What is the difference between open loop and closed loop control system ?

close loop system is that in which the output is feedback to input, and at input node the output and input are compared and actuated signal is fed to the system. Physically close loop system is fully automatic, and the input depends on output.

In open loop system there is no any feedback circuit and the system is not automatic. Control can be made manually. 

e.g- A.C with temperature sensor and control circuit is a feedback system. 

       When any one ride a bicycle the speed is controlled manually by rider is an example of open loop system.

Open Loop Control System: An open loop control system is the system, in which the desired output is only depends on the input signal. If there is disturbances in between, the output does not give any changes with respect to this disturbances. An open loop control system is generally known as system without feedback.

Closed Loop Control System: The closed loop control system is the system, in which the desired output depends on the input and the feedback element. If there is any disturbances occur in the system or it may be outside, the system controller automatically changes with respectively. This system is known as Feedback control system. 

open loop control  system acts completely on the basis of input and output and has no effect on output means feedback element is absent thas why it is also known as non-feedback control system.In closed loop control system the changes in output ,affects the inputs by usinf feedback, so thats why it is also known as feedback control system.

Closed Loop control systems are those systems in which Output is feedback to the input while reverse is Open Loop.

A closed loop control system is one is which the output is feed back to the input node. Hence the output is dependent on the feedback. Whereas an open loop control system is one in which the output is generally only dependent upon the input and has no feed back. 

Precisely, a closed loop has a feedback where as an open loop doesn't. 

close loop use singal from sensor(feedback) then take decision as per design, how ever open loop have no any feedback element.

Closed loop system is that in which input depends on output and the open loop system's input is not dependable on output 

In simple words:

Open loop control system is system in which input of system is independent of output and also it is one way process control.

while in close loop control system input of system is dependent on output and can be changed to get desired output. it is cyclic process.

An open-loop control system takes input under the consideration and doesn’t react on the feedback to obtain the output. This is why it is also called a non-feedback control system.and a closed loop system is also referred as a feedback control system. These systems record the output instead of input and modify it according to the need

Open loop control system doesn't feed back according to input but Close loop do have feed back which controls the output according to output need.