Showing 10 results for mousavi
S. R. Mousavi-Aghdam, M. R. Feyzi, Y. Ebrahimi,
Volume 8, Issue 1 (March 2012)
Abstract
This paper presents a new design to reduce torque ripple in Switched Reluctance Motors (SRM). Although SRM possesses many advantages in terms of motor structure, it suffers from large torque ripple that causes problems such as vibration and acoustic noise. The paper describes new rotor and stator pole shapes with a non-uniform air gap profile to reduce torque ripple while retaining its average value. An optimization using fuzzy strategy is successfully performed after sensitivity analysis. The two dimensional (2-D) finite element method (FEM) results, have demonstrated validity of the proposed new design.
S. R. Mousavi-Aghdam, M. R. Feyzi,
Volume 10, Issue 3 (September 2014)
Abstract
This paper considers a new switched reluctance motor (SRM) structure aiming at high starting torque with low volume. For some applications such as EVs (Electrical Vehicles), the motor volume and starting torque is a critical point in its design. In many methods, reducing the motor volume causes reduction in starting torque and decreases the motor efficiency. Unlike conventional SRMs, the rotor pole is skewed in the proposed structure along the motor axis. An approximated two-dimensional finite element method (FEM) is used to speed up computational time and some comparisons with three-dimensional FEM are considered for more reliability. Final results show the efficiency of the proposed structure.
S. M. Mousavi Gazafroodi, A. Dashti,
Volume 10, Issue 4 (December 2014)
Abstract
In this paper, a novel stator current based Model Reference Adaptive System (MRAS) estimator for speed estimation in the speed-sensorless vector controlled induction motor drives is presented. In the proposed MRAS estimator, measured stator current of the induction motor is considered as a reference model. The estimated stator current is produced in an adjustable model to compare with the measured stator current, where rotor flux identification is needed for stator current estimation. In the available stator current based MRAS estimator, rotor flux is estimated by the use of measured stator current, where the adjustable model and reference model depend on each other since measured stator current is employed in both of them. To improve the performance of the MRAS speed estimator, both the stator current and rotor flux are estimated in the adjustable model by using the state space equations of the induction motor, adjusted with the rotor speed calculated by an adaptation mechanism. The stability of the proposed MRAS estimator is studied through a small signal analysis. Senorless induction motor drive along with the proposed MRAS speed estimator is verified through computer simulations. In addition, performance of the proposed MRAS is compared with the available stator current based MRAS speed estimator
M. Mousavi Moaiied, M. R. Mosavi,
Volume 12, Issue 1 (March 2016)
Abstract
In this paper, combined GPS and GLONASS positioning systems are discussed and some solutions have been proposed to improve the accuracy of navigation. Global Satellite Navigation System (GNSS) is able to provide position, velocity and time with respect to coordinated universal time. GNSS positioning is based on received satellite signals, so its performance is highly dependent on the quality of these received signals. The effect of noise and multi-path can often be large enough to produce significant errors in positioning. Satellite navigation is difficult in this situation. In such circumstances, GPS or GLONASS alone are often not able to ensure consistency and accuracy in positioning due to the absence (or low quality) of signals. The combination of these two systems is an appropriate solution to improve the situation. In positioning a receiver, one of the ways that is often used to reduce the error due to observation noise and calculation errors is Kalman Filter (KF) estimation. In this paper, some changes in the structure of the KF is applied to improve the accuracy of positioning. Process of updating KF's gain, is done in fuzzy form based on the parameters available in RINEX files, including the P code pseudo-range used as an input of the proposed fuzzy system. Simulation results show that applying a fuzzy KF based on P code pseudo-range on the available data sets, in terms of noise and blocking condition, reduces the positioning error respectively from 24 to 14 meters and 90 to 25 meters.
S. R. Mousavi-Aghdam, M. R. Feyzi, N. Bianchi,
Volume 13, Issue 1 (March 2017)
Abstract
This paper presents analysis and comparative study of a novel high-torque three-phase switched reluctance motor (SRM) with magnetically isolated stator segments. In the proposed SRM, each segment has a concentric winding located on the center body of it and two diametrically opposite windings which form the motor phase. There are four salient poles in the stator segment. Two of them share their flux path in the center body of the segment. The rotor has a solid structure including twenty two salient poles. In this unique SRM, stator segments topology, number of the stator segments poles and the rotor poles, and angular distance of the stator segments are selected so that the motor properly operates in both directions. Two-phase design with different pole combination is also possible. During operation, there are short flux paths along two adjacent rotor poles and excited segment poles. Therefore, the proposed SRM has all benefits of the short flux path structures. The principle and fundamentals of the proposed SRM design are detailed in the paper. The motor is analysed using finite element method (FEM) and some comparisons are reasonably carried out with other SRM configurations. Finally, a prototype motor is built and experimental results validate the performance predictions in the proposed motor.
