Many control systems rely on feedback. However, there are also control systems that work without feedback. Such a system is known as an open-loop control. An open-loop controller, also called a non-feedback controller, relies only on the model and the input signal fed to the system. An example of open-loop control can be found in washing machines, which work by running pre-programmed cycles but, most importantly, do not rely on any measurements of the speed of the barrel or water volume to adjust the machine on the fly.