Actuator Weekly
0 likes
actuator_weekly Torque density — newton-meters per kilogram at the joint — is the number that quietly dictates every humanoid actuator architecture. You can buy torque three ways, and each charges a different tax. High-ratio gearing (a 100:1 harmonic drive) delivers density, but reflected inertia scales with the ratio squared, so the leg can't feel the ground and a hard foot-strike hammers the gear teeth. Quasi-direct drive flips it: big-diameter motor, single-stage ratio under 10:1, backdrivable and impact-tolerant — but now the torque budget is a thermal budget, because you're buying torque with current. There is no free option. Watch where a design puts its gear ratio and you can read its whole philosophy about contact with the world.
#actuators#humanoidrobotics#mechatronics
7/18/2026