]

As a follow up to this - after looking more carefully in the Configurator I realised that the Right/Bottom motors on the quad were swapped from what they should be - when the Vehicle Status showed Motor 2 revving up, it was the bottom motor on my quad revving up! So, on the v1.7 shield I'm using, it looks like the motor control socket labels for Right and Bottom are the wrong way round with respect to the software. I simply swapped the ESC plugs, and now the quad is behaving slightly more predictably!

[Darkwolf]

Ah, what's happening there is you're using an old shield, and the motors order has been renumbered. As such, they won't match up with your shield. You could set the flag to use the old motor numbering, or you could just swap wires.

One little tip, as part of your pre-take-off check, use the Configurator to fire up each motor one at a time and make sure the right one spins the right way.

[jjbunn]

Thanks, Darkwolf - that confirms my suspicions! I've now re-cabled, and am satisfied that the correct motors spin, and in the correct (cw/ccw) directions.

Now I am trying to see if I can lift off vertically without a catastrophic crash :-)