Faculty Publications
Permanent URI for this communityhttps://idr.nitk.ac.in/handle/123456789/18736
Publications by NITK Faculty
Browse
10 results
Search Results
Item Space vector-based synchronised bus-clamping pulse width modulation algorithms for three-level voltage source inverter in overmodulation region(2012) Veeranna, S.B.; Yaragatti, R.Y.; Beig, A.R.The main objective of the present work is to develop space vector-based synchronised bus-clamping pulse width modulation algorithms to improve total harmonic distortion and higher DC-bus utilisation of the three-level inverter in overmodulation region. The proposed algorithms can generate synchronised pulse width modulation waveforms with all possible pulse number preserving all the waveform symmetries. The results of the proposed algorithms are evaluated and compared with conventional space vector pulse width modulation algorithm. It is shown that the proposed algorithms give improved results in terms of total harmonic distortion and DC-bus utilisation than that of conventional one in overmodulation region. The proposed method is implemented and verified experimentally on a constant v/f drive fed from insulated gate bipolar transistor (IGBT)-based voltage source inverter using Motorola power PC-based embedded controller. © 2012 The Institution of Engineering and Technology.Item Cumulant-based correlated probabilistic load flow considering photovoltaic generation and electric vehicle charging demand(Higher Education Press Limited Company, 2017) Bhat, N.G.; Prusty, B.R.; Jena, D.This paper applies a cumulant-based analytical method for probabilistic load flow (PLF) assessment in transmission and distribution systems. The uncertainties pertaining to photovoltaic generations and aggregate bus load powers are probabilistically modeled in the case of transmission systems. In the case of distribution systems, the uncertainties pertaining to plug-in hybrid electric vehicle and battery electric vehicle charging demands in residential community as well as charging stations are probabilistically modeled. The probability distributions of the result variables (bus voltages and branch power flows) pertaining to these inputs are accurately established. The multiple input correlation cases are incorporated. Simultaneously, the performance of the proposed method is demonstrated on a modified Ward-Hale 6-bus system and an IEEE 14-bus transmission system as well as on a modified IEEE 69-bus radial and an IEEE 33-bus mesh distribution system. The results of the proposed method are compared with that of Monte-Carlo simulation. © 2017, Higher Education Press and Springer-Verlag Berlin Heidelberg.Item Electric Field Reduction in an EHV Substation for Occupational Exposure via Transposition of Conductors(Institute of Electrical and Electronics Engineers Inc., 2018) Devarajan, D.; Punekar, G.S.An attempt is made to reduce the maximum value of rms electric field (E-field) via the transposition of conductors in a 765-kV substation with reference to the occupational exposure. The method is applied to a extra-high-voltage substation, which is under construction. The effect of transposing the bay conductors (alone) and the bus conductors (alone) on the E-field distribution (at 2 m above the ground) over the area of the substation is discussed. Also, the topology of substation conductors that results in the minimum value for the maximum of rms E-fields is obtained via simultaneous transpositions of the bus and bay conductors. The area of the substation where the rms E-field exceeds the reference value of 10 kV/m (International Commission on Non-Ionizing Radiation Protection occupational exposure limit) is also reported for the existing topology. For this topology, the computed maximum value of the rms E-field over the area of the substation is 13.06 kV/m. This E-field is reduced to 7.999 kV/m with the best configuration of substation conductors obtained via transposition. The charge-simulation-method-based generalized algorithm for obtaining the best topology (among all permutations) of substation conductors, which results in the minimum value for the maximum of rms E-field magnitudes over the substation area is also reported. © 1986-2012 IEEE.Item Effect of curbside bus stops on passenger car units and capacity in disordered traffic using simulation model(Taylor and Francis Ltd., 2022) Raj, P.; Asaithambi, G.; Ravi Shankar, A.U.Representation of traffic in terms of Passenger Car Unit (PCU) is imperative to estimate capacity in disordered traffic. Many studies have been conducted on investigation of impacts of traffic and geometric conditions on traffic characteristics and PCUs. However, the sensitivity of PCUs due to roadside frictions are not adequately studied. To address this gap, this study aims to estimate PCU values for vehicles under the influence of curbside bus stop, which is the most common roadside friction in developing countries. Lack of space for providing exclusive bus bays and higher demand for public transport buses in urban roads justify the need for this study. Methodology of this study involves development and validation of a microscopic simulation model to quantify the impact of curbside bus stop on PCU as well as capacity. The results indicate the significant differences in PCU values due to the presence of curbside bus stop with varying traffic volume and composition. © 2020 Informa UK Limited, trading as Taylor & Francis Group.Item Visualization and Assessment of the Effect of