Setup Servos - rotorflight/rotorflight GitHub Wiki

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The purpose of the servo configuration is to convert the commanded servo angle into servo PWM signal.

In this section you want to adjust the mechanical properties of the servos and the swash plate.

NOTE! Servo limits are for avoiding mechanical issues! DO NOT use servo limits for adjusting maximum roll/pitch/collective. Use mixer min/max for this.

First you should remove the servo arms. The servos could move unexpected. You need to identify what type of servos you have. Typically helicopter collective servos are 1520µs and tail servos 760µs. Servos 1-3 are usually collective servos followed by servo 4 with the tail servo.

If possible, do this initial setup before installing servos to the frame. This prevents defects due to wrong settings. If the servos are already installed detach the servo arms.

To be added: Explanation of servo_pwm_rate.

Connect the Servos to the correct pads in the flight controller. Small servos can usually be powered by the FC onboard BEC, but for larger servos you might need a separate BEC. Setup the servo mixer as required for your particular helicopter. See this page for servo configurations for different type of swashplates.

You should start the initial set up with standard settings and adjust those values later. Use the save bottom often to not lose any adjustments you made.

  1. Go to the Servo Tab in the Rotorflight configurator.

RFC-0.2.0_Servo_Tab

Fill in Servo Center the corresponding us for each servo. In this case Servo 1-3 1520µs and Servo 4 760µs .

Fill in the minimal and maximal servo way. For 1520µs Servos in both fields 500µs and for 760µs servos enter in both fields 250µs.

Fill in the rate for each servo. For 1520µs Servos in both fields 500µs for 760µs in both fields 250µs.

Leave trim, speed fields at 0 and don´t reverse servos at this point.

  1. In the next step we will center the Servos shafts. Testing the servos will (almost always) require the flight controller connected to a battery as they will not work if the FC is just powered by the USB. Connect a battery to a smoke stopper and power up the FC. Be careful as servos could move unexpected. Once the Battery is connected go to the system tab and enable servo Override.

Servo_System_Override_0.1.0.png

Go back to the Servos tab. In the lower part is now a servo override section visible.

RFC-0.2.0_Servo_Tab_Override_Enabled Make sure all Angle fields are at 0 and click on enable Servo 1-4. The servos shafts will now move to the center position. If necessary reverse the servos. All collective servos should work in the same direction. Move the slider left and right and check if the servos are working as expected. If not check if you have the right speed,…

  1. Bring the servos shafts back in the center position and connect the servo arms. Set the arms as close as possible to the 90deg position on the servo.

  2. Use the servo trim field to bring the servo arms to 90 degree position.

  3. If you have adjustable lower linkages now would be a good time to level your swash plate. If your links are not adjustable use the servo trim field to level the swash plate. https://www.youtube.com/watch?v=fGcu8SjIab4

  4. In the next step we want to find the individual mechanical limits of the servos. Move each servo in small steps until the minimum and maximum mechanical travel is reached what the servo/swash plate allows. Do one servo at a time and center the other servos while you are doing this. Don´t worry in this step about to much blade angle. We will limit the movement in the mixer settings.

  5. Check that the combined movement of the servos doesn´t create mechanical problems. Try all min max combinations of the servos you have. E.g. 1 max, 2 min, 3 min + 1 min, 2 max, 3 min+,… If you encounter a mechanical problem reduce the servo travel.

  6. Check that all servos are moving equally. This step is usually not necessary with high quality servos. Add 10deg angle of each servo and check if the swash plate in the new position is leveled. If not adjust the servo rate until you have an equal swash plate movement.

  7. Do the above steps in the same way for your tail servo. In case your tail servo center position is off center you will have smaller and larger ways for one or the other side.

  8. Save all settings and continue with the next step.

Additional information:

As more accurate you do the mechanical set up as easier will the tuning and mixer set up be.

Additionally you can use CLI commands to set up your servos. See CLI Servo Examples).