Novel Switching Table for Direct Torque Controlled Permanent Magnet Synchronous Motors to Reduce Torque Ripple

Sivaprakasam Arumugam,Manigandan Thathan 전력전자학회 2013 JOURNAL OF POWER ELECTRONICS Vol.13 No.6

The Direct Torque Control (DTC) technique for Permanent Magnet Synchronous Motors (PMSM) is receiving increased attention due to its simplicity and robust dynamic response when compared with other control techniques. The classical switching table based DTC results in large flux and torque ripples in the motors. Several studies have been reported in the literature on classical DTC. However, there are only limited studies that actually discuss or evaluate the classical DTC. This paper proposes, novel switching table / DTC methods for PMSMs to reduce torque ripples. In this paper, two DTC schemes are proposed. The six sector and twelve sector methodology is considered in DTC scheme I and DTC scheme II, respectively. In both DTC schemes a simple modification is made to the classical DTC structure. The two level inverter available in the classical DTC is eliminated by replacing it with a three level Neutral Point Clamped (NPC) inverter. To further improve the performance of the proposed DTC scheme I, the available 27 voltage vectors are allowed to form different groups of voltage vectors such as Large - Zero (LZ), Medium - Zero (MZ) and Small - Zero (SZ), where as in DTC scheme II, all of the voltage vectors are considered to form a switching table. Based on these groups, a novel switching table is proposed. The proposed DTC schemes are comparatively investigated with the classical DTC and existing literatures through theory analysis and computer simulations. The superiority of the proposed DTC method is also confirmed by experimental results. It can be observed that the proposed techniques can significantly reduces the torque ripples and improves the quality of current waveform when compared with traditional and existing methods.

Biocalorimetric and Respirometric Studies on Metabolic Activity of Aerobically Grown Batch Culture of Pseudomonas aeruginosa

Sivaprakasam, Senthilkumar,Mahadevan, Surianarayanan,Bhattacharya, Madhuchhanda Korean Society for Biotechnology and Bioengineerin 2007 Biotechnology and Bioprocess Engineering Vol.12 No.4

Biocalorimetry has proved to be a useful tool for scale up and control of bioreactors. The findings reported here are fundamental data required for scale up and control of a reactor for the treatment of saline tannery wastewater. The study deals with biokinetics of a halo-tolerant bacteria Pseudomonas aeruginosa isolated from tannery saline wastewater (soak liquor). Batch experiments were performed in a biocalorimeter and the isolated strain was grown in a glucose-limited mineral salt medium (MSM) at optimized growth conditions. Tessier model is found to fit well for the growth of P. aeruginosa in biocalorimeter. Biokinetic constants are evaluated and simulation is done to validate experimental results with theoretical values. Respirogram and heat profiles are seen to follow the biomass growth curve. Oxycalorific coefficient is validated with the theoretical values and those noticed in the published literature. There is a good correlation between experimentally determined heat yields and the theoretical values predicted by elemental and enthalpy balances. The heat yield and biomass yield values indicated the behavior of the isolated organism in a substrate-limited well defined growth media (MSM).

Novel Switching Table for Direct Torque Controlled Permanent Magnet Synchronous Motors to Reduce Torque Ripple

Arumugam, Sivaprakasam,Thathan, Manigandan The Korean Institute of Power Electronics 2013 JOURNAL OF POWER ELECTRONICS Vol.13 No.6

The Direct Torque Control (DTC) technique for Permanent Magnet Synchronous Motors (PMSM) is receiving increased attention due to its simplicity and robust dynamic response when compared with other control techniques. The classical switching table based DTC results in large flux and torque ripples in the motors. Several studies have been reported in the literature on classical DTC. However, there are only limited studies that actually discuss or evaluate the classical DTC. This paper proposes, novel switching table / DTC methods for PMSMs to reduce torque ripples. In this paper, two DTC schemes are proposed. The six sector and twelve sector methodology is considered in DTC scheme I and DTC scheme II, respectively. In both DTC schemes a simple modification is made to the classical DTC structure. The two level inverter available in the classical DTC is eliminated by replacing it with a three level Neutral Point Clamped (NPC) inverter. To further improve the performance of the proposed DTC scheme I, the available 27 voltage vectors are allowed to form different groups of voltage vectors such as Large - Zero (LZ), Medium - Zero (MZ) and Small - Zero (SZ), where as in DTC scheme II, all of the voltage vectors are considered to form a switching table. Based on these groups, a novel switching table is proposed. The proposed DTC schemes are comparatively investigated with the classical DTC and existing literatures through theory analysis and computer simulations. The superiority of the proposed DTC method is also confirmed by experimental results. It can be observed that the proposed techniques can significantly reduces the torque ripples and improves the quality of current waveform when compared with traditional and existing methods.

