Robotics
Quasi-Direct Drive (QDD)
ActivePublished
Key
innovation
Low gear ratio + high-torque motor: a backdrivable, impact-tolerant joint with force control without an extra sensor.
Category
Robotics
Abstraction level
Building block
Operation level
Robot control
How it works
A high-torque-density motor delivers torque almost directly, and the small gearbox amplifies it with minimal friction and backlash. The low ratio preserves mechanical reversibility, so joint torque can be read from motor current to implement impedance/force control and to cushion impacts in software.
Problem solved
Classic high-ratio-geared drives provide high torque but are poorly backdrivable, have backlash and friction, tolerate impacts poorly and make precise force control difficult.