ABSTRACT
The equation of a proportional-integral-derivative (PID) controller is known as
O A K K
dt K d
i c d= + + +∫ε τ ε τ ε (6.1)
where the parameters Kc, τi, and τd already explained in the earlier chapters have a range of values typically from 0.5 to 500 in their respective units. Proper selection of a set of values from these three parameters for the best-controlling performance is known as tuning, i.e., tuning of controller parameters. Of course, trial values can be selected, and control action is observed. If the performance is satisfactory, then these parameters are selected; alternatively, another set is selected, and the performance test has to be repeated. But this type of hit-or-miss method is not suggested as, during the performance the test, there may be too much stress and strain over the equipment, which may cause accidents or damage to the plant and equipment. However, at this point, it is also necessary to know how the performance of a controller is judged.
