Noise Filtering in PID Control | Understanding PID Control, Part 3

This video describes how to make an ideal PID controller more robust when controlling real systems that don’t behave like ideal linear models.
- Download Code Examples to Learn How to Automatically Tune PID Controller Gainshttps: bit.ly/2HKBh12
Noise is generated by sensors and is present in every system. The derivative in an ideal PID controller amplifies high-frequency noise. Even if that noise is relatively low amplitude, the derivative will sense it and possibly amplify it enough to impact the controller. To protect against high-frequency noise impacting the system, you can modify the derivative path with a low pass filter to reduce the noise before it causes any problems.
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[@BrianBDouglas]

Thanks for watching, everyone! Write your questions here and I’ll try to answer if I can. Cheers!

[@mosmanxia3291]

Can Kalman filter be used in this derivative step?

[@BrianBDouglas]

Mosman Xia maybe in the derivative path, I’ve never done that though. A Kalman filter is used to estimate a state using a model and measurements. So usually you’ll see it in the feedback path blending the sensor measurement with a prediction to create an optimal estimation of whatever you’re measuring. This can act like a low pass filter and remove that high frequency sensor noise before it even enters the PID controller.

[@draganostojic6297]

Hello Brian, for my PID, I put a LPF in front of the PID controller to suppress high frequency due to sampling (avoid antialiasing). My thinking is that this will also suppress noise and eliminate the need for a filter in front of just D. Is this reasoning correct.

[@BrianBDouglas]

Dragan Ostojić yep that would work too. If it’s a linear LPF then you can put it before or after the D path because of the commutative property of linear systems. If you put it before the P and I path then the LPF would also affect those paths then as well. It all depends on what exactly you’re going for and how you want to implement it. If your anti-aliasing filter had the right cutoff frequency and roll off characteristics for your PID controller then you’re done.

[@roki8035]

Hey Brian, I never understood why it is possible to calculate a slope at the current time step. Isn't a Derivate in a controller acausal?

[@theKiroo]

Your fan since 2014 I've immediately recognized your voice and I was like"...wait...is this Brian?!" Thanks so much, I owe so much to you sir

[@leoshen4676]

Me sitting here wondering did I fail to learn at school or the school failed to teach 😂 Thanks Brian best lecturer out there

[@hackerstreak6270]

Amazing explanation! I was looking for just this kinda video the whole time! Thank you so much and keep doing such videos.

[@shubhamkothari2709]

Thank you for this amazing one! The clarity of each and every concept is so simply explained by you, it just makes the topic much more interesting understanding the practical implementation.

[@SABIRALI-gf3fv]

Thank you so much for your time Mr. Brian Douglas.

[@martinevans8965]

These videos are so clearly explained. Nice work.

[@brajlecz9485]

These videos are a lifesaver. Thank you for making them.

[@wiloberlies9598]

Once again, great stuff Brian...looking forward to the next video. Thank you!

[@xuhan4682]

Great Lecture. Well explained and compact.

[@vheisshu]

great lecture. require minimal algebra for the explanations which is great for a non-mathematical literate like me. Amazing Brian!! thank you.

[@mohamedkandil8782]

Awesome Brain! keep rocking !!

[@abdelkaderbelabed3868]

Hi, Brian your videos about control theory is great, I hope you will talk about MPC controller

[@tonyyuan4857]

@Brian， Thank you for your great video. for 9:34, the alternative approach, how should it be implemented in a discrete structure? If SN/(S + N) is "c2d"ed, a differential structure will appear.

[@richardatkinson2376]

thank you do much for these videos, i learned a lot. may i ask what software are you using for this video presentation.

[@pranavdheer5971]

This is really amazing!!

[@Rancrom]

If you could release all these videos before my exam Friday next week, that’d be great!thanks!

[@karunamudliyar5625]

Thank you Brain for this wonderful video. Are you going to talk about discrete PID control in future? Thanks.

[@varokke137]

I am from future. He did.

[@karunamudliyar5625]

@@varokke137 Thanks..!! Have a nice day..!!

[@yoyomemory6825]

Thaaaanks for the clear explanation !!!!

[@user-kt3ni8xr4c]

Thanks for this didactic videos,its very useful.

[@rahulranjan1601]

Thanks for making such a good video.. 🙂

[@ronaldos3738]

Wow you are pretty good explaning this thinks, thanks a lot

[@nhattienle1985]

So incredible! Your video is so goodd

[@engineeringeveryday]

Thanks for teaching.

[@enen2777]

Great lecture!

[@Olavotemrazaodenovo]

Congratulations from Brazil.

[@yakhunt9424]

Parts 1 and 2 were great, but this made my head explode

[@kafi251974]

thanks for this video

[@uzairarifawan]

which microcontroller is best for Simulink models? I'm designing QuadCopter and I'm getting little bit to confuse that how to implement practically this Simulink model. Thanks in Advance. and your lectures are very awesome and easily understandable.

[@vladpanainte8443]

Hello Brian, I have a sensor with long time response in the system. Let's say that the system will detect an error and will activate the actuators in order to correct it. I am afraid that in reality the error will be corrected but the system will keep the actuators activated for a longer time than it is necessary and we will use a lot more resources than it is necessary. Is there any option to delay the controller's response? The sensor can't be changed, maybe there is another option for trolling this system?

