What are Lead Lag Compensators? An Introduction.

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This videos covers the very basic definition of what a lead/lag compensator is. Every control system engineer should have a basic understanding of lead/lag compensators since along with PID control it is a very popular control technique. This is the first video in a series where I will explain a lead/lag controller, when to use them, and how to design and tune them.
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I will be loading a new video each week and welcome suggestions for new topics. Please leave a comment or question below and I will do my best to address it. Thanks for watching!

[@divyabharathi-bo5og]

Every college needs lecturers like you who concentrate on the concepts rather than making us score in our exams with their crude methods! Thank you Brian!

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It's 2023 ,and i know you're still saving lives

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And it's 2021

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It's same with my uni. I'm learning "Automation", literally.

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Thank you so much, Brian. I am currently studying 3rd year Mechanical Engineering, and have lost my interest in Engineering due to poor lectures. However, after seeing your videos, I am more motivated and inspired to study Engineering now, and realise how amazing Engineering is. Hopefully, you can expand your good work, make it 'big' like Khan Academy one day. Wish you all the best!

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You are a Universal teacher and I am your Universal Students. Excellent and lucid Lectures. Hope our teachers are like you.

[@JDanger_]

My professor linked to this video from a lecture as a supplement, and I can see why. Wonderfully helpful good sir!

[@JohnSmith-ed1sr]

Thank you Brian! Learned more from you in 11 minutes then 12 weeks in class! Was happy to donate to your book. Thanks again!

[@mohamedabdelkader8786]

I'm returning for your videos from time to time to refresh my knowledge and understand things at work. Thanks Brian!

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Its been almost 6 years since I started to know Control systems. Since then Whenever I need a refresh or forget sth I come back to your video... You are the best sir... Always helpful and always I learn sth new..Thanks and Good Luck

[@stevenjensjorgensen]

Great explanation! This offers a good introduction and review on what lead/lag compensators are. I tend to agree with your statement and see "controller = compensator." In that, given that the system performs in a particular way, I want give control commands that "compensates" for the undesired performance and turn it into a desired output.

[@aerohk]

Hello! Off topic - Can you talk about state space representation if you are planning on making more videos? I heard that control engineer frequently use the state space approach to design system.

[@aeytam]

Thank you so much for putting all the efforts into these videos Brian. You are the best.

[@michaelcrossey3532]

Absolutely fantastic explanation. You are a brilliant human being.

[@19hashan93]

Brilliant Lecture. As Usual... Once again, you fixed the big mess I had in my head. Thanks a Million.

[@onlyAerik]

I'm taking notes from Modern Control Engineering by Katsuhiko Ogata, ed. 4 In chapter 6 section 5, Ogata doesn't really say they're trying to distinguish a controller from a compensator, but does nonetheless describe a compensator in a unique way. >In building a control system, we know that proper modification of the plant dynamics may be a simple way to meet the performance specifications.This, however, may not be possible in many practical situations because the plant may be fixed and not modifiable.Then we must adjust parameters other than those in the fixed plant. In this book, we assume that the plant is given and unalterable. >In practice, the root-locus plot of a system may indicate that the desired performance cannot be achieved just by the adjustment of gain (or some other adjustable parameter). In fact, in some cases, the system may not be stable for all values of gain (or other adjustable parameter). Then it is necessary to reshape the root loci to meet the performance specifications. >The design problems, therefore, become those of improving system performance by insertion of a compensator. Compensation of a control system is reduced to the design of a filter whose characteristics tend to compensate for the undesirable and unalterable characteristics of the plant. It's only in chapter 7 around Nyquist techniques that Ogata starts using the phrase >... controller (or compensator) ... And then by chapter 8, 'controller' alone is used exclusively concerning PD, PI, and PID. The overall trend seems to rely on two modes: 1. Ogata uses 'compensator' when your first and largest reason for modification is stability; you're compensating for inadequacies. Then they use 'controller' when stability is almost a given, and concerns are more with time-based requirements. 2. There is frequent mention of how PID controllers are modified on-site, implying that a compensator is not. Which I guess further implies that a controller has a human interface, and a compensator does not.

[@acepivoter]

nice

[@mohibkhan6963]

Great lectures.Telling us the physical significance of the mathematics and also building our intuition. A lot of thanks Brian Douglas. And waiting for more lectures. Keep it up.

[@JoeGormanPB]

This guy is the plug. Seriously thank you so much, I wish I would have found these videos earlier in the semester.

[@sharikosatia]

thanks, learned in 10 minutes more than I did in class.

[@youssefehab9633]

Hallo Brian, thank you for your awesome intuitive illustration. I believe the last meant when you introduced the lead lag compensator the locations for the poles and zeros were reversed.

[@mnada72]

Simply you are amazing, finally after relentless struggle I understood Lead/Lag compensator 😭

[@developersclub3810]

10:25 these questions, I'm glad you touched upon them..

