We now move on to the description of the controllers of an excitation system. So, far we have been discussing the issues related to the modeling of the power apparatus that is the exciter. But an exciter in some sense is incomplete without this kind of discussion of the excitation system is incomplete without the discussion of the controllers associated with the excitation system. In the previous class we did the physical models of an excitation system we did not actually derive in detail the model, but listed down the things which ought to be modeled. In today's class in today's lecture we discuss one of the major control systems associated with the excitation system that is the automatic voltage regulator. So, in the previous class we studied two kinds of excitation systems the static excitation system whose basic model is a static one with limits which are determined by the generator terminal voltage. The control signal here is effectively obtained from the excitation system controllers. The brushless excitation system is a bit more complicated in the modeling aspects. The main issue here of course is that the exciter alternator has to be modeled by a dynamic model not a static model. And the diode rectifier which is an uncontrolled rectifier has got a a limit that is its voltage cannot go negative the output voltage to the field cannot go negative. So, there is a limit associated with that the control rectifier associated with the brushless excitation system is modeled in a similar way to a static excitation system that is it is a static model with limits that is given on the left hand side. Of course, IEEE has come up with standard excitation models. In fact, the IEEE type AC1A model which describes the model of a brushless excitation system is given here. The functional block diagram of an excitation system including not only the power apparatus, but also the regulators, limiters and stabilizers which effectively form the control system. Remember a control system is designed by us it is more of a mathematical logic which is implemented using some physical elements. So, you can have analog or digital implementations of the mathematical logic which really determines the behavior of the controller. Now, the mathematical logic in fact is a mixture of you know differential or dynamical equations which have to be effectively numerically or implemented or implemented using analog blocks. Now, the most important or the core function of an excitation system controller is regulation of the generator terminal voltage. So, what it does is essentially keeps the terminal voltage of the synchronous generator the main synchronous generator almost constant. Now, so this is shown in a functional block diagram here you can pay attention to that there is a regulator. Regulator is something which tries to bring in this case the voltage near or equal to a set point value it is called the reference value, but regulation is not the only function which is actually done by any excitation system controller. You also find that there are additional blocks corresponding to what is known as a power system stabilizer and limiters and protective circuits. So, you can have the overall functional block diagram contains something more than a regulator. Now, we will try to understand each of these blocks one by one. First of all is the regulation block. The regulation block essentially takes a reference or set point voltage. You compare it with the measured voltage, measured terminal voltage of the synchronous generator and use this error signal to drive a controller which in fact gives the control system which is used by the control rectifiers of the excitation power apparatus. So, this is a controller. So, this is a controller or regulator you know. Now, this controller of course is a mathematical function. It is some mathematical function like some things we will describe in a few moments from now. The voltage regulator effectively compares the set point which is given by us and the actual terminal voltage. Now, there is one point about the set point itself the voltage reference of a synchronous generator terminals is typically going to be one per unit. We are going to really try to keep the generator terminal near about its rated value, but it is not sacrosanct that V ref should be equal to 1. You must have done in a course on any course on synchronous machines or electrical machines that by changing the excitation system voltage. Remember the change in a voltage reference here finally affects the control signal and eventually affects the voltage which is going to apply to the field of the main synchronous generator. So, by changing this reference voltage say by increasing it you are going to change effectively the field voltage and therefore, the reactive power output of the generator. So, if you recall a synchronous generator in its most simplest steady state model can be represented in this fashion. This is the synchronous machine terminals if the machine does not have saliency you can represented by a synchronous reactance which is nothing but equal to x d or x q because they are equal. So, this is a kind this is a steady state model of a synchronous machine. So, by changing E f d if I change the field voltage I effectively can change the reactive power output of the generator. Remember the real power output of a generator can be changed only by changing the mechanical power or the mechanical torque of the machine. So, that is one thing you should keep in mind. So, if you look at the steady state model of a non salient synchronous machine by changing E f d you can change the reactive power output. So, of course, we do need to maintain the terminal voltage near about 1 per unit, but in case you change if you change try to keep this voltage slightly greater than this. Remember that this although I have represented the rest of the system as a voltage source it actually is something like this. So, the correct way of representing the rest of the system could be this is at an angle delta the rest of the network. Now, the rest of the network again consists of transmission lines etcetera simplified model of that could be inductances etcetera. So, if I change the magnitude of the voltage the terminal voltage effectively the reactive power output of the machine will change. So, q of the machine can be changed by changing the reference value of the terminal voltage of a synchronous machine. So, of course, we will not want v ref to be very much different from 1 per unit after all the voltage in a synchronous machine has to be maintained at roughly what its rated value is if you have a voltage is much larger than that you will have problems of insulation and more importantly you may have over fluxing in the machine. So, one of the important issues here is what determines v ref well one of the thing is how much reactive power has the generator to be to supply. Of course, by reducing v ref one can make the generator absorb reactive power.  So, a plant operator a power plant operator could tweak around this v ref near about the rated value of the synchronous machine. So, you of course, we can expect v ref to be say 1.02 or 1.03, but please do not expect it to be 1.5 or so that would really be much larger than the rated value and that would tax the insulation of the synchronous machine windings and moreover the flux in the machine the fluxes in the machine would become greater the flux densities in the machine would exceed the saturation value in this case. So, remember the flux densities in the core are dependent going to be dependent on the voltage of the machine divided by the frequency of the machine. So, in steady state b will be proportional to v by f. So, one of the reasons why you cannot exceed make v ref too large is that you will go into saturation if you go into saturation the machine becomes non-linear that is one of the it will increase if the flux level increase it will increase the heating in the machine as well. So, that is one of the major points which you should remember when setting v ref of course, v ref can be less you can have v ref as 0.98 per unit that is also feasible like you know you may under low load conditions want the generator to absorb reactive power in that case you would reduce v ref of the machine. So, this is basically what goes into deciding what v ref of the machine is. Now, once you have got v ref you have decided what v ref should be the power plant operator has some freedom in deciding that he compares it is compared with the terminal voltage of the machine. So, now the question which you would you know which needs to be asked is this controller whichever is there is it going to drive this error to 0 that is will it make v ref exactly equal to be the answer is well it depends on the mathematical function used in this controller. Now, another interesting variation which you see other of interesting variation which you see is instead of maintaining v is equal to v ref in some machines or in some situations v ref is you know you try to maintain v ref equal to v in most machines. So, this error is driven either to 0 or near 0 that is what your controller should do it depends on the mathematical function you are using, but the aim of course, would be to reduce the error almost to 0 that is v ref approximately equal to v. So, that is why it is called a regulator a voltage regulator, but in some situations you would not necessarily try to keep v ref v almost equal to v ref, but you can have