The Science of LiDAR: Why Your Vacuum Sees Ghosts
Most modern robot vacuums from brands like Roborock and Dreame use LiDAR (Light Detection and Ranging). The turret on top spins at 300-600 RPM, firing thousands of laser pulses per second. These lasers reflect off walls and return to a sensor, allowing the vacuum to build a 2D SLAM (Simultaneous Localization and Mapping) model. However, mirrors and glass are “LiDAR transparent” or “highly reflective,” causing the laser to bounce and create a “phantom room” beyond the wall.
Navigation Troubleshooting Flow
Is it spinning freely? Clear hair/lint.
Use a dry Q-tip on the bottom sensors.
Hyper-Specific Brand Fixes
Roborock (S7/S8 Series)
If your Roborock map looks tilted or “drifted,” the most common culprit is a dirty Wall Sensor (the small rectangular window on the side). If this sensor can’t track the distance to the baseboard, the entire SLAM algorithm accumulates error. Wipe it with a microfiber cloth and toggle “Map Saving Mode” off and on to reset the orientation.
Roomba (iRobot j/s Series)
Roombas often use VSLAM (Visual SLAM) via a camera. If your Roomba fails at night, ensure you have adequate lighting. Most users ignore the “Incomplete Map” error which is actually caused by low light levels preventing the camera from identifying fixed landmarks like door frames.
The Refinement Loop: Forcing a Map Rebuild
Sometimes the map data becomes fundamentally corrupted. In the Roborock or iRobot app, don’t just “Edit” the map. Delete the existing floor map entirely. Before starting the new “Mapping Run,” place physical barriers (like the box the vacuum came in) in front of any floor-length mirrors. Once the perimeter is established, you can remove the barriers; the vacuum will have registered the mirrors as solid walls.