[@UlyssesLizarraga]

When we have a closed loop system, we are concerned about robustness, which can be determined by something called phase margin and gain margin. The higher the phase margin (measured in degrees) the more tolerant our system is to become unstable due to disturbances; therefore we are interested in modifying the phase to give us a nice "cushion" for uncertainties. Adding a phase compensator might introduce some undesired phenomena such as modifying the original bandwidth. Thanks for the video Brian

[@rhonielguillenredula2507]

This one really helped me recall the fundamentals of control design. Thank you so much!!!

[@francesconigri745]

it's 2024 and I am sure you are still saving many lives

[@kirtikansal6946]

thnx for the wonderful vedio @brain Douglas and all the guys who comment here also remove many confusions..thnx to them tooo

[@ka-ew8ui]

from the comments below i see that you deliver a great explanation by the examples of the real life you give, but i hope that you make more videos with mathamatical examples also because i cant really have the full picture sometimes of what you are saying , it would be awesome if you do this, i know its boring for you because you do it faster using matlab but it would be really helpful for us in our studies if you could do that. thank you in advance

[@austinfox4130]

Anecdotally, in my field of servo controlled hydraulic systems compensation is a passive or "dumb" action where a particular variable is acted on by a dedicated system, mechanical or electronic. Whereas a controller performs active analysis on a system and can respond to varying conditions and adjust things on the fly, and have its parameters modified to fit different conditions over time. Often controllers are used to actively adjust setpoints in compensators. For example, a pressure compensator may control the flowrate of a pump by constantly adjusting itself to maintain constant pressure at different pilot pressures. That pressure compensator is itself controlled by a proportional servo valve which can actively adjust that pressure compensation gain if desired.

[@tkzsfen]

this is something that i will also vote for!!! it's probably the most mentioned thing in my labs and tutorials, but i never got even close to understanding it completely :(

[@achimbuchweisel2736]

Very good presentation/explanation. Thank you a lot.

[@drsandeepvm5622]

Super simplifying explanation 👌👏 thank you so much for your support to the learners

[@ninahooper9608]

You are literally the best person ever. Thank you.

[@wonderfriend]

Sir, you make understanding so easy. thank you so much.

[@chiutom4479]

This is very useful video to explain lead/lag compensator.

[@anantikamehra1694]

This is seriously awesome. I wish you were my teacher.

[@suman3316]

Hello sir your videos are awesome sir..... Please make videos on state space analysis also

[@AJ-et3vf]

Awesome video lectures sir! You're an immense help for us to grasp the concepts and theory of control. Thank you very much

[@laurasmarrito8479]

Thank you very much for clearly explaining these topics. It was very helpful.

[@nichoyeah]

THANK YOU FOR ALL YOUR VIDEOS

[@Brandon_Behnen]

To answer your question posted at 2:20 I would look at the two terms based upon intended definition: Controller - send instruction before execution, then correct execution error Compensator - send instruction after execution in order to correct execution error

[@Adhithya1002]

🥳🤯

[@laallyal]

Brian, this is truly great stuff! Thank you very much! Improvement suggestion: at 4.35 you use a very dark blue. It strained my eyes when i tried to read it against the black board. However the light blue worked perfectly :) Cheers again!

[@ashwinimohan6467]

active ckt is required for designing controllers pi, pd,pid . and a passive ckt for compensators lag,lead,leadlag. i guess that's the difference.. awesome video btw

[@anishayush9383]

Controller is for time domain response analysis and compensator is for frequency domain analysis of a system.

[@abdulsamirkhan3813]

Sir.! Your videos are amazing and helps alot in clear understandings of topics. I have a question regarding definitions of controller and compensator.. Can we say that " Controller is used to improve time response characteristics and compensator to improve frequency response characteristics" .?

[@TheJeenesan]

Thank you very much for sharing your knowledge. I saw all your control system videos and all were very useful. Maybe state space representation lectures would be great.Thanks again and all the best!

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wish my control system lecturer was like you.

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zajebisty jesteś gościu nie zmieniaj się

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From 2022 you're helping me

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[@R0kmyS0X]

Controller is what converts the error into feedback. Compensator is something that changes the system to make up for design shortcomings. thats my guess

[@thomasyen5706]

Fantastic Lectures! It really helps a lot!

[@luisgerardorodriguez7964]

For what I know, a compensator has the function of compensating the effects of increasing the proportional gain. Ideally, the proportional gain should be big, so that the output can follow the input, however, increasing the proportional gain too much can make the system unstable, and that is the moment where the compensator has relevance.

[@AlexStevens3]

These videos have been extremely helpful, thank you!

[@cecilialogatto6209]

I think that a compensator is a type of controller which compensates the specifications with one or more couple of poles and zeros. Instead the controller can be just proportional, or integral and so on

[@tarunasudhakar6684]

You're just brilliant! I LOVE THESE SO MUCH THANK YOU

[@MaziarFooladi]

The best explanation I've ever seen on this topic! Awesome job Brian!!!!! Thanks!

