Identification and control of dynamic systems using neural networks.

The aim of this thesis is to contribute in solving problems related to the on-line identification and control of unknown dynamic systems using feedforward neural networks. In this sense, this thesis presents new on-line learning algorithms for feedforward neural networks based upon the theory of variable structure system design, along with mathematical proofs regarding the convergence of solutions given by the algorithms; the boundedness of these solutions; and robustness features of the algorithms with respect to external perturbations affecting the neural networks' signals. In the thesis, the problems of on-line identification of the forward transfer operator, and the inverse transfer operator of unknown dynamic systems are also analysed, and neural networks-based identification schemes are proposed. These identification schemes are tested by computer simulations on linear and nonlinear unknown plants using both continuous-time and discrete-time versions of the proposed learning algorithms. The thesis reports about the direct inverse dynamics control problems using neural networks, and contributes towards solving these problems by proposing a direct inverse dynamics neural network-based control scheme with on-line learning capabilities of the inverse dynamics of the plant, and the addition of a feedback path that enables the resulting control scheme to exhibit robustness characteristics with respect to external disturbances affecting the output of the system. Computer simulation results on the performance of the mentioned control scheme in controlling linear and nonlinear plants are also included. The thesis also formulates a neural network-based internal model control scheme with on-line estimation capabilities of the forward transfer operator and the inverse transfer operator of unknown dynamic systems. The performance of this internal model control scheme is tested by computer simulations using a stable open-loop unknown plant with output signal corrupted by white noise. Finally, the thesis proposes a neural network-based adaptive control scheme where identification and control are simultaneously carried out

Qualitative behaviour analysis of feedback-controlled Buck-Boost power converters thru three different techniques

This work is based on the comparison of three techniques for analyzing the qualitative behaviour of nonlinear dynamic systems, including the study of their finite and infinite equilibrium points. The qualitative techniques used are: the direct method of Lyapunov, The theorems of Dickson and Perko for second order quadratic differential systems and the linearization around finite equilibrium points. These techniques provide information about the local or global stability of nonlinear systems. The state feedback controlled Buck-Boost power converter will be used as a case of study.Este trabajo se basa en la comparación de tres técnicas de análisis del comportamiento cualitativo de sistemas dinámicos no lineales, incluyendo el estudio de los puntos de equilibrio finitos e infinitos. Las técnicas cualitativas utilizadas son: el Método Directo de Lyapunov, los Teoremas de Dickson y Perko para sistemas cuadráticos de segundo orden y la Linealización alrededor de los puntos de equilibrio finitos. Estas técnicas aportan información respecto a la estabilidad global o local del sistema no lineal. Como sistema dinámico no lineal se utilizará el convertidor de potencia Buck-Boost realimentado por medio del vector de estados

Dynamic systems behaviour analysis and design based on the qualitative theory of differential equations: the Boost power converter case

El títol de la versió pre-print de l'article és: Characterization of the trajectories space of a class of second order nonlinear systems :Agraïments: FEDER-UNAB-10-4E-378. Eliezer Colina-Morles is supported by the Prometeo project sponsored by Secretariat of Higher Education, Science, Technology and Innovation of Ecuador

Understanding chaos through a Jerk circuit

A simple Jerk circuit that allows studying chaotic dynamics in terms of theoretical variables x, x, x and x, and their equivalent experimental outputs was modeled and implemented. The designed circuit presented a chaotic behaviour depending on the value of a single parameter A -? 1/RA. The variation of A allowed observing the occurrence of a fork trajectory and its evolution into chaos, facilitating to understand the chaotic behaviour in this easily implementable electrical circuit.Seville (Sevilla

Dynamic systems behaviour analysis and design based on the qualitative theory of differential equations: The Boost power converter case

This paper uses the qualitative theory of differential equations to analyse/design the dynamic behaviour of control systems. In particular, the Poincaré compactification and the Poincaré - Hopf theorem are used for analysing the local dynamics near the finite and infinite equilibrium points. As an application, a large signal characterisation of a Boost type power converter in closed loop, including its equilibrium/bifurcation points and its global dynamics, which depends upon the value of the load resistance, is studied

Entropy as an event detector in a class of Hybrid Dynamic Systems. study case: A steam boiler

In a Hybrid Dynamical System (HyDS) event occurrences can be generated by many causes. Also, these events may be controlled or uncontrolled (wanted or un-wanted) which in turn might generate imbalances and/or disorder in the system, with the potential of causing catastrophic faults. In order to be able to deal with controllable events regulation it is important solving an early detection problem, whenever there is no 100% reliable method for detecting them. The main objective of this work is to study and implement an innovative method to detect certain events in a HyDS, such as faults, starts and/or plant shutdowns, setpoint changes, among others. The proposed method is based on the estimation of entropy balance in the system and its efficiency as an event detector is illustrated using Matlab computer simulations on a steam boiler case of study. It is also showed how the entropy balance may be used as an event detector in different operation regions of the process.Guayaqui

International Journal of Control

This paper uses the qualitative theory of differential equations to analyse/design the dynamic behaviour of control systems. In particular, the Poincaré compactification and the Poincaré--Hopf theorem are used for analysing the local dynamics near the finite and infinite equilibrium points. As an application, a large signal characterisation of a Boost type power converter in closed loop, including its equilibrium/bifurcation points and its global dynamics, which depends upon the value of the load resistance, is studied.Cuencavolumen 88; número

Qualitative behaviour analysis of feedback-controlled Buck-Boost power converters thru three different techniques

This work is based on the comparison of three techniques for analyzing the qualitative behaviour of nonlinear dynamic systems, including the study of their finite and infinite equilibrium points. The qualitative techniques used are: the direct method of Lyapunov, The theorems of Dickson and Perko for second order quadratic differential systems and the linearization around finite equilibrium points. These techniques provide information about the local or global stability of nonlinear systems. The state feedback controlled Buck-Boost power converter will be used as a case of study.Este trabajo se basa en la comparación de tres técnicas de análisis del comportamiento cualitativo de sistemas dinámicos no lineales, incluyendo el estudio de los puntos de equilibrio finitos e infinitos. Las técnicas cualitativas utilizadas son: el Método Directo de Lyapunov, los Teoremas de Dickson y Perko para sistemas cuadráticos de segundo orden y la Linealización alrededor de los puntos de equilibrio finitos. Estas técnicas aportan información respecto a la estabilidad global o local del sistema no lineal. Como sistema dinámico no lineal se utilizará el convertidor de potencia Buck-Boost realimentado por medio del vector de estados