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Estimating the Position of the Arm

For this tutorial, our OpMode is named HelloRobot_ArmEncoder!

Estimating the Position of the Arm using Telemetry

Let's start by creating a simple program for moving our robot's arm. The one below will look very similar to the code created during Part 2: Robot Control!

Adding Telemetry

Finding the Position with Telemetry

Save the OpMode and run it.

Use the gamepad commands to move the arm to the 90 degree position. Once you have the arm properly positioned read the telemetry off the Driver Hub to determine the encoder count relative to the position of the arm.

Remember that the encoder position is set to 0 each time the Control Hub is turned on! This means that if your arm is in a position other than the starting position when the Control Hub is turned on, that position becomes zero instead of the starting position.

Adding RUN_TO_POSITION to the Program

Lastly, we can remove the final "else" of our statement for now since we are now using RUN_TO_POSITION mode.

Despite our power being a positive value for both directions, the arm will move up or down based on the set position!

Testing the Program

If you try running this code you may notice that the arm oscillates around the 90 degree position. When this behavior is present you should also notice the telemetry output for the encoder counts fluctuating.

Recall RUN_TO_POSITION is a Closed Loop Control, which means that if the arm does not perfectly reach the target position, the motor will continue to fluctuate until it does. When motors continue to oscillate and never quite reach the target position this may be a sign that the factors determining tolerances and other aspects of the closed loop are not tuned to this particular motor or mechanism.