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tootoonchian--farid
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Design and Prototyping of Multi-Turn Wound Rotor Resolver
, M.Sc. Thesis Sharif University of Technology ; Nasiri-Gheidari, Zahra (Supervisor) ; Tootoonchian, Farid (Co-Supervisor)
Abstract
Resolver is a position sensor that is suited to be used in polluted environments with wide temperature variation, and high vibration. An important factor to determine the accuracy of resolver is its number of windings’ pole pairs that so-called “Speed” of resolver. Higher speed resolvers have higher accuracy in the price of losing absolute position information. Therefore, multi-turn resolvers are employed to have the high accuracy and high reliability along with absolute position information simultaneously. Multi-turn resolvers are consisted of two individual resolvers with different speeds in a common frame. In this thesis design considerations of multi-turn resolvers include proper...
Determining the Optimal Excitation Signal in order to Performance Improvement of Resolver
, M.Sc. Thesis Sharif University of Technology ; Nasiri Gheidari, Zahra (Supervisor) ; Tootoonchian, Farid (Supervisor)
Abstract
The need for position sensors has increased substantially with the development of electric vehicle motion control systems. In industrial applications, encoders are commonly used for positioning, but in polluted industrial environments, with large temperature variation and vibration, the resolver is preferred to optical encoder. Resolver is a two-phase synchronous generator with a high frequency AC excitation voltage instead of DC voltage. Therefore, the output voltages of the resolver are amplitude modulated (AM) voltages which in order to determine the output position, it is necessary to extract the envelope of these signals using R/D converter. In envelope extraction methods, to ensure...
Determining the Optimal Excitation Signal in order to Performance Improvement of Resolver
, M.Sc. Thesis Sharif University of Technology ; Nasiri Gheidari, Zahra (Supervisor) ; Tootoonchian, Farid (Supervisor)
Abstract
The need for position sensors has increased substantially with the development of electric vehicle motion control systems. In industrial applications, encoders are commonly used for positioning, but in polluted industrial environments, with large temperature variation and vibration, the resolver is preferred to optical encoder. Resolver is a two-phase synchronous generator with a high frequency AC excitation voltage instead of DC voltage. Therefore, the output voltages of the resolver are amplitude modulated (AM) voltages which in order to determine the output position, it is necessary to extract the envelope of these signals using R/D converter. In envelope extraction methods, to ensure...
Presentation of a novel absolute variable-reluctance tubular resolver
, Article IEEE Transactions on Instrumentation and Measurement ; Volume 72 , 2023 ; 00189456 (ISSN) ; Zare, F ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2023
Abstract
Resolvers have robust performance in harsh environments due to their electromagnetic structure. Among different types of resolvers, variable reluctance (VR) ones suggest higher reliability, simpler configuration, and lower cost. The same features are available for their linear counterparts. Since the application of linear machines is increasing, low-cost, high-precision linear position sensors attract more attentions. However, the accuracy of linear resolvers strongly influenced by longitudinal end effect and the edge effect. The edge effect can be suppressed using tubular configuration and the longitudinal end effect must be considered and suppressed in the design process. On the other...
Cogging force mitigation techniques in a modular linear permanent magnet motor
, Article IET Electric Power Applications ; Volume 10, Issue 7 , 2016 , Pages 667-674 ; 17518660 (ISSN) ; Nasiri Gheidari, Z ; Sharif University of Technology
Institution of Engineering and Technology
2016
Abstract
Modular linear doubly salient permanent magnet motors are well adapted to linear propulsion systems because of their distinct characteristics, such as high efficiency and power density, reduced maintenance and initial cost, low noise and permanent magnet (PM) leakage flux, and fault tolerance capability. However, such motors suffer from high cogging thrust. In this study, various techniques based on previously proposed methods for PM machines are applied on the studied motor and evaluated by using non-linear three-dimensional time-stepping finite element analysis; three novel, optimised techniques are then presented. The techniques presented are based on the minimisation of the variation in...
An optimized axial flux variable reluctance resolver with concentric windings
, Article 24th Iranian Conference on Electrical Engineering, ICEE 2016, 10 May 2016 through 12 May 2016 ; 2016 , Pages 1284-1290 ; 9781467387897 (ISBN) ; Nasiri Gheidari, Z ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2016
Abstract
Radial flux variable reluctance resolvers (RFVR2s) are widely used in variety of applications. However, they suffer from an intrinsic error which is called static eccentricity (SE). Although most of the errors in the resolvers can be suppressed using electronic methods in resolver to digital (R/D) converters, static misalignment is an exception. In this paper an axial flux configuration is proposed for variable reluctance (VR) resolvers with concentric windings. Then the proposed structure is optimized to achieve the minimum sensitivity of accuracy against SE. The performance of the presented structure, so called axial flux variable reluctance resolver (AFVR2), is validated using 3-D time...
