 Hello, I am Milka Jagle, working as assistant professor in Department of Mechanical Engineering, Vulture Institute of Technology, Solapur. Today we are going to learn what is open-loop and closed-loop control systems and we are going to see various examples, practical examples in our day-to-day life. At the end of this session, students will be able to describe open and closed-loop control systems. So, what is open-loop, what are the advantages, disadvantages of open-loop, practical examples of open-loop, what is closed-loop advantages, disadvantages, practical examples and difference between open and closed-loop. Let us see what is open-loop control system. A control system in which the control action is totally independent of output, then the system is known as open-loop control system. The figure below shows the open-loop control system. It is a simple process. So, input has no effect on the output. So, let us see the advantages of open-loop control system. They are simple in construction and design. They are economical because there is no any feedback element present in the open-loop control system. They are easy to maintain because they have less number of components. They are stable because as the input is given to the system, we get the output. There is no any external disturbance taken into account and there is no any feedback element so that it can continuously change the input. So, they are stable. They are convenient to use when the output is difficult to measure. So, let us see the disadvantages of open-loop control system. They are inaccurate because there is no any measurement device which compares the input and the output. They are unreliable. Any change in the output cannot be corrected automatically. Now, I want you to list down the open-loop systems that you come across in your day-to-day life. So, I want you to just list down the open-loop control systems, the practical examples you face. So, just think about the systems around you which works on open-loop control systems where you do not give any feedback signal so that you can get an output. So, let us see few examples of open-loop control system. So, the first example is electric hand dryer. The hot air comes out so as it does not take into account whether the hand is dried or not. It just gives the hot air out. Let us see the next example that is washing machine. Here, when the time is set, the machine stops working whether the washing action is completed or not. It does not take into account. So, this is another example of open-loop control system. In the same way toaster, the toaster works on the preset time independent whether the toasting action is completed or not. So, the other example is electric switch. When the light is on using electric switch, it continuously gives the light independent on whether the light is needed or not. The next example is volume on the stereo system. So, let us see the closed-loop control system. It is a system in which output has an effect of the input quantity in such a manner that the input quantity will adjust itself based on the output generated. So, the figure below shows the closed-loop control system. Here it has the components same as a controller open-loop control system. But we have an additional element known as feedback element here. So, you can see your feedback element. The output is given back to the feedback element and that is input to the controller once again. So, there is a comparison between input and the output. So, we can get a desired output. These are the advantages of control system. So, though they are more accurate even in the presence of non-linearity, highly accurate and the bandwidth range is large. It facilitates the automation. The sensitivity of system may be made small to make the system more stable. They are less affected by noise as the external and noise disturbances are eliminated. So, due to the presence of feedback element, they are costlier and they are complicated to design. They require more maintenance as compared to open-loop. Feedback leads to oscillatory response. Overall gain is reduced due to presence of feedback. The stability is the major problem and more care is needed to design a stable closed-loop control system. Now, I want you to pause the video and think about various closed-loop control system you come across in your day-to-day life. The closed-loop where the input has an effect on the output. So, I want you to list down the practical examples as similar to the open-loop control system. We have just gone through it. So, these are the closed-loop control systems, water level controller. So, when the level of the water is reached to the desired level, supply is switched off automatically. Next example is electric iron. Here, the heating element adjusts itself according to the temperature. The voltage stabilizer here, the desired voltage is inputted to the appliance. And last is air conditioner. The desired temperature can be occupied or can be obtained by using this air conditioner. So, these are the differences of open-loop and closed-loop. They are simple in construction, but in closed they are complicated. Feedback is absent in open-loop whereas feedback is present in closed-loop. They are easy to maintain because less number of components are present in open-loop. They are easy to maintain because less number of components are present in open-loop. And in closed-loop they are difficult to maintain. They are cheap because feedback element and most of the, it is easy, they are cheap and they are expensive. These systems, open-loop systems are slow whereas closed-loop systems are fast. Manual error may cause, so they are inaccurate whereas the manual, there is no any error in the closed-loop. They are, open-loop system are stable and the stability problems occurs in closed-loop because there are continuous change in the inputs given due to the presence of feedback. Open-loop are more sensitive to noise, disturbance and changes in the environment whereas closed-loop systems are less sensitive and to noise and external disturbances. Optimization is not possible because it is the simplest and optimization is not possible and optimization is possible in closed-loop. Open-loop are used when inputs are known ahead of time whereas closed-loop are used when inputs are not known ahead of time. These are the references. Thank you.