Closed-loop control

How it is used

Used in lectures, specifications and design discussions, often as an adjective: a closed-loop system, closed-loop speed control. Servo axes, temperature control and robot joints are closed-loop. The opposite is open-loop control.

Example sentences

1. With closed-loop control, the conveyor keeps the same speed even when the load changes.

2. The stepper runs open loop, but the servo axis uses closed-loop control with an encoder.

Common collocations

• closed-loop system
• closed-loop position control
• close the loop
• control loop

Related terms

• open-loop controlControl without feedback: the controller sends a command but does not measure the result, so it cannot correct errors caused by load changes or disturbances.
• feedbackInformation about the actual output of a system, such as the measured position or speed, that is sent back to the controller so it can correct any difference from the target.
• PID controlA common feedback control method that calculates its output from three terms: proportional (the present error), integral (the error built up over time) and derivative (how fast the error is changing).
• setpointThe target value a control system tries to reach and hold, such as a temperature of 60 °C, a speed of 1,500 rpm or a pressure of 6 bar.
• servo motorAn electric motor with a built-in position sensor, usually an encoder, so that a drive can control its position, speed and torque very precisely. Robot joints are normally moved by servo motors.

More terms: Control Systems

• controller
• process variable
• tune
• overshoot