Auto Mode- Change The Initial Spool Up / Take Off Speed

(Bobby Watts) #1

Hello, I have looked all over for an answer to this but haven’t found anything yet…

My question pertains to a fully auto mission. Flying a big hexacopter (about 55lbs) and what I’m finding is that as soon as I initiate a mission on the ground (aircraft is on the ground, motors not even spinning), the motors spool up quite fast and the aircraft launches off of the ground quite fast. It then goes into a nice stable vertical climb.

So my question is not how to slow down the climb rate, which I assume would be (WPNAV_SPEED_UP), my question is how do I slow down the initial takeoff speed itself? Any way to slow down this initial acceleration into flight? The actual climb rate itself is perfect and I don’t want to adjust that.

Running the latest Hex Copter firmware with a 2.1 Cube.

Thank you!

(Mike Boland) #2

That is the correct method it should follow.
This has been discussed by the Dev’s and the behaviour you see is to ensure there is no ‘I’ term buildup during the spool up and takeoff.

If you let a copter spool up slowly then the Nav controller can build up a slight deviation from position and as the copter attempts to lift off slowly it will try correcting its position, much to it’s detriment and anything around it.

So although the speed of launch is a bit daunting, especially for large copters, it is the best way to achieve a trouble free lift off.

If in doubt, arm in Loiter and try a slow pinup and takeoff.
Don’t be near the copter.

(Bobby Watts) #3

Hey thanks for the reply - much appreciated. I can understand their concern. Just curious if the devs would ever put in a parameter to change this speed? I know it is very possible for this aircraft to lift off gently and smoothly, as it has done it hundreds of other times with ‘other’ flight controllers. Would really love to see this if at all possible…


1 Like

@rmackay9 any thoughts on a smoother takeoff for Bobby?

(Rick) #5

Lowering WPNAV_ACCEL_Z will decrease vertical acceleration. This can make it a bit less aggressive.

(Randy Mackay) #6

@Anubis’s advice good I think. If you’d like to slow down how quickly the motors spool up these two parameters may help as well:

  • MOT_SPOOL_TIME: Time in seconds to spool up the motors from zero to min throttle
  • MOT_SLEW_UP_TIME: Time in seconds to slew output from zero to full. This is used to limit the rate at which output can change. Range is constrained between 0 and 0.5.
1 Like

Thanks guys!

(Bobby Watts) #8

Thanks for the reply everyone! Will give it a shot and report back…

1 Like