---
id: joint-configuration
title: "Joint Configuration & Actuators"
status: established
source_sections: "reference/sources/official-product-page.md, reference/sources/official-developer-guide.md, reference/sources/official-dds-services.md"
related_topics: [hardware-specs, locomotion-control, manipulation, equations-and-bounds, safety-limits]
key_equations: []
key_terms: [dof, actuator, joint, pmsm, dual_encoder, force_position_hybrid, lowcmd, lowstate, motor_cmd]
images: []
examples: []
open_questions:
  - "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
- Defined by: [[hardware-specs]] (physical platform)
- Enables: [[locomotion-control]] (leg joints)
- Enables: [[manipulation]] (arm + hand joints)
- Bounded by: [[safety-limits]] (joint limits, torque limits)
- Numerical limits in: [[equations-and-bounds]]