Lec-35 The Nyquist Stability Criterion and Stability Margins

[@webtechsindia]

This is very good... i still remember 2 years before i was totally confused when my teacher taught this... But his explanations are so very good. you feel there is nothing very difficult.... This channel itself is a gift to the world....

[@tensorbundle]

This prof is himself a book. Such a crystal clear and comprehensive lecture I never found in the best of all control engg. books. I studied Dorf's, Norman Nice's , Schaum's outline and Azzo's books for sketching nyquist plot. Those books made me forgot everything what Ive learned and then I found this lecture. Now I understand Nyquist citerion well. He is a talented prof.

[@Gauravkumar-ht2oh]

NPTEL-One of the best initiatives by MHRD.

[@RohitDwarkadasApurvaee23m561]

one of the best and only best Prof on control system . Thanks Prof. M Gopal for such beautiful lectures.

[@srikarsana7146]

i cant expect any thing less from m gopal sir .......i think m gopal sir shoudl have wrote a book . super super super super ....................................a simplified version yet expalined the total ..............what a video sirjeeeee..................

[@anirbanmajumdar1256]

he did write a book though. Nagrath and Gopal - its in the market.

[@piaakashyap21]

The topic starts at 19:30

[@swathipai1254]

For me at 39:59

[@nishant1877]

for me it never started.god level.

[@poojapandey9977]

thanks a lot..

[@Adityasingh-sq7gd]

🤣

[@junaidrahman4204]

ha ha ha........

[@BrianSibanda8]

You know control engineering by experience and your explanations are awesome. Thanks so much

[@jamoh1461]

Listening to you lectures is like reading a article... explanation is so precise and to the point...

[@dobraOsoba]

Great videos. Watched 13 lectures in the past 5 days. BTW, it's also understandable with the speed of 1.5x (you have to be in he html trial though, to use this youtube feature) . Good when you don't have much time, and you want to watch ALL the lectures teee hee :D I also find that the speed of 2x is good for revision.

[@Gr3atmov3]

I've passed the final examan thx to this man. Worth watching...

[@szuprio]

totally worth a watch..... amazing video! Finall understood nyquist.... thank you so much sir....

[@shraddhajha4185]

awesome lecture ever ....tq so much sir ...ur lectures r so crystal n lucid to understand

[@SP-qp3lq]

after 10 years also this type of content is only available at NPTEL only..

[@HuanNguyen-cj8yn]

At 35:58 I still don't understand how the total angle contributed by s-beta2 phaser is 0. Can someone explain in more detail?

[@bbesirli09]

Absolutely outstanding teaching.

[@vamsikrishna5391]

Super simplified explanation of the most confusing n complicated topic thanks sir

[@dhruvpatel3085]

I think the way P and Z were defined, there seems to be a typo at time frame 44:29. The number of encirclement N is written wrong accidentally by prof. It is suppose to be N = Z- P

[@phoenixakapulse]

GURU JI....!! thanku for such nice explanation of nyquist criteria. i had been searching content in different books but i wasn't satisfied.

[@AdithyaBS]

In my text book, it said that N=Z-P and i was getting the answers wrong everytime. Professor explained why it is P-Z( because of the angle criterion we have to consider before mapping). Thank you Sir. :)

[@Hamalaw-lg9th]

this guy is so good at explaining things

[@shiprabhanu9562]

Such great professors! 9 years ago

[@Blackstar25109]

This guys has a book on Control Systems. No wonder his explanation is great.

[@hrithik161293]

I just realized that there are normal humans in IIT when the professor said "I know time is up, don't look at the watches". . . That was so damn funny

[@tanuchauhan4614]

m gopal sir ! hats off to you ! really great explanation and practial relaion (y)

[@Sn3innovationsLLC1]

Excellent lecture. The Nyquist Stability Criterion is an extremely important topic. I'm actually simplifying the discussion through a series of videos on our channel where I discuss specific examples related to circuits. This would be a great refresher and simplified version for engineers and designers looking for just the necessities to apply.

[@leanh7036]

I don't know why if we go around a contour in s-plane that encircle a pole; the corresponding contour in complex axis will encircle the complex coordinate's origin.

[@vishal3415]

Nyquist+Bode plot covered very well!! Thnks :)

[@hrishikeshraskar580]

this man is good :)

[@ItaldesignSchigera]

This guy is great

[@abhinavparri5084]

very well explained.......kudos to u

[@oyindenyafatarakeme]

I got lot at the 40-42 mins how are the poles of 1+ G(s)H(s) also the poles of G(s)H(s). And how are the zeros of 1 +G(s)H(s) the poles of the closed loop transfer function

[@shuvroneilsinharoy1107]

oyindenyafa tarakeme : G{s) = NG/DG; H(s) =NH/DH NG=numerator of function G DH=denominator of function D Similarly for NG and DG. we find G(s)H(s) =NG*NH/(DG*DH) Now, 1 + G{s)H{s) = 1 +{NGNH /(DGDH)} =(DGDH + NGNH)/DGDH T{s) = G(s)/l + G{s)H(s) = NGDH/(DGDH + NGNH) we conclude that (1) the poles of I + G(s)H(s) are the same as the poles of G(s)H{s), the open-loop system, and (2) the zeros of l + G(s)H{s) are the same as the poles of T{s), the closed-loop system.