Twelve-slot two-saliency variable reluctance resolver with non-overlapping signal windings and axial flux excitation
, Article IET Electric Power Applications ; Volume 11, Issue 1 , 2017 , Pages 49-62 ; 17518660 (ISSN) ; Nasiri Gheidari, Z ; Sharif University of Technology
Institution of Engineering and Technology
2017
Abstract
In this study, a new 12-slot two-saliency variable reluctance (VR) resolver with simple non-overlapping windings is proposed. The excitation winding in the proposed resolver is replaced with one axial coil that is perpendicular to the signal windings. Both distributed and non-overlapping concentric windings with uniform coil turns are used. The rotor has two upper and lower saliencies located in front of each other. The shape and width of each saliency are determined based on the optimisation. Compared with conventional 12-slot VR resolvers, the proposed resolver has a simpler rotor structure and the advantages of two-saliency resolvers against eccentricity, absolute output position, and...
Analytical modeling of variable-reluctance tubular resolver based on magnetic equivalent circuit and conformal mapping
, Article IEEE Transactions on Instrumentation and Measurement ; Volume 70 , 2021 ; 00189456 (ISSN) ; Zare, F ; Tootoonchian, F ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2021
Abstract
Compared with flat linear structures, tubular linear machines do not face edge effects, making their performance better than their flat counterparts. In this article, a novel linear variable-reluctance resolver with tubular configuration is proposed. To optimize the design of an electromagnetic structure, modeling methods are used. Thus, in this article, an analytical model for the proposed resolver is presented. This model is based on the magnetic equivalent circuit (MEC) method and is considerably less time-consuming than finite element analysis (FEA), yet provides accurate results. A conformal mapping is employed to compute the permeance of the air-gap. The proposed model is then utilized...
Static eccentricity fault location diagnosis in resolvers using siamese-based few-shot learning
, Article IEEE Transactions on Instrumentation and Measurement ; Volume 72 , 2023 ; 00189456 (ISSN) ; Khajueezadeh, M ; Tootoonchian, F ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2023
Abstract
Static eccentricity in the resolver, with higher probability and severity occurrence, gradually injects instability into the drive system; thus, its exact location diagnosis is mandatory. Whereas, most existing investigations rely on frequency analysis of signal voltages for resolver fault diagnosis, artificial intelligence (AI) is at the center of attention for electric motors fault diagnosis. Yet, sufficient data collection brings some challenges for AI. Therefore, intrigued by the idea of few-shot learning to overcome the data scarcity challenge, a convolutional neural Siamese network is employed with limited data to diagnose the static eccentricity location under each stator tooth via...
Throughput Analysis in Multi Hop Cellular Networks
, M.Sc. Thesis Sharif University of Technology ; Ashtiani, Farid (Supervisor)
Abstract
OFDMA multi-hop cellular network (MCN) is the topic of a wide range of research today. In this thesis, we analyse this type of networks, regarding shadowing status, mobility patterns and different service requirements. In the multi-hop (MH) scenario, six fixed relays are set up in each cell, which split the cell into seven subcells. For mobility modeling, each subcell is split into several sub-regions. Mobile nodes are able to maintain at each sub-region with a random time distribution and migrate from it to one of its neighboring sub-regions. We also consider three types of services requiring specific number of subcarriers with specific BERs. The set of subcarriers is distributed among...
Throughput Analysis of a Cognitive Multi-hop Wireless Network Overlaid on a Cellular Network
, M.Sc. Thesis Sharif University of Technology ; Ashtiani, Farid (Supervisor)
Abstract
In this thesis, we evaluate the maximum stable throughput of a cognitive multi-hop IEEE 802.11-based WLAN overlaid on a cellular network. In the considered scenario, the secondary users operate in the downlink or uplink frequency band of primary network and transmit their data in free primary channels using OFDM technique. The activity of primary nodes is modeled independently by ON-OFF alternating states. To model the scenario, each secondary user is modeled with an open queueing network. The queueing network can model the transmission of data as well as the effect of primary users. By writing the traffic equations of the queueing network and applying the stability conditions, we are able...
Analysis of the Effect of Frame Aggregation in IEEE 802.11 Standard
, M.Sc. Thesis Sharif University of Technology ; Ashtiyani, Farid (Supervisor)
Abstract
In this thesis the effect of frame aggregation mechanism in maximizing throughput in Wireless Local Area Networks (WLANs) have been investigated. Frame aggregation has become a part of the IEEE 802.11 standard as the amendment IEEE 802.11n. First, we have a quick review on access control layer in IEEE 802.11 standard then illustrate the necessity of frame aggregation. Afterwards, we propose an analytical model for the analysis of an IEEE 802.11n network comprised of an Access Point (AP) and several conventional nodes, all in the coverage area of each other. This analytical model focuses on downlink throughput; therefore only AP uses frame aggregation and the other nodes use basic IEEE 802.11...
Network Coding-based Packet Relaying in Wireless Networks
, M.Sc. Thesis Sharif University of Technology ; Ashtiani, Farid (Supervisor)
Abstract
In this thesis, we propose two new network coding-based packet relaying schemes suitable for multiple unicast scenarios in a random access network. In such networks the channels may have memory dependent upon the random access scheme. Thus, the optimal scheme for memoryless channels reported recently in the literature is not necessarily optimal in random access networks. In our proposed schemes, we convert a multiple unicast scenario to a combination of multiple anycast and a few multicast scenarios. By such an approach, we exploit the channels between relay node and the other nodes, instead of using only one channel at each packet transmission, for as many as possible. By simple analytical...
