IRANIAN JOURNAL OF ELECTRICAL AND COMPUTER ENGINEERING (IJECE)
Year:2005 | Volume:4 | Issue:2|Papers Count:9

Parallel Hybrid Electric Vehicle powertrain (PHEV), combining an electric motor with an auxiliary power unit, improves vehicle performance and fuel economy, reducing the effects of private cars on air quality in cities. These advantages can be enhanced by using a dedicated control strategy to identify the optimal power flow distribution at each instant of time in the main powerdrive sources as a function of the state of the powerdrive components and the actual driving conditions. In this connection the literature analysis has evidenced as the research efforts in the field of PHEV optimal power flow management should be oriented not only to develop precise and robust control strategies that can improve the vehicle performances, but also to lower the required computational resources making the solution strategy suitable with the vehicle dynamics and allowing, moreover, a cost effective hardware implementation. To develop this complex activity, fuzzy logic (FL) was used. As demonstrated by the simulation studies developed, FL enables the optimal power flow management problem to be solved by handling its intrinsic non-linearity using rules, membership functions, and the inference process. This results in improved performance, simpler implementation, and reduced design costs compared with rigorous mathematics based approaches.

The paper proposes a modified constant voltage/ frequency (V/f) control algorithm for a 3-phase induction motor (IM) fed from a space vector pulse width modulated (SVPWM) inverter. This algorithm is experimentally verified using ordinary data acquisition card (DAC). A compensation method utilizes the stator resistance voltage drop space vector, in the stationary frame, is synthesized to correct the on-line stator voltage space vector and maintain the stator flux constant during the steady state as well as transient conditions. Moreover, an estimated value of the load torque is used to correct the command angular frequency of the IM and improve the performance of the PI-controller with load torque perturbations. The SVPWM switching patterns, which represent the reference stator voltage space vector, is realized by generating dependent digital words on the DAC digital lines. Accordingly, the computer storage memory is minimized and a saw tooth carrier generator is eliminated. Experimental results have been carried out to verify the effectiveness and applicability of the proposed control algorithm.

A novel pulse width modulation (PWM) switching strategy is developed through carrier modification, which eliminates the restriction in the fundamental component of a conventional switching scheme in the linear region. The proposed strategy is suitable for single-phase full-bridge inverter. The performance evaluation and comparison are based on the fundamental component, the total harmonic distortion (THD) and number of pulses per cycle. The aim of the novel method is to achieve overmodulated fundamental voltage values with modulation depths in the linear range, while improving THD and further reducing lower order harmonics dominancy. A significant enhancement in performance is validated by simulation and numerical commutations. In addition, a performance comparison of proposed method with harmonic injection PWM methods is also provided.

In this paper, an ingenious digital speed control scheme for a Switched Reluctance Motor (SRM) drive is presented. It is based on discrete P, PI and PID control algorithms. The scheme is implemented by using an ADµC812 flash microcontroller. The real time experimental results given in this paper show that the speed control method proposed could provide accurate speed control over a wide range of speeds and can also perform accurately at different operating conditions (steady state/transient operation under soft chopping mode). The closed-loop SRM speed control system is seen to achieve ±1 RPM speed accuracy. Complete descriptions of the experimental system along with software operating instructions are presented.

In this paper the traditional and state-of-the-art educational methods and experience in teaching of power electronic devices for undergraduate students are described. The main attention is dedicated to possibilities how to improve the study using e-learning methods. The interactive screens with animations created for better understanding features of power semiconductor devices are presented.

In this paper, a class of new Duty-Cycle Modulators (DCM) is investigated. Although the duty-cycle involved in each case is a nonlinear function of the control signal, a numerical analysis indicates that one could develop an excellent linear approximation for an appropriate choice of design parameters. The class of DCM proposed combines duty-cycle modulation and analog signal processing techniques in a single operational amplifier circuit. Simulations are conducted under constant and variable controls using Electronic Work Bench in order to test and validate the proposed class of modulation circuits. As an implication, the class of signal conditioning systems investigated in this study will have a number of applications in industrial instrumentation.

Outliers are data values that lie away from the general cluster of other data values. Detecting the outliers of a dataset is an important research topic for data cleaning and finding new useful knowledge in many research areas, i.e. data mining, pattern recognition, etc. In the past decades, many useful algorithms were proposed in the literature. In this paper, a new fuzzy kernel-clustering algorithm with outliers (FKCO) is presented to locate critical areas that are often represented by only a few outliers. Theoretic analysis also shows that FKCO can converge to a local minimum of the objective function. Finally, based on the information theory, a new criterion for finding outliers is also proposed. Simulations of different types of datasets demonstrate the feasibility of this new method.

An approach for tracking dynamic arterial vessels in X-ray angiogram sequences is developed. Firstly, original images are segmented into binary ones by using multi-scale filtering technique. Then, a discrete deformable model is employed to automatically track the vessel segment of interest, labeled by start point and end point selected by operator. The model deforms from its initial position, which is the line connecting start and end point, until stops at the real location of the target feature. Measurements of intensity similarity on end points and displacement similarity on middle points are introduced into the external energy to avoid model shrinking and shifting along the object during deforming. A rediscretization process is carried out after each deformation to ensure the continuity and smoothness of the model with an effect of decreasing the sensitivity to weighting parameters. The method is tested on several clinical angiogram sequences and results are presented.

This paper presents a general software reliability growth model (SRGM) based on nonhomogeneous Poisson process (NHPP). Although many research have been devoted to unify some NHPP models, most of them either only consider imperfect debugging, learning phenomenon, or take fault removal efficiency as a constant. Consideration of the variation of fault removal efficiency during debugging period in the exiting models is limited. The general model in this paper is the first unified scheme of some NHPP models which take fault removal efficiency as a function of debugging time. Fault detection rate (FDR) is usually used to measure the effectiveness of fault detection of test techniques and test cases. Most researchers assume a constant FDR in deriving their SRGMs. Because of learning process of testers, some researchers take FDR as increasing functions over testing period. Some literature take FDR as decreasing functions because failures removed first have higher detected rate. A bell-shaped FDR function is proposed which integrates both learning phenomenon and inherent FDR. As a special case of the general SRGM, a NHPP SRGM called PBbell-SRGM is put forward which integrates the proposed FDR function and fault removal efficiency. PBbell-SRGM is evaluated using a set of software failure data. The results show that PBbell-SRGM fits the given failure data better than some selected NHPP models.