Now showing 1 - 10 of 124
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    Electromechanical modelling of piezoelectric vibration energy harvester with a novel dynamic magnifier Elektromechanische Modellierung eines piezoelektrischen Vibrationsenergie-Harvesters mit einer neuartigen dynamischen Lupe
    (25-09-2020)
    Kote, Suresh
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    Krishnapillai, Shankar
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    In piezoelectric energy harvesting devices, the relative displacement between the two ends of the harvester beam decides the output power from the piezoelectric patch. A novel four bar mechanism with a helical spring is used as a dynamic magnifier to improve the relative displacement and thereby the output power from the harvester. This dynamic magnifier is placed between the base excitation location and the composite harvester beam to form two degrees of freedom (2DOF) piezoelectric energy harvester. Electromechanical coupled analytical equations for the voltage and output power are derived using a lumped electromechanical model. The model is developed assuming linear transverse vibrations of the harvester. A dynamic magnifier is fabricated for the required frequency range and the suitable dimensions of the harvester beam are estimated using commercially available software. Experiments are conducted for base excitation amplitude of 0.05 mm and the performance of the proposed 2DOF harvester is studied for the output voltage and power. The proposed 2DOF harvester has shown 110 % improvement in output power in first mode and 270 % improvement in second mode compared to the conventional single degree of freedom (SDOF) cantilevered harvester for given identical input conditions. The measured frequencies and output power are validated with analytical solutions and are found to be in good agreement. Further, the effect of mass ratio, stiffness ratio and base excitation amplitude on the output voltage and power is investigated using analytical expressions.
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    Analytical and experimental studies on lateral dynamics of a railway vehicle moving on straight track
    (01-12-2010) ;
    Kumar, Hemantha
    In this paper numerical simulation and experimental studies of the lateral dynamic behaviour of a railway vehicle are presented. A typical Indian railway vehicle of the Alternating Current /Electrical Multiple Unit /Trailer (AC/EMU/T) type running on broad gauge track has been chosen for the analysis. A 17 degree of freedom (dof) linear mathematical model of the vehicle has been formulated for the analysis. Kalker's creep theory is applied to evaluate the tangential contact forces acting between wheel and rail. Linear governing equations of motion of the vehicle on a straight track have been solved. Natural frequencies have been determined from the above mathematical model. A comprehensive study of the lateral stability of the railway vehicle has been performed. Dynamic response studies were carried out in the time domain for the vehicle moving on a straight track with the track alignment and gauge irregularities considered as input. Extensive experiments were carried out and analytical results are found to compare well with experimental results.
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    Optimal semi-active preview control response of a half car vehicle model with magnetorheological damper
    (09-10-2009)
    Prabakar, R. S.
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    Narayanan, S.
    The control of the stationary response of a half car vehicle model moving with a constant velocity over a rough road with magnetorheological (MR) dampers is considered. The MR damper is modelled by the modified Bouc-Wen model. The MR damper parameters adopted in the vehicle model correspond to an actual fabricated damper and are determined so that the MR damper model characteristics match with experimental characteristics. The random road excitation is considered as the output of a first-order linear shaping filter to white noise excitation. The control and response statistics of the nonlinear vehicle model with MR damper are obtained using the equivalent linearization method in an iterative manner and the results are verified by Monte-Carlo simulation. The MR damper performance is sought to be improved by suitable choice of input currents to the levels of performance of an active suspension based on H∞ control without and with preview by a mean square equivalence of respective control forces. The H∞ optimal control with preview minimizes a performance index which is a weighted sum of vehicle performance measures such as sprung mass acceleration, pitch acceleration, front and rear suspension strokes, road holding and control forces with the weights obtained by solving a multi-objective optimization problem using a non-dominated sorting genetic algorithm II (NSGA II). © 2009 Elsevier Ltd. All rights reserved.
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    Dynamic response of railroad vehicles: A frequency domain approach
    (01-01-2008)
    Gangadharan, K. V.
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    Ramamurti, V.
    A very elaborate Finite Element (FE) model and a rigid body model of a typical electrical multiple unit trailer coach are described. These models were used to find the dynamic response to track irregularities in the frequency domain. The Power Spectral Density (PSD) of track irregularities was used as input to the system. The influence of different track irregularities on dynamic response and coupling between vertical and lateral dynamics was investigated. Extensive experiments were carried out, and analytical results were compared with the measured response. Copyright © 2008 Inderscience Enterprises Ltd.
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    Longitudinal dynamics of a tracked vehicle: Simulation and experiment
    (01-04-2012)
    Janarthanan, B.
