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Localization: Distance Resets and MCL

Odometry drifts over an auton. RW can correct it with distance sensors in two ways. Both need the sensors set up as in Robot Configuration, and field-centered positions from setPose().

Distance resets

resetPositionFront(), resetPositionBack(), resetPositionLeft() and resetPositionRight() reset X or Y from one sensor. Each returns true if it reset.

  • Use sensors on all sides, or only the sides you want
  • Each reset traces the sensor's beam to the wall it actually hits, so angled readings and readings near corners work
  • It skips readings that hit the wall too steeply, land too close to a corner (e.g. Override's loaders), or disagree too much with odometry

Monte Carlo Localization (MCL)

MCL is an optional particle filter that keeps correcting odometry while the robot drives.

  • Turn it on with startMcl() after startOdometry() in runPreAutonomous()
  • It accounts for distance sensor delay, ignores readings blocked by robots and game elements, and recovers if the robot gets shoved
  • It moves the position gently, so motions never see a sudden jump
  • The selector screen shows its uncertainty and how long each update takes on the Brain. If that's more than a few msec, lower mcl_particles
  • If the position lags while driving toward or away from a wall, adjust distance_sensor_delay_msec

MCL is new

It has only been tested in simulation (see Testing on a Computer). Try it on a practice field first, and watch the Brain screen to confirm the position stays right before using it in matches.

Override (2026-27) tips

  • Set distance_reset_corner_margin to about 18 so the corner loaders don't throw off readings
  • Wall centers are the cleanest place for resets; Cup+Pin stacks start against the walls about 24" either side of each center
  • Robots can't be touching the perimeter at the end of auton for the Autonomous Win Point, so back off after resetting against a wall
  • Rule R11 caps drivetrain motors at 55W total, and drive encoder readings come from the first motor in each motor_group. In a mixed 11W/5.5W drive, list an 11W motor first