title: Simulink: PID Controller - difference between back-calculation and clamping for anti-windup?
body: <p>I need to implement an anti-windup (output limitation) for my PID controller. Simulink is offering two options: <code>back calculation</code> and <code>clamping</code> (<a href="http://www.mathworks.de/de/help/simulink/examples/anti-windup-control-using-a-pid-controller.html" rel="noreferrer">documentation</a>) which seem to deliver equal results. I know what back calculation is doing mathematically. It requires to define the back-calculation gain <code>Kb</code>. This gain is dependent on how long my controller is saturated, therefore it is actually a dynamic value (because I may have a high variation of saturation times). Do you see a way to control this value? (in this case it probably would be necessary to build my own PID Controller as shown in the documentation above or in the picture below.</p>
  
  <p><img src="https://i.stack.imgur.com/TTtmv.png" alt="PID controller with anti-windup using back calculation"></p>
  
  <p>Which brings me to the question, what is <code>clamping</code> actually doing? And what are other differences? Which one is faster, which one is more robust against stiff slopes? Does anybody has experiences using both?</p>