Feedbackcontrole

Feedbackcontrole, typically called feedback control in English, is a control strategy that uses information about the output of a system to influence its input with the aim of reaching a desired state. The basic elements are a plant (the process to be controlled), a sensor that measures the output, a controller that computes a corrective signal from the error between reference and measurement, and an actuator that applies the correction.

In a closed-loop arrangement the controller continuously uses the measured output to reduce the error. This is usually achieved through negative feedback, which tends to stabilize the system and improve accuracy; positive feedback is rare in simple control and can cause instability unless specifically designed. The most common practical controller is the PID (proportional–integral–derivative) type, though many others exist.

Design and analysis rely on models of the plant, expressed as transfer functions or state-space representations. Performance is judged by stability, speed of response, overshoot, and steady-state error. Techniques from the time domain (root locus) and frequency domain (Bode plots, Nyquist criteria) are used, along with modern methods such as robust and adaptive control and model predictive control for complex or uncertain systems.

Applications span industrial process control, motor speed and position control, temperature regulation, aerospace autopilots, robotics, and consumer electronics. With advances in digital computing, most feedback controllers are implemented in software or embedded hardware. Key challenges include sensor noise, communication delays, nonlinearities, and actuator saturation, which drive ongoing research in compensation, estimation, and robust control design.