FeedForward+CV > 100

Hi, I have a feedforward implementation I am trying to accomplish. I was wondering what would happen when cv is at 70 and Feedforward wanted to add 40 to that? I assume it would limit to 100. Would the PID continue to operate as normal so eventually when the disturbance becomes visible to the PID the cv would rise to 100 and feedforward beyond 100 would not effect the integral term or cause erratic CVEU response?

I am using PIDE in rslogix 5000

Thanks

you have saturated your output - it is not going to work
Think about it - the PID wants 70% CV to maintain setpoint, the FF wants 40% CV, Something has got to give as the process cannot keep up so the error will get larger
assumptions - 100% of the PID CV is 100% of the analog output.

Ok so I should Limit my Feedforward value to keep CV+FF within CV's range. Still from what I was reading on FeedForward in the PIDE pdf I am reading is that CV=deltaFF+CV. So if I limit feed forward values (say to 30 to give me even 100)then the inital CV jump would be from 70 to 100. So this would then be the equivalent of setting CV to 100. From there the PID should resume normal control? I am thinking that I should reset Integral value at CV jump. If PIDE then resumes normal control is there a way to keep feedforward active so I can have the increased CV until disturbance is read by the PID. Or am I looking for more of a gain/ bias on the CV?

I've used the PIDE but never its FF capabilities. It doesn't seem clear from the documentation how integral windup is handled when the controller output is saturated while FF is used.

Unless someone here knows for certain how to prevent integral windup with FF, you're best bet is to create a simple simulation that allows you to experiment with the PIDE configuration so that you clearly understand how it behaves and explore ways to achieve desired behavior.

I am going to try to mirror the in-use PIDE with one using FF when I get the chance today or tomorrow I will let you know what happens the best I can as I don't understand how the PIDE should respond with the FF as it is described in documentation.

I was able to do minor testing with the live PIDE. The FF looked like it provided a bump to the CV equal to the change in FF value. After the bump the PIDE behaved normally and started controlling from the new CV point. On a dummy PID I tried testing FF+CV>100. The CV did limit to its range but I was unable to get conclusive results on what happens to the integral term as I was forcing PV and SP manually so it was unclear if effect on Intergral was from CV spike or my manipulation of PV.

The feed forward in the setup I had used the deltaFF value as the addition to CV, and the CV did resume control afterwards. So to me it looks like FF in the PIDE block gives a temporary boost to CV. So when FF removed the deltaFF is then subtracted from current CV.

When I get non production time with the devices I will try adding large FF, letting CV settle to a low value and then setting FF to 0.