2. Thesis and Dissertations

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    Development and Implementation of Magneto-Rheological Fluid Damper In Two-Wheeler Vehicle With Real-Time Control
    (National Institute Of Technology Karnataka Surathkal, 2023) Kiran, Pinjala Devi; Kumar, Hemantha
    The present-day automotive systems are equipped with a combination of various electromechanical sensors, actuators and devices to improve the ride quality according to the preferences of the riders. Suspension systems are one of the most important areas in which tremendous amount of research was being pursued while different technologies have been developed and incorporated. Magneto-rheological dampers are one of the technologies which can be implemented in the vehicular suspension to obtain a varied damping with respect to the road profile. This study carries out various MR damper designs which can be fabricated and implemented in two-wheeler vehicles depending on the fixtures and complexities. Two different piston designs namely axial flux based and radial flux-based designs are designed considered in the space and dimensional constrains of specific two-wheeler motor vehicles and E-bicycle (E-bike) i.e., Splendor plus (make: Hero motor corp.), Pulsar 200cc (make: Bajaj Auto) and Crest (make: Atlas cycles). The design parameters are considered by the Matlab optimization tool box considering the maximum dynamic range as the prime requirement. With the obtained dimensions, FEMM analysis is performed to obtain the magnetic flux density being produced in the fluid flow gap, estimating the flux produced for influencing the MR fluid in the damper. the designed MR dampers are fabricated and characterized for the force-velocity characteristics with respect to the changes in current under varied frequency sine excitation. These characteristics are considered for mathematical modelling. The characterization results are utilized in mathematical modeling considering either parametric or non-parametric models for the designed damper modelling. Kwok model is considered in the parametric modeling whereas the polynomial model is considered in the nonparametric modeling. Due to the reduced complexities and ease of implementation polynomial model is considered for modeling most of the MR dampers in the studies performed. The mathematical model is used in the simulation of Quarter car and two-wheeler suspension with the designed MR damper. iv Parallelly with respect to the design parameters considered for, the designed MR damper is fit to the two-wheeler vehicle and tested for certain road conditions at specific velocities. The control logic is implemented with the help of FPGA based controller and data acquisition cards namely NI cRIO 9045, NI 9230, NI 9403 and NI 9205. Different control logics were implemented in this study and the nonlinear control model namely Sliding mode control was providing better performance in reducing the body vibrations of the vehicle. The obtained results show satisfactory performance results while implementing the MR damper in the rear suspension of the two-wheeler vehicle considering the sliding mode control strategy. With the inspiration of axial and radial flux piston designs, a novel design namely hybrid radial flux piston design was designed and fabricated for a prototype MR damper. This damper utilized the orientation of the coil wound and the effective design to generate both the axial and radial fluxes with in the piston core. The characterization results of this damper also show observable change in the damping force with respect to the change in current supplied to the damper. Polynomial modeling of the damper designed is implemented in the quarter car and two-wheeler models in MATLAB / Simulink and the sprung mass acceleration is considered as priority. The obtained results confirm the effectiveness of the designed damper in vehicular implementation.