v ref almost equal to v minus k into the magnitude of current going out of the machine. So, you can have a situation like this is well. So, you can instead of having a control system like what I have shown you before that is just having v what you can have is this is known as a load compensator. So, the thing is that of course, I should this usually is positive the point is that instead of keeping v equal to v ref for almost equal to v ref we will keep v plus k i is equal to v ref. So, in case i is large and depending on this value of k if it is non zero you will find that v ref is not maintained at v is not maintained at v ref, but slightly lower than v ref. Now, the question is why do this at this additional complication here the thing is that if you have got 2 machines which are connected to the same bus. So, this is 2 synchronous machines connected to the same bus and both these machines have an excitation system. So, both these machines have an excitation system both are trying to maintain the voltage of this bus a constant at v ref. Now, what will happen is that in case both these machines are trying to maintain the voltage here at v ref the question arises is how much which each individual machine contribute to keeping this voltage at v ref. Now, normally what we do is we make this change to the automatic voltage regulator. So, that if a machine contributes that if a machine contributes more current you know or more load more current in that case this gets modified this additional term essentially reduces v makes v ref slightly less than v rather makes v slightly less than v ref. The reason it is done is that you can then impose a sharing between these 2 generators if one generator supplies more current automatically what is done is that this becomes larger if this becomes larger v ref will not be maintained v will not be maintained at v ref but slightly lower value. So, what will eventually happen is that this synchronous generator will start if this i increases effectively what will happen it will try to reduce this is the exciter power apparatus this is the controller if this one of the generators takes on more load it tends to decrease it will tend to decrease the final exciter voltage. And therefore, that what happens is that it prevents one generator from taking all the load. In fact, by choosing a case appropriately for both machines for both machines if I choose my k appropriately I can actually impose a proper sharing agreement between these 2 generators. So, no one machine pushes in more current than what is necessary. So, what happens is that you make the excitation system or the exciter field voltage a function of the load current. So, if you have got 2 alternators or 3 alternators which are bused together they are connected to the same bus and your automatic voltage regulator is trying to maintain the voltage of that bus at v ref. So, each generator has got an independent voltage regulator which is trying to maintain one common bus voltage at v ref then to impose the sharing of reactive power one may have to put this additional component in the control system which makes the excitation field voltage dependent on i. So, if one generator starts pushing more current it automatically self corrects. So, that is the basic idea. So, the sharing of the generators can be imposed by choosing appropriate values of k for each generator is it ok. But of course, if the generators are not bused together in fact typically what happens is each generator is connected to its unit transformer it is called the generator transformer which steps up the voltage and the generators are bused together at the high voltage side. So, this is the low voltage say 15 k v 15 k v and this is 220 k v and or 440 or 400 kilo volts say. So, if you have got a situation like this each generator maintains its own terminal voltage constant it is not maintaining a common bus voltage at v ref. So, in this case it is not necessary to have a load compensator for sharing of because you are not maintaining a common bus voltage at v ref. So, but in case two generators are bused at a common point directly the terminals of the generator are connected to a common bus and then you step it up say or use it for other purposes. In that case you need to have a load compensator to ensure that while trying to meet a common objective the sharing of the load is done as per our design this k value. So, I leave it as an exercise for you to show that indeed if I choose k 1 and k 2 appropriately for say two identical generators I can or two different generators for that matter by choosing the k value appropriately I can impose a sharing of reactive power between the two generators. So, this is something I request you to try to prove. So, the steps are just to make things simpler assume two identical generators assume that they are supplying the same amount of real power they have got the same mechanical power input say that is the values are equal. Let us assume that the v ref for both the automatic voltage regulators independently I mean the two independent automatic voltage regulators is the same and these two machines are bused together at a common point then by choosing k 1 and k 2 appropriately the reactive power sharing can be imposed as desired by us. So, you can choose k 1 k 2 as per your reactive power sharing requirement in this situation. So, this particular function of v ref is being modified this the summing point being modified by applying an additional correction signal here you can say which is dependent on the loading of the machine alters the characteristic of the machine alters the voltage you are not no longer maintaining v is equal to v ref, but maintaining v plus k i approximately equal to v ref. So, this is called a load compensator it is usually not used in situations where a common objective is not being met by two excitation systems for example, in this case when the machines are bused together at the high voltage side and your voltage regulator is trying to maintain these voltages constant it is not necessary to apply this load compensator and in such situations it may be absent. So, please chew upon this point now if you look at the other functions which are shown in this block diagram there are limiters and a stabilizers, but we will come to that a bit later in fact I have already given you an hint where this limiter may come into into play. For example, if I have given v ref 1.05 and you also see that the frequency of rotation of the machine has come down it is my less than the normal say 50 hertz the frequency has come down in that case the flux level in the core may be higher than what is sustainable by the core in the sense this core will start heating up. So, and will also get saturated. So, in such a situation you may require to have some overriding functions which prevents the flux in the machine from becoming too large. So, what you have to do is if effectively under such situation if you see that the flux limit is being exceeded what you would do is override what you want to have rather override the regulator in the sense that do not aim to achieve v ref is equal to say 1.05, but reduce this v ref to a point at which the flux is not exceeding its rated value. So, this kind of predictive and limiting functions can be there basically what they do is override v ref or at least change v ref. So, what you have usually is the stabilizing and limiting functions. So, what you have normally is v ref and in case the generators are not bused together right at the terminals this is the structure of the summing point of the voltage regulator, but v ref itself may be overridden in the sense that some additional controls if you for example, if I put some additional input here say 0.05 per unit I add at this point. So, what will happen is that if I if the controller here the controller here drives this to 0 what you will have is v ref is equal to v minus 0.05 or in other words v ref minus v plus 0.05 is equal to 0. So, what in effect by doing this I have done is increased v ref. So, if you have any additional signals adding on to v ref the in effect compromise on this voltage regulation function or we will no longer be equal to v ref. So, for example, if there is an overfluxing situation you may adjust this becomes minus you may adjust this v ref by an additional signal which adds on to this summing point. So, I may add on minus 0.05. So, as to so I augment this summer what comes out of this summer. So, finally, v ref v will not be equal to v ref, but slightly less than v ref. So, this is what effectively a limiting functions does the other function which we have seen here is. So, actually I will read all this. So, you have got v ref this is the structure of a voltage regulator summing point without load compensation. So, we just have v here this is what is normally required you may have overriding additions or subtractions from limiters and you may even seek to modulate you may wish to modulate you may wish to modulate this voltage reference by some external stabilizers Now, we shall discuss these stabilizers later in the course, but remember you can modulate these things. Now, one of the important things about limiters and stabilizers is which you should be very clear about is that limiters normally gives 0 output if the machine has not hit any limit. Similarly, a stabilizer gives 0 output when the machine is in steady state. So, the overall regulation function of this voltage regulator eventually boils down