 We will continue a little bit discussion about our CD-ROM drive, there are a lot of fundamentals that we saw last time with respect to it. We will just kind of brush up some of the things again and proceed then for like know some kind of conclusions that we can draw from from this exercise. Okay, so let's go ahead and like know have a look at some of the Okay, so now what we saw we will quickly go through here. Okay, so the goals that we said was to kind of develop some kind of a philosophy for this design of mechatonic systems and appreciate some of the things that solutions that are already existing in the existing devices. Okay, so let's see what we did. We did a lot of things for CD-ROM drive and you can see if we started off with this CD surface and like know thought about like know different kind of ideas that can come up for like know looking at this data and like know registering it digitally into the computer and then like we came across this multiple systems. Okay, so CD ejecting system or the gross positioning system, fine positioning system something like that. Okay, so this summary of these systems is something up here. Okay, so these are the main systems that we saw that the gross positioning system then the fine positioning system and then focusing system and then CD tray handling system and CD rotating servo system. Now this CD handling tray handling systems or servo system are something which we are we are we have not like we have just seen the CD tray handling system but servo system or CD rotating servo is just a motor which will kind of like know get to drive at a at a speed which is controlled by the position of the the device. So we'll talk about that a little bit maybe but it's not very it's just maintaining the speed to certain extent for the CD disk and maybe I can tell you right now only that this CD systems are constant linear velocity systems which means like now the linear velocity at a point on the surface of the CD which is under the CD head. Okay, under this laser that velocity will be constant. Okay, so as we know that okay if I rotate the CD at constant angular velocity then the the linear velocity at multiple points on the surface of the CD will change its omega r you all you all know that. Okay, so to maintain this velocity constant here we want to the linear velocity to be constant at the surface here I will need to vary the velocity of angular rotation of the CD in some kind of a way okay and that can be maintained by using something called phase locked loop kind of a drive for the for this motor. Okay, so this is a BLDC kind of motor a brushless DC motor okay and it is controlled by speed is controlled by using this phase locked loop kind of a drive and it is it's drive and other systems we'll see little later. Okay, it is like a three phase kind of a motor three terminals are typically output for BLDC motor and we control these phases to kind of like you know maintain some speed of a drive. Okay, so that is a disk or servo system for the CD which is rotating and we'll have a chance to see CD motor some time okay or maybe I can flash you some picture of it okay so if you see this maybe if I go here you can see this is a opened up CD servo motor and it's cover you can see up here okay so this is the cover of the of the motor and this is the motor open okay so you can see that right this is a motor and this is like a cover of a motor this cover will have a magnet inside and on the top there is some kind of a disc here inside that there are balls okay if you just move this around you'll hear some sound of balls there okay think about why those balls are present up there and if you see this notice this motor on this motor at one point you'll find there are this maybe I can rotate it like that and show you here at this point there are if you see see there are this small little sensor that you see up here okay where my finger is okay those are hall effect sensors to sense the field okay one there is one all different sensor another one is up here okay so those are hall effect sensors okay so that is a mechanism for CD drive okay disc drive basically then what we saw we saw then various this subsystems and these components and things like that so you remember all these different different things that we saw and then this is a mechanism like know some kind of a way to kind of prevent a backlash in the system and the stripper motor that is used for for driving this and this is another kind of a fundamental we saw that okay you need these two supports to guide on one side and only one single support can be there on the other side is okay if you start putting both the support supports on the other side also then if the alignment of these two rods is not exactly parallel then you'll see that the the drive will jam in no time actually okay so if you start driving at some position you'll find that the system gets jammed okay so that is what we don't want to have okay then this is another way of like no preventing backlash okay by using like a spring loaded two racks with you give kind of a pre compression in the spring so that two racks are getting pushed like no away from each other and then like no you engage them into into the pinion and then like this mechanism will start working that okay the the one rack is pushing on the pinion tooth on one side and other rack is pushing on pinion tooth on the other side of that other side of the gap so that way like you'll find this this arrangement works for preventing