Glossary: 30 Humanoid Robotics Terms Explained in Plain English

A quick reference for the acronyms and jargon that show up constantly in humanoid robotics coverage.

This field loves an acronym. Here's a working reference for the terms that come up most often across this site and everywhere else you'll read about humanoid robots.

Hardware

QDD (quasi-direct drive): a low-gear-ratio actuator design that trades some peak force for backdrivability and impact tolerance.

DoF (degrees of freedom): the number of independent ways a joint or robot can move; more DoF generally means finer, more complex control.

SEA (series elastic actuator): an actuator with a spring built into the drivetrain, giving cheap torque sensing and passive shock absorption.

BMS (battery management system): the electronics that protect a battery pack from unsafe charge, discharge, and thermal conditions.

Payload: the maximum weight a robot can reliably lift or carry, usually quoted separately from the robot's own body weight.

Software and AI

VLA (vision-language-action model): a model that maps camera input and a text instruction directly to motor commands.

RL (reinforcement learning): training a policy by rewarding good outcomes and penalizing bad ones through repeated trial and error, usually in simulation.

Sim-to-real transfer: moving a policy trained in simulation onto real hardware, and everything that can go wrong in that handoff.

WBC (whole-body control): coordinating every joint toward multiple goals — balance, reach, task completion — simultaneously rather than one at a time.

MPC (model predictive control): repeatedly solving a short-horizon optimization problem to choose the next action, using a physical model of the robot.

ZMP (zero moment point): the classical bipedal-balance criterion of keeping the center of pressure within the robot's support polygon.

Domain randomization: varying simulation parameters during training so a policy generalizes better to the messier real world.

Teleoperation: a human directly or partially controlling a robot remotely, often used both for real tasks and for collecting training data.

Industry

RaaS (robotics-as-a-service): paying for robot access via subscription or usage fees instead of buying the hardware outright.

TAM (total addressable market): the theoretical full size of a market if every possible customer were captured — a number to treat skeptically in a young industry.

Pure-play: a company whose business is concentrated in one theme (here, humanoid robots) rather than diversified across many product lines.

Picks-and-shovels: an investing term for companies that supply components or infrastructure to an industry rather than making the end product themselves.