FRC 2019

Team 254's 2019 FRC robot code for Backlash. Backlash's code is written in Java and is based off of WPILib's Java control system.

The code is divided into several packages, each responsible for a different aspect of the robot function. This README explains setup instructions, the function of each package, and some of the variable naming conventions used. Additional information about each specific class can be found in that class' Java file.

Setup Instructions

General

1. Clone this repo
2. Run ./gradlew to download gradle and needed FRC/Vendor libraries
3. Run ./gradlew tasks to see available options
4. Enjoy!

Visual Studio Code (Official IDE)

1. Get the WPILib extension for easiest use from the VSCode Marketplace - Requires Java 11 or greater
2. In .vscode/settings.json, set the User Setting, java.home, to the correct directory pointing to your JDK 11 directory

IntelliJ

1. Run ./gradlew idea
2. Open the FRC-2019-Public.ipr file with IntelliJ

Eclipse

1. Run ./gradlew eclipse
2. Open Eclipse and go to File > Open Projects from File System...
3. Set the import source to the FRC-2019-Public folder then click finish

Basic Gradle Commands

• Run ./gradlew deploy to deploy to the robot in Terminal (*nix) or Powershell (Windows)
• Run ./gradlew build to build the code. Use the --info flag for more details
• Run ./gradlew test to run all of the JUnit tests

Code Highlights

• Path following with an adaptive pure pursuit controller and motion profiling

  To control autonomous driving, the robot utilizes an adaptive pure pursuit controller to control steering and a custom trapezoidal motion profile generator and follower to control velocity.

• Motion planner that constrains superstructure motion to within the frame perimeter

  To keep the superstructure within the frame perimeter during movements that may be dangerous, the robot follows a tuck motion planner, named because it tucks the wrist down before moving the rest of the superstructure, until it is safe to untuck.

• Limelight-based vision system for target detection

  The robot used 2 Limelights, toggled through a manager class, to find and track vision targets. Information about targets were used to auto steer the robot towards vision targets through a P feedback loop, which was used mainly for driving to the loading station, or to auto aim the turret for scoring on the rockets and cargo ship.

• Prismatic superstructure motion to mimic a linear actuator

  The robot used the vision system to identify the scoring position, and synchronized the arm and elevator motion to move the end effector forward, while maintaining the same wrist angle and height. This allowed the robot to score over defenders.

• Suction climbing through a state machine

  The robot's suction climbing mechanism at the FIRST Championship in Houston was controlled through a state machine, that regulated each step of the climbing process. The suction was created through a vacuum with feedback about the pressure provided through a digital pressure switch.

• Field relative turret

  To allow for easier and more accurate use of the turret, the turret could be controlled relative to the field, which uses the robot's gyro heading to turn to cardinal directions.

Package Functions

• com.team254.frc2019

  Contains the robot's central functions and holds a class with all numerical constants used throughout the code (see Constants.java). For example, the Robot class controls all routines depending on the robot mode. In addition, the RobotState class keeps track of the current position of the robot's various frames of reference.

• com.team254.frc2019.auto

  Handles the execution of autonomous routines and contains the actions and modes packages.

• com.team254.frc2019.auto.actions

  Contains all actions used during the autonomous period, which all share a common interface, Action (also in this package). Examples include driving paths, auto aiming the turret and scoring, and auto steering. Actions interact with the subsystems, which in turn interact with the hardware.

• com.team254.frc2019.auto.modes

  Contains all autonomous modes. Autonomous modes consist of a list of autonomous actions executed in a specific order.

• com.team254.frc2019.controlboard

  Contains code for the driver to use either joysticks or gamepad and the operator to use a gamepad. Also contains a wrapper class specifically for Xbox controllers (see XboxController.java).

• com.team254.frc2019.loops

  Contains codes for loops, which are routines that run periodically on the robot, such as for calculating robot pose, processing vision feedback, or updating subsystems. All loops implement the Loop interface and are handled (started, stopped, added) by the Looper class, which runs at 100 Hz. The Robot class has one main looper, mEnabledLooper, that runs all loops when the robot is enabled.

• com.team254.frc2019.paths

  Contains all paths that the robot drives during autonomous mode. Each path is made up of a list of Waypoint objects. The PathBuilder class, which is also included in this package, transforms these waypoints into a series of Arc and Line objects.

• com.team254.frc2019.planners

  Contains various planners for superstructure motion to avoid superstructure collisions with itself or the drivebase.

• com.team254.frc2019.statemachines

  Contains the state machines for the end effector, overall superstructure, and two climbing mechanisms.

• com.team254.frc2019.states

  Contains states and other classes used in various subsystem and state machine classes.

• com.team254.frc2019.subsystems

  Contains code for subsystems, which are consolidated into one central class per subsystem, all of which extend the Subsystem abstract class. Each subsystem uses state machines for control and is a singleton, meaning that there is only one instance of each. Subsystems also contain an enabled loop, a read periodic inputs method, and a write periodic outputs method, which are controlled by the SubystemManager class.

• com.team254.lib.control

  Contains all the classes used for the robot's path following. The robot's steering is controlled by the AdaptivePurePursuitController class.

• com.team254.lib.drivers

  Contains a set of custom classes for motor controllers (TalonSRX's and Spark MAX's) that include classes for creating motor controllers with factory default settings, handling errors, reducing CAN Bus usage, and checking motors.

• com.team254.lib.geometry

  Contains a set of classes that represent various geometric entities.

• com.team254.lib.motion

  Contains all motion profiling code used for autonomous driving. Trapezoidal motion profiles are used for smooth acceleration and minimal slip.

• com.team254.lib.physics

  Contains the DriveCharacterization class which represents the characterization for specifically a differential drivetrain. While this class did not end up being used during this season, it differs from 2018, so is being released, nonetheless.

• com.team254.lib.util

  Contains a collection of assorted utilities classes used in the robot code. Check each file for more information.

• com.team254.lib.vision

  Contains various classes that help with tracking and storing information about vision targets.

• com.team254.lib.wpilib

  Contains parent classes of the main Robot class that get rid of loop overrun and watchdog print messages that clutter the console.

Variable Naming Conventions

• k*** (i.e. kDriveWheelTrackWidthInches): Final constants, especially those found in the Constants.java file
• m*** (i.e. mPathFollower): Private instance variables