Unitree G1: Fixed Hands Without Grasping Capability - Diagnosis

⚠️ SAFETY WARNING / FIRE RISK. This device contains high-capacity lithium batteries (approx. 54V). Puncturing, bending, or accidental short-circuiting during disassembly can cause explosions or violent flames. The intervention requires maximum precision and the assistance of a specialized robotics technician is recommended. ReeFix provides this diagnosis EXCLUSIVELY for educational and informational purposes.

CAUSE A: Passive Hardware Configuration (Factory Fixed Hands)

• Probability: 45%
• Key Signals:
  • Obvious absence of motorized joints or cable drives in the fingers.
  • Rigid fingers, part of a unibody shell without independent articulations.
  • Lack of any tactile or auditory feedback (servomotor hum) when attempting to send a grasping command.
• Quick Checks:
  1. Documentation Consultation: Verify the exact version of your Unitree G1. The "G1 Basic" version comes from the factory with passive end effectors (fixed non-motorized hands), while only the "G1 EDU" versions support active hands.
  2. In-depth Visual Inspection: Carefully observe the hand structure. If there are no joint slits between the phalanges and the fingers are fused into a single block of plastic or metal, the configuration is passive.
• Why It Happens: This is not a malfunction, but a precise design and economic choice by the manufacturer. The basic model is designed for locomotion, pushing, or pure support tasks, without active manipulation.
• Costs and Decision:
  • Cost: High. To gain grasping capability, a complete hardware upgrade is required, purchasing a motorized robotic hand module (such as the proprietary Unitree Dex3-1 model or the Inspire Robotics RH56DFX five-finger module). The cost of these components varies from €1,500 to over €6,000 depending on the model and integrated tactile sensors.
  • Operational Decision: Component Replacement/Upgrade. It is not possible to repair a passive hand; an active module must be installed and the control software (SDK/ROS2) updated.
• Output for Technician: "Verify the hardware version of the Unitree G1 hand module. If identified as passive, propose a quote for the purchase and installation of an active motorized hand module (e.g., Dex3-1 or RH56DFX) with a corresponding software update (SDK/ROS2) to map the new joints."

CAUSE B: Flexible Wiring Interruption (RS485 Bus or Power)

• Probability: 30%
• Key Signals:
  • The hand (active model) appears completely inert, with no movement or motor hum when the robot starts.
  • Communication errors (timeout, no ping) in system logs or via the Unitree SDK.
  • The main system does not detect the hand as an active device on the bus.
• Quick Checks:
  1. Wrist Visual Inspection: Check the flexible cable that runs through the wrist joint. Look for signs of wear, crushing, excessive bending, or sharp cuts caused by arm joint movements.
  2. Continuity Test (only with device off and battery removed!): Using a Fluke digital multimeter, measure the continuity of the individual pins of the flexible cable connecting the wrist to the arm's control board. If you find an interruption on one of the power lines or the data bus, the cable must be replaced.
• Why It Happens: Continuous wrist rotation and flexion movements can wear out or break the internal conductors of the flexible wiring (which carries power and RS485/USB bus signals), interrupting communication between the robot's motherboard and the hand motors.
• Costs and Decision:
  • Cost: Medium. If the problem is only the cable, the original or compatible spare part has a low cost (approx. €30-80), but requires specialized labor for wrist disassembly and wiring, bringing the total to approx. €150-300.
  • Operational Decision: Wiring Repair/Replacement. This is a highly recommended intervention if the robot has active hands that have stopped working.
• Output for Technician: "Perform continuity tests on the flexible wrist wiring. Check for correct power voltages and signals on the RS485 bus. Replace the flat cable if interruptions or short circuits are found."

CAUSE C: Software or Firmware Configuration Error (SDK/ROS2)

• Probability: 25%
• Key Signals:
  • The hand is active (has visible joints) but does not respond to software commands.
  • No obvious hardware errors in the logs, but ROS2 nodes or SDK APIs fail to initialize the device (e.g., /dev/ttyUSB1 or similar).
  • Status LEDs on the hand (if present) are on, indicating power is present but the logical link is missing.
• Quick Checks:
  1. Serial Port Verification: Access the onboard operating system (NVIDIA Jetson Orin) via SSH and verify if the serial port associated with the hand is correctly detected (e.g., using ls /dev/ttyUSB*).
  2. SDK Log Check: Start the diagnostic script or Unitree ROS2 nodes and analyze the terminal output to identify any timeout errors or firmware mismatches.
• Why It Happens: A failed firmware update, incorrect SDK parameter configuration, or loss of read/write permissions on the serial port can prevent the software from controlling the hand motors.
• Costs and Decision:
  • Cost: Low. If resolved independently or through manufacturer remote support, the cost is zero or limited to software consulting fees (approx. €0 - €100).
  • Operational Decision: Software Reset/Configuration.
• Output for Technician: "Verify correct serial port mapping on the onboard system. Flash the correct firmware to the robotic hand and test communication via the official Unitree SDK."

CONCLUSION AND FINAL DIAGNOSIS

Based on this technical evaluation, resolving the issue of fixed or non-grasping hands on the Unitree G1 strictly depends on the hardware version you own:

1. If you own the Unitree G1 Basic version (Cause A - 45% probability): The robot is equipped with passive factory hands. This is not a malfunction, but a design choice. The only solution to gain grasping capability is to perform a complete hardware upgrade by purchasing an active hand module (such as the Unitree Dex3-1 three-finger model or the Inspire Robotics RH56DFX five-finger model). This operation requires a significant investment (from €1,500 to over €6,000) and software integration via SDK/ROS2.
2. If you own the G1 EDU version with active but non-functional hands (Cause B - 30% probability): The most probable cause is wear or breakage of the flexible wiring inside the wrist joint. In this case, repair is highly recommended and cost-effective (estimated cost between €150 and €300), as it restores full functionality of the existing module without having to replace it entirely.
3. If the hardware is intact but unresponsive (Cause C - 25% probability): The problem lies in the software configuration or firmware. Correct reconfiguration of the serial ports or resetting the ROS2 nodes will solve the problem at almost no cost.

It is recommended not to attempt to disassemble the 54V lithium battery without due precautions, to avoid short circuits or fire risks. For any complex hardware intervention, always rely on technicians specialized in advanced robotics.