Speed-sensorless Predictive Current Controlled PMSM Drive With Adaptive Filtering-based MRAS Speed Estimators

Ridvan Demir 제어·로봇·시스템학회 2023 International Journal of Control, Automation, and Vol.21 No.8

In this study, the stator currents-based model reference adaptive system (MRAS) estimators, which uses adaptive filtering algorithms, called the least mean squares (LMS) and least mean Kurtosis (LMK) algorithms, in the adaptation mechanism, are proposed for speed estimation of the PMSM. The proposed MRAS estimators have been directly estimated the rotor speed of the PMSM by taking into account the error between the measured stator currents called the reference model and the stator currents at the output of the adaptive model. The performance of proposed estimators and the finite control set model predictive current control (FCS-MPCC) based speed/position sensorless PMSM driver are tested and verified in simulations. In addition, the proposed estimators are compared to a fixed-gain PI controller-based MRAS. Simulation results and mean square errors (MSEs) obtained from both LMS and LMK-based MRAS algorithms demonstrated that the proposed estimators have higher performance compared to MRAS using a traditional PI controller. Moreover, the proposed estimators have eliminated the need for a fixedgain PI controller, which is often used in MRAS structures.

Sintering and Microstructure Characteristics of 42CrMo4 Steel Processed by Spark Plasma Sintering

Ridvan Yamanoglu,William Bradbury,Eugene A. Olevsky,Randall M. German 대한금속·재료학회 2013 METALS AND MATERIALS International Vol.19 No.5

Rapidly solidified micron sized 42CrMo4 steel powder with a size range of 150-250 μm produced by plasma rotating electrode process was consolidated using a recently developed spark plasma sintering (SPS) process. The relationship between sintering parameters (temperature and soaking time) and microstructural properties was investigated. The effect of slow and high heating regimes on the consolidation of sintered compacts has been also investigated. Maximum relative density (99.2%) was obtained at 1000 °C, under 50 MPa pressure, with 8 min holding time and 200 °C/min heating rate. The microstructure of sintered steel was influenced by carburization occuring inside the graphite SPS process die. The diffusion of carbon produced martensite structure near the surface region and hardened the surface. This effect was investigated in detail using optical microscopy and hardness measurement. Scanning electrone microscopy was also used to examine the fracture surface of sintered compacts. High heating rate promoted the relative density at low temperature compared to high temperature.

In-plane vibrations of cracked slightly curved beams

H. Ridvan Oz 국제구조공학회 2010 Structural Engineering and Mechanics, An Int'l Jou Vol.36 No.6

In-plane vibrations of slightly curved beams having cracks are investigated numerically and experimentally. The curvature of the beam is circular and stays in the plane of vibration. Specimens made of steel with different lengths but with the same radius of curvature are used in the experiments. Cracks are opened using a hand saw having 0.4 mm thickness. Natural frequencies depending on location and depth of the cracks are determined using a Brüel & Kjaer 4366 type accelerometer. Then the beam is assumed as a Rayleigh type slightly curved beam in finite element method (FEM) including bending,extension and rotary inertia. A flexural rigidity equation given in literature for straight beams having a crack is used in the analysis. Frequencies are obtained numerically for different crack locations and depths. Experimental results are presented and compared with the numerical solutions. The natural frequencies are affected too much due to larger moments when the crack is around nodes. The effect can be neglected when it is at the location of maximum displacements. When the crack is close to the clamped end, the decrease in the frequencies in all modes is very high. The consistency of the results and validity of the equations are discussed.

In-plane vibrations of cracked slightly curved beams

Oz, H. Ridvan Techno-Press 2010 Structural Engineering and Mechanics, An Int'l Jou Vol.36 No.6

In-plane vibrations of slightly curved beams having cracks are investigated numerically and experimentally. The curvature of the beam is circular and stays in the plane of vibration. Specimens made of steel with different lengths but with the same radius of curvature are used in the experiments. Cracks are opened using a hand saw having 0.4 mm thickness. Natural frequencies depending on location and depth of the cracks are determined using a Bruel & Kjaer 4366 type accelerometer. Then the beam is assumed as a Rayleigh type slightly curved beam in finite element method (FEM) including bending, extension and rotary inertia. A flexural rigidity equation given in literature for straight beams having a crack is used in the analysis. Frequencies are obtained numerically for different crack locations and depths. Experimental results are presented and compared with the numerical solutions. The natural frequencies are affected too much due to larger moments when the crack is around nodes. The effect can be neglected when it is at the location of maximum displacements. When the crack is close to the clamped end, the decrease in the frequencies in all modes is very high. The consistency of the results and validity of the equations are discussed.

