Francesco Gambelli

• 01How many

  Car

  One or two drive units per vehicle

  Humanoid

  About 25 to 30 in the body, plus the hands

  What links themDesign for volume: tolerances and manufacturing spread decide the result in both.

• 02Voltage

  Car

  400 to 800 V battery

  Humanoid

  Tens of volts

  What links themBoth are inverter-fed machines with fast switching edges. Common-mode current, EMI and bearing voltage scale with dv/dt and parasitic capacitance, not with bus voltage alone: a 48 V GaN drive can switch as fast as an 800 V SiC one.

• 03Operating point

  Car

  High speed, wide constant-power range, field weakening

  Humanoid

  High torque at low or zero speed; holding a pose is pure copper loss

  What links themOne torque-speed plane and one set of loss maps. The design point moves from the constant-power corner to stall.

• 04Sizing

  Car

  Peak torque for launch, continuous power for gradient and top speed, efficiency over a drive cycle

  Humanoid

  Peak torque for seconds (standing up, stairs), heat on the RMS torque of the cycle

  What links themBoth are sized on a duty cycle: a drive cycle for the car, a task cycle for the robot.

• 05Cooling

  Car

  Liquid loop: water-glycol or oil

  Humanoid

  Sealed joint with little airflow, and a limit on skin temperature

  What links themSame loss sources, different heat path: a coolant jacket versus conduction through housing and structure into still air. Thermal models, control strategies and materials help in both cases.

• 06Mass

  Car

  Carried once by the chassis

  Humanoid

  Paid twice: every gram in a distal joint loads the proximal ones

  What links themSpecific torque and specific power are the figures of merit in both: N m/kg for the joint, kW/kg for the traction drive.

• 07Transmission

  Car

  Commonly a single fixed reduction

  Humanoid

  From 6:1 planetary to 100:1 strain-wave or a roller screw; reflected inertia grows with the ratio squared

  What links themMotor and reduction are designed together. The ratio trades motor size against what the load feels.

• 08Mechanical loads

  Car

  Road and torque transients through a compliant driveline: wheel slip, torsional resonance, potholes

  Humanoid

  Impacts and falls, and contact forces often estimated from motor current

  What links themBearings and gears set the lifetime in both.

• 09Magnets

  Car

  Strong push towards rare-earth-free motors: wound-rotor and reluctance topologies, ferrite magnets

  Humanoid

  Torque density relies on rare-earth magnets, and their supply is a known bottleneck

  What links themResearch on rare-earth-free machines serves both: alternative topologies, and magnets without rare earths.

Sources: McKinsey, humanoid robot supply chain analysis; Wensing et al., IEEE T-RO 2017.