New/first post here!
Anyone have an idea why my throttle continues to advance in speed after I arm? I arm the motors, advance to idle, and then the motors continue to speed up faster (seems way too fast for an idle speed). Video here: https://www.youtube.com/watch?v=PpZB-MHaq9E&list=UUQP_rPKfubcuPaxqnrbtlAw
Just seems way to abrupt and quick for idle. I tried changing throttle_min and mot_spin_armed with no change. Does this look normal for you? This is the first time I've mounted props after doing the esc calibrations etc.
Replies
Apparently Bernardo solved his problem described in his topic (almost identical to this one) and closed his topic, but forgot to tell everyone what his solution was. Furthermore, one cannot even send him a PM unless you are first friends with him. Not very helpful of him. Does anyone else know what solved his problem? Maybe it will also solve the current problem too.
Hi,
just saw your post.
there are two points:
1* I had wrong ESC from a heli, not too good for a multicopter.
Now I use X-Rotor 40A (black series) from HobbyWing, very good stuff. Perfect calibrating and flying :)
SimonK ESC seems to have problems with lower kV brushless motors.
2* just after starting the motors (in stabilize_mode) while the copter is still on ground, the FC tries to stabilize the craft. So the effect I saw in your video is normal.
With the calibrated copter go outside, start in stabilize, raise power to take off quickly to 1.5 or 2 meters, then switch to althold, you'll see the copter will hoover normally and respond to stick inputs. (supposing all the settings and calibrations done in every detail !!!!!!!!!!!!!!!!
Im having the same issue... but can't seem to figure it out. is it safe to attempt a madin flight
Solved the problem, and there are two separate issues at play here:
1) The throttle seems to increase after idling because you are in stabilize mode and the Pixhawk sees that it is not perfectly level.
It may be hard to see this if your idle speed is too high (see point 2 below), but you may notice that the multi-rotor motors do not accelerate uniformly. Instead, some of the motors will accelerate, while those on the opposing side will decelerate or stay the same. This is a result of the Pixhawk attempting to level itself, and the rate at which this happens is affected by your PID settings. As in the video above, if you have your multi-rotor physically constrained, you will see that the motors will spin up quite high because the Pixhawk is unable to level itself due the constraints.
If you have done the RC calibration and ESC calibration and made no changes to the limits (or trims) on your radio TX, 0% throttle should not allow the motors to accelerate in this way. They should spin at the MOT_SPIN_ARMED value even if the multi-rotor is off level. However, if your RC throttle is even slightly higher than the calibrated RC throttle minimum, your Pixhawk will start trying to level itself, and the motors will spin at the speed defined by a different parameter: THR_MIN.
If you have your throttle calibrated properly, you should notice that when your multi-rotor is armed and you raise the throttle from 0% to ~1%, your motor speed will jump up. This boost is a result of the difference in those two parameters: THR_MIN - MOT_SPIN_ARMED. This is normal, and it is assumed that you will take off relatively quickly after arming. It is typically not a good idea to sit on the ground with the throttle higher than 0%, as the multi-rotor may tip over as it tries to level itself and is somewhat constrained by its own weight.
2) The idle speed being too high is related to the MOT_SPIN_ARMED parameter at 0% of the calibrated throttle input. After calibrating your ESCs, 0% of your RC calibrated throttle should align with the throttle delivered to the motors defined by MOT_SPIN_ARMED.
If MOT_SPIN_ARMED is too low, the motors will not spin at 0% throttle input after arming the copter. If MOT_SPIN_ARMED is too high, the motors will spin uncomfortably fast after arming at 0% throttle, and if it is exceptionally high your multi-rotor may even take off at idle speed. If the MOT_SPIN_ARMED parameter is slightly too low, you may notice that one or more of your props chatters back and forth instead of spinning. When your throttle is at exactly the calibrated 0%, your motors should spin at this "idle" speed, and the props speed should not increase on its own until the throttle is raised slightly above 0%.
Hope that helps for anyone else who experiences this issue!
Hi Chris,
if you have a little time I would be happy if you can look over my post?
I'm getting valuable help, but I'm still stuck.
The issue is exactly what you describe, but with the APM2.5 (3DR)
http://diydrones.com/forum/topics/motors-spin-at-high-rpm-at-0-1-th...
Thank you!
You are very correct! A combination of re-doing all of the compass/rc/accelerometer calibrations and the MOT_SPIN_ARMED and THR_MIN all solved the problem. Copter behaves perfectly in flight and on the ground now... Thanks for the detailed description for those to follow!
Hi Daniel Degallier,
I seem to have the same thing happening with a quadcopter here. Idle speed seems unreasonably high, and the motor speed keeps increasing without change in throttle pwm after idle start. Have you found the source of this increasing idle speed?
- Chris
Have you calibrated your TX radio using the Initial setup Wizard in MP?
Also your log files show compass offset problems that you need to try to correct.
And you flipped your TX several times to flight modes that require a GPS. Not a good idea without a working GPS!
I suggest you go back to the beginning and do a lot more reading.
Start with the "Instructions": http://copter.ardupilot.com/wiki/introduction/
Dig deep and work through all the section on "first time" setup.
Then you can search here and elsewhere including youtube for more info.
Thanks for the reply, Greg.
I have done the TX Calibration several times with the wizard.
Is the compass offset because I don't have the GPS plugged in? I am planning to test fly it indoors, so a GPS is no use anyway.
No worries on the flight modes, I was checking them with no props on to see that they all showed up correctly on the Droid Planner on the tablet.
Having read it all through several times, I just want to know if it's within tolerance to do a test flight without GPS in stabilize mode. Thoughts?
I am not aware that the compass offsets are effected by GPS being off. But you do have a potential problem with the compass. Something is bothering it either during or after calibration. Either a mass of metal, electrical noise or a bad compass.
Try relocating it away from ESCs, power wires and RX. Values that high are considered a problem, before getting PH exchanged I had readings just over -500 on the one axis and flew ok.
If you are going to chance it. I would get outside with plenty of space over soft grass if your area has any this time of year and try hovering at low height in ALT hold or Stab.
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