New methodology to design complete mould QFT multivariable controllers

This project has been proposed in the doctoral thesis of professor Igor Egaña Santamarina of the Public University of Navarre, called “Design of complete mould QFT multivariable controllers”. Professor Mario Garcia Sanz, from the Department of Automation and Computer Science of the Public University of Navarre, has supervised the project.

Air traffic controllers and wind generator controllers

Control engineering involves the design of mathematical laws that modify the way in which industrial processes progress. That way, for example, when the way in which warming power affects the temperature of the oven is established, it is possible to determine how power must be modified so that opening and closing of the door produces a minimum effect in the inner temperature. But control engineering is present in many other industrial processes. For example, when the ABS reduces the braking of a car to avoid the blocking of wheels, or in case of an electronic circuit that tunes the exact frequency of a digital radio.

The doctoral thesis is set within the Quantitative Feedback Theory (QFT), whose development started at the end of the 50s under the supervision of professor Horowitz. Since then, some of the technical applications based on QFT are air traffic controllers of the most modern airplanes, monitoring systems of high precision satellites, sewage treatment plants or robotic. Similarly, in Navarre, Mario Garcia Sanz –director of this thesis- applies at the present this technology in the design of control systems of a wind generator of 1,5 MW for the company M. Torres Diseños Induatriales S.A.

More efficient way to reduce “coupling”

The doctoral thesis of Igor Egaña has been focused on the study of multivariable systems, that is, with multiple entries that affect multiple outputs. According to professor Egaña, the main characteristic of this kind of processes is that when measuring an error in an output and trying to reduce it acting one of the inputs, causes a failure in various outputs. That is known as the coupling effect between the links. In that sense, the thesis defends a more efficient way to reduce those interactions between links.

As a consequence of the theoretical study, it has been analysed the inclusion of some elements of the controller that usually are not considered in multivariable processes: the elements located outside the main diagonal of the controller.

To verify the validity of those theoretical results, the methodology has been applied in two different processes. On the one side, the introduction of a controller in an industrial robot of the type SCARA has proved the viability of the technical proposal. On the other side, the design of the control algorithm for the heat exchanger of a milk pasteurisation plant, which according to professor Egaña is a process with more complex characteristics from the control point of view, has strengthened the applicability of the new contribution made by this doctoral thesis.