University of California, Riverside

Department of Electrical and Computer Engineering

Closed-Loop Time Domain Model Validation using Coprime Factor Perturbations

Closed-Loop Time Domain Model Validation using Coprime Factor Perturbations
Raymond de Callafon
University of California, San Diego

Date: October 18, 2004
Time: 11:00 am
Location: Bourns Hall A265

This talk addresses the time domain model validation problem for uncertainty models that are structured using coprime factorizations. A model validation technique is proposed in which measurement data is used to validate a derived uncertainty model. Newly proposed model validation techniques are based on a fractional representation approach and addresses the problem of correlation between the input and output signals inherent to closed-loop systems. The model validation problem for coprime factorizations is considered for closed-loop time domain data in the cases of noise-free and noisy measurements where the results rely on a linear relationship between input and output data.


Raymond de Callafon became an assistant professor with the Dynamics and Control Group of the Department of Applied Mechanics and Engineering Sciences in July 1998. He completed his Ph.D.and M.Sc. studies in the mechanical engineering and controls group at the Delft University of Technology in the Netherlands. De Callafon’s interests include experimental modeling and design and implementation of feedback control systems.

Raymond de Callafon works on control systems from an experimental point of view. He uses experiments and data based models as a tool to improve product designs and create feedback control systems for electromechanical systems. Once a prototype product is built, de Callafon gives it a test-run and observes the dynamic behavior by collecting time domain data. The measurements form the basis of the dynamic experimental modeling and the development of the control system. “This approach gives you a realistic and robust control system because it is closely linked to reality”, said de Callafon. He says this process could be applied to just about any dynamic system that allows experiment design. To that end, de Callafon did much of his Ph.D. research with Philips Research Laboratories in the Netherlands. He worked on a motion controller for a wafer stepper used to fabricate integrated circuits. He also developed models and controllers for a pick-up mechanism in a compact disc player. In both cases, the goal was to reduce and control the mechanical flexibilities and vibrations through feedback control.

More recently, de Callafon works on the modeling and design a high precisions servo control system using piezoelectric dual-stage actuator in a hard disk drive; a collaboration with the Center for Magnetic Recording Research at UC San Diego. Currently, scientists are trying to pack up to 1 terrabit per square inch onto hard disk drives. To achieve that kind of dense storage, you need a small and accurate actuator, together with a well-tuned position control system, to follow the tracks on the disk using the read-write head.

Closely related to the modeling and control of mechanical systems is the reduction of vibrations and sound by active feedback control. Data based modeling techniques are more important in these applications because of the lack of physical models that can accurately describe sound and vibrations disturbances in complex forced-air cooling systems. De Calalfon uses is control relevant model estimation techniques to design optimal filters for active sound cancellation. Applications are found in air ventilation, computer and data projector systems. De Callafon said he decided to come to UC San Diego in 1997 for the opportunity to help establish the new Dynamics and Control Group, and because he could complement the existing strengths of the group by bringing expertise in experimentation and system identification. He also enjoys teaching students, especially in laboratory and design courses. “It is important to get students excited about what controls can do. They need to design and implement control systems, conduct experiments and see what results can be obtained. That way, they will understand the importance and hands-on applications of the control theory they are learning in class.”
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Electrical and Computer Engineering
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