A control system manages or regulates the behavior of many devices you use every day — from lightbulbs or thermostats to the engine in your car or industrial generators. Control systems operate in two ways: as open-loop control systems or closed-loop control systems.
An open-loop control system is a one-way signal flow system, meaning that an input is given to a controller which begins a process, leading to a final output. An example of an open-loop control system is a timed, electric clothes dryer. The input is the amount of time the dryer is set to run. An input of 30 minutes controls the heating elements for the duration of the process, at which point the output is clothes that are more dry.
The challenge with an open-loop system is that it does not send feedback to adjust or regulate the output. With a timed dryer, if the clothes are still somewhat damp after 30 minutes, there is no feedback signal returning to the controller to tell the timer to run longer.
In this case, a closed-loop control system is ideal because a closed-loop system sends signals back to the controller and regulates the processing system to achieve a desired output.