to this and this the summing point in this regulation function boils down to taking the difference between v ref and v in steady state if no limit is violated. So, the voltage regulator in some sense gets in is completely enabled when no limit violation is taking place. However, if any limit violation is taking place some input will manifest at this point due to the limiting function and we will no longer be equal to v ref it will get overridden in some sense by this additional superimposed signal. During transients the stabilizing function augments this v ref say you can be during transients you could be sending in a modulation signal how to derive this modulation signal is something we will discuss later. We may modulate this point why we need to do it well by using this modulation function we expect that we will try to improve the dynamic performance of the synchronous machine. So, this is what essentially is the things you will see at any summing point one of the questions you may ask is well you have got this controller or regulator which takes this error does some mathematical function on it and derives the control signal which goes to the power apparatus the excitation power apparatus. The question is can we not shift these limiting functions to this point. So, can we not instead of changing the summing point here can we have these overriding functions acting here the answer is yes you can. So, in some implementations of regulators this limiting the output of limiting functions and stabilizing functions are in fact added at the control signal level the control signal which is sent to the excitation power apparatus that is to the control rectifier of the power apparatus excitation power apparatus. So, you can have this kind of alternative structure where you are having the summing junction here for the limiting and the stabilizing function. Now, before now the main important point here is now what is the structure or mathematical function which are typically used in the controller block which is shown here and also what are the mathematical functions which are used to implement these limiters and stabilizers. Now, to understand this we will actually have to understand what are known as transfer function blocks. Well you do not have to understand this in terms of what are known as transfer function blocks, but most of the excitation system control system representations which are available in the literature come in the form of block diagrams. So, you should be able to write down the dynamical equations or the differential equations or the mathematical functions which really correspond to these block diagrams. So, mainly there are what are known as transfer function block diagram. In fact, I have already shown you a transfer function block diagram we call this this IEEE model of a brushless excitation system is in fact a transfer function block diagram you see this S function here. Well this S function is in fact the Laplace variable we have used of course, we have without actually explicitly defining these we have already used the summation blocks this is a product block. So, these are what are known as typical block diagrammatic you know components which are used in trying to model an excitation system of course, this transfer this block diagram here which uses Laplace variable S. In fact, 1 upon S is what is known as is essentially an integrator in integration function. So, this 1 upon S here represents an integration function. Now, this of course, was a model of the power apparatus. So, what we did was roughly model the excitation alternator by a differential equation and then converted it into a block diagrammatic representation of this kind. We now move on to the block diagrammatic representation not of the power apparatus, but of the control system. Now, control system are something which we will be implementing. Now, what should be the structure of any control system? Now, it is usually made up of gain blocks, integration blocks, summation blocks and so on and compactly written down in terms of input output relationships or what are known as transfer function relationships. So, let us just take a minor diversion we need to build up this kind of expertise and try to understand some basic transfer functions which you will see. For example, consider the block 1 upon 1 plus S t this is a transfer function block. In fact, the simplest block 1 can have is of course, a gain block. A gain block is a simply multiplies u by k to get y. A transfer function block on the other hand means something more. In fact, in a transfer function block inherently or you know implicitly there is some numerical or actual implementation integration being done. So, this S in fact, is a Laplace variable 1 over S represents an integration function and S of course, is a derivative function. So, what is 1 upon 1 plus S t derived from? In fact, if you look at the dynamical equations if you look at these dynamical equations I have written them in. In fact, this dynamical represent dynamical model using differential equations is actually how this has to be interpreted. Why is well why does this mean this? It is not very difficult to see. Suppose, I do replace d x by d t here by its appropriate Laplace transform value. What you will get is if I apply Laplace transform on both sides of the equation you will have S into x S is equal to minus 1 upon t x of S plus 1 upon t u of S and y of S is equal to u of S. So, what you will have here is you get this on to this side you will have x of S into 1 plus S t is equal to u of S and as a result of it of these equations you will have y of S is equal to 1 upon 1 plus S t into u of S. So, that is why this differential equation after doing Laplace transform transformation of this differential equation you get effectively this input-output relationship. In fact, input-output relationships have been discussed in the past. In fact, our when we talked about the modeling of a synchronous machine when we actually correlated what we get from measurements the frequency response obtained from measurements we did use a transfer function representation of the synchronous machine. Therein also the basic differential model differential equation model of the synchronous machine was reduced to an input-output relationship in by using this Laplace transform variable S. So, remember that 1 upon 1 plus S t represents this transfer function of course, one should be a bit careful and precise well there is no 1 to 1 mapping between this and this. In the sense that a different model of you can have a different state space or different differential equation model to get this input-output relationship. For example, d x by d t is equal to minus 1 upon t x plus u and then y is equal to 1 over t of u will also give you the same transfer function can you verify that you will get S of x S is equal to minus 1 upon t x of S plus u of S y of S is equal to 1 over t u of S. So, you will have so what you will get eventually is 1 plus S t of x of S is equal to t times u of S y of S is equal to 1 upon t u of S. So, from these equations what we can get effectively is y of S is equal to 1 over 1 plus S t u of S is that y of S is equal to 1 plus S t upon t into u of S. So, we will have equal to I am sorry. So, u of S by t is equal to y of S is equal to 1 of we will just redo this. So, what you will have here is a y of S there was one small error which I did in our previous this should have been x this should have been x. So, please note this error. So, this should be x of S in that case of course, you will get this particular relationship. And just to recall what I was doing just now I was just trying to show that this is an alternative representation of the same transfer function. So, what you will have is it should be x of S it should be x of S and as a result of this we will get. So, what I wish to say here is this is one possible representation of the transfer function, but this is another representation of transfer function. So, there is no unique way of representing transfer functions by state space. So, this is one example of that, but usually in this particular course I will just take this particular representation is very convenient of 1 upon 1 plus S t. In fact, I can split up this if you look at this particular differential equation this is one possible representation of this transfer function. So, if you look at this differential equation I can rewrite it as kind of a integrator this is u and this is y. This is x, x is equal to y, this is x dot if you integrate x dot you get x, x dot is equal to 1 upon t u minus x. So, this is what exactly this says the x dot that is d x by d t is equal to u minus x divided by t. So, this is what effectively is a block diagrammatic expansion you can say of this transfer function. So, if you see this remember this now see this what we have drawn. So, right now is actually quite interesting the transfer function itself that is what I mean 1 upon 1 plus S t is an interesting transfer function if you look at some simple things it does. If you have got u and y here if I give a step change in u what will y be in fact you can prove this by actually solving the state space equation and prove this that if u is a step then y is going to be something like this, this is y and this is u. So, the step change has some interesting features you see that at the instant of the step this transfer function has an output 0 it does not change. Suppose the initial conditions associated with