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    In recent years virtual dynamic system simulation has become very important in the design and development stage, as new strategies can be examined without expensive measurements and with reduced time. This paper describes the development of a simulation model for transient analysis of the longitudinal dynamics of a heavy tracked vehicle. The driving inputs for this simulation model are obtained from a powertrain model. The main elements of the powertrain include the engine, Torque Converter (TC), transmission and drivetrain. Here the engine is modeled based on the engine maps from steady-state experiments. The TC is modeled based on its characteristic map from experiments. A fairly simple transmission model is used which is based on static gear ratios assuming small shift times. The final drivetrain model however includes the rotational dynamics of the sprocket. The simulation model developed is validated by comparing the predicted values with the measured data from experiments. The results have demonstrated that the developed model is able to predict fairly accurately the acceleration and braking performance of the heavy tracked vehicle on both soft and hard terrain. © 2011 ISTVS. Published by Elsevier Ltd. All rights reserved.
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    Predictions on the dynamic stresses on practical cement mills using cyclic symmetry
    (03-12-1992)
    Ramamurti, V.
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    This paper reports the findings on the dynamic response of cement mills due to the random loading of the moving cylpebs. Input dynamic pressure inside the mill has been estimated based on experiments conducted on model mills. Cyclic symmetric approach in conjunction with the random vibration theory has been used as the tool for the analysis. The study covers the full range of cement mills. The limitations of the approach are also presented. © 1992.
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    Comparative Study of Performance of Optimized Valve for Different Flow Indices of Rheological Model
    (01-01-2020)
    Manjeet, Keshav
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    Smart fluids have always been an area of interest to most researchers due to their varying characteristics with respect to external stimuli. Rheological fluids such as electrorheological and magnetorheological fluids are popular among them. In the present study, the flow of a rheological fluid through an annular valve has been modelled using the Bingham model and the Herschel-Bulkley fluid model to include the shear thinning and thickening effects at high shear rates. Damping force, dynamic range and time constant have been defined as the valve’s performance indices and volume constraint geometric optimization has been done for various flow indices. Performance indices for the optimized valve are then compared for different flow indices.
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    Vertical dynamic studies of an Indian railway vehicle moving on a straight track
    (01-01-2010)
    Kumar, H.
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    This paper presents numerical simulation and experimental studies of the vertical dynamic behaviour of a typical Indian railway vehicle of the Alternating Current/Electrical Multiple Unit /Trailer (AC/EMU/T) type running on broad gauge track. Linear governing equations of motion of the vehicle, modeled as a 10 degree of freedom (dof) rigid body, have been solved and natural frequencies determined. Dynamic response studies were carried out in the time domain for the vehicle moving on a straight track with different irregularities of the track and wheel, such as wheel flat, welded joint defects and average vertical profile (AVP), imparted as excitation forces through Hertzian springs connected to the vehicle/track interface. The behaviour of the vehicle has been compared for air spring and coil spring as secondary suspension. The ride dynamic performance of the vehicle has been evaluated in terms of Sperling's ride indices for both ride comfort and ride quality at different speeds. Extensive experiments were carried out and analytical responses were found to compare well with experimental results. © Civil-Comp Press, 2010.
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    Using neural networks for the diagnosis of localized defects in ball bearings
    (01-01-1997)
    Subrahmanyam, M.
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    Two neural network based approaches, a multilayered feed forward neural network trained with supervised Error Back Propagation technique and an unsupervised Adaptive Resonance Theory-2 (ART2) based neural network were used for automatic detection/diagnosis of localized defects in ball bearings. Vibration acceleration signals were collected from a normal bearing and two different defective bearings under various load and speed conditions. The signals were processed to obtain various statistical parameters, which are good indicators of bearing condition, and these inputs were used to train the neural network and the output represented the ball bearing states. The trained neural networks were used for the recognition of ball bearing states. The results showed that the trained neural networks were able to distinguish a normal bearing from defective bearings with 100% reliability. Moreover, the networks were able to classify the ball bearings into different states with success rates better than those achieved with the best among the state-of-the-art techniques. © 1998 Elsevier Science Ltd. All rights reserved.
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    A new rollover detection system for tripped and untripped rollovers for antiroll safety systems
    (01-01-2017)
    Nair, Hari M.
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    High centre of gravity (CG) off-road vehicles are susceptible to rollovers, which can be tripped or untripped, caused by external impacts or during high speed manoeuvres, respectively. Tripped rollovers are very common and fatal, yet most of the safety systems can detect only untripped rollovers. A few that can detect both kind of rollovers are found to have a tendency to overestimate roll state of the vehicle, causing the unnecessary triggering of antiroll safety systems. This paper proposes a more accurate rollover sensing system for tripped and untripped rollovers with sensors for measuring suspension deflection, along with conventional sensors on wheels and axles. An algorithm for calculating Rollover index (RI) through estimation of tyre forces was developed in Matlab, by receiving the aforementioned sensor measurements as input. Simulations were conducted in CarSIM, using a sports utility vehicle (SUV) for a number of on and off-road events and time domain data of sensor measurements from these events were used as input for estimating RI (Rs). Validation of Rs was done by comparing it with the RI (R) obtained from actual tyre forces from CarSIM. Specific RIs available in literature were also estimated for the same manoeuvres for comparison with Rs. Simulation results showed that Rs can detect both tripped and untripped rollover scenarios with better accuracy.