Relative Servos

How to add the Relative Servos robot skill

  1. Load the most recent release of ARC (Get ARC).
  2. Press the Project tab from the top menu bar in ARC.
  3. Press Add Robot Skill from the button ribbon bar in ARC.
  4. Choose the Servo category tab.
  5. Press the Relative Servos icon to add the robot skill to your project.

Don't have a robot yet?

Follow the Getting Started Guide to build a robot and use the Relative Servos robot skill.

How to use the Relative Servos robot skill

This skill is similar to the Horizontal and Vertical servo skills. However, the difference between this skill and the others is that it allows you to specify a Master Servo. The slave servos will move into relative positions of the Master. If you move the master servo from ANY skill, the slave servos will move to their relative positions. You can use scripting or the checkbox to Pause and Unpause this skill whenever you like, preventing the slave servos from moving.

Note that servo selection of all robot skills also has an Advanced button to select multiple servos. That option may be preferred over this robot skill. You can read about it here.

If the ratio of 2 is used in the Relative Servos skill settings, the relative servo will move double the master's value. Here's an example:

If the master is in position ten and the slave ratio is 2, the slave will move to position 20.

Ratios can also be in decimal format. That means you can have a ratio of 2.5. For example, 2.5 times 10 is 25. If the Master were in position 10, the slave would be in position 25.

Lastly, ratios can be negative values as well. This is done by putting a minus sign in front of the number. Such as -2.

*Note: The slave position will never be lower or higher than its min/max limits.

Main Window

1. Servo Slider
Press and hold the left mouse button down in this area to adjust the servo slider value. The servo slider value will be displayed here, and it will be between the minimum and maximum servo positions set up in the skill settings.

2. Pause Checkbox
This checkbox will enable/disable the operation of the relative servos.


1. Title Field
This field contains the title of the skill. You can change it if you'd like. *Note: Changing the title will also change the title in the controlCommand() associated with this skill.

2. Master Servo Settings
This section allows you to set up the Master servo movement parameters such as servo port, board index, servo configuration, max/min degree limitations, and inverted direction.

3. Relative Servos Settings
This section allows you to set up the Relative servos movement parameters such as servo port, board index, servo configuration, max/min degree limitations, and inverted direction.

4. Add Servo Button
This button attaches a new relative servo to the Master servo. Once added, it appears in the relative servos settings section.

How to use Relative Servos

1) Add the Relative Servos skill to your ARC project (Project -> Add Skill -> Servo -> Relative Servos).

2) Set up your Master servo and add a relative servo or two in the skill settings. Adjust the relative servo settings as well.

3) In the Main Window, adjust the Master servo position and watch as the relative servos move.



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Wow how come I never saw this before, simple but effective for multiple servos ,head arms etc..