Digital control seminar series (LADES-GIMSCOP) organized by Mauricio de Souza (UFRJ, Brazil)

Title: "Nonlinear input transformations for disturbance rejection, decoupling  and linearization”.

Presenter: Sigurd Skogestad

Date: 05 October 2020

Abstract. The goal of my research is to develop simple yet rigorous methods to solve problems of engineering significance. The topic of input transformations is something I have been working on for the last year or so, and I think it has a lot of promise. The starting point is that I observed that industry frequently used static model-based calculation blocks for various purposes, such as counteracting nonlinearity, disturbances and coupling. Industry also frequently uses cascade control.

However, there is little theory for when to use these solutions, and we have found that the use of input transformations forms a good basis. The starting point is a nonlinear process model, which is transformed to a simpler model through the use of an input transformation. It is really very simple. Consider a nonlinear model dy/dt=f(y,u,d) and introduce v=f(y,u,d) as the transformed input to get a nonlinear transformed system dy/dt=v which is linear, decoupled and independent of disturbances. This transformation is a special case of feedback linearization, but we have extended the idea by adding a tuning parameter, by allowing for static process models and by making use of cascade control in a systematic way. The method has been tested on many process control examples. 

Video: https://youtu.be/mMoj7F1bC8w