this state x is 0 then if I give a step change in the transfer function we will find that x remains 0 and as a result y also remains 0. So, there is no instantaneous change in y given an a step change in u. So, x y just remains where it is but as time passes you will find that y tends to become equal to u. So, the steady state gain of this transfer function is 1 that is y becomes equal to u. Now, of course the same thing can be got the same you know inference can be obtained directly by setting S is equal to 0 in this transfer function. So, a shortcut method of finding the steady state gain of any transfer function is to put S is equal to 0 in the transfer function. So, if you give a step input the steady state value or the steady state gain for a step input can be obtained by simply putting S is equal to 0. So, you can say that this transient gain or the high frequency gain of this transfer function is actually 0 it does not instantaneously respond but in steady state it takes on the value. Now, what is the nature of this curve? In fact, you will find it y is equal to u 1 minus e raise to t by capital T. So, if this step occurs at time t is equal to 0. So, this is a step change of magnitude 1 occurring at time t is equal to 0 the responses like this the time constant t appears here in the response. So, it is a good idea whenever you come across any transfer function block you should be able to correlate it with its time response under various test inputs. If you look at another interesting and important way of looking at transfer functions or what interpreting how they behave is to look at the transient behavior. So, the transient behavior or the what you call the frequency response we have actually seen the transient behavior for a step change the frequency response of the transfer function can also be obtained that is you vary the frequency and see the gain that is u y upon u in steady state. So, what do I mean by a frequency response of any transfer function? You take this block feed it by inputs of varying frequency in steady state if it is a transfer function normally a transfer function in steady state would at the output if it is actually a stable if it is a stable system that is it is associated with the state space whose Eigen values on the left hand side of the imaginary axis then what you will see is that the output you will get also a sine wave, but it its magnitude would have changed and it would have also got some phase shift it could have got some you know it can have some phase shift. So, you take any transfer function this is how you would measure the steady state frequency response. So, whenever people say a frequency response it is implicit that they are talking of the response under sinusoidal steady state conditions for input sinusoids inputs u which are at different frequency. So, what you do it you do this experiment which I have shown you on the sheet here at a particular frequency record the gain that is how much is the amplitude with respect to the input amplitude. So, that is the gain and also measure the phase shift. So, the phase shift of this there will be some phase shift between this signal and that. So, you measure the phase shift. So, that is what will give you what is known as the frequency response. Remember frequency response implicitly is the steady state frequency response of this system. So, you will get a gain which is a function of frequency that is one important thing. So, the gain is a function of frequency the phase also is a function of frequency it turns out for 1 upon 1 plus s t the steady state gain is 1 steady state frequency what you call the 0 frequency when I say steady state actually it means 0 frequency the 0 frequency gain is 1. Whereas, the high frequency gain is low how do I know this phase shift and the gain well you can do it very simply using a transfer function. If I give you a transfer function if I want to know what is its gain and phase shift all I need to do is put s is equal to g a omega corresponding to that frequency which you are interested in getting the frequency response and you can get the answer. So, this is something of course, you have done before, but we are just revising that. So, this is how it is represented. So, this is called a frequency response or rather the transfer function evaluated at this frequency. So, what is the magnitude gain well that can be obtained simply by obtaining the magnitude of this complex number. So, that is what you will give you the gain and the phase shift is again obtained by looking at the argument of this complex number which results. So, what one thing you will notice is that this will always give a negative phase shift this transfer function has a negative phase shift. In fact, at omega is equal to 0 the phase shift is 0 phase shift is 0 degrees at omega tending to a very large value a large value in this context means that omega t is much greater than 1. In such a case you will find that omega t omega t or t omega much greater than 1 you will find that the phase shift is minus 90 degrees of this transfer function. Similarly, at omega is equal to 0 the gain is 1, but the high frequency gain is 0 which correlates well with the step response. Just at the instant at which the step is given you can say that the input signal in some sense is kind of changing very fast or it has got a high rate of change or it has got a very high frequency component. The transfer function does not respond very well or it has a very low gain to high frequencies. We will move on to one more transfer function that is it is a kind of a important transfer function just as the previous one was this is s t upon 1 plus s t this is an interesting transfer function again. You can verify that a steady state space representation of this is y is equal to u minus x. So, this is a change. So, this is a steady state representation of this system or rather state space representation of this system. So, if you look at this can you guess what is going to be the response for a step change in input. Well, you can actually work it out, but it is not difficult to see that first thing is that the high frequency gain of this is going to be 1. If you look at the frequency response with omega large the gain of this is going to be 1. For low frequencies the gain is going to be equal to 0. So, in fact we will not work it out, but a step change for a step change the response of this y is going to be like this. The final value is going to be 0 the initial value is going to be equal to whatever this value. Suppose this is 1 then this is also 1. So, this is known also as a wash out transfer function. It is called a wash out transfer function 3. The characteristic is that it is got a characteristic of a in a sense a high pass filter. It prevents slow changes from going through, but it allows fast changes to go through. So, its steady state gain is 0 its high frequency gain is 1 and this is the state space representation. Now, from state space representation one can easily get a block diagrammatic representation. So, it is quite simple. So, if you look at this it is simply what it was before the only thing is this is an integrator. You can represent a integrator is in Laplace domain is represented by 1 upon s. So, this is u this is y and oh this is not y. y in this case is this is subtracted u minus x this is x, but there is an additional u y is equal to u minus x. So, this is y this is u this is x this is x dot and this is u minus x. So, this is known as a wash out block remember this extra thing here completely changes what you get.  So, it is not surprising you have got a block diagram of this kind in which in fact, this is nothing, but this whole thing is nothing, but 1 upon 1 plus s t.  So, this is as far as one of another of the transfer functions goes. In the next class we will look at a few more transfer functions talk about what are known as what is a p i a proportional integral regulator and a proportional regulator. We look at as I mentioned some time back the lead lag blocks these are also special transfer functions and we will also look at the effect of limiters there are two kinds of limiters. So, far I have implicitly assumed you know what a limiter is, but you can actually have some variations of limiters themselves and they eventually affect how the system response is going to be. Typically a control system will be made out of either plane gain blocks in addition to summers multipliers and so on and transfer functions. When I say transfer function blocks the transfer function blocks themselves represent a linear system, linear state space. Of course, if you put limiters in the transfer function in that case or limiters in transfer function blocks the blocks which I have shown you if I insert a limiter it no longer is a linear system, but if you just remove that little bit complexity transfer functions implicitly are obtained for linear systems or linearized systems non-linear systems are linearized around an equilibrium point. So, using these blocks or these mathematical functions or these you can say mathematical dynamical functions we can actually try to design a control system which meets our objectives. So, I have not I have just discussed some of the control systems which are used of course, rather the transfer functions block diagrams which are used we can use these block diagrams selectively to get the dynamical as well as steady state response that we desire. So, that is what we will do in the next class.


