I’ve been setting up my Pixhawk with a SKY-Hero Spyder X4 (420kV motors and 40A ESC).
All has gone great and hardware appears to be functioning as it should. I am now tuning in the stabilize mode.
What has put a roadblock on me proceeding with the ALT and POS tuning is that I cannot get the motors to run up with full throttle.
I’ve done the auto trim and the stabilise P values (at 4.8) are good since any movement with the right stick and then back to neutral results in the frame levelling off just fine. I can take off from the ground well but the motors back off as soon as I’m in the air requiring me to add throttle but keeping the throttle at 100% results in the total load maxing out at around 24-25A.
I’ve done the ESC calibration both in Auto and Manual and running up the throttle in this mode (bypass) results in a lot of power drawing over 35A with the four motors.
I’ve even disabled the throttle curve in advanced settings. The throttle mid value is also high (at 700) and the MAX_THR is at 1000. One thing to note, all my radio channels endpoints are 1100-1900. Could this be the problem? I performed the radio calibration many times and the process does recognize these exact limits.
Seems like there is some limiter somewhere or tuning param preventing the actual PWM to motors from ever reaching their limits and going above 24Amps draw when they could actually pull 10A more resulting is a much more aggressive liftoff.
Please look at the logs and tell me what issue this could be. I’m at my wits end
Hi,
Not sure 100% but your two front engines (1 and 3) are working harder all the time and sometimes they are at max pwm . It looks like it is not sending 100% to all four engine to keep stability (on pitch axis).
I would suspect that you have a non well balanced copter or some difference between motor/props at the front compare to the back generating different thrust.
Try to move battery to balance your copter around its center of gravity
M
thanks for the response. I noticed the same and yes, the battery can be moved back to help out. However, the upper range limit is 1900 for the PWM output to the motor, why is it never reached and yet I ask for 100% throttle which should launch this thing in the upper atmosphere
I tried an experiment since I am starting to believe that the barometer/altimeter comes into play in stabilize mode. I kept the platform secured on the ground and went to 100% throttle and got 100% output from the motors with 35A current draw. Never had that before. However, removing the “anchor” and flying it like I should resulted in the same behaviour with altitude never reaching above 2m in height and motor backing off even with throttle at 100%.
I am running the 3.1.2 arduCopter firmware and seriously considering going to 3.1.3 since I’ve read similar cases from another forum. Some guy went to 3.1.1 and all was ok.
I am not experiencing motor sync issues even though these are advertised as SimonK ESCs. One more thing, I do not have a canopy on my frame yet so the Pixhawk is exposed to some rotor wash.
Could this be affecting the altitude issue, even though I;m not even in Alt hold but only stabilize?
[quote=“yvesOttawa”]thanks for the response. I noticed the same and yes, the battery can be moved back to help out. However, the upper range limit is 1900 for the PWM output to the motor, why is it never reached and yet I ask for 100% throttle which should launch this thing in the upper atmosphere
[/quote]
It does go up to 1900 (or close) see screenshot of motor 1 but not the other motor (motor 2 is at 1600).
If it goes up in the air straight, it means that you have an imbalance and it can not go 100% on all 4 motors otherwise it would flip over.
Thanks for your continued remarks. I’ve tried with the battery further at the back. The power distribution is much improved with about 100 mS difference between the forward and rear motors.
Unfortunately, no better. Still not getting enough power through the motors at 100% throttle. They are just not spinning up once the initial take off has been made.
I also upgraded to 3.1.3 and added the canopy to rule out rotor wash affecting the bark but as figured before, the bark doesn’t come into play in this stab mode.
Next step is to try with a Naza controller I have lying around. If I can get thrust with it, then I need to go back and evaluate the Pixhawk. Even though it is saying it is outputting PWM of 1900 which is maximum, I can’t really believe that if the motors are not responding.
Just to update. All is working now. Found out after the Naza test that it behaved the same way.
The final verdict: The ESCs were programmed for a fixed battery type: 6S, not set to auto like we had assumed. So in 4S, the ESC just did not supply the required load therefore could not spool up to 100%.
Will never assume anything like this again…happy that we can proceed with remaining Pixhawk features now
