What Is Feedforward Control? | Control Systems in Practice

A control system has two main goals: get the system to track a setpoint, and reject disturbances. Feedback control is pretty powerful for this, but this video shows how feedforward control can make achieving those goals easier.

The error in a feedback control system is the summation of three different error sources: setpoint changes, disturbances into the system, and noise within the system. Feedforward can be used to remove a lot of the setpoint and disturbance error before it ever gets to the controller. In this way, the feedback controller can be tuned to correct for the small modeling errors in the feedforward path while still ignoring the higher-frequency noise in the system. In some systems, this combined feedforward/feedback architecture is a better system than feedback on its own.

After watching this video, you’ll have a better understanding of what feedforward control is and why it is used. If you would like to practice the concepts from this video, this is a good tutorial that covers designing a feedforward system to control temperature in a heat exchanger.

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[mikhailhyde]

That eye tracking analogy was one of the most impressive teaching demonstrations I've ever experienced

[BrianBDouglas]

Hi everyone! I hope you enjoyed this video. If you have any questions or comments you'd like me to see, please leave them on this comment so that I get notified and can respond. Cheers!

[johncgibson]

This channel is gold. I am trying to make my Betaflight helicopter to dive with terminal speed exactly the same as CC3D controlled same craft. I look at both source code and couldn't understand if their PID schemes can be configured to be equivalent. And this episode explains the feedforward part just the way I need.

[Danfranschwan]

Brian's other channel is amazing!
Great to see that Matlab chooses from the best

[cyy]

Thanks for the brief and easy-to-understand explanation of the feed forward concept. This is going to help my next project.

[adaptine]

Nice video. Ships using dynamic positioning actually uses feedforward from the wind measurement in order to counteract the gusts.

[TomTalley]

Very well done. I wish there was a feed forward controller on the youTube algorithm to increase the value to technical advertiser's for excellent technical content like yours.

[jackmurray]

Great explanation! This guy is a gold mine for control systems education.

[LimingGao]

This video is incredibly enlightening and helpful for me. Thank you, Brian!

[MonkeyyRajaB]

Hi, I have a simple plant transferfunction of 1/ms+b, a simple cruise control model for a school assignment. Now I have to use feedforward so I need the inverse of the plant transferfunction. This would be ms+b. But I cant make this in Simulink as the transferfunction block gives the error that the numerator has a higher order than denominator. Is there somebody here who can help me with this problem?

[tamenekebebe]

would do video on fuzzy PID controller in mat lab

[berkantceylan]

Your matlap video is awesome. But I can't solve a question about feedforward. Can you help me share it here? @Brian Douglas

[dfisjyn]

can I send u pictures of a block diagram? there are some inputs that I don't understand. The block diagram is a reference from Process Systems
Analysis and Control by Donald R. Coughanowr Steven E. LeBlanc Third Edition

[jasonliu]

Please explain why at about 10:00 why y[s] shall be set to 0? y[s] shall be equal to setpoint???

[AliHassan-xtxb]

You are such a good teacher. I hope you made these videos while i was in my undergraduate. Any ways, Brian I am designing a controller for a wind turbine that will predict the wind speed ahead and adjust the out put accordingly in order to control the frequency in the power system.


I need some help regarding that. where can I reach you?

[ussamasajid]

Haven't seen a better description of noise filtration than the red-dot analogy.

[ved]

Two things that might help people understand this better.
(i) Why is it
0=u*Gp+D* Gd.
The confusion is because the u in this equation is not the same as input.
In actuality the u reffered here is actually u'.
The actual equation is:
Y(s)=Gp*u+Gd*D+Gd*u'
Assuming your plant dynamics are tracking Y(s)=Gp(u)
Gd*u'+Gp*D=0
In other words add a perturbation to your input u called u' that perfectly cancels the disturbance response. (ii) In the end example, Brian refers to the Simulink controller as feedforward or non-feedforward.
It is important to note that the feedforward only has disturbance rejection feedforward and not the setpoint feedforward he originally discussed in the video.

[kevinwood]

I noticed that you mentioned setting Y(s) = 0.Did you mean setting input-Y(s)=0 instead since we want the error to go to zero and not the output?

[chrishughes]

Is this the type of studd one learns in a control theory course?

Also, did you use perlin noise to implement the red dot animation?

[DANA-djle]

15:43 why we set "0=u*Gp+D* Gd" ?? if we do, we can't follow R. does't it? I think "R=y=u*Gp+D* Gd" is correct. doesn't it?
if i am thinking wrong, enlight me