One of our main strategies was going to be to get out to the fleet concentrated areas and have a conversation. That's when you get the best information from our sailors. You can't do it via Navadman, you can't do it via email, you need to have a conversation with sailors and we have stuck to our guns and we're having a great time doing it. Well, I tell you, me and CNP, Chief of Naval Personnel, Amber Moran, we came out from Washington and we had an opportunity to do three all hands calls with the sailors on the base and one of our responsibilities, I believe, is to make sure that we are communicating to the fleet, giving them feedback. They send us questions, they share their concerns with us and to be able to come out and talk to them face to face, I believe, is a great opportunity that we have and it's important. During our enlisted all hands call, one of the things we talked about was tuition assistance. They were just wondering, curious if we were going to have any changes in that. They talked about the force of our Navy, were we going to see any declines in personnel and of course we put that to bed by saying no, we have stabilized the force, we are right where we need to be and we don't see any of those changes coming any time soon. We talked about our new final multiple scores that they've been hearing about, they were able to hear that from Amber Moran first hand and basically the people programs that Chief of Naval Personnel is responsible for, they had an opportunity to ask questions and hear it first hand and then they gave us some feedback with regards to overseas screenings, some of the challenges that they're having when they get their orders in a small amount of time to execute and we'll take that back and we'll do whatever we can because one of the things that I tell sailors is we're supposed to leadership set sailors up for success and we provide the conditions so they can be successful. So we take that information back to DC and if it's a policy and we can change it for the better, then that's what we'll do. I think one of our goals is to be able to provide a sailor and their families more stability. If that has to do with changing of location, if that has to do with deployment lengths, if that has to do with any type of pay changes, they just want to know and we're working on making sure that we can provide them and manage their expectations. But if we can give them more stability in their careers, I believe that's one thing that we need to work on. I do believe that we have a great Navy, but one of the things that I talk to our chiefs mess about is never, ever, ever settle. We'll always have opportunities to do something better. We'll always have an opportunity to look ahead and foresee something coming and we need to make sure that we go out and try to solve that before it becomes a problem. So never get comfortable and always look for an opportunity to do something better. I believe our Navy provides each sailor an opportunity. And I would hate to think that there's any sailor out there that feels that they don't have the opportunity to succeed. So from the most junior to the most senior, it's all about having opportunities and then being able to walk through those doors that are open for you. But one of the things that we're visualizing is when a sailor comes through boot camp, we issue them, for lack of a better term, a tablet. And instead of all these different paper manuals that they have to read and look through, issue them this e-tablet. And they'll take that e-tablet onto their A-school. They'll take that e-tablet onto their first command and we'll develop applications. So instead of them having to look for updates, we'll send them like a banner that says, you have a new update just like my iPhone does now. And I just push the button and it gets updated. So we are looking at being more innovative. We need to catch up with technology. We're a little bit behind the power curve, but we are doing what we need to do so we can catch up.


Good afternoon everyone, I am Bharat, this is Kanika and Komal and our project is to develop a notification system to the existing collaborative community's portal. So nowadays in all the modern consumer web applications, notification system has become a very important part of it. So in collaborative community's portal, the main job of notification system is to keep the users updated about all the events which are happening in the system. So the main motivation behind this is that we wanted to simplify the process through which a user needs to go in order to keep himself updated with all the activities happening in the system. So these are few technologies used by us in this project and those two frameworks are used for building notifications and feeds which we will talk about in the next section. We basically divided the notification system into two subsystems, one for sending personal notifications and therefore feeds. So what is the difference is that basically notifications and feeds, they are similar in the sense that both of them are used for sending some messages or some information to the users. But the difference is that one is specific to users. This personal notifications is specific for a particular user whereas feeds are common to members of a community or members of a group. So this is actually the workflow of the Django notifications framework. We use this framework to build the notifications. So whenever an activity occurs in the system, a notification signal is sent and all the attributes which are given to that signal define that activity and when that signal is sent, it is saved to database as an instance and then when the user goes to notification tab, they are retrieved from database and they are filtered based on the recipient and then they are showed to the user. And it is similar for Django activity stream which we used for, Django activity stream is the framework which we used for building feeds and it is similar, the only difference is that feeds are filtered on basis of the recipient rather than a particular user. So these are the features we have given to our notifications or feeds that are the basic features that is marked as red, marked as unread, delete, delete all unread or delete all red. The basic, the major feature of our notification or feed is the linking part that is like our notifications looks like this and if you will click to this PQR group, it will redirect you to this group and it will be automatically marked as red. What was the major feature and the basic features are here like you can delete an individual notification and you can mark any notification as red or unread or this all notification and unread notification are basically the filters and mark as red, unread, delete, all delete, red and delete, unread are the functionalities we provided for our notifications. And yeah, so for a notification or a feed to exist, there must exist some events. So be it a community or a group, the major event is joining or leaving to a community or there may be article state change or there may be role changes in community or a group. So here is the flow chart of all the article state changes, be it a community or a group or the role management of author, publisher or admin. So each arrow here depicts a notification or a feed or both. So yeah, this is the basic structure we kept for notification and feed and this target, verb, sender, these are all arguments that are sent along with our signal that will further put it into our database and these underlined ones are the links we have given to notification or feed. So for example, suppose article state is changed from publishable to published. So author should get a notification saying that congratulations, your article got published. So this is the example where sender is publisher because a publisher can only publish the article and recipient will be the author itself and it's the notification generated saying that your article got published. So the feeds, as she said, when an article state is changed from publishable to published, the author of the article gets a notification saying that your article has been published along with that a feed is sent in the community to all the members so that they come to know about the published article. Feeds are sent using action signal. So these are the arguments which are sent and this is the structure of a feed. IIT Bombay is the name of the article and the verb is article has been published and root is the author of the article. So the main challenge in the notification system was to make it real time. For example, when a new notification comes, the user doesn't have to refresh the page to check for the upcoming notifications. For that, we added a batch which shows the under notification count which updates itself without page refresh and this is done using a JavaScript API which sends HTTP requests at regular intervals of time. Futurescope right now sending requests at regular intervals of time consumes a lot of resources. So this problem can be overcome by the use of web sockets and the notification system has not been integrated with the reputation system. Like when an event occurs due to a user's reputation, notification is not sent in that case. Thank you. So actually event logging their work is to store all the events which are occurring and corresponding to each event which occurs, we are sending a notification or a feed. So that part is done only the part related to reputation. Like for example, an author's reputation goes down. So we are not sending a feed to the community that this reputation has gone down. So since these projects were independent, so the integration of reputation system and notification system has not been done but otherwise corresponding to all the events which are occurring right now in collaborative communities, all the notifications and feeds are going. But maybe this can be integrated with that. This is very easy to integrate but it was like their system got integrated a bit later and our system had been joined. So somewhere I saw also the term called group. So what's the difference between community and group? The difference between a community has certain groups. A group can be public or private group. For example, there is a community named Psyche. Okay, it's just like a sub-community. So just one more thing, it's maybe common to all the people working on collaborative systems. Like somewhere I felt that you are not considering edits after an article has been published. Once an article has been published, it cannot be edited. It cannot be edited. But in fact, papers are itself being retracted these days. Yeah, it's not a major issue but yes, it's right. Refining is done. Like if an article is in draft state and it changes to visible state. Visible state that means only community members can edit it. So they can refine it to a bit more level. It's not published yet. So they'll refine it. And then after visible state, it will move to publishable state. That is only publishers can refine or edit or view it. Then if publisher feels so that it can be published and it is refined and it is good, then the article will be published. So then it can't be edited anymore. But there is a refinement going on. So it is a separate system, independent system, correct? So how easy or difficult is it to combine with or attach it with some other system? So we have used frameworks. We have used Django framework and Django notification framework. And for feed, we have used activity stream framework. All we used is the function provided by them. So we modularized our code and we just made a new separate app. So it's like using that framework would be very easy. You just have to design your own display and template and that's it. According to your needs. So basically my system should have an event logging mechanism. No. It's not that. Already merged. So event logging and this as a combined unit can be used in some other system. But again, we have to look into several features because once the event is there, it is for what you said you are not displaying. So some community member got a vote down. So a reputation system goes down for some and that event is there. And that event comes to your feed or not. No, it doesn't come. It's like we are sending. Suppose for example, we are sending a notification when a role gets demoted or promoted. So suppose someone is publisher and its reputation goes down and he becomes an author now. So he will get a notification that you are no more a publisher now because he should be informed. Okay. He or she should be informed. So that will be implemented with reputation system. Event logging. So the event, okay, not event. So there's an event that some person's reputation goes down. Okay. Then reputation system also goes down. Okay. It's like suppose you click on some button. Suppose there is any event. I mean we are sending the notification and event being stored. These two are happening. No, that I got that you are sending notification. But there are some rules on which you are sending notification. Correct. So you are filtering some things. So for example, that if reputation system goes down, so you are filtering it to decide whether this need to be sent to an author or to group or to nobody. Correct. So if I have a system and I want to use your system, that also means that I need to program your system in some manner so that it can understand the verbs or the functionality of my system. Okay. So can that be modularized? So at least that particular thing that what are the events and what should be the feed? At least that should be modularized. So it will be very easy to integrate their system. Yes. Okay. Thank you. Hi. I have a question. So you said the regular intervals. So how frequent are those? Right now it's five seconds but you can change it. So how frequent are you willing to go before you go to WebSockets? No, no, no. I'm just saying. I'm just saying how about you make it one second? Yeah. So why did you not use WebSockets? This functionality was provided by the framework itself. Okay. So when do you think would the WebSocket make sense? At what frequency do you think the WebSocket would make sense? WebSockets maintain a continuous. Yeah. WebSockets will consume much less resources than those. So I will just say just read on this because on non-chrome browsers, the WebSocket implementation is still a pooled Ajax request. Yes. So if you're not on Chrome, then your users are still going to be following the same thing. There is something called Django channels. So what it basically does is whenever you like, if you implement your system using that, it will check whether the browser is compatible with WebSockets or not. If at all it's not compatible, then it will fall back to things like long polling, polling, short polling, those kind of things. Cool. Thank you.


