servomechanisms

A servomechanism, or servo mechanism, is a closed-loop control system that uses feedback to ensure a prescribed output follows a desired input. It typically integrates an actuator, a sensor, a controller, and a feedback path. The system continuously compares the commanded value with the actual output and applies corrective action to minimize error.

In operation, a user provides a reference input, such as a target position or speed. The sensor measures the actual output and sends a feedback signal to the controller. The controller computes the error between the reference and the measured output and generates a control signal that drives the actuator. The actuator, which may be electric, hydraulic, or pneumatic, moves the load and, in turn, provides the next feedback signal to complete the loop. Common controllers include proportional, integral, and derivative (PID) schemes, often implemented digitally.

Servomechanisms can be classified by what they regulate. Position servomechanisms aim to reach and hold a specified position; speed servomechanisms control velocity; torque or force servomechanisms regulate output torque or force. They can be configured for rotary or linear motion and may use various sensors such as encoders, potentiometers, resolvers, or tachometers to provide feedback.

Historically, servomechanisms emerged from early feedback control research in the 20th century and have since become central to precision automation. They are widely used in robotics, CNC machinery, aerospace control surfaces, industrial automation, and many precision positioning systems.

Performance characteristics include accuracy, bandwidth, stability, and dynamic response. Practical limitations arise from nonlinearity, friction, backlash, and sensor noise, all of which influence loop design and tuning.