the backlash so you move now pinion in other direction you have a contact that is happening with the rack on one side with the lower rack and on the other side with the upper rack say for example okay so now in fine positioning we again saw that okay for fine positioning we need to have a compliant kind of a mechanism which which guides the system to go in a fine final motion so why this kind of a compliant beams are needed that beams that you see here why they are needed here okay why why don't we provide in this guide by same way as we have provided with some kind of a rod or some kind of a you know support to guide okay the main reason for that is a friction okay so friction is the reason which prevents us if you remember the mobile example like no if you push something the friction is what prevents you to kind of do fine positioning now when we have this motion coming up because of the compliance of some linkages or some linkages are bending and getting that motion in place then actually what happens is like no you're preventing the friction to happen okay so there is no friction in this motion that will happen and then since there is no friction then all the non-linearities in the mathematical are in the physical sense coming because of the friction they are gone for example when you reverse the direction of the motion then friction force changes its direction that is a sudden kind of a discontinuity in the in the friction force okay which is not desirable that is a non-linearity okay so that's why I like know all many linear controllers for such a fine application may not work very well if the friction is present okay so friction is handled in this in this case by changing the design in the mechanical domain such that you don't have the friction coming into the picture so this is like a one of the kind of characteristics that we we are talking about that okay you you you change the mechanical domain too so as to have ease of control implementation in the in the electronics kind of a domain or electrical domain okay so because we saw in the presence of friction it is very difficult to control the system or very fine position the system very accurately and reliably robustly all the time so that is a reason okay so so so this system is serving for two purposes one is like no fine tracking that is there and other is like you know the fine focusing circle okay so this is a focusing these two servos are happening and we saw in the last class what are the sensors to kind of have those servos working okay so what is the feedback that they they'll get is where we we stopped in the last class okay so here like you know you can see the all these kind of things very clearly okay how the coils are placed then there are magnets and then this is a lens from which the laser beam is coming and then this is a so so the magnetic field direction one can see here so one can kind of like you know do a lot of kind of thinking here saying okay oh look how these coils are running and based on that like you know can i know okay which direction when the current is passed which direction motion is going to happen if i want to move it in one way or the other way how these coils should get energizing all those kind of thinking one can do a sort of big issue but we'll see if i don't think we need to do that in this part but if needed one can do all that kind of stuff okay so here ben we came for the sensing mechanism okay so so first like you know the again i'm explaining this you know for the sake of understanding we have these three beams that are focused on the surface of the city the central beam is for the data and then these two side beams are for making sure that you know you are on the track or you are in the proper data track so how that happens is what we want to kind of see huh so there's some kind of a system here but i'll explain it first with with respect to the optics ray diagram and then like you know we'll come back to these elements how these elements are now implementing the same ray diagram we'll talk about that later after the ray diagram is done so let's come to this uh yeah okay so this is a photo detector on which these are four like no four elements a b c d here and e and f are on the side so let us go to the ray diagram so so you remember that okay we have this kind of a facility is there where like no your three beams are going to fall their reflections are going to fall on these three places one is here and the center beam will be here and second side beam will be here okay and e and f are like no full photo diodes like no it is there is a little larger area in e and f than in this a b c d case okay so now let's see the ray diagram okay so the the optics what happens actually is the laser gets split into three beams that as we have seen and then it is made to fall on these multiple mirrors or whatever that reflectors to get basically to take it on the surface of the c d okay and when it comes on the surface of c d that's when it looks like you know the the picture that i showed you about like the actual c d surface image okay um then it gets reflected from the surface and then it travels back okay now because there is a beam splitter here the beam splitter will have a function that okay so look even while going like no this beam would have split and part of the beam would have gone here but we are not interested in that part right now what we are interested in only what is a transmitted part of the beam so also like no this white