what is the trick to get better kp,ki,kp parameter in auto turning pid?

I have some problem with kp,kd,ki parameter.

we know when chosing auto turning in pid, the system will be finished when It seeked to the kp,ki,kd? But maybe the process turning need more time to search kp,ki,kd untill the system stable but maybe it never get the right kp,ki,kd and the system will be unstable.

So what's the trick or tip to search better kp,ki,kd ?.. Do you think we should use manual mode pid until the pv (pesent valuve) reach near sv (set poid) then we will go to auto mode pid and use auto turning function to get better kp,ki,kd ?

My personal recommendation for finding the PID parameters would be using estimation algorithm in a manually basis and calculate them based on the test result. If you access to reliable tables or papers on process estimation , you can estimate the process plus finding optimum parameters.

If you don't have those information, using the embedded tuner is the only option.Try to use fine adjustment of the parameters. Asymptotic convergence of the process value to set-point can be considered as the finishing tuning with an acceptable result.Time that you needs to reach the set-point depends on the process type and it is important to calculate the dynamic of process.In case on non-linear elements in your process,or other cases, the conventional tuner algorithms can not lead to reliable parameters.Try alternative methods.

The algorithm is discussed HERE in detail.With the help of the instructions and equations, you can write your own estimator and tuner can be coupled to any arbitrarily PID controller. When you automated your ideas in an FB, you can implement it manually via an ES /OS while start up a machine or a process.Data gathered in this phase can be analyzed later and all calculations can be done with an EXCEL sheet.



I hope these comments help you
HD Hosseini