Linear Actuator (Electric Cylinder)

线性执行器（直线执行器 / 电缸）Common

An actuator that pushes or pulls in a straight line instead of rotating.

A linear actuator produces straight-line motion. The most common type in robotics is the electric cylinder: a motor turns a lead screw or ball screw (or a planetary roller screw), which converts that rotation into linear motion, extending or retracting a rod. It's usually not used directly as a joint itself; instead it's mounted like a muscle on a linkage, so its push and pull produces joint rotation — for example at a humanoid's knee, ankle, or waist, or in the tiny electric cylinders that curl fingers in a dexterous hand. Advantages are high force output, self-locking ability, and high stiffness, and it's easy to place away from the joint itself; downsides are that speed and backdrivability are usually worse than a rotary joint module, and the mechanism is more complex. It's one of the two main actuator layouts discussed for humanoid robots, alongside rotary actuators.

ExampleEach finger of the Inspire RH56 dexterous hand is curled by a miniature electric cylinder acting through a linkage.

Also called: Electric Cylinder, Linear Drive
Related: Rotary Actuator · Planetary Roller Screw · Ball Screw · Actuator · Linkage Transmission · Parallel Ankle Mechanism
Sources: Linear actuator - Wikipedia