HelixFollower

HelixFollower is a path following command used to follow paths generated by BobTrajectory using the FRC Java Command Structure.

Set up dependencies

1. Add the following to your build.gradle, This allows you to pull the dependencies needed from a github repository:

   repositories {
      jcenter()
      maven { url "https://jitpack.io" }
   }

2. Add these lines to the dependencies block:

    compile 'com.github.TripleHelixProgramming:HelixUtilities:master-SNAPSHOT'
    compile 'com.github.Team319:BobTrajectory:master-SNAPSHOT'

Integrating into your robot

To integrate the path follower into our robot you will need to create a class that extends HelixFollower and implement the required methods.

public class PathFollower extends HelixFollower {

    private Drivetrain drivetrain = Drivetrain.getDrivetrain();

    // These are the 2 PID controllers that will handle error for your total travel distance and heading
    private PIDController headingController = new PIDController(15, 0, 0, 0.001);
    private PIDController distanceController = new PIDController(10, 0, 0, 0.001);

    public PathFollower(Path path) {
        super(path);
        // Make sure to require your subsystem so you don't have conflicting commands
        requires(drivetrain);
    }

    @Override
    public void resetDistance() {
        // We need to reset the encoders back to 0 at the start of the path
        drivetrain.resetEncoders();
    }

    @Override
    public PIDController getHeadingController() {
        // Here we return the PID controller that we're using to correct the heading error through the path
        return headingController;
    }

    @Override
    public PIDController getDistanceController() {
        // Here we return the PID controller that we're using to correct the distance error through the path
        return distanceController;
    }

    @Override
    public double getCurrentDistance() {
        // Here we need to return the overall robot distance traveled in FEET in this example we are averaging 
        // the two sides of the drivetrain to give is the robot's distance travelled
        return (drivetrain.getLeftPosition() + drivetrain.getRightPosition()) / 2.0;
    }

    @Override
    public double getCurrentHeading() {
        // Here we need to return the current heading of the robot in RADIANS (positive counter-clockwise).
        return Math.toRadians(drivetrain.getHeading());
    }

    @Override
    public void useOutputs(double left, double right) {
        // Here we will use the values in FPS and send them off to our drivetrain. In this example the max velocity
        // of our drivetrain is 12 FPS. We are dividing the two provided parameters by the max veocity to convert them
        // into a percentage and sending them off to our drivetrain.
        drivetrain.setRawPercentOutput(left/12.0, right/12.0);
    }
}

Running Paths

To run a path you'll create a new PathFollower instance and pass in the desired path to run.

autonomousCommand = new PathFollower(new RightTurn());