There are several different types of controller but all have one thing in common Ė they have the same input which is the error.† The error is the difference between the setpoint and the process variable, between where you want to be and where you currently are.
Error = Setpoint Ė Process Variable
The differences between the different controllers lies in what each one does with or to the error.† The On/Off controller, the simplest, merely checks the error to see if it is positive or negative.† If a positive error means turn the output on, then a negative error will turn the output off.† The Proportional controller multiplies the error by itís Proportional Gain and sends the result off as itís output.† The Integral controller integrates the error over time and sends the result of the integration to its output.† The Derivative controller differentiates or calculates the derivative of the error with respect to time and this result is itís output.† Each controller does something different and so the output from each controller is different even though the input to them all is the same.
A presentation on this topic in pdf format.
PowerPoint presentation on Introduction to Control
There are a number of different types of controller.† These are:
∑ Proportional Control (PowerPoint presentation)
∑ Integral Control (PowerPoint presentation)
∑ Derivative Control (PowerPoint presentation)
††††† See the Power Point Presentation
A sample problem where
Diagrams.† A block diagram is a very useful way of
representing a control system.† You must
first understand the basic features
of a block diagram.† The block diagram is
not only useful for providing a graphical image of a control system.† It can also be used, in conjunction with the