Open Loop Control System vs Closed Loop Control System

There are two major types of control systems. They are open loop and closed loop. In this article, a comparison is made between these two control systems.

Open Loop Control System	Closed Loop Control System
The control action is generated based on the reference set point only. The actual value of the controlled variable has no influence on control action.	The controller compares the reference set point and the measured output and generates a control action to make their difference to zero.
The output signal is not measured.	The controlled variable is measured and fed back to the controller. It is also named as FEEDBACK CONTROL SYSTEMS.
Presence of nonlinear elements, disturbances or process parameter variations leads to improper operation.	The closed loop system is capable of compensating the effects of nonlinearity, disturbances, model errors or process parameter variations.
The open loop control is simple and cheap as there is no requirement of sensors and transmitters.	Closed loop systems are more expensive but it keeps up the process variable at set point at all conditions.
The design of an open loop system is simple as there is no need for stability analysis. They are generally stable.	Closed loop systems require proper tuning otherwise it may become unstable.
The accuracy of an open loop system depends on the input calibration.	Closed loop control systems are more accurate and reliable.

Also, read the different types of process control schemes 
Feedback Control
Feedforward Control
Ratio Control
Cascade Control
Override control
Adaptive Control