Matlab 'pidtune()' function Algorithm

Good evening,

can someone maybe explain me how the Algorithm of the pidtune() function works?

Thanks in advance!

Answer 1

[Steven Lord]

See the Algorithms section on its documentation page. The References section on that same page may also be of interest.

[Ann-Christin Schlupek]

Thanks for your answer, but I want to understand how exactly the algorithm chooses the parameter of the controller?

Answer 2

[Sam Chak]

Hi @Ann-Christin Schlupek

The PID Tuning Algorithm is described on this page.

In slightly technical terms, pidtune() contains a set of instructions that tells MATLAB what numerical operations to perform repeatedly, in what order, and under what conditions, until all three tuning objectives are achieved:

1. Closed-loop stability
2. Adequate performance
3. Adequate robustness

according to some tuning rules such as the popular Ziegler–Nichols, Aström's AMIGO, Skogestad's Internal Model Control, and Chien-Hrones-Reswick. Suggest you to make a Google search on these tuning rules.

I haven't looked into the algorithm. But from the perspective of control system design, those operations can range from basic arithmetic calculations (identifying the search direction of the stability regime for the PID gains via the Routh–Hurwitz criterion, computing eigenvalues, etc.) to complex data analysis (linearization, computing step-response characteristics, computing gain margin and phase margin, etc.).

By default, if the designer doesn't know what the performance requirements are or what the stakeholder really want, then the algorithm will automatically choose a crossover frequency (loop bandwidth) based on the plant dynamics, and designs for a target phase margin of 60°.

[Ann-Christin Schlupek]

Where can I look into the algorithm?

[Sam Chak]

Hi @Ann-Christin Schlupek

The pidtune(), like most commericial software such as

• https://controlstation.com/
• https://www.picontrolsolutions.com/

is a proprietary PID tuning algorithm. However, you can search the m-file and take a glimpse.

edit pidtune