Package frc.rebuilt

Class RobotBumpSim

java.lang.Object
frc.rebuilt.RobotBumpSim
public class RobotBumpSim extends Object
RobotBumpSim — standalone robot-bump physics simulation for MapleSim.

What this class does

Simulates the robot's 3D pose (Z height, pitch, and roll) as it drives over the raised bumps on the 2026 FRC REBUILT field. It also implements a frictionless-slide model that prevents the robot from "ghosting" through a bump when it lacks the speed to crest it.

How it works

  • Four swerve module contact points are tracked independently in the XZ plane.
  • When any module first touches a bump's ascending face the sim enters ramp mode: it captures the robot's current field-X velocity (simXVel) and absolute field-X position (simXPos), then owns them for the duration of the crossing attempt.
  • While on the ramp, only gravity acts along X (frictionless surface). If simXVel decays to zero before the peak the robot slides back to flat ground.
  • The robot exits ramp mode when it either backs off (all module Z ≈ 0) or successfully crosses over the peak (modules come back to flat ground on the far side).
  • A diagonal approach reduces effective deceleration via contactFactor = |cos(2 * robotYaw)|, making 45° crossings easier.

Minimum crossing speed: sqrt(2·g·h) ≈ sqrt(2·9.81·0.165) ≈ 1.80 m/s.

Quick-start integration with MapleSim


 // 1. Construct once, typically in startSimThread() alongside your MapleSim drivetrain.
 RobotBumpSim robotBumpSim = new RobotBumpSim(drivetrain.getModuleLocations());

 // 2. Call every simulationPeriodic() AFTER MapleSim has stepped.
 Pose2d simPose = mapleSimDrive.getSimulatedDriveTrainPose();
 ChassisSpeeds fieldRelativeSpeeds = mapleSimSwerveDrivetrain.mapleSimDrive.getDriveTrainSimulatedChassisSpeedsFieldRelative();

 // subticks should match the number of physics sub-steps you pass to your ball/object sim.
 // A value of 5 works well for a 20 ms loop (4 ms sub-steps).
 Pose3d simPose3d = robotBumpSim.update(simPose, fieldSpeeds, subticks);

 // 3. When on the ramp, override MapleSim's pose so the robot physically slides back
 //    instead of the correction being purely visual.
 if (robotBumpSim.isOnRamp()) {
     mapleSimDrive.setSimulationWorldPose(robotBumpSim.getSimWorldPose(simPose));
 }

 // 4. Log or visualise the 3D pose (e.g. with AdvantageScope).
 Logger.recordOutput("Drive/Pose3d", simPose3d);

Tunable constants

  • WHEEL_RADIUS — effective contact radius of a wheel against the ramp surface (metres). Increase this to make the robot appear to "float" higher above the bump.
  • CHASSIS_HEIGHT — offset from the average module-contact Z to the robot body origin. Set to your chassis clearance height if you want a visually accurate robot body Z.
  • BUMP_COR — coefficient of restitution for vertical collisions with the bump. 0 = perfectly inelastic (no bounce), 1 = perfectly elastic.

Field geometry

The bump geometry is encoded as XZ line segments with Y-range guards. Each bump has two segments per side (ascending face + descending face) at X positions symmetric about field centre. See BUMP_LINE_STARTS / BUMP_LINE_ENDS for the raw coordinates. All positions are in metres, origin at the Blue Alliance driver-station corner.

  • Constructor Details

    • RobotBumpSim

      public RobotBumpSim(Translation2d[] moduleOffsets)
      Creates a new RobotBumpSim for a swerve drivetrain.
      Parameters:
      moduleOffsets - Robot-relative module positions in order FL, FR, BL, BR (metres). Typically obtained via CommandSwerveDrivetrain#getModuleLocations().

  • Method Details

    • isOnRamp

      public boolean isOnRamp()
      Returns true while the robot is on the ramp in frictionless-slide mode.

      When true the caller must call getSimWorldPose(Pose2d) to obtain the corrected 2D pose and feed it to MapleSim via setSimulationWorldPose, so the robot actually slides backward rather than just appearing to.

    • getSimWorldPose

      public Pose2d getSimWorldPose(Pose2d latestMaplePose)
      Returns the 2D pose that should be set on MapleSim while on the ramp.

      The X coordinate is replaced with the frictionless simXPos; Y and rotation are taken from latestMaplePose so MapleSim continues to own lateral motion.

      Parameters:
      latestMaplePose - The most recent 2D pose read from MapleSim (used for Y and rotation).
      Returns:
      A corrected Pose2d to pass to setSimulationWorldPose.

    • update

      public Pose3d update(Pose2d robotPose2d, ChassisSpeeds fieldRelativeSpeeds, int subticks)
      Advances the bump simulation by one 20 ms period and returns the robot's 3D pose.

      When the robot is on the ramp the returned pose uses simXPos for X, giving a physically accurate visual position. The caller must also call getSimWorldPose(Pose2d) and apply it to MapleSim so the actual simulation position matches (see the class-level Javadoc for a complete integration example).

      Parameters:
      robotPose2d - Robot's 2D pose from the MapleSim drivetrain.
      fieldRelativeSpeeds - Field-relative chassis speeds from the MapleSim drivetrain.
      subticks - Physics sub-steps per period. Must match the subticks value used by any companion ball/object sim so they stay in sync. Typical value: 5 (= 4 ms sub-steps per 20 ms loop).
      Returns:
      A Pose3d with physically correct X, Z, pitch, and roll.