Unitree G1 stuck on stairs and in the rain: Diagnosis

SAFETY WARNING / RISK OF FIRE AND INJURY. This device contains high-capacity lithium batteries and high-torque joint motors. Drilling, bending, or exposure to water resulting in internal short circuits during disassembly can cause explosions or flare-ups. Furthermore, the robot's joints can activate suddenly, posing a serious crushing risk to fingers and limbs. Intervention requires maximum precision and the assistance of a specialized technician is recommended. ReeFix provides this diagnosis EXCLUSIVELY for educational and informational purposes.

OBSERVED SYMPTOMS

The Unitree G1 humanoid robot systematically gets stuck in two specific conditions:

• On stairs: Interruption of movement during ascent or descent, with attempts to correct posture before a safety shutdown.
• In the rain: Immediate stop or sudden shutdown as soon as the robot is exposed to water.
• Additional indicators (to be checked): Communication errors on the internal bus (CAN/Ethernet), system logs indicating sensor anomalies (such as noise in LiDAR data or IMU inertial unit misalignment), or complete shutdown due to a short circuit.

WHAT TO EXCLUDE

Based on the described behavior, we can exclude the following primary causes:

• Single mechanical failure: The blockage is not due to a single broken joint, as the robot attempts to move and correct its posture before stopping.
• General power problem (when dry): If the robot powers on and responds to commands in a dry environment, the battery pack and main power circuit are intact.
• Obvious structural damage: In the absence of impacts or falls, the analysis lies in sensory perception or internal electronic integrity.

FINAL CAUSE

The diagnosis for the Unitree G1 getting stuck in these conditions highlights a serious environmental vulnerability of the device, combined with physical limits of traction and trajectory calculation.

1. Water Infiltration and Internal Short Circuit (Lack of IP Certification)

• Probability: 75% (in case of rain exposure)
• Explanation: The Unitree G1 does not have any IP certification against water and is designed exclusively for indoor or dry environment use. The user manual strictly prohibits exposure to rain, snow, or wet surfaces. Water quickly penetrates through the unsealed joints of the torso and limbs, reaching the motherboard (NVIDIA Jetson Orin NX), motor drivers, or sensor connectors. This causes immediate short circuits or alters the impedance of high-speed communication lines (CAN/Ethernet bus), leading to a safety shutdown or robot power-off.
• Estimated repair cost: From €200 to €500 for oxidation cleanup and contact restoration; over €1,500 in case of motherboard or damaged motor driver replacement.
• Key signals: The robot shuts down or gets stuck immediately in the rain and does not restart correctly even after being externally dried.
• Quick checks (DIY):
  1. Do not attempt to restart the robot if it is wet to avoid permanent damage to the electronic boards.
  2. Immediately remove the battery (if safe and possible) and place the robot in a dry, ventilated environment.
• Safety notes: Water inside the battery compartment can cause a short circuit of the lithium cells with a risk of fire.

2. Compromised Optical Perception (LiDAR/Cameras) from Water

• Probability: 15%
• Explanation: Water droplets on the lenses of the 3D LiDAR (Livox MID-360) and depth cameras (Intel RealSense) deflect laser beams and infrared light. This refraction phenomenon generates an extremely noisy and inconsistent point cloud. Navigation algorithms interpret this noise as non-existent obstacles, triggering a safety shutdown. On stairs, where millimeter precision is required to calculate step height, the slightest optical distortion prevents trajectory planning, blocking movement.

If you experience navigation anomalies, a common error on technical forums concerns the Livox MID-360 point cloud being absent or corrupted. Often this behavior is caused by internal micro-condensation or dust accumulation that deflects laser beams, crashing the localization node.

• Estimated repair cost: €0 (resolvable independently with cleaning) or €80-150 for professional sensor recalibration.
• Key signals: The blockage occurs on stairs or in the presence of high humidity/fog, with logs reporting noise errors in LiDAR data.
• Quick checks (DIY):
  1. Thoroughly dry the protective lenses of the LiDAR and cameras with an optical microfiber cloth.
  2. Test the robot on a flat, dry surface to check if navigation is restored.

3. Attitude Estimation Error (Slipping on Wet Surfaces)

• Probability: 10%
• Explanation: Wet stairs drastically reduce the friction coefficient of the robot's feet. If a foot slips even a few millimeters during placement, the inertial measurement unit (IMU) detects an attitude anomaly inconsistent with the force and joint torque sensors. To prevent a disastrous fall, the firmware instantly activates emergency mode ("Safe Mode").
• Estimated repair cost: €0 (resolvable by drying the surface) or €150-300 for replacing worn foot pads.
• Key signals: The robot visibly slips or attempts to correct its posture in an oscillatory manner before getting stuck.
• Tools needed (for technician): iFixit Precision Screwdriver Kit, WD-40 Specialist Dry Contact Cleaner, Dielectric Silicone Grease, Fluke Digital Multimeter.

Output for technician: "The Unitree G1 humanoid robot exhibits systematic blockage or shutdown following exposure to rain or during navigation on wet stairs. As the device lacks IP certification against water, severe liquid infiltration inside the torso or joint modules is suspected, leading to altered impedance of the internal communication bus (CAN/Ethernet) or transient short circuits on the motor drivers. It is required to disassemble the protective covers using appropriate tools, visually inspect the electronic boards for traces of oxidation or saline deposits, and perform a cleanup with dry contact cleaner. If the internal hardware is dry and intact, analyze system logs (ROS2/syslog) to check for sensor timeout errors, 3D LiDAR point cloud anomalies, or discrepancies in foot force/torque sensors during the foot placement phase on slippery surfaces."

Operational Decision

In case of rain exposure, immediately turn off the robot and do not attempt to restart it to avoid destructive short circuits; it is essential to contact a specialized technician for opening, drying, and internal circuit cleanup (estimated cost €200-500, unless severe damage to electronic boards requiring component replacement for over €1,500). If the blockage on stairs occurs in a dry environment, proceed with cleaning the optical sensors and software recalibration (minimal or no cost); replacement of components or the entire robot (cost over €16,000) should only be considered in the presence of permanent damage from oxidation or short circuits on the main electronic boards.