our life should not be dearer to us than Jesus's life was to him when Jesus was on this earth his life was not very dear to him i'm not saying Jesus was suicidal i'm not saying Jesus just hated life Jesus wasn't one of those debited out or depressed walking around always always having something negative to say Jesus said i am the way the truth and life so everything about Jesus was happiness and life Jesus says i came to give you life and more abundantly there was nothing about Jesus that's suicidal or down yet Jesus did not value his life very dear to him he always laid it down can i ask you a question are you valuing your life dearer than Jesus valued his life to him an apostle john tells us today he says that if Jesus did this for us lay down his life he says we ought to lay our lives down for our brethren see for most of us we love the message that Jesus came it was like oh my goodness i just want to give Jesus a little bit more money such a great sacrifice became like human died man i just my love just grows deeper for Jesus but see what that is it's not only so that your love will go deeper for Jesus but so that you will follow his pattern and so that your commitment to Jesus will go higher can somebody say amen i really want to encourage each one of us disciples murderers all the people who brought Christianity to us lived with this motto if Jesus's life was not dear to him our life should not be dear to us if Jesus's life he laid it down so that i can hear about the gospel i should lay my life down so other people can hear about Jesus for the glory of God can somebody say amen i want to tell you about few of these men that Jesus had around him who did some really incredible things for for God James the son of Zebedee and the elder brother of John was killed by King by Herod Agrippa so James is a disciple of Jesus and he ends his life being killed because he followed laid down his life for Jesus the second one is Matthew the tax collector most of you know Matthew because Matthew wrote the gospel of Matthew in Hebrew he was preaching in Ethiopia when he suffered martyrdom by the sword i mean Matthew decided that Jesus laying his life down for the world is good but Jesus is my mentor i am gonna lay my life down also for the world in Ethiopia James the brother of Jesus somebody said if you don't believe that Christianity is real how hard will it take to convince your brother your God that is that is a miracle in itself and so Jesus had a brother the half-brother of Jesus he was a leader of the church and he was the author of the epistle by his name and this James at the age of 94 history says that he was beat and stoned and finally had his brains bashed out with the Fullers club imagine Jesus's brother who could have said Jesus died for my sin this is for free i don't need to do anything then why did he at 94 years of age not just keep this faith to himself and live all of his days celebrating maybe writing a book that Jesus was my brother see most of us think that to believe in Jesus is free but to follow Jesus costs everything most of the time disciples were shut down and they were said if you're not gonna preach about Jesus we will not hurt you but if you talk about Jesus you will be beaten and disciples chose not to value their life very dear to them Matthias was an apostle who filled the vacant place of Judas he was stoned at Jerusalem and then beheaded Andrew was the brother of Peter so Peter had a brother he was name was Andrew he preached the gospel throughout Asia upon his arrival at Edisa he was arrested and crucified on the cross and the two ends of which were fixed transversely in the ground which is where we get the term St. Andrew's cross so this is how Peter's brother history says was crucified why because to Peter's brother as it was to Peter they said this Jesus did not value his life very much to bring salvation don't think the angel was suicidal this is not angels dream I want to be crucified of course not they all wanted to live just like you they all had dreams just like me they all had ambitious just like all of us the only difference between them is they followed a master who laid his life down to save them and they said we cannot he became he was God became man we are men we cannot hold our life to dear that will end anyway we will lay it down as well Peter was condemned to death and was crucified upside down at his own request because he said he was unworthy to be crucified in the same manner as his Lord becoming a Christian at those days did not necessarily mean you're not going to have troubles it just simply means you will have salvation and you also will follow the pattern of Jesus to lay your life down to bring others to Jesus Jude the brother of James was also crucified at this city Barthela Mayu he preached in several countries and translated the gospel of Matthew into the language of India he was cruelly beaten and then crucified by people there Thomas who was the doubting Thomas he preached the gospel in India where pagan priests murdered him with pin spears and tortured him with red hot plates on his body and finally burned him alive Philip evangelized at the city where hostile Jews had him tortured and crucified upside down Simon preached the gospel in the city and in Africa and even in Britain where he was crucified in about 74 AD John the beloved disciple who was the brother of James from Ephesus he was ordered to Rome where he was affirmed to be cast into the boiling oil he escaped by miracle without injury and then the emperor banished him to the Isle of Patmos where he wrote the book of Revelation he is the only apostle who escaped violent death so Jesus had 12 apostles all 12 followed his pattern please understand following Jesus did not mean dying like Jesus it meant living like Jesus and living like Jesus means this you lay your life down for God's call and sometimes it could end good sometimes as we see with 11 it didn't end so good even with John at the last time of his life but there was one more apostle that the church had and this apostle was Judas he was so bestowed by betraying Jesus that he committed suicide it's interesting that all 12 did not die normal death even him who walked away from Jesus can I tell you something we as a church we as youth group there's three things you can do with your life is you can either waste it you can either wreck it or you can lay it down to God


There's a lot of recognition of how faith, the role that faith can play in the work of peace activists and certain peace movements in calls for social justice around the world. And so why is it so unusual that when it comes to gender justice, when it comes to women's rights advocacy, that faith isn't going to play an important role? Fortunately, secular feminism, especially as it's understood within the West, has been very resistant to religion, especially when it comes to advocating for women's rights. There really hasn't been a place for religion in that. More recently, there's been this attention on religious feminism and Islamic feminism in particular. Many Muslim women, their religion is an important part of their identity, their personal identity, and an important part of their advocacy work. There's actually great potential for religious and secular frameworks of women's rights to be compatible and complementary with each other, as long as that partnership recognizes women as agents of their own religiosity. That women are agents in how they identify with their religion, that their lived experiences with their religion is important, is legitimate. Their interpretations of their own religion is important and legitimate. It may be different from traditional religious authority. It may be the same, but we need to pay attention to those experiences and their perspectives that have often been silenced. From a secular feminist perspective, if we are not taking that into account, if we are not willing to engage women's own understanding of religion, their own agency and their religiosity, then we're silencing women. We're silencing women on a very important part of their identity. We've got to look beyond the religious institution, which is largely patriarchal, and those official leaders within religion, which again are oftentimes male across all religions, and really see people's own lived experiences and perspectives on religion in their own lives and what that identity means for them. That's something that both secular feminists and religious feminists agree on, is that the importance of recognizing and honoring women's own perspectives and beliefs and experiences.