rays that are coming back part of them will get reflected and get get to the laser but we are not interested in those parts of the rays which are going to go to the laser okay they'll not disturb anything up there okay so only part that is we are interested in is like no whatever is getting partially reflected um so you you know this beam splitter thing right okay beam splitter is where like no the beams are passed when beam is passed like no part of the beam will get transmitted and part of the beam will get reflected okay it's like a only part transmission happens there okay so and then like no part of the light here so there you can get this beam splitter 50 50 beam splitter or 30 70 beam splitter or that kind of a kind of a specification you get beam for beam splitter okay so 70 part gets transmitted and only like no some part will get reflected like that there are specifications okay so we don't get into those details but like the idea is to kind of like to split the beam so that one part of the beam gets transmitted and that part gets reflected in the perpendicular direction so so for this green incident waves rays here like a part will get reflected in this direction okay because the beam splitter has this mirror in this kind of a tilted passion okay but we are not interested in this reflected part that is coming going there okay we are only interested in this point that in the translated I mean transmitted part okay so so also like no this white rays some part will get like no transmitted which are which we are not interested we are only interested in reflected part and that's where that that part goes on to the photo diode okay so photo detector when it comes like so so it this beams will look on the surface like this and on the photo detector they look something like that okay so this is like a reflected like no reflections of a beam on the photo detector so these two side beams are going to fall on these two E and F areas and like no the center spot is going to fall on ABCD areas area areas okay so if I say like no A plus B plus C plus D is going to be my data signal okay so all that is falling on that central area A plus B plus C plus D will form the data signal okay so if the data is not there like no you will get this full reflection here if data is there or either way whatever okay if the data is there then like no I don't get this reflection so A plus B plus C plus D will deem out when the data is not there or when the data is there whatever you want to say okay for the for the lands whenever it comes here on the instead of pits on the land here then like no I'll see full reflection up here okay and I'll see like no that so that in that sense I can make make out a distinction binary distinction between the zeros and ones that are there on the surface of the city okay that's how like no this this data is red now comes to sensing so now we want to sense whether the thing is on the track or not for that these are the two side beams that are used here okay now these two side beams get reflected in on E and F parts now imagine if you have some small error in the in the motion and like no it goes off the track okay so now the beams are positioned is something like this okay so you'll find that like you know the beam which is say on track E is now start interfering with the data more moment it starts interfering with the data previously it was not then its intensity is going to go down okay so whatever you are getting on E is going to go down the intensity and that's how you said okay it has started moving in this direction okay same thing will happen to this spot E see this spot E is spot F here has not yet started interfering with this other track it's important to see that okay they are a little little closer to the central track than to other two tracks so it's there so so the the right position of this part is not exactly in the middle of these two tracks okay otherwise this not happen okay so so so this position is this little more closer to the the track that is getting sensed okay so that's why I like know when small error small motion happens this direction it starts interfering with the track data and its intensity goes down moment its intensity goes down we'll have to kind of see that okay this is alert error correction signal and we'll move it in the other direction same thing will happen so so see if if E and F both would have started going down in intensity because F is now interfering with the other track then we would our our goal is lost E and F we don't want we want E and F to be having a differential kind of a sensing so that we have a tracking error nicely captured okay so so you can see that you know this F like the spot has not yet started interfering with this but E has already started kind of quite good interfering with the with the data track okay so so so the same thing will happen in the other direction also then F will start interfering with the data track and this E has not yet started with interfering with this other data track and then you'll see the differential intensity signal will come E minus F is going to kind of give you the tracking error okay is that part clear any doubts or questions about that so yeah so what if right now in this figure in the the three red the pink color beams what if there is a what if there was a land I mean the black part right below the F beam yeah yeah see what what will happen is first he will start dimming out E and F both start dimming out at the same time