Robotics
Cycloidal Drive
1931ActiveUpdated: 17 September 2026Published
Key
innovation
A compact, high-ratio, high-torque-density gear in which a cycloidal disc rolls against a ring of pins — low backlash, high stiffness and shock-load tolerance.
Category
Robotics
Abstraction level
Building block
Operation level
Robot control
Use cases
RV reducers in industrial robotsHumanoid robot jointsPositioners and rotary tablesDrives requiring high torque and low backlash
How it works
1) The input shaft rotates an eccentric. 2) The eccentric moves the cycloidal disc in an orbit. 3) The disc's cycloidal profile successively engages the ring pins, causing the disc to rotate slowly in the opposite direction. 4) This slow rotation is picked up by the output pins/rollers and transferred to the output shaft. The ratio depends on the number of pins relative to the disc's lobes.
Problem solved
The need for compact, stiff and durable high-ratio, high-torque reducers that tolerate shock loads — critical in the joints of robots that carry heavy loads.
Evolution
1931
Cycloidal drive patent (Lorenz Braren)
Inflection pointPatenting of the cycloidal drive design.
1980
RV reducers in industrial robotics
Cycloidal (RV) reducers become common in industrial robot joints.
2026
Cycloidal actuators in humanoids
Proprietary cycloidal actuators used in the legs of the Agility Digit 5 humanoid.