but I could be wrong. What I'd like to do is turn over to you because I have a pile of terrific questions here and I've categorized them and I want to give you the opportunity to hear your voice and stop hearing my voice and me. So the first one comes from the Enrique Pinalosa fan club and there seems to be a number of members of that club.  For Enrique Pinalosa, what problems did you encounter in implementing your plans for pedestrian spaces and green parks and how did you deal with these problems? Well, there was a huge conflict because cars used to be parked. Again, the main conflict is not that I'm a car hater or anything. Cars are wonderful. But the fact is that there is a conflict between, again, for space and for money between cars and people. In most developing country cities, the most basic element of a civilized human environment which are sidewalks is lacking. And where they exist, very often cars are parked on them. So we're talking about something which is very simple, but just getting cars off the sidewalks and making some half decent sidewalks where a wheelchair could go was a very difficult war. There was a movement to impeach me. Very well financed movement by some shop owners who were used to the cars going almost into their shop. But this was, but in fact, at least in Bogota, we didn't have to do any authoritarian thing because actually it was in the law. We were only really doing what was in the law. So even though it was very difficult, the battle was very difficult, what was very beautiful is that at the end, even most of those people who opposed these processes realized it was much better that the environment had improved, that safety crime had gone down, that the sales were better than before in most cases. But it was difficult, especially this battle to take away some space from cars in order to give it to pedestrian spaces. But people in the end realized this is better. Thank you. Andy Altman, you're over here and I see that you have a question that you wanted to ask, so please step forward or get a mic. Thank you. I just wanted to actually follow up on Daryl's question because I had a very similar one on our tour yesterday of Dharavi and you see this incredibly intricate network of the informal economy. I'm just sitting here thinking that we've discussed a lot about the housing question, but the employment question and the replacement of that employment. If you think that at least maybe let's say two, 300,000 people, maybe more, we don't have a census, are working there. Let's say 300,000 people, just to give an equivalent, that is probably the size of a mid-sized city central business district or even a large city central business district, could be somewhere up say 50 to 75 million square feet if you were to take an office at 250 square feet, multiply it by 300,000 people. This is an enormous employment center that one is also talking about relocating, not just housing. So the question is to follow up is, and maybe I'd like to hear from PK and maybe from Joaquin, is what are the models for how one approaches the negotiation of the employment sector? We clearly have different models of how the housing might work in terms of the vertical development, but I'm still unclear how that complicated a network of the informal economy that seems so connected to one another, how can that be replaced and what models do we look to to even begin that process of negotiation that may occur in this redevelopment? I think that is what we are talking about. Most important is Daravi, kind of employment generation. There are about more than 800 families survive only on rag pickers. They are living there. The larger recycling industry for all of Mumbai, not only Mumbai for Maharashtra, the PVC industry is one of the best in biggest industry where even Japan could not invent a mission how to recycle the plastic thrown out. It is discovered by the people that industry is existing there. How are you going to replace that? That's not going on the first floor, it's not going to go beyond the second floor. Where is that explanation? When I'm talking about transparency is not there. When I'm talking about where these things are in your stomach. Why it is not transparent? You're talking about every information has been collected. Why it has not been published? Why the information is not clear? Most important thing is that income generation activity. What is the category of income generation activity? You have enumerated. How many leather industries? Three times the government of Maharashtra rehabilitated all the leather industries. All of them got land, Devanar, Malad, Orega. They are there. What happened to them? What are the other industries there? What industry is not existing in Dharavi which is going to be replaced? What is the mechanism of that? What is the statistic of that? How many people are having this kind of industry? What are their existing sizes? And what is going to be offered? I think most important is the minute the vibrant economy of Dharavi is gone, it will become another communal hell. That is there only because of that economy.  Thank you. Just a line. I think what has happened in Dharavi is that the government has been completely lured by this presentation convincing that the government is going to make 10,000 crores profit or something like that. So the point is that Dharavi has been made into a tradable model ignoring completely the nuances of Dharavi. The point is on the economic front, it is not the question of just accommodating the present economic activity but actually planning for its expansion, facilitating existing economic activity so that this economic activity which is so important is furthered and not led to or strangulated in Dharavi. I think that is the key point we need to understand and we have to make a point that mass housing or housing for the urban poor cannot be a tradable proposition. It can only be a way to seeing how living conditions, quality of life and work, that means working and living together, which is really the model in Dharavi, is furthered as a mixed use situation or context. Jose. If it helps to enlighten the discussion, I didn't mention in my presentation in 1970 the number of jobs in Ciudad Nesa were two jobs per 100 inhabitants. 1990 that number was 25. That means one job per household, local jobs. What I like to show is that in a sense housing is not actually the place where people sleep. It's actually an economic infrastructure. In those 20 years in a community that grew from 250,000 people to more than one million, there was not a single unit of housing built by the state in Ciudad Nesa. Not a single unit of housing. Nevertheless, the economy and actually the vitality that Nesa has today has nothing to do with government action or it actually has to do with a shift in how the government decides where to put in the chips, literally. So, don't build the housing, but really focus on whether those 225 square feet, which are the relocation, what I keep hearing about Dharavi, is actually going to allow for the economic infrastructure to keep on growing. Otherwise, you're actually shooting yourself in the foot. Yes, Enrique. Okay, very quickly. I just, it just occurred to me that when one reads about how London was before the trams, let's say London 1800 or something like that, it must have been overcrowded and even worse because it without sewage and it must have been very similar to, in a certain ways. So, it would be interesting to study how this evolved into what happened later. But just my big worry, again, it's not just the existing slums today. I think while we are meeting here now at this very same time, other new slums are being born in the outside of the city. So, I think developing country cities have two tasks. I mean, the population of Mumbai will be at least twice as much in 20 years or so. What is going to happen is much easier to solve to prevent the problem than to try to solve it once it's created. So, I don't know whether there is a lot of proactive activity in order to avoid future slums because even the ones now will not be able to have enough space to house all the growing population. Rakesh, you will have the last word on this. You will have the last word on this question. That's very rare. The issues raised especially about two issues I want to address. One is that the government is trying to be greedy. It seems to be the kind of allegation about the project and that's why they are lured into it. Four and a half years ago, clearly the real estate prices did not warrant the kind of premium that exists right now and the government was absolutely not interested in any premium. They were interested in better quality housing and in fact I was the one who persuaded the government that the developer should not be walking away with crazy profits instead of which you have to also try to get back something if they wind up getting some crazy profits and which is why reluctantly they accepted so on behalf of the government, I'd like to see this. This is the only project of its kind anywhere in India. I'm not aware adequately about the world but anywhere in India where income generation has been the number one priority of the project. There isn't any other project, slumber rehabilitation or others where income generating, setting up industries, setting up businesses and giving higher advantage and mileage and