okay that's not going to happen because there is a small kind of a see this land area here between the two tracks is much larger but these spots are not in the middle of the land area to begin with that's the important kind of a consideration here to begin with they are like no more closer to the to the data track which is which this is a data that we are interested in for this data track it will be this spot will be closer so this relative positions of these three spots is what is important okay so they are adjusted in such a way that they are closer to the to the data track but they have not they are not touching to the data track in a normal kind of full position like this this position okay but I mean I may not have drawn it really like you know that kind of a nicely here but this this spot is more closer in the normal position to the reading data track than the neighboring tracks this spot is also more closer to the reading data track than to the neighboring track okay so then moment the small error starts happening either this direction or the opposite direction like immediately it will start interfering and it will get a differential signal but at that time other F is or say if E has started interfering F will not interfere yet but but immediately once you see the error you are going to correct it so it will not happen ever like that of course if you kind of like no go pass that correction and go beyond like that okay this is interfering then like no you are actually coming out of the close I mean the good control loop which which should not happen actually so you'll have some kind of torrents and design in such a way that this is not happening okay sir yeah for sure please ignore the question if there's a lot of physics required why are there only three sports oh you're right I mean you if you're right in your physics also for nature okay there should be infinite number of spots okay that's perfectly fine okay but we are not interested in those spots because those reflections are not going to fall in the in the any of these spaces here one and other thing is like no the intensity as you as you if you have seen this physics a little bit more detail like you'll find that okay the in the when there's kind of a transmission grating happens for a laser beam the central spot is much stronger than side spots and then like no as you kind of go away away away when your side spots will diminish in the intensity also yes yes so that's so their intensity also low and they are not falling in the on the photodiode any way we are not worried about them yeah yes good good I mean it's good that you know I I'm glad that you are thinking in physics and in all these different domains it's very good see that's what I this like you know kind of a thinking is what is important in this course or like no in in general for any development of a new conceiving a new new system like no this kind of a critical thinking is essential actually with the practical thing and theoretical thing both I mean both domains nice and we'll do like no we'll do this is I think the very very I mean I would say quite complex system okay not all the mechanical systems are this or like no more complex than this but like no if you are if you can understand and appreciate this particular system no a lot of different systems will be very like you know very easy to design for you and it's not very difficult you'll be able to design them very nicely say for example you might have seen like no the scanner system for example is is is very very simple as compared to this and you can relate whatever fundage we have learned from this system very nicely to the scanner system also okay so if you understand this system well like or the concepts that we are kind of taking away from the system well then like no they'll help you long way to design many many different kind of interesting mechanical systems I'll give you some examples that we have done in our lab but there is a lot of other things that can be possible okay by just extension like no further extension further extension kind of thing of the concepts that we have learned or started with this foundation okay so this particular then we can move on to the focusing part okay and focusing part yeah in the like when the information like when the rays pass through the beam splitter isn't information lost due to so how do you compensate for like we just stronger laser that's it so so see the when the beam splitter as you as the name suggests it will speed the beam part of the beam only what we are interested in so so we have to ignore the rest of the part which are which we are not interested in that much kind of intensity of the beam is lost okay but it's okay I mean we we use a laser which is a little bit higher power and we we we can do away with that no problem sir can't something better be done for example like the tilted mirror so it can be made to uh during the incident time it can be made to be at that 45 degree angle or whatever and during the reflection it can be made at some other angle so that like you don't need a beam splitter then you get another reflector yeah but then you need to move the mirror right yeah like periodically move the mirror but periodically how old what is the period of that motion can you think about see when the data is coming and like no really getting reflected you are not stopping at any point to read the data on the surface is continuously moving cd how fast you can do this motion right this is to do