> ## Documentation Index > Fetch the complete documentation index at: https://docs.wuji.tech/llms.txt > Use this file to discover all available pages before exploring further. # Product Introduction This manual covers a non-tactile Wuji Hand 2.1 (Beta) prototype. Its parameters and behavior don't represent the final product. ## Overview Wuji Hand 2 is WUJI TECH's biomimetic dexterous hand with 20 active degrees of freedom, built for research, robot integration, human-machine interaction, and other scenarios. In Wuji Hand 2.1 (Beta), the product provides: * A 20-DoF biomimetic five-finger body in which each active joint drives independently and the thumb supports opposition * MIT force-position hybrid control with user-tunable parameters * A factory-standard wrist flange with wrist mounting drawings included * A joint-level Wuji SDK (Python) interface for device discovery, state reading, and command output It also includes a Wuji Glove–based teleoperation (teleop) demo and simulation models (skeleton only, in URDF, MJCF, and USD formats). The models load in simulators such as MuJoCo and Isaac Sim without hardware—see the [Wuji Description model guide](https://docs.wuji.tech/docs/en/wuji-description/latest/integration/) for downloads and loading steps. ## Specifications The core specifications below cover structure, dimensions and weight, drive and control, and electrical characteristics—for product selection, simulation modeling, and integration.

Category	Parameter	Typical value or description
Structure & DoF	Active DoF	20 (4 per finger)
	Joint count	20 (4 per finger)
	Grasp configuration	Full opposition, with lateral abduction supported
	Kinematic configuration	Serial direct-drive rotary joints, no nonlinear kinematic coupling
	Min grasp diameter	0 mm
Dimensions & Weight	Weight (with soft pad and output cable, excl. adapter mount and adapter flange)	800 g
Dimensions & Weight	Dimensions	180 mm × 80 mm × 40 mm
Drive	Drive type	Back-drivable direct-drive rotary joints
Drive	Control algorithm	FOC vector control
Control & Communication	Control frequency	1000 Hz × 20 axes
	Communication interface	Ethernet
	Control mode	MIT force-position hybrid control
	Communication protocol	Ethernet
Electrical	Operating voltage	12 V DC
Electrical	Power adapter	12 V 20 A (included)

## Mechanical Structure This section describes the overall structure, the communication and power interface layout, and the naming and motion parameters of each degree of freedom, to help you understand the mechanical structure and how to use it. ### Overall Dimensions The figure below shows the overall dimensions of Wuji Hand 2 with all five fingers fully extended and together, for workspace planning and mounting design. Wuji Hand 2 overall dimensions

Dimensions in mm: length 180, width 80, thickness 40. ### Structure Diagram

A–E correspond to the five fingers: | No. | Finger | | - | - | | A | Thumb | | B | Index | | C | Middle | | D | Ring | | E | Little | 1–5 correspond to common anatomical regions of the hand: | No. | Region | | - | - | | 1 | Distal phalanges | | 2 | Intermediate phalanges | | 3 | Proximal phalanges | | 4 | Metacarpals | | 5 | Carpals | ### Degree-of-Freedom Configuration

Wuji Hand 2 degree-of-freedom configuration

1–8 correspond to: | No. | Joint | | - | - | | 1 | thumb\_cmc\_flex | | 2 | thumb\_cmc\_abd | | 3 | thumb\_mcp | | 4 | thumb\_ip | | 5 | mcp\_flex | | 6 | mcp\_abd | | 7 | pip | | 8 | dip | ### Joint Motion Direction and Range The index, middle, and ring fingers share the same structure, each about 137 mm long. The little finger is slightly shorter, about 134 mm. The thumb module differs slightly, about 140 mm. The figure below uses the thumb and little finger as examples to show each DoF's motion direction and angle range:

Joint motion direction and range (thumb and little finger as examples)

**Thumb** | Joint / Motion | Range | | - | - | | Base abduction/adduction (`thumb_cmc_flex`) | -68° \~ 74° | | Base lateral swing (`thumb_cmc_abd`) | -85° \~ 40° | | MCP flexion/extension (`thumb_mcp`) | -60° \~ 90° | | IP flexion/extension (`thumb_ip`) | -60° \~ 90° | **Four Fingers (Index / Middle / Ring / Little)** | Joint / Motion | Range | | - | - | | MCP flexion/extension (`mcp_flex`) | -60° \~ 90° | | MCP lateral swing (`mcp_abd`) | -40° \~ 40° | | PIP flexion/extension (`pip`) | -60° \~ 120° | | DIP flexion/extension (`dip`) | -60° \~ 90° | ### Communication and Power Interface Wuji Hand 2 communicates with the host over an RJ45 interface and supports external power. The figure below shows the location and connection of the communication and power interfaces:

Use the original supplied cables to ensure communication stability and power safety. In Wuji Hand 2.1 (Beta), the external interface form will change in later versions (no longer the XT30 + RJ45 two-cable direct layout). Leave room in your integration design. ### Three-Layer Structure: Skeleton, Soft Pad, Skin Wuji Hand 2 has three layers, each handling load-bearing, contact compliance, and surface protection: | Layer | Name | Role | | - | - | - | | Inner | Skeleton | Core mechanical structure that carries the joints, transmission, and motors, and determines whole-hand kinematics and load capacity | | Middle | Soft pad | Biomimetic soft tissue over the skeleton, mimicking the hardness and compression travel of human soft tissue for anthropomorphic contact and cushioning | | Outer | Skin | Passive protective layer over the soft pad that provides surface friction, wear resistance, and appearance protection, with no sensing
user-removable and replaceable
Always run the hand with the skin fitted—don't operate it without the skin | In Wuji Hand 2.1 (Beta), fingertip soft-pad hardness is still being tuned and the skin design isn't finalized. The current prototype's feel, appearance, and soft-pad life don't represent the final product. ### Back-of-Hand Status Light The logo light on the back of the hand shows the device state at a glance. The device drives the light itself — it works without a host connection. The status light requires a hardware batch equipped with the back-of-hand light, plus firmware v2.2.0 or later. When multiple states are active, the status light uses this order from highest to lowest priority: fatal error, joint fault, firmware update, no joint detected, warning, running, powering up/self-check, and ready. The table lists each visible light pattern and its meaning.

Color	Pattern	Meaning
White	Breathing (1Hz)	Ready: all online joints ready, none enabled
Blue	Breathing (1Hz)	Powering up / self-check
White	Solid	Running: at least one joint enabled
Yellow	Slow flash 1Hz	Warning: a non-critical issue is present
Blue	Slow flash 1Hz	Firmware updating
Red	Slow flash 1Hz	Fault: a joint fault is present
Red	Solid	The startup check did not detect a joint, or a detected joint reported a fatal error

During a firmware update, the status light continues to flash blue slowly. Joint restarts during the update don't trigger the warning pattern. ## Electrical Characteristics The pinout uses a standard RJ45 port and supports 100BASE-TX. ## Package Contents For the hand body itself—its structure, specifications, and interfaces—see the earlier sections. Besides the hand, the package includes the following:

Name	Qty	Description
Power adapter	1	Rated 12 V 20 A
Power adapter AC cable	1	China-standard 3-prong plug
RJ45 cable	1	Shielded Cat5e, 2 m
XT30 male-to-female extension cable	1	14 AWG, 2 m
Adapter mount	1	—
Adapter flange	1	—

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