Integrated robot joint actuator
Unitree A1 joint motor integrated robot joint actuator
Planetary-geared joint motor from the A1 quadruped with 33.5 Nm maximum instantaneous torque, 21 rad/s joint speed, 20–40 V supply, 15-bit encoder and RS-485 control at 1 kHz, weighing 605 g.
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Key specifications
| Voltage (max) | 40 V |
|---|---|
| Data / bus | RS-485 (1 kHz control) |
| Peak torque (max) | 33.5 Nm |
| Speed (max) | 200 rpm |
| Supply | 20–40 V |
| Weight | 605 g |
| Encoder | 15-bit motor encoder |
Summarised in our own words from Unitree Robotics (Yushu Technology Co., Ltd.)'s published data; series maxima, individual models vary. Last checked 2026-10-30. Source 1
Notes on this data
Still listed on unitree.com; current production status not stated.
Specify Motion is not affiliated with Unitree Robotics (Yushu Technology Co., Ltd.). Unitree and A1 joint motor are used only to identify the product. Comparisons use published figures; always confirm against the current datasheet.
Unitree A1 joint motor replacement and alternative options
Use these supply-network options as a starting point for an engineering check. We can also help source the original Unitree part. Published series figures do not establish an exact-model or drop-in replacement: confirm ratings, fit, interfaces and approvals for your application.
High-rigidity Wanshsin inline planetary with three backlash classes down to super-precision, for machine tools, automation and AGVs.
| Published maximum | A1 joint motor | WSH |
|---|---|---|
| Peak torque | 33.5 Nm | 7,200 Nm meets or exceeds |
| Rated torque | — | 2,400 Nm |
| Speed | 200 rpm | 6,000 rpm meets or exceeds |
Right-angle version of the high-rigidity WSH, with a spiral bevel stage and ratios up to 200:1.
| Published maximum | A1 joint motor | WSHR |
|---|---|---|
| Peak torque | 33.5 Nm | 4,200 Nm meets or exceeds |
| Rated torque | — | 1,400 Nm |
| Speed | 200 rpm | 6,000 rpm meets or exceeds |
Wanshsin inline planetary designed for high radial loads, offered in three precision classes.
| Published maximum | A1 joint motor | WTH |
|---|---|---|
| Peak torque | 33.5 Nm | 6,150 Nm meets or exceeds |
| Rated torque | — | 2,050 Nm |
| Speed | 200 rpm | 6,000 rpm meets or exceeds |
Figures are the highest published for each series and are not always measured the same way. A higher figure is not automatically a better choice: mounting, duty cycle, feedback, connectors and approvals matter too. An engineer will check the fit against your application before recommending anything.
Typical applications
What an integrated robot joint actuator is
An integrated robot joint actuator packages a brushless motor, a reduction gear, encoders, a servo drive and often a brake or torque sensor into one module that bolts in as a robot joint. Gearing may be planetary, strain-wave or cycloidal. Many are designed for legged robots, humanoids and cobots, with low gear ratios or quasi-direct drive to keep the joint back-drivable and responsive. Communication is typically over CAN or EtherCAT, with position, velocity and torque control modes.
When engineers choose an integrated robot joint actuator
Choose an integrated joint actuator to build robots faster with fewer parts, especially legged, humanoid, exoskeleton and collaborative robots. Back-drivable versions suit force control and impacts. The trade-offs are torque density, precision and industrial qualification: low-ratio designs trade output torque for transparency, and some units are aimed at research rather than production duty. For industrial arms with heavy duty cycles, a dedicated harmonic actuator or motor and gear set may be better.
How to specify the Unitree A1 joint motor
Send these with your enquiry and an engineer can confirm the right A1 joint motor variant or an equivalent:
- Peak and continuous output torque (Nm)
- Output speed (rpm)
- Gear type and ratio
- Back-drivability and torque sensing
- Supply voltage (V DC)
- Communication interface and control modes
- Mass and size (kg, mm)
Common mistakes to avoid
- Using peak torque as continuous torque
- Ignoring thermal limits in legged robots
- Overlooking bus bandwidth with many joints
- Assuming research-grade units meet industrial life requirements
Unitree A1 joint motor: frequently asked questions
Can you help replace Unitree A1 joint motor or source the original?
Send the full model code, quantity and required date. Our engineers can check original-part availability and assess suitable alternatives, including Motion Control Products options where appropriate. We confirm compatibility and any changes needed before recommending a replacement.
What is the Unitree A1 joint motor?
Planetary-geared joint motor from the A1 quadruped with 33.5 Nm maximum instantaneous torque, 21 rad/s joint speed, 20–40 V supply, 15-bit encoder and RS-485 control at 1 kHz, weighing 605 g. Published series figures include voltage 40 V, peak torque 33.5 Nm, speed 200 rpm, weight 605 g. It is made by Unitree Robotics (Yushu Technology Co., Ltd.); Specify Motion can help source it or propose an equivalent.
Who makes the Unitree A1 joint motor?
The Unitree A1 joint motor is made by Unitree (Unitree Robotics (Yushu Technology Co., Ltd.)) and is listed here for engineers comparing options. Specify Motion is not affiliated with Unitree Robotics (Yushu Technology Co., Ltd.); brand names are used only to identify the product.
What is the voltage of the Unitree A1 joint motor?
The published series maximum voltage is 40 V. Individual models and sizes in the A1 joint motor range vary, so check the exact variant against your duty cycle, mounting and environment, or ask our engineers to confirm the right size for you.
Is there an alternative to the Unitree A1 joint motor?
We can assess suitable replacement options. On published figures, Wanshsin WSH and Wanshsin WSHR are options to assess from our supply network. An engineer confirms the fit against your application before recommending anything.
What is a quasi-direct-drive actuator?
A quasi-direct-drive actuator uses a high-torque motor with a low gear ratio, typically below about 10:1, so the joint is back-drivable and responds quickly to external forces. This suits legged robots and force control. The trade-off is lower output torque than high-ratio joints of similar size.
Why integrate the drive in a robot joint actuator?
Integrating the drive reduces cabling and lets each joint communicate over a shared bus, which simplifies robot design. It also allows the drive to sit close to the motor, improving control. The trade-off is that heat from both motor and drive must be managed inside the joint.
Further reading: How to select a harmonic actuator · Frameless motor sizing robot joints · Gearboxes and harmonic drives
Other integrated robot joint actuator series
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