 Hello everyone, welcome to this session. I am Priyanka Bansore and today we are going to study about types of control systems. These are the learning outcomes of this video lecture. At the end of this session students will be able to describe different types of control system then students will be able to differentiate between open loop and the closed loop control system. These are the contents we will be covering in this session. Now before moving towards pause this video for few seconds and you have to recall the types of control systems. According to the classification of control system it is divided into natural and manmade then again manmade is divided into manual and automatic control system and again open loop and the closed loop control systems are the types of automatic control system. So in this session we will concentrate on open loop and the closed loop control system with an examples. Let us start with open loop control system a system in which output is dependent on the input but controlling action or input is totally independent of the output or we can say the changes in the output of the system. We can see in figure one there are the two blocks controller and the process. So firstly reference input r of t is applied to the controller which generates the actuating signal u of t that is required to control the process and which is to be controlled and the process is giving out the necessary desired control output that is c of t. Let us see the advantages of open loop control system. So first such systems are simple in construction, second it is very much convenient when output is difficult to measure, then third such systems are easy from maintenance point of view. Generally these are not troubled with the problems of the stability and the next systems are simple to design and hence it is economical. Now these are the disadvantages of open loop system. So first one these systems are inaccurate and unreliable because accuracy of such systems are totally dependent on the accurate pre-calibration of the controller. Then second these systems give inaccurate results if there are variations in external environment and it can't change the internal disturbances in the system after the controller stage. The last one any change in the output cannot be corrected automatically. So for that purpose to maintain the accuracy and quality of the controller is necessary from time to we will discuss example of open loop control system. So here this is the block diagram of automatic toaster system. So here relay is the controller and heating process of braille are taken place. Desired time and the power both are inputs to the controller and the output of the toaster is what actual toast means the toast prepared at the last stage. So in this system the quality of the toast it depends on what time for which the toast is heated. Then again it depending on the time setting braid is simply heated in the system in the oven and the toast quality is observed by the user and has no effect on the inputs. We will discuss about closed loop control system a system in which the control action is somehow dependent on the output it's called closed loop system. So in closed loop system feedback is required and feedback control systems are referred to as closed loop system. So moving towards let us see what is feedback. So feedback is what it's a key tool that can be used to modify the behavior of the system means with the help of feedback we have to modify the behavior of the system then it compares the output signal with input signal in order to generate the error signal with the help of that we have to achieve or generate the desired output with the help of feedback we have to reduce the error also. Here this is the block diagram of closed loop control system. So here the various signals are represented R of t is the reference input then B of t is the feedback signal E of t is the error signal then M of t is the manipulated signal and C of t is what it's a controlled output. So in such systems output is fed back to the input for comparison with the reference input that is R of t applied to it which is called feedback signal. Then this feedback signal is compared with the reference input with the help of what error detector and it gives error signal that is what E of t is equal to R of t plus minus B of t this error signal is then modified by controller and decides the proportional manipulated signal for that process to be controlled. This signal then actuates the actual system and it produces the output. So output is control 1 that is C of t. Now we will see the advantages of closed loop system. So first accuracy of the system is always high because the controller modifies and manipulates the actuating signal such that error in the system will be 0. Then second less affected by noise third bandwidth is very high then the fourth one is very accurate then sensitivity of the system may be made small to make the system more stable and the system senses the environmental changes as well as the internal disturbances also. According to that it modifies the error these are the disadvantage of closed loop system. So first one they are costlier then complicated to design due to feedback then it required more maintenance then feedback leads to oscillatory response. First overall gain is reduced due to presence of feedback here feedback is necessary. So due to that overall gain is also reduced and the next stability is the major problem and more care is needed to design a stable closed loop system. We will discuss an example of the closed loop system that is home hitting system. So here this is the closed loop system the hitting system is operated by the ball and desired temperature as the reference input and this is compared with the feedback signal that is actual temperature is sensed by the thermal sensor. Then the difference between these two means the difference between the desired temperature and the actual temperature it actuates the wall mechanism to change the temperature as per our requirement and finally house temperature is controlled output. Here controlling action or input is dependent on the output. So this is an example of closed loop system finally we have to compare the open loop and the closed loop control system. So here some points we will discuss left hand side is the open loop control system and the right hand side is the closed loop control system. So all of you know the definition of the open loop and the closed loop. So output is dependent on the input but controlling action is independent of the output and in the closed loop the control action is somehow dependent on the output. Here the feedback is absent and in the closed loop feedback is present. Then in open loop error detector is absent and in the closed loop error detector is necessary. In open loop it is inaccurate and unreliable again it is highly sensitive to the disturbances. In closed loop it is highly accurate and reliable then less sensitive to the disturbances. Then in open loop bandwidth is small and in the closed loop bandwidth is large. Then open loop circuits are simple to construct and cheap and closed loop circuits are complicated to design and hence the systems are costly also. These are the references of this video lecture. Thank you.