Easy xLogic, User Manual

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If the heat output is increased or reduced too quickly, then the control loop starts to sway. The
room temperature fluctuates. It is either too hot or too cold. To prevent this, the person must
carefully and slowly reduce or increase the heat output.
Loop error
The loop error is the difference between the command variable and the process value. In other
words: the deviation of a process value from a set value.
e = SP – PV
The loop error e brings about a change to the manipulated variable M.
The example above illustrates this very well: if, with a desired temperature of 20 °C (=
command value w), the room temperature is 22 °C (= process value PV), this results in the loop
error:
e = SP – PV = 20 °C - 22 °C = -2 °C
In this case, the negative sign indicates a reversing action: the heat output is reduced.
In a control loop's state of equilibrium, the loop error is zero or very small. If the command
variable changes or there is a disturbance, a loop error arises. The loop error is corrected by
means of the manipulated variable M.
Controller
Controller
Controller Controller basics
basics
basics basics
A controller can be simply portrayed as follows:
The comparing element and the controller function describe the conduct of the controller.
The following describes the most important types of controller. A controller's step response tells
us a lot about its conduct. The step response describes how a controller reacts to the erratic
change in the process value.
There are 3 important basic types of controller:
Proportional-action controller (P controller)
Integral-action controller (I controller)
Differential-action controller (D controller – we're not touching on this here)
These are combined for a real controller. For instance, the PI controller:
P Controller