Papers by elena niculescu
Many motions parameters can be measured and the motion sense detected based on the output signals... more Many motions parameters can be measured and the motion sense detected based on the output signals of the rotary incremental encoder. The former method for resolution improvement supposes additional electronic circuits for detect and count the positive and negative fronts of the pulses generated by the sensor. This paper proposes an alternative method for resolution improvement and sense discrimination, adequate for the computerized study of rotary incremental encoders, using an experimental system that contains the sensor, an IBM-PC compatible computer and an intelligent interface with 80C552 microcontroller. Such experimental system is very useful in higher education or in research activities.
In this paper, the authors intend to show how to apply the circuit description in parameter space... more In this paper, the authors intend to show how to apply the circuit description in parameter space for a standard worst-case circuit analysis (WCCA). DC or AC or transient worst-case circuit analysis can be performed only by testing the circuit for the vertices of a polytope in conjunction with a circuit simulator or computational environment. In order to validate and show the effectiveness of this approach, DC and AC worst-case circuit analyses of an analog electronic circuit performed in conjunction with a general-purpose circuit simulator are presented and discussed.
The paper proposes an easy extraction path of almost static and dynamic parameters of a power MOS... more The paper proposes an easy extraction path of almost static and dynamic parameters of a power MOSFET based on a laboratory technique that requires only one test circuit. Hard switching the power MOSFET on a resistive load, the gate charge, the forward transconductance, the on-state resistance and the switching times, and the intrinsic capacitances are extracted from the waveforms of the gate voltage, drain voltage, and drain current. The extraction procedure for all these parameters of device is described step by step in the paper. A simple test allows students to evaluate the switching performance of a power MOSFET and to teach the difference between MOSFET technologies comparing the Figure of Merit (FOM) index of devices. This test can be repeated for many MOSFETs and IGBTs to compare their overall switching performance and to observe the device behavior for various operating conditions of the device under test (resistive or inductive loads and different supply voltages, and drive gate currents) and it can be used as an education tool in Power Electronics at its basic level.
The resulted cold laminated aluminum foil is rolled in bales; the foil is then unrolled and rewou... more The resulted cold laminated aluminum foil is rolled in bales; the foil is then unrolled and rewound in rolls with some imposed parameters: the exterior diameter of the roll, the length and mass of the rewound foil. These parameters must be measured with imposed precision and during the technological process. The paper presents a measurement method that solves this practical problem in the aluminum processing industry; the method is based on the pulses generated by two rotary incremental encoders and an IBM-PC compatible computer displays the measured values, enables the parameter prescribing and assures a simple dialog with the user. An error analysis is also presented; it enables the estimation of the maximum probable absolute error for each parameter.
This paper presents a computational algorithm for the parameter D 2 (quantity that determines the... more This paper presents a computational algorithm for the parameter D 2 (quantity that determines the decay interval D 2 T s ) in DC-to-DC fourth-order PWM converters (Cuk, SEPIC, Zeta, low-ripple input-current boost converter etc.), with discontinuous conduction mode and parasitic resistances. The computation algorithm, based on the steady-state model obtained through the state-space averaging method and easy implemented with MATLAB, supplies the value of the parameter D 2 that is a necessary quantity for dynamic and static analysis, and design of control loop of these converters. A fourth-degree equation has been obtained for the low-ripple input-current PWM boost converter, SEPIC, Zeta and Cuk PWM converters with parasitics. Including the parasitic resistances increases the degree of the equation with unknown D 2 and makes the value of this parameter dependent on the duty ratio, load resistance, all converter parameters and coupling coefficient of inductors.
It is presented a modality to compute the boundary between the discontinuous (DCM) and continuous... more It is presented a modality to compute the boundary between the discontinuous (DCM) and continuous (CCM) operating modes in the DC/DC fourth-order PWM converters with parasitic resistances. To reach this goal, an averaged model of the converter has been used. The boundary between DCM and CCM, considered to be the critical load resistance R crit , or, equivalently, the critical value of the inductor conduction parameter k ctrit , is found as the positive root of a second-degree equation with unknown R crit or k ctrit . The algorithm carried out and implemented with MATLAB environment allows studying the effect of the parasitic resistances and the coupling of inductors over the boundary R crit or k tcrit , the steady-state properties and the external characteristics of the converter. The simulation results show that the parasitic resistances and the inductor coupling change the boundary between the discontinuous and continuous conduction modes of a fourth-order PWM converter.
An approach of the worst case analysis of the analog electronic circuits based on the circuit des... more An approach of the worst case analysis of the analog electronic circuits based on the circuit description in parameter space is proposed. A DC, AC or transient worst-case analysis can be performed only testing the circuit for the vertices of a polytope in conjunction with a circuit simulator or computational environment. In order to validate and show the effectiveness of this approach, DC worst-case analyses of analog electronic circuits with symmetrical and asymmetrical tolerances in conjunction with a generalpurpose circuit simulator are presented and discussed.
The shape recognition in robotics is often based on models; a model description results by proces... more The shape recognition in robotics is often based on models; a model description results by processing many imprints of the same known shape. The paper presents some experimental results obtained in 2D-shape description by geometrical parameters. A program simulates the shape exploration with a tactile matrix sensor, generates the binary imprint and computes many geometrical parameters that describe this imprint. The program can generate almost all possible imprints of the explored shape that can be a geometrical one, a shape previously learned or a shape created by the user. This program is very useful in shape recognition study.