Roadworks on Traffic Congestion Using AVL Data of Public Transit(Springer Nature, 2022) Harsha, H.; Mulangi, R.H.; Kulkarni, V.Congestion-free movement of traffic during peak hours in urban areas is rarely witnessed nowadays. Several factors are responsible for traffic congestion, and a large amount of reliable data is necessary to investigate them. In this study, we investigated the effectiveness of automated vehicle location (AVL) data of public transit in evaluating the effect of route diversion due to roadworks on traffic congestion. The public transit vehicle data from Mysore intelligent transport system were used for the purpose. In the preliminary analysis, the spatiotemporal variations in the speed data of public transit were visualized using spatiotemporal speed plots. A comparison study of traffic states in an urban street and an arterial road was conducted using a visualization tool. The data from Inner Ring Road of Mysore city were used to evaluate the effect of roadworks on traffic congestion. The road links of Inner Ring Road were evaluated for two scenarios: normal scenario and route diversion scenario. The results revealed that the spatiotemporal visualization technique can be used to diagnose the changes in traffic congestion, especially near intersections and bus stops. It is concluded that the AVL data from public transit buses proves to be a potential data source for traffic state prediction and evaluation of traffic congestion. © 2022, The Author(s), under exclusive licence to Springer Nature Switzerland AG.Item The Spatiotemporal Patterns of Bus Passengers: Visualisation and Evaluation using Non-negative Tensor Decomposition(Springer Nature, 2023) Shanthappa, N.K.; Mulangi, R.H.; Harsha, H.M.Spatiotemporal analysis of passenger mobility patterns provides valuable information regarding the travel behaviour of passengers at different spatial and temporal scales. However, in the spatiotemporal analysis of passenger mobility patterns, a few questions are yet to be answered: how does passenger travel behaviour change during different seasons? In developing countries like India where land use distribution is complex, do travel characteristics have a relationship with spatial regions of different land use? And what is the influence of people from nearby sub-urban and villages on the passenger mobility of urban areas if transit service is provided? Hence, this study developed a methodology to visualise and analyse spatiotemporal variations in the bus passenger travel behaviour among different spatial regions at hourly, daily, and monthly temporal resolutions using non-negative tensor decomposition (NTD). Six-month electronic ticketing machine (ETM) data of the Davangere city bus service is collected. Land use data is also collected from the urban development authority of Davangere city. NTD was found efficient in extracting spatiotemporal patterns. From the analysis, it is observed that passenger mobility patterns across different spatial regions varied during different seasons and within a season as well. Pertaining to spatial variations, passenger origins and destinations are aggregated with respect to spatial regions with uniform land use or similar travel characteristics without giving any geographical inputs. Also, the mobility pattern of sub-urban and village people varied unconventionally. Thus, developed research methodology has the potential of unveiling the spatiotemporal variations in passenger mobility, which can act as a base for designing transit facilities and framing policies. © 2023, The Author(s), under exclusive licence to Springer Nature Switzerland AG.Item Application of Public Transit AVL Data for Evaluation of Delay Variability(Institute for Transport Studies in the European Economic Integration, 2023) Harsha, M.M.; Mulangi, R.H.; Panditharadhya, B.J.The travel time is the significant factor in evaluating efficiency and performance of public transit system. A greater percentage of travel time is accounted by bus stop delays which depends on passenger count, bus stop characteristics, traffic condition, bus performance, etc. Many of the Indian transit agencies store the passenger details stage wise not stop wise, which makes it difficult to evaluate delay variability at bus stop level. In this connection, Automatic Vehicle Location (AVL) data from Intelligent Transport System (ITS) implemented at Mysore, India is considered for evaluating bus stop delay variability. The collected data is used for estimating delay at five stops by adopting trajectory-based formulation. The probability distributions have been utilized to model the variability in delay. The performance has been analysed using Kolmogorov-Smirnov (KS) test. The daily variability of delay at bus stops has been evaluated using Coefficient of Variation (COV). The results of the performance evaluation of delay distributions show that the Generalized Extreme Value (GEV) distribution is the best descriptor of the delay variability in terms of accuracy, robustness, and survival capacity. In the absence of passenger data collection systems, method of evaluation of delay using AVL data presented in this study is helpful. © 2023 Institute for Transport Studies in the European Economic Integration. All rights reserved.Item Modelling personal safety perceptions at bus stop: employing hierarchical confirmatory factor analysis and structural equation approach(Aracne Editrice, 2023) Sethulakshm, G.; Mohan, M.Vehicle-pedestrian interactions occurring