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Design of Robust PID Controllers with Constrained Control Signal Activity

  • Olof Garpinger
Publiceringsår: 2009
Språk: Engelska
Dokumenttyp: Licentiatavhandling


This thesis presents a new method for design of PI and PID
controllers with the level of control signal activity taken into
consideration. The main reason why the D-part is often disabled in
industrial control loops is because it leads to control signal sensitivity
of measurement noise. A frequently varying control signal with too
high amplitude will very likely lead to actuator wear and tear. For this
reason it is extremely important for any PID design method to take this
into account.

The proposed controllers are derived using a newly developed design
software that solves an IAE minimization problem with respect to
H∞ robustness constraints on the sensitivity- and complementary
sensitivity function. The software is shown to be fast, easy to use and
robust in giving well-performing controllers.

By extracting measurement noise from the process value of a real plant,
one can estimate its effect on the control signal variance. The time
constant of the low-pass filter, through which
measurements are fed, is varied to design controllers with
constrained control signal activity. By comparing control signal variance
and IAE, the user is also able to weigh actuator wear to estimated

The proposed PID design method has shown to give very promising results
both on simulated examples and real plants such as a recirculation
flow process.

Optimal Youla parametrized controllers are used both as a quality check
of the designed PI and PID controllers and as a tool for determining
when these are valid choices compared to more advanced controllers.



  • Control Engineering
  • measurement noise
  • constrained control signal activity
  • linear systems
  • disturbance rejection
  • PID control
  • process control
  • Youla parameterized controllers
  • algorithms and software


  • LCCC
  • Tore Hägglund (Professor)

Box 117, 221 00 LUND
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