Feedback and Feedforward Control

[Random]

Hey John, I'm very appreciative of everything on apmonitor as I try to relearn process control. ( I have a Ph.D. in chemical engineering and this was my worst class as an undergrad). One of the issues I have with Exercise 2 is that I think the valve should be placed downstream of the overflow tank. I do this for two reasons, the first is that overflow tanks are used to allow uninterrupted operation of the upstream side; so a valve on the upsteam side defeats this purpose. The second reason for placing the valve on the downstream is to prevent de-priming the pump. The LC & FC should connect to both the valve and the pump, the FT should be upstream the tank. The tank then needs to be sufficiently sized to handle any operational variability. Ideally, you might want to use multiple pumps in order to maintain continuous downstream operations. Thanks for the videos.

[silentsound]

Please what is the textbook name that exercise took from? Thank you

[freeenergytransformer]

Feed-forward design is a type of voltage regulator circuit that doesn't require negative feedback. It's simpler than a negative feedback design and is less likely to oscillate, making it more stable. However, it can be less accurate than a negative feedback design and is more sensitive to component variations.

[manuel_youtube_ttt]

@APMonitor.com I'm having a hard time understanding the feedforward part of the Exercise 3. Why is the temperature measured in the tank a measurement of an input disturbance? I would have expected to have a measurement of the disturbance maybe in the input pipe that feeds the polluted water. Measuring the temperature in the tank feels like measuring the output (like when dealing with a feedback controller). May you explain this a little more please?

[Capsaicinophile]

Thank you for the good explanation. However, in exercise 4, shouldn't the TT be connected to an FC, because you are actually controlling the flow of the fuel, not the temperature.

[manish]

It is a nice video. I have not understood why controller 2 is feedback controller. It seems to me that it is feed forward.

[allypezz]

Let's consider gas flow: * Feedback is the system recognizing High flow rates and controller signal adjusts flow i.e. the system is going 'flow is too high, therefore I am going to control flow' ? *   *Feed forward is the system picking up an increase in pressure and going ' uh oh this is not good, this is going to affect the flow rate of the gas. Let's correct the high flow rates by adjusting the temperature to compensate for the pressure' ? * *If I am correct, is adjusting the pressure still feed forward or does that make it feedback? Essentially is 'fixing' the pressure by adjusting the pressure (e.g. controlling a compressor when flow rate is the focus downstream) feed forward? *