Robotics hardware glossary
One page per term, written as the answer we give on a call. Each entry states what the thing is, where it is the right choice, and what to ask a supplier in writing.
harmonic joint module
A harmonic joint module is a rotary actuator built around a strain wave gear: one compact stage gives a high reduction ratio with near-zero backlash. It is the usual answer where precision and torque density matter more than shock tolerance.
planetary joint module
A planetary joint module is a rotary actuator whose reduction comes from one or more planetary gear stages. It trades a little backlash and length for shock tolerance, efficiency and cost — the usual choice for legs, ankles and wheeled bases.
degrees of freedom in a robot hand
Degrees of freedom (DOF) in a robot hand count the independent joint motions it can control. Active DOF are driven by motors; passive DOF move with the object. Compare hands on active DOF, not on the headline total.
tendon-driven robot hand
A tendon-driven robot hand places its motors away from the joints — usually in the forearm — and pulls cables to move the fingers. It keeps the hand light and compliant, at the cost of cable wear and more complex calibration.
rated torque versus peak torque
Rated torque is what a joint can deliver continuously without overheating; peak torque is what it survives for a short time. Size the axis on rated torque and reserve peak for transients.