[@1998zakwan]

This saved my semester

[@jessysaintauret3615]

Hey Brian Great video as usual. I have one question though at 5:10 when you derivate y(t)= sin (Xt+phi) , its derivate should not be dy(t)/dt= X cos (Xt+phi) ?, or maybe that's why you shifted it with 90deg? Thanks

[@BrianBDouglas]

Yep, exactly why I shifted it 90 deg :)

[@gabrielvoss6251]

yeah but you have also written down that noise = y(t)=asin(W t + f0) which is wrong because it's cos. This particular aside, your videos are amazing and you explain everything very clearly@@BrianBDouglas

[@bikkyrouth4553]

Because sin(90+fi) =cosfi

[@vladfarias]

Excellent!!!!!!!!!!!!

[@thomassaook7787]

Many thanks Brian, I need to implement and code PID in digital form via C++ or as they call it "Discrete PID" . Would you please help, or just provide a link where I can start up?

[@andrewnforsyth]

i'm just trying to learn enough to set a control strategy for a refrigeration condenser. after all of my "actuator" hardware is instantiated in the application, it only asks for 3 settings P I D, which i assume are unitless whole numbers? does it differ across different controllers or is there some sort of standard in place?

[@fernando.liozzi.41878]

Thanks!

[@rafaymohsin9216]

Who are the people that dislike this video. Great teacher, great lecture

[@vansytnut7177]

Thank you

[@MohamedAli-xb7kh]

Thanks a lot 🌸

[@zihaoyuan8810]

This dude's hand draw is insane.

[@jayaprakashms6769]

Hello Douglas .. have a good day

[@thirumurthym7980]

nice video . thnx

[@ThomasHaberkorn]

what if one limits the sample rate for the sensor signal, would that also cut off higher frequencies?

[@waizoongwong6930]

I finally understand why we need a filter...

[@vonromerlabas9946]

do you have any book recommendations for PIDs?

[@myozinaung]

Hi sir, when we normally use a low-pass filter, we face the phase lagging. For the real-time signal, phase lag is undesirable. How can we eliminate the phase lag caused by a low-pass filter?

[@BrianBDouglas]

Hello, good question! Not all phase lag hurts a real-time system. If you look at a Bode plot for a low pass filter you'll see that there is almost no phase lag at the low frequencies (passband) and that there is 90 degrees of lag at the high frequencies (stopband). So if you're using the low pass filter to block undesirable noise, the low pass filter will only add lag to those high-frequency noise signals (not a big deal) and not add very much lag to the low-frequency​ signals you want.

[@601106790]

HI Brain Douglas could you please make some vedios about filters in control systems? I am looking forward to studying them @Brain Douglas

[@jafariarshadbarg6945]

I want the simulation file of adjusting the pid fines by the pso algorithm using the three-phase induction motor optimization method by direct torque control. Can anyone help?

[@moromoro1839]

thanks

[@CaptnCall]

"Thinking makes my head hurt" I now know how Ralphie on the Simpsons feels.

[@animafun5696]

where does the 90 degress come from in 5:10

[@DmpDk]

Chilling late night watching the videos, learning a ton, love the blackboard animations *Video hits **2:30**, My entire world turns incandescent hot glowing white* JEEEZUUUSSS FAAAACK MAAH POOR RETINAS!! Anyway, love your video's, learning a ton

[@nicholasn.2883]

I didn’t know this was like whole thing.

[@sorooshkeivanfard6383]

very very bombe

[@nabilandadamslaboratory3422]

How would I implement a low pass filter in a digital PID controller?

[@N00B283]

With an FIR or IIR filter. Pre requisite would be discrete maths and knowledge on transfer functions, Laplace transform and z-transform. If you wan’t to be able to do it yourself without the aid of a program. But really by then you should probably be studying electronics engineering or control engineering 😛 but really this stuff is 5th semester stuff

[@muhammadgamal9071]

How to choose the value of N ??

[@kunalsalvi8382]

Hey Brian, love your videos. But could you make the background white so it's easier to see? Anyways, great video 👌

[@Cars0ndh]

You could try inverting the colors on your monitor to make the background white.

[@loaymassalha8066]

Thank you Brian How can we use PID block to calculate a signal derivative And may you explain with examples Hope you can explain about Feedforward control together with Feedback controller (I need to improve an existing feedback steam pressure control by adding a feedforward control part acting on steam flow measurement)

[@BoneAppleTea]

**Click** Noice!

[@jateenbhagat5496]

isn't the derivative wrong 5:20

[@Vivenk88]

No. Derivative of sine is cosine. Cosine can also be expressed as a phase shifted sine. It's the same he's used there.

[@Green-zw9pv]

😭 rocket science

[@aslamaddoor2522]

Hey bro What is your degree What about your education??

[@aslamaddoor2522]

I am just curious!!

[@lululu111]

low pass filter

[@noahd8673]

This video was really confusing. Why did we start taking derivatives of frequency’s, when before we were taking derivative of the difference between actual and desired value? also when u were talking about low pass filters where u talking about hardware or software? cause it seemed like hardware but then u said we are multiplying the low pas filter by the derivative, which also made no sense just by itself, which seems like software, and then u started talking about wiring things in parallel and series which made me think hardware, but you started doing more math which made me think software.