Content Distribution Service Analysis in Vehicular Ad-Hoc Networks
, M.Sc. Thesis Sharif University of Technology ; Ashtiani, Farid (Supervisor)
Abstract
Car accident damages take about 7 percent of GPD of Iran every year. As a result of car accidents, the economy of the country is damaging irreparably. The amount of road casualties equals casualties in a complete war. Considering the aforementioned conditions, the researchers are thinking about new technologies to reduce the cost of the accidents. So the use of Vehicular ad-hoc Networks (VANET) is inevitable in the near future. Content distribution service is one of the emerging services of VANETs. This service is used in both safety and comfort related applications. Content distribution describes delivery of media content such as Video, Audio, Image, Text, Software, and Video Games over...
Performance Analysis of Cognitive Radio Networks With Capability of Spectrum Mobility
, M.Sc. Thesis Sharif University of Technology ; Ashtinani, Farid (Supervisor)
Abstract
In cognitive radio networks, secondary users try to use empty channels that primary users provide for transmitting data. First, the secondary users sense the target channels. If the selected channel is empty, they send their data. When the primary user returns, the secondary user has to find another empty channel for transmitting data. The process of changing channel is called hand off. In recent years, there are challenges in the spectrum mobility of for reducing delay time of secondary users packet. In this thesis, we assume that the secondary users network is an ad-hoc network. We use contestation based method for reducing collision between secondary users. In this thesis, we present an...
Energy Harvesting in Wireless Communication Networks
, Ph.D. Dissertation Sharif University of Technology ; Ashtiani, Farid (Supervisor)
Abstract
In this dissertation, we focus on two types of EH cooperative networks. In the first type, the source and relay nodes access a shared channel according to a random access protocol. Also, they harvest energy from non-RF environmental resources. The relay node has data and energy buffers to store the packets of the source and the harvested energy, respectively. Our main goal is to find the optimal relaying protocol at the relay node. In this regard, the first type of the EH cooperative networks are investigated in two different scenarios. In the first one, the MAC channels of the nodes are independent of the applied policy at the relay node, and thus the throughput of the network is fixed....
Analysis of Age of Information in Multisource Communication Networks
, M.Sc. Thesis Sharif University of Technology ; Ashtiani, Farid (Supervisor)
Abstract
In this thesis, we investigate the age of information in multisource networks. To this end, in the first phase of this thesis, we evaluate the Age of Information (AoI) in slotted ALOHA network. Regarding the interactions among the nodes in such a network, we model the memory of this network with a Trellis and find the peak Age of Information (PAoI) by using this Trellis. Then, we evaluate Age of Information-constrained regions and achievable throughput regions in the slotted ALOHA network and optimize Age of information in a symmetric case. In the second phase, we propose an efficient prioritizing scheme from AoI point of view and find the distribution of AoI and PAoI in such a scheme with...
Cooperative Networks from the MAC Layer Viewpoint
, Ph.D. Dissertation Sharif University of Technology ; Ashtiani, Farid (Supervisor)
Abstract
Cooperative networks have attracted much attention in the last decade. Being introduced to mitigate the inefficiencies in the physical layer, cooperation can also be beneficial in upper layers, such as MAC layer. Using cooperative communications is specifically more challenging in the random access networks, where collision is a main concern. Delay, as one of the main performance metrics in random access networks, can decrease significantly by using cooperative communications. Transmission delay, i.e., the required time for delivering one packet form its source to destination, is an important metric in many communication networks, such as the networks in which each node generates and...
Latency Analysis and Improvement in Distributed Storage Systems
, M.Sc. Thesis Sharif University of Technology ; Ashtiani, Farid (Supervisor)
Abstract
Today, with the proliferation of smart devices and the advent of various innovative applications, there has been an exponential surge in the number of users in telecommunication networks. Consequently, the data traffic rate is escalating considerably. This has created a major predicament for wireless networks due to the limited frequency spectrum. Therefore, the conventional centralized architecture makes it difficult for the network to address these numerous simultaneous requests. This issue can be solved by designing new architectures. In a way, network information is disseminated to the network's periphery and the contents of the primary data center are provided temporarily in closer...
Traffic Analysis in Cellular Networks based on OFDMA Access
, M.Sc. Thesis Sharif University of Technology ; Ashtiani, Farid (Supervisor)
Abstract
OFDMA modulation method is a multiple access technique that is resistant to fading effect in cellular communication systems. In OFDMA, multiple access is performed both in time and frequency, so more users can be served with less delay than other protocols. In this thesis, based on queuing theory, we seek to present a traffic model for OFDMA system traffic analysis in single-cell mode and in the next section in multi-cell mode. Then, by examining and comparing the analytical results and the simulation results, we show that our proposed model for traffic analysis of the OFDMA system is a suitable and effective model. Also, since users in the multimedia environment need different types of...