within a limited space are quite common at bus stops, making it essential to comprehend passengers' perception of safety near bus stops. Since the sense of perceived safety is subjective, developing a standardized tool to measure travellers' perception of safety, especially of bus users, is complex. The first part of this study aims to identify the indicators for measuring the perceived safety at bus stops, and the second part focuses on modelling the overall perceived safety of users’ at bus stops using structural equation modelling. The research examined the safety factors according to 14 indicators which were further reduced to five latent constructs using exploratory factor analysis. Perceived safety is taken as a second-order latent construct, and the second-order confirmatory factor analysis found that safety derived from five latent variables, namely bus stop facility, bus stop location, bus operator behaviour, other users' behaviour, and pedestrian facility, are potential indicators of overall perceived safety at the bus stop. The results recommend that providing night light facilities, adopting measures to avoid improper stopping of buses and left-side overtaking, avoiding bus stops on curves and junctions, and ensuring better sidewalk facilities could improve perceived safety. Structural equation modelling revealed that safety perceptions are negatively influenced by previous accident victimization and witnessing, age, educational qualification and total household vehicles. The results conclude that female respondents perceive less safety than males, and no effects can be attributed to the frequency of travel and trip length. The research findings will be helpful for the planning agencies to prioritize measures to improve travellers' feeling of safety. © 2023, Aracne Editrice. All rights reserved.Item Spatiotemporal capacity estimation of bus rapid transit system based on dwell time analysis(King Saud University, 2024) Angadi, V.S.; Halyal, S.; Mulangi, R.H.The performance study of an urban transport system, particularly a Bus Rapid Transit System (BRTS), must report on its operations and reliability. Such study of BRTS comprises numerous facets, including capacity, which directly influences how the system practically operates and serves the commuters. Hubballi-Dharwad Bus Rapid Transit System (HDBRTS) has been operational since 2018. A performance study is necessary to evaluate the performance of HDBRTS, which aids in its upgradation and improvement. The current research uses the experimental technique through an innovative and inspired basis to comment on the HDBRTS's performance by estimating the corridor's operational capacity at different spatial and temporal fluctuations. The selected route of the HDBRTS comprises combined segregated (exclusive traffic environment) and unsegregated (mixed traffic environment) stretches. The current study mainly conducted a video graphics-based survey to acquire the necessary data on identified spatial and temporal trends at various HDBRTS bus stations. The essential data gathered consists of Dwell Time (DT)-based data at each station, summarising the total time a bus takes to serve passengers at a station. DT is inversely proportional to the capacity of the particular bus station, which is related to the Failure Rate (FR). FR values of all the bus stations of the route were analyzed using DT, and then capacity values were calculated at different spatiotemporal patterns. Study results show that the busiest stations of the identified routes with critical DT values have FR values in the range of 1–2%, contradicting previous studies. The variations in the capacity of the stations, both spatially and temporally, were graphically represented with the minimum capacity of the segregated stretch as 36 buses/hr and the unsegregated stretch as 31 buses/hr. Finally, the Level Of Service (LOS) of the chosen study corridor was developed using the K-Means clustering algorithm and validated using the Silhouette Coefficient technique. The silhouette coefficient values obtained range from 0.52 to 0.74, indicating a reasonable structure. © 2023 The AuthorsItem Designing safe and accessible bus stops: an exploration of the interplay between perceived safety at crosswalk and transit ridership(Routledge, 2025) Sethulakshmi, G.; Mohan, M.Measuring personal safety perception is inherently complex, involving a multifaceted array of factors. This research advances the field of knowledge by developing a novel factor structure to assess pedestrian safety perceptions and modelling overall safety as a latent construct through a second-order Confirmatory Factor Analysis. Data were collected from 568 pedestrian interviews on safety perceptions near bus stops. The study concluded that perceived safety can be measured using four latent constructs: crosswalk infrastructure, crossing environment, management measures, and driver behavior, which collectively contribute to overall crosswalk safety. Using Structural Equation Modelling, the study confirms that as perceived safety while accessing bus stops via crosswalks decreases, bus ridership also declines. Findings also reveal demographic differences, with women, older individuals, and prior accident victims perceiving bus stop environments as less safe. Results suggest that policymakers should prioritize dedicated crosswalks and control speed and aggressive driving to maximize perceived safety at bus stops. © 2025 Informa UK Limited, trading as Taylor & Francis Group.