 Hello everyone, I am Melka Jagle, working as assistant professor in mechanical department Poulchen Institute of Technology, Sulapur. Today we are going to study difference between control systems, open loop control system and closed loop control system. So, let us start learning outcome. At the end of this session, students will be able to differentiate different between open loop control system and closed loop control system. So, let us start what is open loop control system? System in which output is directly controlled by the input. Here, if you see it does not have any feedback element, so these systems are also known as non-feedback systems. See, output has no effect on the control action. In open loop control system, there is no any comparison of output with the input. So, just input is processed and it is given as output. The external disturbances does not take into account. So, let us see the block diagram for open loop system. So, here the input of the system is given to the controller, here the controller gives the control signal which is the output of the controller and it is given to the process or a system. Here in this process, there may be some disturbances like external or internal. Internal disturbances are within the process and external disturbances may be noise or any some external environment factors and the output that is known as controlled output. So, this was block diagram of open loop system. So, I just want you to pause the video for a few seconds and think about open loop control systems that you come across in your day to day life. So, let us see the examples of open loop control system. The first example is Emotion Heater, here the output of the heater is the heat which is generated. Here there is no any mechanism to find out the temperature of the heater or when the temperature is reached its maximum, there is no any mechanism to switch off the heater. The next example is Traffic Control System. In this traffic control system, there is after few laps of time, the signal is indicated at the signal at the post and it does not take into account the density of traffic waiting on the side of the road, it just gives a signal after some interval of time. The next example is Electric Iron. Here the input of the electric iron just take into account that electric iron is not an electro automatic iron. Here it is a simple electric iron whose supply is to the iron and it is given back as a heating of the element. The next example is Water Tank. Here it is a simple water tank where the input is water and output is also water, but it does not indicates the how much the water is filled at the upper level, so someone has to wait there to see whether the water tank is full, there is no any mechanism whether the tap should be off or on. So here is the Close Loop Control System. Close Loop Control System is a system in which output has an effect on the control action of the input. Here the output is feedback to the input, they are also known as feedback systems. Here the output has an effect on the control action. So as you see here in the block diagram for close loop system, the input is given to the controller and the output of the controller is the control signal. The controller does the action on the signal and it gives the control signal and that signal is given as input to the process or a system. Here there are as we discussed there are two disturbances that is internal disturbances and external disturbances. Internal disturbances are formed inside the system and external may be the environmental factors affecting the system. And if you see the output is given back so that there is comparison between the output and the input to get the desired output. Here the measuring element is nothing but the feedback element. So this was the block diagram for close loop system. So feedback, what is feedback? Feedback is a key tool that can be used to modify the behavior of a system. Feedback compares output signal with input signal in order to generate error signal to achieve or generate a desired output. So if you see the diagram here the output is feedback to the input that is comparator here comparator is a summing point. So feedback is given back to the input so as to see the difference between output and the input. So I just want to take few seconds to think about the various closed systems that you come across in your day to day life. So these are the example first one is air conditioner for the closed loop control system. The air is conditioned and the humidity is controlled according to the requirement. Water tanks with float valve here automatically the knob is off so as to stop the supply of water. Electronic water heater with which indicates the temperature. Electric iron with thermostat here the temperature of iron is maintained and refrigerator. Now let us see the comparison of open loop and closed loop. The first is they are simple in construction as there are no any feedback element and simple number of components are also very few. So there are simple in construction but whereas they are complicated in construction. Feedback is absent in the open loop whereas feedback is present in the closed loop control system. As there are few number of maintenance few number of components and feedback is also absent so they are easy to maintain whereas closed loop because of feedback elements and many components that is difficult to maintain. As open loop systems are cheap in cost and closed loop are expensive. They are slow in operation or working but closed loop are fast in working. They are inaccurate because the output is not compared to the input whereas in closed loop due to feedback structure they are the output is compared to the input. The system is stable there are no any stability problems in open loop system whereas closed loop are they are unstable. They are more sensitive open loop system are more sensitive to the disturbances and the changes in the environment where our closed loop systems are less sensitive and the disturbances does not affect the systems. Optimization is not possible because it is a clear it has no any feedback systems or it has very less number of components. So optimization is not possible whereas open loop there is optimization is a scope. Lastly these are used when open loop are used when inputs are they are used when inputs so these are the references thank you.