that yeah and and and you know actually by saving this kind of a like no doing this kind of a additional thing what we are saving from the practical perspective we are saving just the laser power I mean the people that have like you know see one milliwatt to increasing the laser power from one milliwatt to two milliwatt is not a big deal it's hardly any cost if you think of your pointer lasers that that has like no some few milliwatts four four five milliwatts of power I mean this is like no you need much much lesser power for the laser which is there in the in the cd rom drive so that perspective also we we don't save much actually you know see I mean people would do these kind of decisions based on their commercial no value viability I mean we don't need to be restricting to discussions for commercial kind of a perspective I mean we should do all academic kind of a possible like no explorations to just see okay what are the fund is there okay but yeah that's the kind of thing okay yeah now let's kind of look at this focusing part of it so in focus you see what happens is I'm sorry okay so let's see so when things are out of focus okay in one direction then the spot gets stretched in in the elliptical kind of a fashion okay in with like the minor axis of ellipse shifting okay its direction okay and then major axis of ellipse or major axis of ellipse is like no is aligned to to nb or b and d and b spots here in this particular case when the deep focusing happens in other direction so like let me let me go to this slide here itself okay yeah and wanted to get this laser pointer here so that I can show you some stuff okay let's get pen here okay so I you see that okay when we are at the focus out of focus in these direction okay so in color okay so we are out of focus in this direction okay this side then you know the the ellipse happens okay like like this for example okay and when you are out of focus so this is a position a here okay so this is a when it is out of focus in this direction then when it goes out of focus in at the b side on the on the opposite side it will go like that okay this is b position here okay so this b position b here okay so so when it is at completely at the at the focus then only it is going to be a perfect circle okay in in one position it will have a major axis of ellipse in this direction in other deep focusing position it will have major axis of ellipse in these directions is how the rays travel okay so in this kind of a you know spherical and cylindrical kind of a lens this the lens has a combination of the spherical and cylindrical parts as I said in the in the previous class as well and that makes it like no behave in this kind of a fashion the spot goes on one side elliptical in one major axis and on the other side in the perpendicular major axis okay like that the spot behaves okay and because and in the center only only the focus okay it is it is perfectly as a as a as a circle of here okay and that's how that's the reason like you know the the the the focusing can be detected now these so if this happens on now your photodiode abcd parts as shown here okay so yeah so focusing on one side it is like you know covering like that and in the other other difficult direction it will go a and c direction so if I consider this signal a plus c minus b plus d then it will have a have a you know error signal covered up there okay and that's how like no I can detect whether it is in focus or it has gone out of focus so is that part clear is there any any question about this part again sir uh what is the parameter that decides which direction the focus is going we don't need to know that we just need to know that okay if it is going in one direction I have the signal positive a plus c minus db plus d will be positive if it is going in other direction a plus c minus b plus d will be negative that is it I don't really need to know whether it is going positive up direction or down direction I'll just so so I mean of course uh uh I need to move the lens in the appropriate direction if it is not going in appropriate appropriate direction typically people just change the sign and like no make it go in appropriate direction so there are a lot of these small small other kind of practical things where you you know whether the sign is positive or not like you know it has a lot of physical way the system is and like you know how your sensors are how their gains are and all these kind of things affect actually so we don't need to worry about so if you say okay oh a plus this signal is what is coming up and I want to move for this signal positive I will need to move it in this direction and then I can give a positive signal to the coils and then like no the coils will move in appropriate direction if that positive signal is taking the coils in the opposite direction I'll just change the sign of the force that is given and I'll change the change them to go in the proper direction okay this we we often need to do in the practical world like no when we are kind of even configuring simple motor and you know the the encoder system like you'll need to do that okay what is the direction of encoder positive that needs to match with the direction of positive force on the motor or PWM positive or whatever direction of the motor positive that needs to get matched okay they need to be mapped properly in the practical world so that then otherwise the negative feedback will happen and it instead of stabilizing the system it will destabilize