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unitree-g1/context/joint-configuration.md

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id title status source_sections related_topics key_equations key_terms images examples open_questions
joint-configuration Joint Configuration & Actuators established reference/sources/official-product-page.md, reference/sources/official-developer-guide.md, reference/sources/official-dds-services.md [hardware-specs locomotion-control manipulation equations-and-bounds safety-limits] [] [dof actuator joint pmsm dual_encoder force_position_hybrid lowcmd lowstate motor_cmd] [] [] [Per-joint velocity limits (dq_max) for all joints Actuator model numbers and detailed datasheets Ankle joint range of motion (not in public specs) Exact gear ratios per joint]

Joint Configuration & Actuators

Detailed breakdown of the G1's joint structure, actuator specifications, and range of motion.

1. DOF Configurations

The G1 is available in three primary DOF configurations: [T0 — Spec Sheet]

Configuration Total DOF Legs Waist Arms Hands Variants
Base (23-DOF) 23 6+6 1 5+5 0 G1 Standard
Mid (29-DOF) 29 6+6 3 7+7 0 G1 EDU Standard
Full (43-DOF) 43 6+6 3 7+7 7+7 G1 EDU Ultimate

2. Joint Enumeration

Leg Joints (6 per leg, 12 total)

Joint Name Axis Type Range (degrees) Range (radians) Notes
left/right_hip_yaw Z Revolute ±158° ±2.758 Rotation around vertical
left/right_hip_roll X Revolute -30° to +170° -0.524 to +2.967 Lateral splay
left/right_hip_pitch Y Revolute ±154° ±2.688 Forward/back
left/right_knee Y Revolute 0° to 165° 0 to 2.880 Extension only, max torque joint
left/right_ankle_pitch Y Revolute — — Range not yet confirmed
left/right_ankle_roll X Revolute — — Range not yet confirmed

[T0 — Official specs for hip/knee; ankle ranges still unconfirmed]

Waist/Torso Joints

Configuration Joints Notes
23-DOF (base) 1 joint: waist_yaw (Z-axis, ±155°) Single rotation axis
29/43-DOF 3 joints: waist_yaw, waist_pitch, waist_roll Full 3-axis torso articulation

Arm Joints (per arm)

Configuration Joints per Arm Notes
23-DOF (base) 5 joints: shoulder_pitch, shoulder_roll, shoulder_yaw, elbow, wrist_yaw Basic arm
29/43-DOF 7 joints: above + wrist_pitch, wrist_roll Articulated wrist (2 extra DOF)

Hand Joints — Dex3-1 (43-DOF variant, 7 per hand)

Finger Active DOF Actuator Type
Thumb 3 Micro brushless force-control
Index 2 Micro brushless force-control
Middle 2 Micro brushless force-control
Total per hand 7 6 direct-drive + 1 gear-drive

Additional Dex3-1 specs:

  • 33 integrated tactile sensors per hand [T0]
  • Force-position hybrid control [T0]
  • DDS topics: rt/dex3/(left|right)/cmd and rt/dex3/(left|right)/state [T0]
  • Message protocol: unitree_hg [T0]

3. Actuator Specifications

All joints use proprietary Unitree actuators: [T0 — Official specs]

Property Specification
Motor type Low-inertia internal rotor PMSM
Shaft design Hollow (reduced weight, internal wiring routing)
Transmission Compact planetary gearboxes
Backdrivability Yes (backdrivable design)
Bearings Industrial-grade crossed roller bearings
Feedback Dual encoders per joint (position + velocity)
Thermal monitoring Built-in temperature sensors per motor
Control Force-position hybrid, torque limiting
Servo rate 500 Hz

Peak Torques

Joint Region Standard (base) EDU Variants Notes
Knee (max) 90 Nm 120 Nm Highest-torque joint
Other joints Not published Not published See open questions

4. Low-Level Control Interface

Joint-level control is performed via DDS publish/subscribe: [T0 — Developer Guide]

Subscription (read robot state)

  • Topic: rt/lowstate
  • Type: unitree_hg::msg::dds_::LowState_
  • Contents: mode_pr, mode_machine, tick (1ms increment), imu_state, motor_state (all joints), wireless_remote, crc checksum

Publishing (send commands)

  • Topic: rt/lowcmd
  • Type: unitree_hg::msg::dds_::LowCmd_
  • **MotorCmd_ structure per joint:**
    • mode: 0 (Disable) / 1 (Enable)
    • q: Target joint position (rad)
    • dq: Target joint velocity (rad/s)
    • tau: Feed-forward torque (Nm)

Key Relationships