Mostly-Used Old-Fashion PID Tuning Methods:
For tuning of PID controllers, industries still use methods like Trial-and-Error, Ziegler Nichols, Cohen Coon, IMC and Lambda which are quite obsolete in today’s world. These methods mostly rely on trial and error steps for questing PID tuning parameters or on some old-fashion empirical rules and equations set back around 1940’s when processes were simple, production grades & rates were not as changing as it is today, product and environmental specifications were not so tight as today. To cope up with these problems PID tuning should be appropriate to achieve the specification, production rate which is required. All these old-fashion PID tuning methods rely on time consuming and large step-test changes by forcing the PID controller to manual mode and producing either too aggressive or sluggish PID control action. Many times, their performance and success rely on the experience of a process control engineer whose knowledge is based on many years of PID tuning and process understanding. Therefore, all these methods will never produce optimal PID tuning parameter values which are required for good PID control in auto or in cascade mode when typical and frequent SP changes and the effect of process disturbances are present. The procedure followed during the old-fashion technique is described below:
A large number of manufacturing plants still use these methods. The reasons which account for usage of these methods are absence of engineering knowledge and understanding, unavailability of robust process control software tools for closed-loop system identification, PID tuning and optimization, and PID tuning parameters simulation and testing without conducting serious plant step-tests due to fear of causing shutdowns and plant problems.