the system okay yeah so is that part okay anything on this more yeah I want to ask for example if the displacement of the disk is too large for the compliant mechanism to cover up is there indeed be such situation come again what is large for the disk to cover up but the there must be a range of this compliant mechanism right okay okay okay so so look okay yeah so normally like no you you'll design the system to kind of like no satisfy the specification so so for example uh you this wiggling or like no the the undulations on the series surface are like no designed to be like no maybe within say a hundred microns then like this compliant mechanism model will be moving only like no plus minus hundred microns or plus minus 50 microns that kind of a motion and that will be sufficient okay so you'll design the system to kind of like no do whatever things typically it's not going to be like no more than 100 to 100 microns I don't expect this motion of the like no undulations on the surface of the CD to happen that way and beyond that if it is there I mean if somebody has scratched your CD so much that you know this scratch is going beyond that then then it cannot focus it is not it cannot work then and they will say okay so CD has damaged okay so this is about the focusing system and now like no you can imagine uh if this this spots here on the track the side spots are going out of focus that can also be detected by the exactly same way so instead of E and F you will have other kind of like no uh four sensors like no A prime B prime C prime D prime and A double prime B double prime C double prime and D double prime in the place of E and F okay and then there also you'll correct for the focus of that thing then your your your your your your uh compliant mechanism will be always maintained maintaining the the tilt also tilt will be also kind of taken care of so if you need that kind of a precision there are some kind of a syndrome times I've seen I I I'll see if I can get a picture of the this photo diode is interesting picture to look at like no you can see that E and F blocks also are kind of showing like uh like um you know the split ABCD kind of a split okay so uh if this is clear then like no maybe we can stop here and like no take up the scanner in the in the next lecture okay and um you know maybe I think it it may be worthwhile to go or like no uh this more such systems maybe in the future at some point again we'll like no do something some exercise with respect to some system like that and uh you know that is form of our fundamentals of like no positioning and making this kind of a choices of different mechanisms and things like that more more okay now um I would like you to pause and like no think over your own summary of lessons that you have learned okay so I would like you to jot them down maybe um this um can be a very useful kind of a learning exercise say if you you like no see something out observe something and then um think about and see what are the kind of ideas which can be generalized for um generally the development of some similar kind of a systems okay so that is what you need to you need to kind of start having getting that ability so that uh whenever you open just don't open from okay okay I don't I just want to know what is there inside no we want to go beyond that and see not only what is there inside but also what we can learn from it okay what are the fundamentals why people have done it the way they have done it inside okay so that is what we want to kind of capture there so um you go go ahead and like no think about uh we have done so much of a discussion based on that what are the kind of things that you can generalize from the thing okay don't go beyond this point unless you uh have a listed kind of a your own um observations and conclusions of how do you generalize these things that you have you have seen so far okay so once you are like no done with that listing then you proceed okay so I'm proceeding right now but you can pause your video and then proceed next turn okay so uh these are some of the summary lessons I can list okay so you may have some more kind of things to add to it uh so so just um you know think okay there might be some kind of a trivial or like no maybe but trivial but important things that maybe you might have learned from this that may be important okay so this is not an exhaustive list of everything that we have for everybody the learning would be different from like making the observations about some things okay so one of the important fundamentals here is to kind of see when we want to kind of have a um uh accuracy to be very very like no fine accuracy positioning say 50 micron in this case then uh the rigid mechanical systems with the gears and other kind of a mechanism can be okay 50 micron 100 micron positioning that can be very easily obtained by our rigid kind of a mechanical systems with gears or other kind of stuff okay of course you need to like no take care of backlash for for sure so again backlash is difficult to handle in the controls okay so that's why you see in in in city rom drive you'll have a way to kind of uh uh take care of the backlash in the mechanical domain itself so that you don't need to worry about that in the in control of backlash okay uh so one of the important things is that okay when we want positioning accuracy moderate okay not really really fine then you can go for this rigid mechanical systems that we had here like no as a rack and pinion or