The data primary processing in electro-energetic system is based on algorithms that perform the n... more The data primary processing in electro-energetic system is based on algorithms that perform the numerical filtration of input signals or the computation of some characteristic values (root-mean-square values and phase differences) of currents and voltages. This paper presents possible methods for computing these characteristic values: method of the average value, modified A4 method, method of the direct root-mean-square value, Fourier method. The main advantages and disadvantages of each method and experimental results obtained using the last method are also presented.
The paper presents a unified steady-state analysis of PWM SEPIC converter with coupled inductors ... more The paper presents a unified steady-state analysis of PWM SEPIC converter with coupled inductors and separate inductors for both continuous and discontinuous conduction modes. The results of this simplified analysis allow to determine the operating point of converters and further the small-signal low-frequency parameters of linear model, and to design the converter too. The expressions of all steady-state properties of converter take the effects of inductor coupling into account. The converter with separate inductors is treated as a particular case of the more general coupled-inductor case.
This paper presents some considerations about a system that measures many parameters of the rolls... more This paper presents some considerations about a system that measures many parameters of the rolls resulted in aluminum processing industry. It is an intelligent measuring system that supposes two rotary incremental encoders, an interface with 80C552 microcontroller, an IBM-PC compatible computer and a driving module. The technological parameters are measured and displayed, with imposed precision, during the rewinding process. The measuring system is characterized by software flexibility and assignment of the foil width and thickness before each measuring process. The results obtained using an experimental system (with the same structure) are also presented.
The paper proposes a procedure to calculate the sensitivity factors of the quiescent drain curren... more The paper proposes a procedure to calculate the sensitivity factors of the quiescent drain current of a FET operating in the active region in conjunction with a general-purpose circuit simulator. Unlike the procedure developed for the sensitivity factors of the quiescent collector current in BJT, this one is not based on the drain current expression of the FET. We showed
A full-order dynamic model of the pulse-width modulation (PWM) DC-to-DC SEPIC converter in discon... more A full-order dynamic model of the pulse-width modulation (PWM) DC-to-DC SEPIC converter in discontinuous conduction mode (DCM) is presented in this paper. The derivation procedure is based on the smallsignal PWM switch model in DCM used in conjunction with a PWM derived SEPIC topology. The small-signal characteristics of the PWM SEPIC converter in DCM obtained in a similar way as the small-signal properties of a linear amplifier are presented in a symbolic form. Such a model can be directly used in conjunction with a computational environment as Matlab, MathCAD and Mathematica to analyze the small-signal low-frequency dynamics of the PWM SEPIC converter in DCM.
Recorded information about transmission system faults or disturbances is essential for determinin... more Recorded information about transmission system faults or disturbances is essential for determining the performance of system components and to analyze the nature and cause of a disturbance in energetics. The systems for disturbance recording perform the monitoring and analysis of different events specific to energetic systems. The root-mean-square (RMS) values and phase shifts of voltages and currents are widely used in post-failure analysis and for monitoring the characteristic parameters of electric lines. This paper deals with the Fourier method adequate for measurement of RMS values and phase shifts in energetic systems. Experimental results obtained using a system for disturbance recording in power stations of energetic system are also presented.
This paper aims to show how the Matlab environment can be used for both modeling and analysis of ... more This paper aims to show how the Matlab environment can be used for both modeling and analysis of DC/DC fourth-order PWM converters with both continuous and discontinuous conduction mode (CCM and DCM), coupled or separate inductors and parasitics included. Based on the SSA method easily modified, the program performs the averaged steady state model and the canonical dynamic (AC small
In this paper we try to present advantages of multiuser OFDM and a hardware implementation, this ... more In this paper we try to present advantages of multiuser OFDM and a hardware implementation, this include adaptive frequency hopping, adaptive modulation, and multiple transmitter cells. An overview of several new which techniques improve the safety of system and the enlargement efficiency.
A method of establishing the boundary between discontinuous conduction mode (DCM) and continuous ... more A method of establishing the boundary between discontinuous conduction mode (DCM) and continuous conduction mode (CCM) operation of fourth-order PWM power converters (Cuk, Sepic, Zeta etc.) with parasitic elements is presented. The boundary between DCM and CCM, considered to be the critical load resistance Rcrit, is found as the positive root of a second-degree equation with unknown Rcrit
This paper aims to show how the MATLAB environment can be used to analyse three topologies of DC-... more This paper aims to show how the MATLAB environment can be used to analyse three topologies of DC-to-DC forth-order PWM converters such as Cuk, SEPIC and Zeta converters. The steady state and dynamic analysis is made for these converters with coupled or separate inductors and parasitic included operating either in continuous conduction mode (CCM) or in discontinuous conduction mode (DCM). The space-state averaging method was used as basically modelling approach that was easily modified in order to provides not only the classical dynamic model of converter but also the canonical averaged dynamic model expressed by its characteristic coefficients. Also, it computes the boundary between DCM and CCM, the decay interval inductor currents, the converter efficiency, the dc and ac small-signal properties of converter. The external characteristics, frequency responses and any functional parameter of converter are computed and plotted too. Some analysis results of SEPIC PWM converter with parasitic included and coupled inductors obtained by running this computer program are given in order to illustrate the usefulness of the program. New models of converters may be added in order to compare their efficiency and accuracy, the results obtained by means of this program based on the space-state averaged models being used as reference in the comparing process.
Uploads
Papers by elena niculescu