Venturing into the unknown

Well I have jumpped into the deep end again.

I am working on a project where I need to controller the discharge rate of feeders based on the rate of one.

What I planned to do was create a PID loop for the slave feeders that where given a set point based on the rate of the master feeder.

This sounds good in theory but I can not wrap my mind around how to do this in a Compact PLC. I have even thought I could use a PI loop and forget the derivative.

I can measure weight on all of the feeders and plan on using this as my control.

If anybody has any pointers that can jog my mind into gear I would appreciate it.

Let me see if I understand, Based on the discharge rate of one feeder, you want to use a loop(s) to control the discharge rate of N feeders to match?
Do you need to control the total discharge rate of the slave feeders or control each feeder to match the master?

Clay what are your feeders feeding? What kind of feeder? Is it a conveyor or a augor?

We do this with plastics and IMO I think you may do better setting up a ratio rather than a PID as a feeders change is not going to be that dynamic.

Clay why look at the discharge of 1 feeder instead of all of them?

Jeff

In most cases like in plastics you would want your additive feeders running much slower than your virgin or regrind feeders. We do ours witha ratio which stays linear with speed changes but I have seen it do with a PI loop also.

With our ball mill, we use an adjustable ratio between the feeders and an overall loop controlling the total feed rate.

We ran our raw material additives fast and used a ratio to add regrind. We could only add about 12% regrind or batteries would have to much insulation between cells.

We did ratio controls for just about everything.

Sorry for the slow responce. I am at a cumsomer site and up to my eyeballs.

Anyway to answer the questions it maybe better to give some more details.

Basically the system is going to make Peanut Butter. My main ingredient is peanuts.

What I want to do is control the rate of my minor ingredients based on the rate of the peanuts.

What I can measure is weight or better yet. I can measure the change in weight of the peanuts and minor ingredients.

My thought is to measure all's rate of discharge and ramp up or down my minor ingredient screws until the ration is correct. I want startup to be as smooth as possible so my thought is to just use a PI loop for each minor to major instead of a PID since it should react faster.

Also I am running this on a Compact Logix PLC, not exactly my strong suit so any pointers there would be a help. Also on the PI loop side. I will have to basically lock the loop from time to time to refill my peanut silo and minor ingredients bins. I plant to run a "fixed" ratio while refilling. Does anybody have any idea what I can expect from my loops at this time?