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DJI N3 - Thrust Spike Question
1179 9 2018-3-27
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MTUDrone
lvl.1

United States
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Hi all,

I have been installing a DJI N3 on a Tarot 650 frame for a senior design project I am working on.  I have been testing the flight controller with my RadioLink AT9S remote control by spinning the motors up without propellers on them, and seeing how they respond to commands.

Pardon me if this is a silly question, I'm an inexperienced drone user.  When testing the throttle, my motors idle as expected at low thrust.  However as I raise my thrust I get no uptick in speed from the motors from a throttle input command of 0% to 57% throttle.  Once my throttle input reaches 58% throttle, the motors all of a sudden spike to 100% speed, and do not get any faster as the throttle input is increased from 58% to 100%.  This observation in motor speed is visualized in the plot I created below (note this was made by visual estimates of motor speed, and is not data taken from the quadcopter):
Drone Thrust Plot.jpg

As an unexperienced drone user, I feel like the motor speed should gradually increase as the throttle input is increased (instead of spiking from idle to 100% motor speed at 57% throttle).  Is something wrong here?  Is this a result of testing with out propellers?  Or does the drone automatically push the motors to full throttle during take off?

Let me know if this is normal or if we have an issue with our throttle input.

Thanks,

Cooper
2018-3-27
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WiSi-Testpilot
lvl.4

Germany
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The throttle is not comparable to that of a model airplane. The easiest way is to use a radio with a self centering throttle stick.

In the first step of the calibration procedure of the sticks the assistant expects all stick in their middle position.

The throttle stick is a multi functional stick:

1) With the CSC the motors start up. After that, all sticks are in the middle again and the engines rotate with the preset idle speed.

2) Now give full throttle and the copter will take off.

3) Now you release the gas stick back to the middle position and the copter is in position hold.

4) If you now move the gas stick from the center, the copter drops or rises in proportion to the deflection of the stick.

Sorry for my bad English,
best regards,
Wilhelm

2018-3-27
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DJI Susan
Administrator

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It is a normal phenomenon. On the ground, the speed will reach 100% if the sticks input more than 50%. This will not happen after take-off.
2018-3-27
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upsdude9351
lvl.2
Flight distance : 3704 ft
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HI,,,New builder here too and I was having the same issues with the same controller and radio,,,, came abut that my initial radio calbration needed to be redone,,,,, and if you go into the advanced parameters of that radio,, I set the maximum values of 65 on the "throttle curve out" 100 on "stick" and when you go back into calibration,,I had slow full range motion of throttle,,, hope this helps,,,  worked for me as far as slowing her down!
2018-3-29
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Multirotor77
lvl.2

Malta
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Hi Cooper,

I am experiencing exactly the same throttle issue (spike just over the middle of the throttle throw) on my quad with an N3 flight controller, E800 propulsion system and a Taranis x9D plus transmitter. I would really appreciate if you could share how you got the throttle to respond gradually and smoothly.  Any other inputs from anyone else are very welcome. To date I have only tested the quad under tied down conditions.

Cheers
2018-11-20
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MTUDrone
lvl.1

United States
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Multirotor77 Posted at 11-20 15:07
Hi Cooper,

I am experiencing exactly the same throttle issue (spike just over the middle of the throttle throw) on my quad with an N3 flight controller, E800 propulsion system and a Taranis x9D plus transmitter. I would really appreciate if you could share how you got the throttle to respond gradually and smoothly.  Any other inputs from anyone else are very welcome. To date I have only tested the quad under tied down conditions.
Glad to help!  DJI Susan was right on the money, it was throttling to 100% because but it was tied town and wasn't rising.  Once the copter gains some height, the N3 flight system senses the vertical acceleration/height gain, and it drops the motor speeds down to hover level if your stick is around 50%.  From what I found, it guns the RPM up until it gets a response to get it off the ground in a swift/safe motion.  Since you're copter (and mine at the times are tied down, it doesn't sense a response and keeps commanding the motors to give max power to try and get "off the ground".  It also doesn't know how much weight you're carrying with it, so gunning it at 100% also ensures your copter gets off the ground as long as it's not carrying more than it's 100% max carry weight.  Hope that helps!  Let me know if you've got any other questions.
2018-11-20
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Multirotor77
lvl.2

Malta
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MTUDrone Posted at 11-20 15:55
Glad to help!  DJI Susan was right on the money, it was throttling to 100% because but it was tied town and wasn't rising.  Once the copter gains some height, the N3 flight system senses the vertical acceleration/height gain, and it drops the motor speeds down to hover level if your stick is around 50%.  From what I found, it guns the RPM up until it gets a response to get it off the ground in a swift/safe motion.  Since you're copter (and mine at the times are tied down, it doesn't sense a response and keeps commanding the motors to give max power to try and get "off the ground".  It also doesn't know how much weight you're carrying with it, so gunning it at 100% also ensures your copter gets off the ground as long as it's not carrying more than it's 100% max carry weight.  Hope that helps!  Let me know if you've got any other questions.

That's very reassuring and I really appreciate your help.  By any chance after the throttle response to stick input settles down, did you have any difficulty landing the Tarot (same as mine) safely and smoothly back on the ground? Once again Many many Thanks and Cheers.
2018-11-21
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MTUDrone
lvl.1

United States
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Multirotor77 Posted at 11-21 02:02
That's very reassuring and I really appreciate your help.  By any chance after the throttle response to stick input settles down, did you have any difficulty landing the Tarot (same as mine) safely and smoothly back on the ground? Once again Many many Thanks and Cheers.

Didn't have any noticeable issues landing the drone once we got it up in the air and working!  Be careful if you're flying in strong wind, had a few issues landing it in that as it was kind of skipping along the ground and blowing as it landed.  Eventually realized committing to the landing is the safest bet.  As soon as the copter is about to touch the ground, drop the control stick to 0 throttle (instead of trying to gently lower the throttle upon landing).
2018-11-21
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Multirotor77
lvl.2

Malta
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MTUDrone Posted at 11-21 09:25
Didn't have any noticeable issues landing the drone once we got it up in the air and working!  Be careful if you're flying in strong wind, had a few issues landing it in that as it was kind of skipping along the ground and blowing as it landed.  Eventually realized committing to the landing is the safest bet.  As soon as the copter is about to touch the ground, drop the control stick to 0 throttle (instead of trying to gently lower the throttle upon landing).

Thanks alot for sharing your experience, especially with landing the craft, that's very reassuring once more. It seems it's now time for me to take the plunge.
2018-11-23
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Multirotor77
lvl.2

Malta
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MTUDrone Posted at 11-21 09:25
Didn't have any noticeable issues landing the drone once we got it up in the air and working!  Be careful if you're flying in strong wind, had a few issues landing it in that as it was kind of skipping along the ground and blowing as it landed.  Eventually realized committing to the landing is the safest bet.  As soon as the copter is about to touch the ground, drop the control stick to 0 throttle (instead of trying to gently lower the throttle upon landing).

I am trying to set Failsafe/RTH on my Taranis. I set RTH on Channel 5 and set Flight modes on Channel 6. When I am assigning the channels in DJI Assistant, everything seems to be working fine on the Channel selection page, but when failsafe/RTH switch is activated and channel changes status it is not overriding the flight mode setting and the flight controller is remaining in the set flight mode. I saw some videos where they set flight modes and failsafe on the same channel for a DJI NAZA v2 controller but could not find how to do this for the N3. Will appreciate if you let me know how to sort this out. Cheers.
2018-12-4
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