Setting Up Your Three Wheel Localizer

Prerequisites

  • Three odometry wheels connected to motor encoder ports on a hub.

Default Values

These are the default values of the ThreeWheelConstants. You can copy and paste this into your static{} block within LConstants:

ThreeWheelConstants.forwardTicksToInches = .001989436789;
ThreeWheelConstants.strafeTicksToInches = .001989436789;
ThreeWheelConstants.turnTicksToInches = .001989436789;
ThreeWheelConstants.leftY = 1;
ThreeWheelConstants.rightY = -1;
ThreeWheelConstants.strafeX = -2.5;
ThreeWheelConstants.leftEncoder_HardwareMapName = "leftFront";
ThreeWheelConstants.rightEncoder_HardwareMapName = "rightRear";
ThreeWheelConstants.strafeEncoder_HardwareMapName = "rightFront";
ThreeWheelConstants.leftEncoderDirection = Encoder.REVERSE;
ThreeWheelConstants.rightEncoderDirection = Encoder.REVERSE;
ThreeWheelConstants.strafeEncoderDirection = Encoder.FORWARD;

Steps

1. Odometry Wheel Setup

Open the file LConstants and navigate to your static{} block. Configure the following:

  1. Encoder Ports:
    • Replace the ThreeWheelConstants.leftEncoder_HardwareMapName, ThreeWheelConstants.rightEncoder_HardwareMapName, and ThreeWheelConstants.strafeEncoder_HardwareMapName with the names of the ports connected to your encoders.
    • The names will match the hardware map names of the motor port that they are connected to.
  2. Odometry Measurements:
    • Input the ThreeWheelConstants.leftY, ThreeWheelConstants.rightY, and ThreeWheelConstants.strafeX values.
    • These values represent the distance of the odometry wheels from the robot's center of rotation on the robot coordinate grid.
  3. Encoder Directions:
    • The Encoder Directions can be changed by changing the Encoder values for ThreeWheelConstants.leftEncoderDirection, ThreeWheelConstants.rightEncoderDirection, or ThreeWheelConstants.strafeEncoderDirection.
    • Run the Localization Test and observe the encoder values
    • If the x value ticks down when the robot moves forward, reverse the direction of both of the parallel pods (left and right).
    • If the x value stays relatively constant when the robot drives forward, that means that one of the parallel pods (left and right) need to be reversed.
    • If the y value ticks down when the robot strafe left, reverse the direction of the strafe pod.

2. Localizer Tuning

We need to adjust multipliers that convert encoder ticks into real-world measurements (inches or radians). This ensures your localizer's readings are accurate.

a) Forward Localizer Tuner

  1. Position a ruler alongside your robot.

  2. Push the robot forward by the desired distance (default is 48 inches).

  3. The tuner will display two numbers:

    • First number: Distance the robot thinks it has traveled.

    • Second number (multiplier)

  4. (Optional) Run multiple tests and average the multipliers for better accuracy.

  5. Input this value in LConstants as ThreeWheelConstants.forwardTicksToInches = [multiplier], where [multiplier] is the value you obtained from the tuner.

b) Lateral Localizer Tuner

  1. Position a ruler alongside your robot.

  2. Push the robot sideways (strafing) by the desired distance (default is 48 inches).

  3. The tuner will display two numbers:

    • First number: Distance the robot thinks it has traveled laterally.

    • Second number (multiplier)

  4. (Optional) Run multiple tests and average the multipliers for better accuracy.

  5. Input this value in LConstants as ThreeWheelConstants.strafeTicksToInches = [multiplier], where [multiplier] is the value you obtained from the tuner.

c) Turn Localizer Tuner

  1. Position your robot facing a recognizable landmark, like a field tile edge.

  2. Spin the robot counterclockwise for one full rotation (or your desired angle).

  3. The tuner will display two numbers:

    • First number: Distance the robot thinks it has spun.

    • Second number (multiplier)

  4. (Optional) Run multiple tests and average the multipliers for better accuracy.

  5. Input this value in LConstants as ThreeWheelConstants.turnTicksToInches = [multiplier], where [multiplier] is the value you obtained from the tuner.

Congratulations on successfully tuning your localizer!