An Improved Coyote Optimization Algorithm-Based Clustering for Extending Network Lifetime in Wireless Sensor Networks

Venkatesh Sivaprakasam,Vartika Kulshrestha,Godlin Atlas Lawrence Livingston,Senthilnathan Arumugam 한국인터넷정보학회 2023 KSII Transactions on Internet and Information Syst Vol.17 No.7

The development of lightweight, low energy and small-sized sensors incorporated with the wireless networks has brought about a phenomenal growth of Wireless Sensor Networks (WSNs) in its different fields of applications. Moreover, the routing of data is crucial in a wide number of critical applications that includes ecosystem monitoring, military and disaster management. However, the time-delay, energy imbalance and minimized network lifetime are considered as the key problems faced during the process of data transmission. Furthermore, only when the functionality of cluster head selection is available in WSNs, it is possible to improve energy and network lifetime. Besides that, the task of cluster head selection is regarded as an NP-hard optimization problem that can be effectively modelled using hybrid metaheuristic approaches. Due to this reason, an Improved Coyote Optimization Algorithm-based Clustering Technique (ICOACT) is proposed for extending the lifetime for making efficient choices for cluster heads while maintaining a consistent balance between exploitation and exploration. The issue of premature convergence and its tendency of being trapped into the local optima in the Improved Coyote Optimization Algorithm (ICOA) through the selection of center solution is used for replacing the best solution in the search space during the clustering functionality. The simulation results of the proposed ICOACT confirmed its efficiency by increasing the number of alive nodes, the total number of clusters formed with the least amount of end-to-end delay and mean packet loss rate.

Evaluation of the effects of oral rinses on the retention and surface topography of the ball attachment complex for implant overdentures

Dhanapriya Gopalakrishnan(Dhanapriya Gopalakrishnan ),Azhagarasan Nagarasampatti Sivaprakasam(Azhagarasan Nagarasampatti Sivaprakasam ),Vidhya Jeyapalan(Vidhya Jeyapalan ),Jayakrishnakumar Sampathkuma 대한치과이식임플란트학회 2023 The Korean Academy of Implant Dentistry Vol.42 No.1

Purpose: To evaluate the effect of two different oral rinses on the retention and surface topography of ball attachments for implant overdentures. Materials and Methods: Thirty metal housing and the nylon cap inserts (Adin, Israel) were placed on the master block and the attachment assemblies were transferred to prosthetic blocks using the direct pickup technique. Group I had ten test samples immersed in water, Group II had ten test samples immersed in Listerine® Cool Mint®(J&J, India), Group III had ten test samples immersed in Colgate Vedshakthi oil-based herbal oral rinse (Colgate-Palmolive, India). The retention force was tested at baseline and after immersion in the respective oral rinses at 360 cycles (simulating 3 months) and 720 cycles (simulating 6 months) of clinical use, using a universal testing machine (Shimadzu, AG-X plus 50KN, Europe, GmBH) at a crosshead speed of 50 mm/min. The data was analyzed using the repeated measures ANOVA test, one-way ANOVA test, and post hoc analysis (SPSS23, Munich, Germany). The surface topography was assessed initially and subsequently after immersion in the oral rinses after 360 and 720 insertion-removal cycles using a stereomicroscope (Leica M205C, Germany). Results: At 360 cycles, the mean retention force (MRF) exhibited by Group I was higher than that of Group III and this difference was significant. The MRF of Group II was also significantly higher than Group III. At 720 cycles, the MRF exhibited by Group I was higher than that of Group II and the difference was significant. Also, the MRF of Group I was significantly higher than that of Group III, and the MRF of Group II was significantly higher than that of the Group III test samples. In Group I, the percentage loss in the MRF at the end of 360 and 720 cycles was 4.96% and 6.37%, respectively. In Group II, it was 6.82% and 9.41%, respectively, and in Group III it was 14.75% and. 16.60%, respectively. Conclusions: Colgate Vedshakti caused the highest surface topographic changes. This corroborates with the lower retention obtained, followed by Listerine® Cool Mint®, and the least changes were observed for samples immersed in water, which corroborates with the greater retention obtained in the study.

A facile and green synthesis of NiCo2O4/Graphene nanohybrids for supercapacitor applications

고태훈,( Sivaprakasam Radhakrishnan ),최웅기,서민강,길명섭,김학용,김병석 한국공업화학회 2016 한국공업화학회 연구논문 초록집 Vol.2016 No.0

We have prepared NiCo2O4 nanoparticles decorated graphene nanosheets (NiCo2O4-rGO) nanohybrids via a dry synthesis technique without using any harmful reagents. As-prepared NiCo2O4-rGO nanohybrids were characterized by scanning electron microscopy, X-ray diffraction. The electrochemical performances of NiCo2O4-rGO nanohybrids were analyzed by cyclic voltammetry and electrochemical impedance spectroscopy. The NiCo2O4-decorated graphene electrode exhibited a maximum specific capacitance of 886 Fg-1 at a scan rate of 5.0 mV/s, and also showed high cyclic stability with retention of 82.1% after 2000 cycle.

