I have done a little bit of work on cascade control. Some things you need to take care of

1. You should first try to tune your slave loop and set you master loop to manual mode. When you are satisfied with the response of the slave then you can begin to tune your master loop.

2. You also need to choose your tuning parameters very carefully as this would affect the overrall stability of the system. What we usually do is to start with a very low proportional gain(Kp) and high reset time(Ti) then go slowly from there. That way your system won't become unstable

3. One thing that might also help is for you to adjust the limits of the manipulated variable for the master loop. Since this is the set point of the slave loop, the limits you set on the master loop will affect how far the set point of the slave loop can change. We usually set it so that it doesn't vary by more than 20% from a specific value.

If you follow some of these principles then you're likely to get an improved performance on your system

Dhaval Abotiyawala

 

ANKURGAMIT

 

SMIT SHAH

 

Lucky123

 What exactly are you trying to achieve by cascading the PIDs. There are numerous things you may be able to do by cascading and each combination will be using different logic to cascade and accomplish the required results.

If you may please draw specifics you may get a better clarification.

SMIT SHAH

Dear Experts,

do any1 have the sample program for the cascade pid control 

I have the look to the previous posts but not found the sample program jut the theories

I want to have a program if possible

 

 I have a project in which i have provided the single pid for heating a viscous material inside a jacketed reactor 

The reaction is exothermic

The control valves have split control 

Meas from 0 to 50 percent of lmn cold water inlet

50 to 100 steam valve will operate

The problem is that how to have a proper control because if i providethe setpoint for the material temperature then it will not reach in 1 to 2 hours so will have to provide large ti 

But doing so if the temperature is reached at that time it will not close my steam valve fast so graph of temperature continues to have an AC curve

 I have face this type of problem,

For cascade control you have to create two pid ,where first pid out put will become setpoint of second pid,

Also with the first pid oprate water valve,and second pid oprate steem valve.

I hope this may help you.

What ever be result please display it here.

 Dear Ankurgamit,

Everyone know this theory of cascade but when you do it in process plant you will get almost drastic result.

In one of my project i need to control flow and pressure simultaneously client need cascade logic and i developed  same for them but system is unstable. If you simulate this on MATLAB you will get result but in practical system it is unstable.  

Any reference project available with you? please share...!!!

New question published by varan_1270 is split to a separate thread with the subject Want to control a pump by a temperature sensor and a pressure sensor at the same time.

Best regards
Jen_Moderator