Configuring AutoBuilder for FRC Pathplanner (What is a ramsete/LTV/Holonomic controller?)

Technical Programming
1

I was interested in using PathPlanner lib to create autonomous paths using a nice GUI.

I had some code in RobotContainer that looked like this:

  public Command getAutonomousCommand() {
    PathPlannerPath path = PathPlannerPath.fromPathFile("chargestation");
    // An example command will be run in autonomous
    return AutoBuilder.followPathWithEvents(path);
  }

Of course, this wouldn’t run because I hadn’t configured the AutoBuilder yet.

So while looking at the docs on the github page, I was on Build An Auto page when I saw 3 different ways of configuring the AutoBuilder.

They were all very confusing; I don’t know what a ramsete, LTV or a Holonomic controller was, and looking at WPILib documentation confused me even more.

I think I need to use a Ramsete controller? But the AutoBuilder.configureRamsete() parameters confused me, what’s a poseSupplier, resetPose, speedsSupplier, and all of these other

Thanks for any help.

2

Not entirely sure what LTV is but ramsete is a “tank” style drivetrain where the speeds outputted by pathplanner are for the left and right sides of your robot, where holonomicmis for something more akin to swerve

3

Thanks I’m pretty sure now that I need to use a ramsete controller, as our test robot is a tank drive.

However, when I call AutoBuilder.configureRamsete(), I’m overwhelmed by the amount of parameters. For example: what’s a poseSupplier, resetPose, speedsSupplier etc.

To clarify, I’m not asking about what type or object to use, vscode already tells me this, for example the poseSupplier is a Supplier, but what even is a Supplier<>? How am I supposed to figure out what to put here?

4

Not entirely sure about the new pathplanner but I can’t imagine it’s changed, usually that would be a method that returns the robot’s pose2d, a method to reset that pose, etc

5

The API docs explain what they are, fyi:

You may need some block diagrams to understand what they’re saying about the controller inputs and outputs, but unfortunately I don’t have any.

It’s a function that takes no arguments and returns a value. This can be either a member function or a lambda (inline function). Supplier (Java SE 17 & JDK 17)

1 Like
6

Thanks for your explanation, are there any classes/methods etc I can use to determine this data, or must I implement them myself?

7

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