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On my controller for my drone there are 4 buttons:

  • Forward fine-tuning
  • Left fine-tuning
  • Back fine-tuning
  • Right fine-tuning

What is “fine-tuning” and how does one decide what direction to “fine-tune” in?

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  • $\begingroup$ I think more details would be useful. Like: What kind of controller is it? $\endgroup$
    – Jacob B
    Commented Apr 21, 2020 at 5:28
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    $\begingroup$ @JacobB it’s not a specific type, just a general controller that came with the drone $\endgroup$
    – user149
    Commented Apr 21, 2020 at 5:29
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    $\begingroup$ then it is probably to adjust the pitch and roll control. For example, if the drone was in level mode and hovering but was going backward, you could press forward fine-tune to have it pitch ever so slightly forward so that it doesn't go backward anymore. And if it was drifting right, you could press left fine-tune. $\endgroup$
    – Jacob B
    Commented Apr 21, 2020 at 5:33
  • $\begingroup$ Sounds kind of like "trim" switches. Forward and backward would be pitch trims. Left and Right would be roll. Left and Right might also be Yaw, but if there are only those four, my guess (without seeing the controller) is that the trims are for pitch and roll adjustments. $\endgroup$
    – Schome1
    Commented Apr 21, 2020 at 12:47

4 Answers 4

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Generally, the term for this is "trim". It is used to slightly adjust the center position of the stick on a controller. If the craft is moving slightly to one direction without you putting any input to the controller, then you would adjust the trim for that stick so that the craft remains stable without stick input. These adjustments are more commonly needed on RC planes without a flight controller to adjust for slightly off control surface servos. It can also be used to correct for a drifting gimbal in the controller.

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Yes, this is the poorly labeled, poorly translated trim option. It allows simple "in the moment" tuning of the performance. while flying. Most prebuilt or toy grade quads will have this option on the controller labeled in some 'creative' fashion like 'fine-tuning' or whatever. However, they are often guilty of offering virtually no explanation of the feature and its usage, or the instructions are so badly converted from Chinese that they make so real sense at all.

Others have posted here that you can just nudge your craft's point of balance in a hover in any direction you need to. If it's pulling left, you trim it right, etc..

However, many quads are affected by the following details:

  • These trim settings are often lost/forgotten/reset after powering down the craft. They are not saved as the unit calibrates on every power-up.

  • The flight controllers on most craft will actually do a level accelerometer calibration on the gyro when first powering up. So if you place the quad on a non-level surface and power it up, it will have an improper tune as it will "zero" the gyro to that angle and tend to drift (which of course can be compensated for using trim if needed.) Many instructions will vaguely say: "place the copter on a flat surface when powering up" or some terrible translation of this.

My son and I currently have 3 small "store-bought" quads we use for practicing/indoor flight and they are all different makes and models but they all exhibit this exact kind of behavior so I have to think it's a standard approach.

If you have a hobby-grade mainstream flight controller, the calibration setting is usually stored and only needs to be done once. I do this on my large quad by completely physically leveling it on the bench using a carpenters level on both forward/reverse and left/right axis (shimming it up with paper/pennies etc until is completely level) then, in the software, run the "calibrate accelerometer" option which takes about 2 seconds and then stores it in the flight controller. After that, you are good and should NOT run it again unless you change something physical in the copter. This done right will ideally make you able to fly well with zero trim adjustments.

This all, of course, depends on the quadcopter you have.

Cheers.

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These fine-tuning switches, called trim, allow a pilot to adjust the value sent by the transmitter when any given stick axis is centered.

For RC aircraft, the value of an axis is some number between 1000 and 2000 (units of µs or microseconds, because PWM receivers output PWM pulses with this duration). A value of 1500 is said to be a centered axis. When setting up a new radio, one of the first steps is to calibrate the center point of each axis so it sends 1500. An improperly calibrated center point, as @JacobB explains, can result in the drone pitching or rolling when the pilot isn't commanding any movement. Radios which use potentiometer gimbals are susceptible to having this calibration slip over time, which is why recalibrating the center point of a radio's gimbals is a fairly common maintenance step. Hall-effect gimbals are far less susceptible to this.

For multirotor builds using Betaflight, this can be accomplished by reading out the values in the "Receiver" tab of the configurator application.

enter image description here

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As stated in my comment, these fine-tuning buttons are for adjusting the pitch and roll control of the drone. (trim)

  • If the drone drifts forward, push the back fine-tune.
  • If the drone drifts backward, push the forward fine-tune.
  • If the drone drifts left, push the right fine-tune.
  • If the drone drifts right, push the left fine-tune.

It's essentially the alternative found on cheaper drones to recalibrating the gimbals.

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