T. Azadmousavi, H. Faraji Baghtash, E. Najafi Aghdam,
Volume 14, Issue 2 (June 2018)
Abstract
This work introduces a new and simple method for adjusting the gain of current mirror. The major advantage of the proposed architecture is that, unlike the conventional variable gain current mirror, it does not need the change of the biasing current to adjust current gain. Therefore, the power dissipation remains constant in all of the gain settings. In addition, the proposed variable gain current mirror have linear-in-dB gain control characteristic, simple structure, and small occupied area. The gain of the current mirror can be simply varied from 1.3dB to 21dB while the 3-dB bandwidth of the circuit remains around 12.3MHz or 33.6MHz at operation frequency range of 1.9MHz-14.2MHz and 6.6MHz-40.2MHz respectively. The proposed circuit draws negligible power of 6.9µW from 1.8V supply voltage. The simulation results of designed variable gain current mirror in 0.18μm standard CMOS technology confirms the effectiveness of the proposed circuit.
T. Azadmousavi, H. Faraji Baghtash, E. Najafi Aghdam,
Volume 15, Issue 2 (June 2019)
Abstract
A power efficient gain adjustment technique is described to realize programmable gain current mirror. The dissipation power changes over the wide gain range of structure are almost negligible. This property is in fact very interesting from power management perspective, especially in analog designs. The simple structure and constant frequency bandwidth are other ever-interesting merits of proposed structure. The programming gain range of structure is from zero up to 18dB under operating frequency range from 72 kHz to 173 MHz. The maximum power dissipation of designed circuit is only 3.1 µW which is drawn from 0.7 V supply voltage. Simulation results in 0.18 µm CMOS TSMC standard technology demonstrate the high performance of the proposed structure.
H. Sheykhvazayefi, S. R. Mousavi-Aghdam, M. R. Feyzi,
Volume 15, Issue 4 (December 2019)
Abstract
In this paper, a new design of permanent magnet linear synchronous motor (PMLSM) for electromagnetic launcher system (EMLs) has been investigated in terms of the requisite amount of average launching thrust force and thrust force ripple minimization through finite element method. EMLs are a kind of technology used to develop thrust force and launch heavy loads with different applications including military, aerospace, and civil applications. A linear motor as a major part of the system plays a substantial role in this application providing sufficient load launch force. Cogging force and its mitigation techniques are principle challenges in linear motor operation leading to thrust ripples and detrimental effects on positioning precision and dynamic performance of the moving part. In the proposed design, some modifications have been made in the conventional PMLSM structure. Semi-closed slot construction is used for the primary and the pole shoes width has been changed to access minimum thrust ripple value. In order to attain further optimization in PMLSM’s thrust ripple profile, some other modifications have been considered in PM’s shape as arc-shaped magnetic poles. The latter assists to enforce air gap flux density distribution as sinusoidal as possible, and makes further ripple reduction. The results exhibit that the proposed structure has low weight and it is more economical compared to conventional PMLSM with rectangular shape magnet. In addition, the Average thrust force and ripple are improved providing suitable thrust force for throwing the load.
S. R. Mousavi-Aghdam, N. Elahi Kachaei,
Volume 17, Issue 2 (June 2021)
Abstract
This paper presents a new single to three phase converter using rotating magnetic field transformer. Conventional transformers have been used in many converters aiming at supplementary improvements and they usually have no critical effect on the conversion technique. In this paper, the conversion technique is based on a special rotating magnetic field transformer in which there are two windings in the primary and six windings on the secondary side. In the proposed converter, first a single-phase voltage source is applied on the primary windings via a switching technique using thyristors to create a rotating magnetic field. Next, the created field induces three phase voltages on the secondary three phase windings. Nevertheless, the created field in the primary side suffers from low frequency harmonics and can be transmitted to the secondary three phase voltages. Hence, design of the secondary windings is modified to mitigate these harmonics. The paper discusses how the harmonics can be mitigated using two sets of three phase windings with appropriate shift. Finally, the proposed converter is modeled using state equations and the simulation results exhibit the effectiveness of the proposed converter.
Aslan Nouri Moqadam, Seyed Hosein Mousavi,
Volume 21, Issue 1 (March 2025)
Abstract
Electromagnetic waves, with their unique properties, offer promising solutions to environmental challenges. This paper explores the utilization of electromagnetic scattering by droplets for cloud fertilization purposes. Specifically, a linearly polarized plane wave is deployed to stimulate a heterogeneous cloud medium composed of spherical droplets with varying size parameters. Through the application of Generalized Mie Theory (GMT) and Discrete Dipole Approximation (DDA) at a frequency of 28 GHz, multiple scattering phenomena and local electric fields are meticulously computed. Various scenarios of scattering, encompassing droplet diameters ranging from 500 µm to 700 µm and diverse volume fractions, are meticulously examined. Employing DDA and dyadic calculations, the exerted forces on individual spherical droplets are rigorously evaluated, with precise determination of force direction and components. The simulations robustly affirm the viability of droplet manipulation via plane wave excitation, thereby enhancing the likelihood of droplet collision and consequent cloud fertilization, ultimately leading to precipitation. Furthermore, the parameters of the incident wave can be deliberately adjusted to steer droplets towards denser regions, thereby augmenting the likelihood of successful fertilization events.
