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PathPlanner Documentation

repository·main·Indexed 19 days ago

https://github.com/mjansen4857/pathplanner

A motion profile generator for FRC robots featuring Bézier-curve-based paths, autonomous routine management, and real-time telemetry. Includes PathPlannerLib for robot code integration with support for Java, C++, and Python, as well as a Flutter-based application for path creation. Key features include FollowPathCommand for trajectory execution, PathfindingCommand for navigating to poses or paths, and a flexible CommandGroup system for sequencing autonomous behaviors.

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What's inside PathPlanner

  1. Overview of PathPlanner features

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    PathPlanner is a motion profile generator for FRC robots (created by team 3015) that provides the following capabilities:

    • Path Generation: Uses Bézier curves for fine-tuned path shaping.
    • Holonomic Support: Decouples robot rotation from direction of travel.
    • Real-time Feedback: Includes real-time path preview and real-time path following telemetry.
    • Event Markers: Allows placing markers along a path to trigger specific code during execution.
    • Modular Routines: Build autonomous routines by composing multiple paths.
    • PathPlannerLib Integration:
      • Robot-side vendor library for path generation and custom controllers.
      • Full autonomous command generation via the PathPlannerLib auto builder.
      • Automatic pathfinding using AD*.
    • Workflow Efficiency: Automatic file management, hot reload (update paths/autos on the robot without redeploying), and automatic saving.

  2. Use the Project Browser to manage paths and autos

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    The Project Browser is the main interface for managing and opening path and auto files. The interface is split into two sections: paths on the left and autos on the right. You can adjust the relative size of these sections by dragging the handle between them.

    Key features include:

    • Sorting: Both paths and autos have independent sorting options.
    • UI Modes: Both sections can be toggled between default and compact UI modes.
    • Creation: Use the icon buttons in the top right of each section to create new folders or new paths/autos.

  3. Define autonomous routines using Autos

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    In PathPlanner, Autos are used to define complete autonomous routines. An auto is structured as a sequential command group containing various types of commands:

    • Path following commands: Allows you to select and reuse any path defined in the project.
    • Named commands: Corresponds to the names used in path event markers.
    • Wait commands: Pauses the routine.
    • Nested command groups: Allows for complex, hierarchical routine structures.

    Integration Options:

    1. Auto Builder (Recommended): Load the auto as a full autonomous command in your robot code using PathPlannerLib's auto builder functionality.
    2. Path Groups: If not using the auto builder, you can use the auto files in PathPlannerLib to retrieve a path group or a list of paths contained within the auto (similar to the legacy path group system).

  4. Understand Path and Waypoint concepts

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    In PathPlanner, a Path represents a single continuous motion segment (e.g., driving from a start point to a game piece). Multiple paths can be chained together to form an autonomous routine.

    Waypoints define the shape of the spline the robot follows within a path. Each waypoint consists of:

    • Anchor Points: The exact $(X, Y)$ position on the field (in meters) that the spline passes through.
    • Control Points: Points used to define the heading (tangent) and fine-tune the spline shape via their distance from the anchor point.

    Key Waypoint Operations:

    • Add: Double-click on the field in the path preview to add a waypoint to the end of the path.
    • Edit: Click and drag waypoints in the path preview or use the Waypoints Tree.
    • Link: Use the Link Waypoint Button to give waypoints a shared name. Updating one linked waypoint updates all others with that name across all paths.

  5. Configure Event Markers and Triggers

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    Event markers trigger commands at specific points along a path.

    Non-Zoned Events

    • The command is triggered when the robot reaches the marker.
    • The trigger goes true for one loop.
    • The command is not canceled unless it is still running when the path ends.

    Zoned Events

    By checking the Zoned Event Checkbox, you create a region with a start and end position.

    • Start Position Slider: The waypoint relative position where the event begins.
    • End Position Slider: The waypoint relative position where the event ends.
    • The associated command is scheduled/canceled based on the robot's position within this zone.

    Note: When a path ends, all commands triggered via event markers are commanded to end. To run a command at the end of a path, place it at the start of the next path or use Autos.

  6. Configure Global Constraints

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    Global Constraints define the kinematic limits of the robot for the entire path, used whenever a specific Constraint Zone is not active. These can be edited via the Global Constraints Tree.

    Available Parameters:

    • Max Velocity: Maximum velocity in meters/sec.
    • Max Acceleration: Maximum acceleration in meters/sec².
    • Max Angular Velocity: Maximum angular velocity in degrees/sec.
    • Max Angular Acceleration: Maximum angular acceleration in degrees/sec².
    • Nominal Voltage: The expected battery voltage (volts). This helps limit speeds during voltage sags (e.g., when using a shooter).
    • Use Default Constraints: Toggles connection to the default constraints in the settings menu.
    • Unlimited: If enabled, the robot moves as fast as torque allows, ignoring velocity/acceleration limits.

  8. How to override controller feedback in PPHolonomicDriveController

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    In certain scenarios, such as targeting a specific game piece, you may need to override the default controller feedback during path following. You can do this by providing a function to the PPHolonomicDriveController class that supplies custom feedback for X position, Y position, or rotation.

    Important Considerations:

    • These are static methods, meaning an override applies to all path following commands currently in use.
    • The provided function is called every loop. Ensure your logic is efficient.
    • You must manually clear the feedback override functions when you no longer want to use custom feedback to avoid unintended behavior.

  9. Use Point Towards Zones

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    Point Towards Zones force the robot to aim at a specific field coordinate while traveling through a designated segment of the path.

    Configuration:

    • Field Position X/Y: The target coordinates on the field in meters.
    • Rotation Offset: An additional rotation (degrees) added to the target angle (e.g., to point away from a target).
    • Start Position Slider: Relative waypoint position where the zone begins.
    • End Position Slider: Relative waypoint position where the zone ends.

  10. Use Event Triggers to bind commands to event markers

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    Event Triggers allow you to bind commands to specific event markers defined in PathPlanner. This provides more flexibility than standard named commands, enabling you to:

    • Bind commands to the start or end of a zoned event.
    • Run a command only while the robot is within a specific zoned event.
    • Combine multiple event triggers to handle overlapping zones.
    • Combine event triggers with other triggers (like subsystem conditions) for complex logic.

    Warning: If you bind a command to an EventTrigger that shares requirements with commands in the auto command group, the auto command group will be interrupted when the EventTrigger is triggered.

    from pathplannerlib.events import EventTrigger

# Bind a command to run while an event is active
EventTrigger('run intake').whileTrue(cmd.print('running intake'))

# Combine an event trigger with a subsystem condition
EventTrigger('shoot note').and(Trigger(self.exampleSubsystem.someCondition)).onTrue(cmd.print('shoot note'))

  11. How the Swerve Setpoint Generator works

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    The SwerveSetpointGenerator is a tool used to calculate safe swerve module targets. It takes a prior setpoint and a desired setpoint, then outputs a new setpoint that respects the robot's physical kinematic constraints.

    Key features include:

    • Torque-limited acceleration: Module acceleration is constrained by the maximum torque the motor can output.
    • Friction-aware torque: Maximum module torque is limited by the friction between the wheels and the carpet to prevent wheel slip.
    • Centripetal force limiting: Module rotation is limited to ensure centripetal force stays within the friction limits, preventing sliding during curves.
    • Internal friction compensation: Accounts for internal module friction, which affects maximum acceleration and deceleration capabilities.