training and all of that is included. National Institute of Design has agreed to set up its campus in Dharavi so that the skills of the people can be upgraded. In fact C.K. Pralad says that there's fortune at the bottom of the pyramid. Government is talking about building additional fortune at the bottom of that pyramid. So Dharavi is one of those things we are talking of sustaining where income generating is priority number one. Everything else is priority two, three and four and I'd just like to clarify that. Thank you. Thank you very much. Any questions about the port? And I don't know about the port so I'm looking forward to this. Before we leave Dharavi, I think we'll never leave Dharavi, right? There's one question that an ex-Minismar commissioner Bombay has asked here. Is that since there are so many doubts raised about the efficacy of the plan for Dharavi as it stands today because there are different views, would it be useful to have a task force examine what really should happen? I know you're ready to move and this would possibly put it back. God knows how long. But since if there are differences, how do we resolve them? And are they ever fully resolvable? Whether they're resolvable. And our task force is what they are sometimes in my country a proxy for killing the project. Yeah. May I have the permission to speak? Please. Thank you so much. Well, I would like to respond to a few observations that have been made at this house. The first was a question which Mr. Sukhankar, our former municipal commissioner, had asked whether any other option to free housing is being contemplated upon. Let me because many of you have come from different parts of the world let me mention briefly that there is a free housing concept in this city and in other parts of the country in the state, not in the country, which provides the government is to provide for a free house to a slum dweller with a minimum carpet area of 225 square feet. How is it done? As I mentioned in my opening remarks in the morning that this is done through using land as a resource that a free house is provided for rehabilitation purposes and some area is allowed for free sale purposes to be exploited commercially. I'm aware that it has tremendous amount of problems and shortcomings but let me give you only a few figures for the city of Mumbai that despite all its problem this scheme called the slum rehabilitation scheme has been able to provide around 69,000 dwelling units free of cost which are today occupied by people and if I recall correctly the number of figures about 1,28,000 dwelling units are under construction so 2,00,000 approximately houses would come free of cost but this is not the only scheme that we have also now two schemes called the basic services to the urban poor and the integrated housing for the slum dwellers. Basic services to the urban poor is in the metro cities where 80% will come from the government of India, 10% comes from the government of Maharashtra and 10% comes from the beneficiary himself if he belongs to a particular community and if he belongs to the open category he contributes about 12% so that's another model which is coming up then there is also a model in which 50% comes from government of India around 40% comes from the state government in the municipal or the local authority and again the 10% contribution comes from the family which is residing in the slums so free housing is not the only scheme today there are various alternative schemes well his view is that government should move away from free housing because it's not sustainable that's his opinion and I would take the opportunity of conveying to the government the sense of this house and what suggestions have been made so I just wanted to mention that free housing is yes one of the policies of the state government but it's not the only policy we have the other schemes also the other point I would like to mention is whether the question of consent was raised that the consent of the people is very important I don't think any one of us can have even two opinions about it and as you said that both the countries and both all of us take pride in the democratic systems that we have irrespective of what the legal position is there is a legal provision saying that if government on government land is to do something then the consent is not required but that's not the way we are going to look at it let me assure this house that the consent of even people of Dharavi is going to be the most important factor in going ahead with the policies over there and it's a democracy you can't take consent for granted neither can Mr. Joachim take the consent for granted because he fought the elections recently and he lost all his candidates lost the election in Dharavi so that's a... I can't help you in that if I remember I think about four or five candidates had fought on this issue and they all lost so this is democracy very vibrant democracy but consent I can assure you will be now there is... I'm not going to the details but let me mention to you that for Dharavi there is going to be an industrial policy there is a commercial policy and there is a residential policy I'm not going to go into details of it but yes I take the sense of the house that employment is going to be the most important aspect which we need to factor into the rehabilitation process and I can assure you that it will be done Thank you very much Mr. Kerr suggested if you could carry that also to the government that an SRA project must manually include social infrastructure and open space as per the planning norms I mean I think that's extremely... we are interested in education and health and recreation Very true In Dharavi we've gone beyond that I'm talking about the SRA policy and the projects Thank you I have a couple of more questions one is about density densification to me urbanity is all about density but some people aren't comfortable with density and I'm wondering what is the perspective of government, of the advocates the NGOs on this question of densification others? Well I think the point has already been made by Mr. Shiddish Patel he pointed out that Dharavi already has one of the highest density and that the rehabilitation if it is going to have a cross subsidizing mechanism is going to add to the density and that's the issue that he has already made Well what we are trying to do since the discussion is more on Dharavi is that the free sale component is likely to be more of commercial in nature so that apart from the families which are going to be rehabilitated there I think there is some confusion about the figures you mentioned you said that I mentioned 70,000 with 236 hectares no we are talking of 144 hectares at the moment in Dharavi that is the total circumference of 236 but we are talking of 144 hectares so if we go we feel that we will go in for commercial or office space so that at least the density would fall sharply after office hours it happens for example in south in this part of the city where we are all assembled today that the density is very high during the day because it's a hub of commercial and office activity but at night or in the evening it tends to fall dramatically thank you Tony I see you there with the microphone please please stand and tell us who you are is this working? Tony Travis from the LSE picking up Henry K Penelos question about whether or not London in its evolution offers any implications for this discussion and I think there is no question that London in the 1830s, 40s, 50s was very heavily, very densely populated at levels not dissimilar to those revealed for Mumbai today infrastructure thinned that out the building of railways took people way out from the centre railways that today we see as an opportunity to re-densify cities helped take people away but in the context of the debate about social housing there's no question that social housing was built to replace slums it provided subsidised low rents however the long term implication of it has been in the London case it doesn't have to be this everywhere that that housing never had sufficient money to maintain it to appropriate standards and in many ways it traps the poor in poor housing even to today so it became reinforcing of poverty did not allow people to move on because it subsidised them in effect to remain poor that is something that definitely needs to be tackled by I think all politicians in all cities even today So Tony you raise a point that is very much consistent with the American experience and it raises the question that I think we're learning a lot from here and are we saying that poor people in concentrated communities are incapable of creating community that is both productive and beneficial to the broader society and to themselves I think what I was only saying is there is a risk of utopian housing solutions in early days in an attempt to sweep away slums that then create large concentrations of poor people which simply works against their likely capacity to develop their own lives and we now tend to think of cities as working better where people of different income levels as far as possible live in broadly mixed areas and I think that that is the lesson of some of certainly Britain's social housing worst experiments It's very helpful So we're going to have to wrap up I want to thank this amazing panel of speakers today Please join me in thanking them