screw type of a drive for cross positioning servo in the city rom drive now when we demand very high accuracy which is much lesser than 20 micron or nanometer kind of a range then we need to employ like you know uh different system okay only rigid body systems may not work in this particular case we can employ the um compliant mechanism system that will kind of do a job for uh you know very very good kind of accuracy with the god about range but there are many there are many other kind of such systems that may be available one of them is a say piso kind of a drives uh piso actuators they can kind of go give very very fine kind of a positioning but their range will be typically limited so compliant motion systems okay or compliant motion uh platforms can be activated by pisos also okay nobody prevents you to do that okay so forever for example like whatever is driven in the uh the stage that block that was compliant mechanism that was driven by the magnetic drive that can be also possible by using piso drive but piso drive the disadvantage is that it will not give the range that is needed for the for the control to happen okay so for example pisos will typically have a range of maybe about uh 100 of 100 microns but in here like you know if you see in focusing servo you may need to go beyond maybe 100 to 100 microns overall kind of a motion so um so typically like no it it is not used and also pisos are costly that's another reason piso might not have been used in ctrom drive and uh for larger range okay of motion you can combine this fine positioning and large gross positioning together as we have seen that is done in the ctrom drive okay then uh this is another very important thing but now some of the examples we already saw one needs to think in mechanical and electro electro in system uh electronic systems to make together okay so it is like a mechatronics kind of a thinking that that will happen here okay um and then maybe always like you know some smarter or innovative ways to design so do not constrain yourself that okay whatever you are thinking is only the possibility kind of a thing there might be some still you can be open to maybe other possibilities then you'll start kind of thinking a little more and like you know get to more finer thing or maybe when you experience some things are not really working so well then also you'll have a opportunity to correct and like you know go ahead then um this components now see this other kind of a thing is that like no this components that you saw in the ctrom drive no the actuators or sensors or some plants you know these kind of components can be useful for developing some other systems okay or you can use the same fundamentals but may not be this component because of like no the power and size uh that is needed but the same concepts can be employed in in other domains okay so we i'll show you some of the examples of use utility of compliant mechanisms for example in in doing 3d printing okay so that we have done in the in our labs okay so that kind of a application one can kind of think about from from from uh inspired from from cd rom kind of a uh system okay um then um you can have some examples of such a kind are like you know the mechanical probing system for men's okay this is another uh thing that we have developed uh so that you have a compliant mechanism which is probing things uh mechanically typically there are electronic probes in the in the to check like no the the ic's okay you have a patch you make electrical contacts and probe some of the devices on the silicon chip to kind of see the response of the devices and thing like that but now you can have a mechanical probing in the sense if you have a say micro cantilever then you can like no have a tip of uh that micro cantilever actuated by a probe okay probe is nothing but like no simple a needle kind of a thing which is now uh controlled by a force in the sense um if you give small touch to this cantilever very tiny micro cantilever like the the the probe which will be mounted on the some kind of other compliant mechanism uh system like a cd rom drive compliant mechanism system and then uh what will happen is even if you do a small like no displacement of the probe by giving like no uh displacement to the base of the cantilever in the in the cd rom drive system base of the compliant mechanism in the cd rom drive system kind of a thing then uh the the cantilever will get like no controlled force okay so the cantilever that you are kind of measuring is getting controlled force okay so that kind of a way is is called mechanical kind of a probing system okay so um this may or may not have been so clear right now but uh think about this okay if you want to kind of probe some mechanical device such that a force that i'm applying is is very controlled force okay but i don't want to use any kind of a mechatronics in the thing i just have a mechanical kind of a way of uh changing this force okay how can i how can i do that okay so so that is a kind of idea there then you'll have a like like no lot of like no fine positioning system for biological cell handling or like no biological cell uh stress stressing system something like that dough can be very delicate systems can be developed based on such a mechanism directly or like no using the concepts from the from the mechanism okay um then uh now like no we'll we'll switch and like no look at the next topic which is based which is on uh another mechatronic system which is a scanner