[@johnoh537]

Thank you so much for the video, Brian.

[@dandymcgee]

As someone with zero experience in this domain, my default understanding would be: A controller is anything that controls something.. i.e. it has an output that is used as something else's input (e.g. how much power to deliver to a motor, or switch an LED on / off, or send a network packet, etc.). You can have hardware controllers and software controllers, and not all controllers are compensators. A compensator is a controller that also has a feedback input from which it reads a signal that it uses to help it make its decision about how to control. All compensators are controllers.

[@omarsh77]

Thank you. great simplification with good knowledge.

[@slow_white]

I had the same confusion about compensator and controller, thanks for mentioning it. btw, like your voice too

[@facundoagustindemarco7106]

I LOVE YOU BRIANNNNN

[@AdityaMishra-pp1gw]

You said that the pole and zero would mathematically cancel each other and it's a silly example but should we cancel them keeping in mind the state space approach and the Asymptotic stability?

[@sobhnathpal934]

Thank you ,you're doing a great job

[@am8821p]

I guess the close loop system needs to be compensated by an additional block to achieve desired response according to particular specifications. And thus this additional block is called a compensator. And this block (the compensator) gives the plant the control signal or actuating signal it is called a controller as well. That is my guess.

[@nijatibrahimov7451]

You are amazing, Brain! Thanks for great tutorials :)

[@chrisschindlbeck]

Compensator = feedforward Controller = feedback

[@stavrosk.3773]

you are a legend man

[@jp4400]

Great video, great explanation. One more subscribed at the channel! Thanks sir !

[@thecaptainkent]

Great stuff. Explains it very well! Do you think you could take a look at designing lag-lead compensators in the root locus, besides doing them seperately? Thanks a bunch!

[@gaddamabhishek4771]

thank you for your example demonstration, sir.... im very helpfull..

[@jasonchen3659]

Good job, this video really explains a lot.

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You are great, really make a difference. Thanks!

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Thank you brain for this..

[@bablubablu490]

Seriously uh nailed it. Thank You Sir

[@bormisha]

Thanks for posting your lectures! Are your lectures going to be focused on linear control systems only or are you planning to also describe the optimal control theory, involving calculus of variations, Pontryagin and Bellman theory?

[@mehranujjan1232]

would have been more intersting if you would have shown the results of adding and removing of zero on matlab, very nice btw :)

[@toughcookie2429]

I have a question, is the gain plot graph of combined lead and lag compensator is correct?? I think there should be a gain (positive or negative) for lead frequencies also.

[@601106790]

What a nice video!! Well done! I have a question: could you explain, the narrower phase lead/lag region is better or wider? thanks

[@kimmovillacorta7677]

you saved me dude

[@husseinpashagharakhani9710]

You are fabulous!

[@aadithyaiyer4514]

If I have a transfer function, how do I know whether it is with or without compensation. I do have a pure integral term in it. does that mean it is without compensation??

[@JC-xc8rx]

What a good Channel! Where I can find your book?

[@Jayshnay]

at about 8:05 you say that the zero induces a "Phase lead" but this isn't a phase lead, this is a phase lag. This lag compensates for a phase lead - hence phase lead compensator. (positive phase change causes a positive shift in time - eg: to a later time)

[@qh4005]

Thank you !

[@technicalboyshreyans]

neatly expalined ... which software u are using in ths video ?? multicolor writing

[@mkschreder]

Subscribed.

[@kjkansara]

I was discussing with my friend about the difference. He said that PI controller increases noise but lead/lag compensators don't. So the use of compensator is more intuitive than the controller. Do tell me if there are more big differences. Thanks.

[@vaibhavbhasin3861]

Great explanation, blue pen isn't visible though :)

[@jawaher7857]

why does the o/p lags i/p by -90 degree? is this always happens with derivatives? or using PID only causes this lag?

[@gustavomarcelo7250]

Hi Brian. I understood having poles and zeros reflects the stability. But I do not really sure why do we need to know the gain and phase shift and does it really matter in control system?

[@phillipmaser132]

Very Nice --- Genius

[@gabrieljalil1562]

Can you go over root locus in the z domain and then go over a lead lag compensator example?

[@bhanuagrawal]

very nice video

[@stevedenny7887]

My professor makes the distinction that a controller adds poles and zeros at the origin, and a compensator chooses where to put them.

[@tiagofigueiro]

+Steve Denny Ok but a classical PI controller, for example, creates a zero away from the origin (although it's goal is to put a pole at the origin). What do we call it?

[@GaneshPatil-vj1qp]

Osmm explanation man !!!😍

[@dhruvinrathod69]

I think Controller - When our focus in control is in time domain. (P, PI, PD, PID) Compensator - When our focus in control is in frequency domain

[@hasannasir1191]

thanks Brian ..

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Mr. Brain you are really fantastic.....

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