Senior Actuation Engineer (Humanoid Joints)

At Mentee Robotics, we are redefining humanoid automation with an AI-first approach - combining perception, reasoning, and dexterous manipulation into fully autonomous systems that continuously learn and adapt.

We are now expanding with a new robotics Engineering center in China, working hand-in-hand with our engineering teams in headquarters. Its mission: to rapidly develop our next-generation full-size humanoid and bring it to life - a walking, working platform that becomes the foundation of our next generation of products. This is a small, senior, hands-on team where speed of iteration is the core value.

We are looking for two Senior Actuation Engineers to design the joints of our humanoid - the single hardest hardware problem on the robot. You will own actuator modules end to end: motor selection, gear reduction, thermal design, sensing integration, and packaging - and you will cover the surrounding mechanical design (limbs, structure) as a secondary duty.

Who you are?

• An actuator specialist first, a general mechanical engineer second
• A first-principles thinker who questions assumptions and iterates fast
• Hands-on in the lab: you build, instrument, and break your own designs
• Comfortable with ambiguity and rapidly changing requirements

Responsibilities:

• Design high torque-density actuator modules for legs, waist, and arms: quasi-direct-drive architectures with planetary reduction - motor selection/specification, gear design, bearings, sealing, and packaging
• Own the torque, speed, thermal, and mass budgets per joint, aligned with the system DOF and mass targets
• Drive quasi-direct-drive vs. high-reduction trade-offs together with the motion control team
• Integrate sensing into the joint: encoders, temperature, and torque estimation provisions
• Design the surrounding structure - limbs, torso frame, brackets - optimized for fast fabrication (machined plates, printed parts)
• Own designs from concept through fabrication: CAD, tolerance analysis, DFM for prototype quantities, and supplier follow-up
• Run joint-level dyno and life testing with the V&V engineer; iterate based on data
• Work daily with electrical and embedded teams on the motor controller integration

Requirements:

• B.Sc. or M.Sc. in Mechanical Engineering or Mechatronics
• 8+ years designing electromechanical actuation systems: BLDC motors with planetary reduction, ideally in quasi-direct-drive (QDD) configurations
• Deep understanding of motor physics: torque constants, saturation, thermal limits, and their impact on transmission choice
• Strong CAD skills (SolidWorks/NX/Creo) and proven concept-to-hardware track record
• Experience with structural design, materials selection, and prototype fabrication methods
• Hands-on lab and test experience with rotating machinery

Advantages:

• Experience designing humanoid or quadruped joint modules (e.g., at Unitree, Wuji, Fourier, AgiBot)
• Experience with gear design and gear suppliers or custom motor winding specification
• Deep experience with proprioceptive actuation and backdrivability optimization
• Thermal simulation and FEA experience
• Comfortable communicating technical topics in English with international teams