Bogdan Cristian Florea

A Petri net approach to multicellular chopper control

In this paper, a new control algorithm for multicellular converters is introduced. The multicellular converters are a class of switched hybrid systems which consist in the association of a number of commutation cells linked with floating voltage sources. The proposed control takes advantage of the hybrid characteristics of the system in order to develop a Petri net model for the converter and design a control method based on this model which ensures a minimum number of commutations. This last aspect of the control is important in order to have a longer life for the components and reduce the harmonic content of the output by reducing the value of dV/dt.

Discrete event control for multicell choppers driving DC machines

In this paper an idea of control for a multicell chopper driving a DC machine is introduced by taking into account the capacitors voltage constraints. The multicell choppers fall into the category of dynamical switched systems and have gained a lot of popularity due to their high performances, compared to the classic chopper structures. They reduce the stress on the components by reducing the value of dV/dt and by distributing the voltage over the n cells (on each capacitor). This last property is very important in high power applications, reducing the costs of the components as well as being able to control each cell individually. The idea of the control algorithm introduced in this paper will be tested on a 2 cells — 2 branches structure driving a DC machine, under ideal and real conditions.

Petri net modeling for hybrid systems control. Application for a multicellular converter

This paper will discuss the principles of using a Petri net in hybrid systems control design. The results will be applied to a high power DC-DC multicellular converter. A Petri net model for the converter will be developed and tested, and the results will be compared with the open loop PWM control of the same multicellular converter.

Influence of control type on chaotic behavior of the Alpazur oscillator

This paper studies the influence of different implementation methods of a simple control algorithm over the chaotic behavior of a specified circuit. Two new methods are presented: one is using a microcontroller and the other is using logical gates. The article also presents a unique approach to modelling a negative resistance as simple as possible, closely resembling a proposed mathematical dependency.

Petri net control strategy for series multilevel converters using a state observer

Multilevel converters are a special type of power converters, which can be classified as hybrid systems. This means that their model contains both continuous and discrete variables, which pose a challenge for the controller. However, this type of power converter has certain advantages, such as improved switching frequency, reduced output ripple and modularity. Petri nets are ideal for representing hybrid systems. In this paper, a Petri net controller will be developed for a series flying capacitor converter. The proposed control strategy will use a state observer in order to estimate the flying capacitor voltages.

An analogical control method of the Alpazur oscillator

The paper presents an Alpazur oscillator analogical control circuit. The oscillator structure and particularities are reviewed and the proposed control circuit is described. Finally, a comparative analysis of this new control method and two digital control techniques developed in a previous paper [12] is accomplished.

An integrated e-learning platform for use in higher education

With the integration of technology in the education process, the traditional methods of teaching must be supported by a more interactive process. Because of the increased portability of devices and the wide spread use of mobile internet connections, the information consumed daily is increasing at an exponential rate. For this reason, students need to be more involved in the education process and the content must be accessible online and presented in a challenging and interactive manner. This paper presents an e-learning platform used in university education which allows courses distribution and online and offline testing for a variety of subjects.

Image enciphering by using Rössler Map

An approach between chaotic behaviour and image indexing is proposed in this paper. A data-base is ciphered, image by image, by using Rössler Map. The image cryptograms are indexed with different methods: colour histogram, auto-correlogram, Color Co-occurrence Matrix (CCM) or Modified Colour Co-occurrence Matrix (MCCM). The experiments will show that the cryptograms stored are quite the same, so the eavesdropper cannot find any information by looking at a specific cryptogram.