PID controllers
Implementation

Until recently, PID controllers were implemented as analogue circuits, usually based on operational amplifiers.

Presently, the controllers are usually implemented in software. The software can run on a microcontroller, digital signal processor or a PLC in case of industrial application, or an ordinary personal computer.

Evaluates mathematical expression:

Integral of the error is replaced by sequential sum of individual error value samples at each step ( ). Derivation is replaced by a backward difference, i.e. the difference between actual and previous error sample Δek = ek – ek-1.

Fig. 9.17: Principial schematics of positional (absolute) PID