servo

A servo is a device or system that provides precise control of angular or linear position, velocity, or acceleration. A typical servo system includes an actuator (such as a rotary or linear motor), a feedback sensor (such as an encoder, resolver, or potentiometer), and drive electronics or a controller. Gear trains or linkage may be included to adjust torque and speed. The defining feature is closed-loop control, where the controller compares the desired position with the actual position and generates an error signal to correct the actuator output.

Operation relies on feedback to achieve accurate and repeatable motion. The controller, often implementing a proportional-integral-derivative (PID) algorithm or similar control law, drives the actuator to minimize error. The feedback loop allows the system to reject disturbances and maintain performance across varying loads and speeds.

Types of servos include rotary servos, which produce angular motion, and linear servos, which provide linear displacement. Electrical servos typically use DC brushless or brushed motors and incorporate gearing to achieve desired torque and speed. In hobbyist contexts, RC servos are compact, self-contained units with an integrated controller and gearing. Hydraulic and pneumatic servos employ servo valves and actuators to deliver high force or rapid linear motion in industrial automation and aerospace applications.

Common applications encompass robotics, CNC machine tools, automated manufacturing, precision positioning systems, and laboratory instrumentation. The term “servo” is often used to denote the whole closed-loop positioning system, distinguishing it from open-loop actuators that lack feedback.