Editing Paths & Autos
In PathPlanner, paths are used to create one continuous motion from some start point to an end point. In other words, each path describes a singular segment of an autonomous routine. For instance, driving from the start point to pick up a game piece, driving from the game piece to a scoring position, and driving from the scoring position to an end position are all separate paths. Paths defined this way can be chained together and reused in the modular auto system.
Within paths, waypoints are the positions on the field the define the shape of the spline that the robot will follow. Each waypoint consists of two types of points: anchor points and control points. Anchor points define the exact position that the spline will pass through, and control points are used to define the heading, or tangent, of the spline as well as to fine-tune the shape of the spline via the control point's distance from its associated anchor point.
Waypoints can be added to a path by double-clicking on the field within the path preview. A new waypoint will be added to the end of the path at the clicked location. Waypoints can be edited by click and drag in the path preview, or via the waypoints tree.
Waypoints Tree:
- Lock Button: Locks the waypoint to prevent it from being changed by dragging it around in the path preview. This will still allow the control point lengths to be changed via click and drag.
- Delete Button: Delete the waypoint from the path.
- X Position: X Position of the waypoint's anchor point on the field in meters.
- Y Position: Y Position of the waypoint's anchor point on the field in meters.
- Heading: The heading, or direction of travel, of the robot while passing through this point in degrees.
- Previous Control Length: The distance between the anchor point and the previous control point in meters.
- Next Control Length: The distance between the anchor point and the next control point in meters.
- Insert New Waypoint After Button: Inserts a new waypoint after the selected waypoint.
Global Constraints define the kinematic constraints of the robot along the entire path. These constraints will be used anywhere that is not covered by a constraints zone. The global constraints can be edited via the Global Constraints tree.
Global Constraints Tree:
- Max Velocity: The maximum velocity of the robot in meters/sec.
- Max Acceleration: The maximum acceleration of the robot in meters/sec^2.
- Max Angular Velocity: The maximum angular velocity of the robot in degrees/sec. This is only available when holonomic mode is on.
- Max Angular Acceleration: The maximum angular acceleration of the robot in degrees/sec^2. This is only available when holonomic mode is on.
The goal end state defines the target state of the robot when the path ends. This can be edited via the goal end state tree, or the rotation (holonomic mode only) can be edited via click and drag in the path preview.
Goal End State Tree:
- Velocity: The velocity that the robot should end the path with, in meters/sec. Non-zero velocities means that the robot will not stop at the end point.
- Rotation: The goal rotation for the robot at the end of the path, in degrees. Only available when holonomic mode is on.
Rotation targets define points along the path where the robot should target a given rotation. When path following, the robot will look ahead for the next rotation target, then attempt to rotate to its associated rotation. Rotation targets can be edited in the rotation targets tree. This is only available when holonomic mode is on.
Rotation Targets Tree:
- Rotation: The rotation that should be targeted, in degrees.
- Position Slider: Controls the rotation target's waypoint relative position along the path.
Event markers define points along the path where other commands should be triggered while path following. Each event marker has a command group associated with it that can be used to build more complex functionality via adding named commands, wait commands, and nested command groups. Event markers can be edited via the event markers tree.
Event Markers Tree:
- Position Slider: Controls the event markers's waypoint relative position along the path.
- Command Tree: Defines the command that will be run when reaching the event marker.
Constraint zones are used to change the kinematic constraints of the robot for a given region of the path. This allows for fine control over the maximum velocity and acceleration of the robot throughout the entire path. Multiple constraint zones can be added to the path and they can overlap. At a given point along the path, the constraints for the zone closest to the top of the list of zones will be used. If there is no constraint zone, the global constraints will be used. Constraint zones can be edited via the constraint zones tree.
Constraint Zones Tree:
- Constraints: Identical configuration to global constraints. Angular velocity/acceleration only available when holonomic mode is on.
- Start Position Slider: Controls the waypoint relative position of the start of the zone.
- End Position Slider: Controls the waypoint relative position of the end of the zone.
This reversal checkbox is only available if holonomic mode is off. If selected, the robot will drive backwards when following this path.
In PathPlanner, autos are used to define a complete autonomous routine. These can then be loaded as a full autonomous command in robot code via PathPlannerLib's auto builder functionality. Each autonomous routine is defined as a sequential command group populated with path following commands, named commands (same as the ones used in path event markers), wait commands, or nested command groups. Path following commands allow you to select any path in the project, this functions as a modular system allowing you to reuse the same path across multiple auto routines.
If you do not wish to use any auto builder functionality, these auto files can be used in PathPlannerLib to get a path group, or list of paths, which will contain all of the paths in the auto. This is similar to previous versions' path group system.
NOTE: The paths chained together in an auto routine do not need to have their start/end positions aligned. PathPlannerLib path following commands will automatically handle transitioning between paths by default if their start/end positions do not align. However, it is your responsibility to ensure that any unaligned start/end positions or sharp angles where paths join will not cause any issues. Discontinuities shouldn't typically be a problem for holonomic drive trains unless you are transitioning between paths with a high velocity. You should avoid discontinuities with a differential drivetrain, unless paths are transitioning between a normal and a reversed path at 180 degrees.
Each auto has an optional starting pose associated with it, which will be used to reset the robot's odometry at the start of the auto routine when using an auto command created with the auto builder. If a starting pose is excluded, PathPlannerLib will not reset the odometry. The starting pose can be edited via the starting pose tree, or by click and drag in the auto preview.
Starting Pose Tree:
- X Position: The X position of the starting pose on the field, in meters.
- Y Position: The Y position of the starting pose on the field, in meters.
- Rotation: The rotation component of the starting pose on the field, in degrees.
The command group tree is used to define the entire autonomous routine within a sequential command group. This command tree works the same as the command tree for event markers. Commands can be added, removed, or reordered. The same rules that apply to command groups when creating them programmatically still apply here.
NOTE: You must hit enter after typing in new names to the named commands dropdown for the new name to be saved.