Idle throttle is too high - hard coded parameters in preconfigured airframes

Hi I am trying to fly a Turnigy micro quad with Pixfalcon and PX4 software.

This is my first time setting up PX4 autopilot. Everything worked out pretty well, except for the idle throttle when the Pixfalcon was armed was too high. With the throttle stick all the way down, the idle thrust is still strong enough to make my quadrotor float (but not taking off).

I am using the latest PX4 firmware available from QGroundControl. I found the manual minimum throttle slider under the tuning tab, but the slider position did not make a difference to me. The idle throttle when the slider was at the left extremity and the right extremity was exactly the same. I tried this using both manual mode and stabilized mode.

Any suggestions on what I can do to solve the problem?

You need to calibrate your ESCs or alternatively manually set the PWM main min parameter in the parameters section to a lower value. Make sure the motors still spin at that value, as you risk to flip the system in-air else.

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Lorenz: Any ideas on different naming for Tuning: Manual minimum throttle? I can see from this thread that it could be confusing as to what this does.

Thank you for your suggestions. I re-flahsed the memory, made sure I got the latest firmware, calibrated ESC and radio again, and set all the PWM_XXX_MIN values to 800 1 by 1(inclduing PWM_AUX_DISARMED, PWM_AUX_MIN, PWM_DISARMED, PWM_MIN under PWM Outputs tab in the parameter tree). But nothing seems to work for me at this stage.

I can make the vehicle heavier as a temporary solution but I think it will be nice if PX4 can handle this problem.

More intuitive description for this slider will be good. The manual flight modes are also confusing to me, I can’t find a clear explanation on what is manual mode for multirotor right now…and how is it different from stabilized mode.

Hi Lorenz: I found out where the problem is. In the airframe selection tab, I chose the Hobbyking Micro PCB under Quadrotor x, which hard set the idle throttle to 1200 PWM. Changing the PWM_MIN parameter does not change this hard-set value.

I switched back to Generic Quadrotor x config, this time I was able to control the idle throttle by changing PWM_MIN.

I think having pre-configured every parameter is nice for ready-to-fly vehicles, but it could be problematic if I decide to customize the vehicle but have no control on these parameters.

What about the Docu that could be improved?

The flight mode description is a bit out of sync with the dev guide:

Regarding Multirotor the User Docu should be accurate at the Moment. There are some plans to perform some changes to the Flight Modes in future releases. The Dev Docu obviously is wrong as for Multirotors there is no (longer a) Mode called Angle, instead there is Stabilized.

Despite the deviation in the Docus regarding your previous Comment: Stabilized is a “Manual” Flight Mode, as is Rattitude and Acro.

@LorenzMeier: Who maintains the Dev Docu?

Thanks for clarifying this. I got confused when I see manual and stabilized mode both being available in the drop down menu.