COVID-19 and Plasmodium ovale Malaria: A Rare Case of Co-Infection

Bilge Caglar,Ridvan Karaali,Ilker Inanc Balkan,Bilgul Mete,Gokhan Aygun 대한기생충학열대의학회 2021 Parasites, Hosts and Diseases Vol.59 No.4

ENERGY ON A PARTICLE IN DYNAMICAL AND ELECTRODYNAMICAL FORCE FIELDS IN LIE GROUPS

( Talat Korpinar ),( Ridvan Cem Demirkol ) 호남수학회 2018 호남수학학술지 Vol.40 No.2

In this study, we firstly define equations of motion based on the traditional model Newtonian mechanics in terms of the Frenet frame adapted to the trajectory of the moving particle in Lie groups. Then, we compute energy on the moving particle in resultant force field by using geometrical description of the curva-ture and torsion of the trajectory belonging to the particle. We also investigate the relation between energy on the moving particle in different force fields and energy on the particle in Frenet vector fields.

A New Approach On The Curvature Dependent Energy For Elastic Curves in a Lie Group

Talat Korpinar,Ridvan Cem Demirkol 호남수학회 2017 호남수학학술지 Vol.39 No.4

Elastica is known as classical curve that is a solution of variational problem, which minimize a thin inextensible wire's bending energy. Studies on elastica has been conducted in Euclidean space firstly, then it has been extended to Riemannian manifold by giving different characterizations. In this paper, we focus on energy of the elastic curve in a Lie group. We attepmt to compute its energy by using geometric description of the curvature and the torsion of the trajectory of the elastic curve of the trajectory of the moving particle in the Lie group. Finally, we also investigate the relation between energy of the elastic curve and energy of the same curve in Frenet vector fields in the Lie group.

Preform-Based Production of Al2O3-Reinforced Aluminium Matrix Composites by Using Various Modification Techniques

Kubilay Ozturk,Ridvan Gecu,Ahmet Karaaslan 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.5

Metal matrix composites have a wide range of applications due to their lightweight, high strength and high wear resistance.In this study, Al2O3-reinforced AA7075 matrix composites were produced by using liquid metal infiltration method in twostages. In the first stage of the production, preforms were manufactured by using Al2O3particles and different binders. Someof the preforms were sintered and some were not sintered. In the second step, liquid metal infiltration was performed on bothsintered and not sintered samples. Some preforms were preheated before the infiltration and some were directly subjected tothe liquid metal infiltration. The casting process was carried out in two different ways: (1) pouring the molten metal into thefired mould and (2) in situ melting of the metal during the mould firing. Fabricated composites were characterized by XRD,light metal microscopy, SEM, EDS, Brinell hardness and ball-on-disc type wear tests. When the microstructural, mechanicaland tribological properties were taken into account, preheating and sintering preforms before casting were determinedas performing best with the hardness of ~ 150 HB and the wear rate of 1.1 × 10−4 mm3/(N m), whereas the in situ meltingcaused decrease in the mechanical strength and wear resistance because of excessive oxidation.

ENERGY ON A PARTICLE IN DYNAMICAL AND ELECTRODYNAMICAL FORCE FIELDS IN LIE GROUPS

Korpinar, Talat,Demirkol, Ridvan Cem The Honam Mathematical Society 2018 호남수학학술지 Vol.40 No.2

In this study, we firstly define equations of motion based on the traditional model Newtonian mechanics in terms of the Frenet frame adapted to the trajectory of the moving particle in Lie groups. Then, we compute energy on the moving particle in resultant force field by using geometrical description of the curvature and torsion of the trajectory belonging to the particle. We also investigate the relation between energy on the moving particle in different force fields and energy on the particle in Frenet vector fields.

Region Specific Brain Organoids to Study Neurodevelopmental Disorders

Praveen Joseph Susaimanickam,Ferdi Ridvan Kiral,In-Hyun Park Korean Society for Stem Cell Research 2022 International journal of stem cells Vol.15 No.1

Region specific brain organoids are brain organoids derived by patterning protocols using extrinsic signals as opposed to cerebral organoids obtained by self-patterning. The main focus of this review is to discuss various region-specific brain organoids developed so far and their application in modeling neurodevelopmental disease. We first discuss the principles of neural axis formation by series of growth factors, such as SHH, WNT, BMP signalings, that are critical to generate various region-specific brain organoids. Then we discuss various neurodevelopmental disorders modeled so far with these region-specific brain organoids, and findings made on mechanism and treatment options for neurodevelopmental disorders (NDD).