.MagLev.Control.Functions.piStep

Information

This is the algorithm of one step of a PI-controller with feed-forward and limited output. The anti-windup measure (either back-calculation or clamped) is formulated straight-forward to avoid iteration. Therefore the code can be:

called in a triggered block of a PI-controller
called in a clocked block of a PI-controller
transferred to a embedded controller

Integration is replaced by an explicit forward Euler.

Anti-Windup measure: A prediction of the output is calculated without limitation is calculated. If there is a difference between unlimited and limited result (i.e. protected variable cropped):

BackCalc: cropped multiplied by the inverse of proportional gain is subtracted from the integrator's input
Clamped : The integrator is stopped (i.e. the integrator's input set to zero).

Interface

function piStep
  extends Modelica.Icons.Function;
  import MagLev.Types.AntiWindup;
  import Modelica.Constants.small;
  input Real u "Reference signal";
  input Real u_m "Measured signal";
  input Real kp "Parameter proportional gain";
  input SI.Time Ti "Parameter integral time constant";
  input SI.Time Ts "Sample period";
  input Real kFF "Parameter proportional gain of feed-forward";
  input Real ff "Feed-forward signal";
  input AntiWindup antiWindup "Anti-Windup measure";
  input Real yMin "Lower limit of output";
  input Real yMax "Upper limit of output";
  input Real pre_x "Previous state";
  output Real x "State";
  output Real y "Result";
end piStep;

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