Au NP/PPy/rGO nanohybrid modified glassy carbon electrode for the efficient non-enzymatic detection of oxalic acid

( Pratigya ),( Sivaprakasam Radhakrishnanb ),( Santhana Sivabalan ),김병석 한국공업화학회 2016 한국공업화학회 연구논문 초록집 Vol.2016 No.0

Oxalic acid (OA), a reducing agent exists widely in plants, animals and microbes. Excess intake of such products may lead to the formation of less soluble salt leading to the formation of kidney stones. In this study, a nanohybrid of gold nanoparticle, polypyrrole, and reduced graphene oxide (Au/PPy/rGO) was prepared by an in-situ chemical synthesis approach. The as-prepared nanohybrid has been applied for non-enzymatic electrochemical detection of oxalic acid in 0.1 M H2SO4 as electrolyte. The modified electrode showed a wider linear range (0.05mM to 7mM) with a lower detection limit of 0.02 mM. The experimental results also showed that the sensor has good reproducibility (R.S.D = 2.59% for 0.5mM, n = 3), high sensitivity of 91 μA/mM and good stability as well. Possible interferences such as glucose, dopamine, uric acid, Zn, Fe were investigated. The above mentioned compound does not interfere with oxalic acid detection.

A high performance non-enzymatic glucose sensor based on copper sulfide microflower nanostructure modified glassy carbon electrode

( Pratigya ),( Sivaprakasam Radhakrishnan ),( Balasubramaniam Saravanakumar ),김병석 한국공업화학회 2016 한국공업화학회 연구논문 초록집 Vol.2016 No.0

A highly selective, sensitive and stable non-enzymatic glucose sensor based on CuS modified electrode was developed. The CuS microflower was prepared by simple solvothermal method without using template. The as-prepared CuS product was characterized by FE-SEM, XRD and cyclic voltammetry methods. The CuS microflower structures are proved to be a good sensing element for the determination of glucose. The CuS modified glassy carbon electrode (GCE) exhibited the lowest detection limit of 1.0 μM over a wide glucose concentration up to 5.4 x 10(-3) M. The fabricated sensor is highly selective towards the determination of glucose in the presence of physiological interferents and metal ions.

Dual functional nickel cobalt/MWCNT composite electrode-based electrochemical capacitor and enzymeless glucose biosensor applications: Influence of Ni/Co molar ratio

고태훈,성재경,Sivaprakasam Radhakrishnan,곽채송,길명섭,김학용,김병석 한국공업화학회 2019 Journal of Industrial and Engineering Chemistry Vol.73 No.-

The nickel cobalt/MWCNT composites with Ni/Co molar ratio of 1:2 showed excellent electrochemicalperformance in term of specific capacitance ( 800 F g 1 at current density of 2 A g 1), good ratecapability and excellent stability, which may be attributed to the combined benefits of bi-metals andMWCNT and porous metal nanostructures, enhancing the kinetics of ions/electron transport at bothelectrode inside and electrode/electrolyte interface. Further, the nickel cobalt/MWCNT compositemodified electrode as electro-catalyst for glucose electro-oxidation demonstrated high sensitivity, goodlinear range and detection limit, which hold great promise as advanced electrode materials forsupercapacitor and glucose electro-oxidation applications.

A hybrid metal oxide/MWCNT aerogels as electrode materials in supercapacitors

( Santhana Sivabalan ),( Sivaprakasam Radhakrishnan ),길명섭,김병석 한국공업화학회 2016 한국공업화학회 연구논문 초록집 Vol.2016 No.0

In recent years CNT based nanocomposites have great attention due to their potential applications in sensors, catalysis, hydrogen storage and energy applications. Aerogels are the mesoporous solids and exhibits high surface area and porosity. Metal oxide aerogels with 3-Dimentional architecture are interconnected with metallic nanoparticles with mesopores. In this work, we have prepared hybrid NiCo2O4/MWCNT aerogels by a sol-gel approach. The crystal nature and microstructures of the materials are confirmed by X-ray diffraction and FE-SEM studies. It exhibits high surface area and porosity. The NiCo2O4/MWCNT aerogels with higher contents (~ 20 wt%) of MWCNT exhibits the highest specific capacitance value of ca. 928 F/g in lower current density, and also shows good cycle stability in supercapacitor behavior.