Open vs Closed Loop Control

There are two types of feedback systems for control systems. **Open Loop** and **Closed Loop** systems. The main difference is if they use feedback to adjust their output. ### Open Loop Control System The controller sends a command to the process based only on the input. There is no feedback from the output, meaning that the system cannot correct for errors or adjust. Additionally, there's an assumption the process will respond perfectly to the input. Pros: - simple - faster response (no feedback delay) - stable, no feedback oscillations Cons: - less accurate, sensitive to disturbances, parameter changes, & calibration errors - no correction mechanism Examples: toasters, traffic lights, washing machine ### Closed Loop Control System The output of the system is measured and fed back to compare with the desired input. The error is then used to adjust the control signal enabling automatic correction for adjusting the control signal. This enables automatic correction for disturbances and uncertainties. Pros: - higher accuracy & robustness - reduces effects of disturbances & uncertainties - better performance Cons: - more complex - potentially unstable - slower response due to feedback loop Examples: thermostat, cruise control, autopilot