[@oyindenyafatarakeme]

Shuvroneil Sinha Roy thanks

[@i4ali1]

the best prof ever!!!

[@wsaaz]

Nyquist starts at 19:25.

[@TestUSer39v]

really excellent teaching...thank u very much sir..

[@toni2zz]

I hope my lecturer was as good as him >O

[@azharansari1268]

good and sequential explanation.. thank you sir,,

[@rakeshmunagala6601]

the topic is starting at 19:24

[@MrShahzaibHussain]

@wsaaz u are a life saver pal.. thnx

[@Shant2111]

Nice lecture! Good Job..

[@arjunbali3194]

Can someone please how by contributing an angle of - 2 pi, any zero inside the contour will correspond to a contour in the w-plane encircling solely the origin and not some other point ?

[@TheOplkij]

Not only zeros, it could be poles too. As I understood, not strict.. G(f)H(s)=N(s)/D(s)=(s-z1)..()/(s-p1).. = let it be K(s). If we calculate it using phasors we can say that angle(K(s)) is equal to sum of all angles of numerator's phasors (s-zi) minus sum of all angles of denominator's phasors (s-pi). The magnitude of K(s) is not interested us here (it is >=0) . Suppose we took zk one of zi and made some contour around it only. Now map it into K(s). We can say that phasor of (s-zk) while s is going along our contour makes full angle (2pi). The angles of other phasors do not change largely. At least they dont make full angle. It will better been seen if you draw any phasor and watch for it's angle changing while s is going along contour. So the angle of (s-zk) makes full angle and sum of another angles can not compensate such changes. Hence tha angle of K(s) should also make full angle (at some direction). When angle of point makes full angle it should go around the origin. The direction of mapped contour and number of encircles are depend on the number of poles and zeros inside initial contour.

[@TheMaha88]

Great explanation..

[@TheTheTu]

as we are shifting the plot finally 1+g(s)h(s)=w to w=g(s)h(s) ,we are shifting our graph on y axis 1 unit down not the x axis 1 unit left ..but this is not what professor told ...anyone please explain this please

[@sayantanchandra3503]

what happened if there is a pole in jw axis ? I cant understand..pls help .

[@shubhamide]

if there is a pole on jw axis then that point if mapped into 1 plus gh then it will tends to infinity so we try to make a small semicircle of radius tending to zero then exclude those points that are lying on the jw axis

[@tropicalidiot]

thankyouuuu....so much from singapore......

[@junkmana]

Oh I understand now, it is the open loop TF of the closed loop, i.e. open loop with the output coming from the H(s) but not joining the summation point.

[@nareshkiran]

awesome explanation thanx

[@pradeepkumarmusham6141]

THERE SOMETHING WRONG IN this , around 42-44 mins , u find sir saying that zeros of 1+g(s)H(s) are the zeroes of g(s)h(s), but it should be 1+g(s)h(s) poles are the poles of g(s)h(s)... NO OFFENSE TO sir, but just got confused and watched video again and again .......this comment might be helpful to someone

[@nitisharora414]

pradeepkumar musham see first comment...u will get answer...explanation by sir is correct...

[@pradeepkumarmusham6141]

Nitish Arora see my comment correctly and watch video during that time,it's just verbal mistake, just before that he told the correct concept , but verbally wrong statement was given

[@leanh7036]

I don't think it is just a rule. Infact, I do have proof for encircling around "zero" case, i hope someone can prove for encircling a pole and feel so grateful as well :)

[@junkmana]

H(s) is the feedback, so how is G(s)H(s) an open loop TF? Shouldn't G(s) be an open loop TF?

[@Gr3atmov3]

Incredible.

[@souhardyasarkar6255]

Gift!!! 😌

[@malangba10]

Thank you Sir...

[@neil2581993]

Thank you very much.... :)

[@dobraOsoba]

yeah, me neither. Maybe it's just a rule that we have to accept. If anyone can clarify this, I would be most grateful.

[@patrik0075]

THANK U SIR!

[@tonydifonzo6953]

Business! , Computers!, Industry!, Technology!,

[@govindjangid6045]

why every professor is not like him in nptel

[@ujjwalvideo]

thanks...

[@godseeker11]

thank you sir

[@suryabhagavan5901]

thanks

[@RababMuhammadALy]

thank you very mush

[@neerajagrawal4570]

nice !

[@hefferbh]

look at his eyes at 43:01 lol

[@antoniodbz5850]

"dabulu plane"

[@shubhamide]

dablew phlane

[@sutikshan100]

god bless you !! lol

[@joerokcz]

lol xD

[@navanshu-007]

desi bhasha main samjade koi

[@choukimath006]

Thank you sir ........