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    Analytical and Experimental Dynamic Analysis of A Four Wheeler Vehicle With Semi Active Suspension System
    (National Institute Of Technology Karnataka Surathkal, 2023) N P, Puneet; Kumar, Hemantha; K V, Gangadharan
    Advances in the automobile industries in several engineering aspects have opened up never ending challenges and scopes. One such interesting challenge is to achieve better ride quality which intends to provide more comfort to the passengers. The road profile randomness is not uniform around the globe. Therefore, achieving a good ride comfort has always been a task for researchers over the years. A key component responsible for ride quality is the suspension system of the vehicle, a major combination of spring and damper. The nature and magnitude of energy dissipation from the damper provides suitable ride quality to the vehicle. Passive dampers provide constant response against any kind of road disturbances since the fluid properties cannot be altered with any external input. Hence, replacing passive damping medium with semi-active medium will provide added advantage to the suspension system in providing greater ride comfort. Magneto-rheological (MR) fluid is one such smart fluid which is known for its semi-active nature when the external magnetic field is varied. This research study deals with synthesis of magnetorheological fluid and its application in damper of a light motor vehicle. In the primary part of this study, a passive damper was extracted from the suspension system of the commercially available light motor vehicle. This passive damper was characterized in the dynamic testing machine (DTM) to understand the dynamic response of the damper towards varying cyclic input. The damping force response from the passive damper was considered as the benchmark for development of MR fluid damper particular for the test vehicle. A quarter car model was developed using the MATLAB/ Simulink and the response of the passive damper characterization was employed in the damping element of the model. As a preliminary study of the MR fluid damper, a small stroke MR damper was designed and developed. For this purpose, an MR fluid was prepared in-house and used as the damping medium in the MR damper. This prototype was then characterized using dynamic testing machine subjected to different amplitude, frequency and DC current inputs. A mathematical model was established which could iv relate the damping force and the current which was then used in quarter car simulation. Based on the above preliminary works, a prototype MR damper with actual scale was then designed using optimization technique under certain geometrical constraints. The designed MR damper piston was analyzed by using finite element magnetic methods (FEMM) to verify the magnetic flux development in the fluid flow gap. MR fluid as the damper fluid was synthesized in-house using electrolytic iron particle (EIP) and paraffin oil. Rheological study of the synthesized MR fluid was conducted to analyze the shear stress as well as viscosity variation against the shear rate and the current inputs. The developed MR damper was then characterized under various dynamic and DC current inputs to study the force versus displacement nature. The hysteresis of the damper was mathematically represented using parametric modeling technique called Kwok model. The parameters of the model were determined for each condition by using optimization method. This model was then used in quarter car simulation to analyze the effect of suspension under off-state, constant current and through skyhook control. The validation of this simulation was carried out by using the suspension with MR damper in a quarter car test rig and the deviation in the results was analyzed. As an important part of this research work, the suspension with the developed MR damper was tested on-road by using a test vehicle. The passive damper in the front suspension of the test vehicle was replaced with MR damper and the suspension was tested at two different velocities. Also, the ride comfort at different conditions was analyzed. As an extended part of the study, a control logic involving single sensor technique was developed. The performance of developed control was tested using the quarter car set up and the comparison of the responses through different current inputs was also presented.
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    Synthesis and Characterization of Magnetorheological (MR) Fluid for Different Engineering Applications
    (National Institute of Technology Karnataka, Surathkal, 2021) Acharya, Subash.; Kumar, Hemantha.
    Magnetorheological fluid (MRF) are suspensions of iron particles in a carrier oil. They are controllable smart fluid whose rheological properties change under the application of magnetic field. The design of Magnetorheological (MR) device and the composition of MR fluid used in it have a significant effect on its performance. In this study, MRF composition suitable for MR damper, MR brake and MR beam were determined based on optimization. Initially, the key ingredient of MRF, that is, iron particles of different average sizes, were characterized to determine their morphology, particle size distribution and magnetic properties. The morphology of iron particles were observed using Field Emission Scanning Electron Microscope. The particle size distribution was measured using particle size analyzer. The magnetic properties of different iron particles were measured using vibrating sample magnetometer. In the first part of this study, optimal dimensions of MR damper and composition of MRF suitable for MR damper were determined. A shear mode monotube MR damper was designed by using optimization technique. A damper was manufactured in accordance with the optimized size and was filled with commercially available commercial MR fluid, MRF 132DG (Lord Corporation) to determine its damping characteristics using damper testing machine. Experimentally determined values were validated with computational ones. Further, six MR fluid samples (MRFs) were prepared composed of combination of three different particle mass fractions and two sizes of iron particles. Rheological tests were conducted on these samples to determine the flow curves at off-state and on-state magnetic field conditions and they were compared with those of commercial MR fluid, MRF 132DG (Lord Corporation). In addition, the sedimentation stability of prepared fluid were examined. These MRFs were filled in the MR damper and their damper characteristics were determined. The area bounded by the force-displacement graphs was used to calculate the energy dissipated which was then used to calculate equivalent damping coefficient. Finally, using multi-objective genetic algorithm (MOGA) optimization, based on maximization of on-state damping coefficient and minimization of off-state damping coefficient, the optimal mass fraction and particle size was determined. iv In the next part of the study, optimal dimensions of MR brake and composition of MRF suitable for MR brake were determined. At first, optimum dimensions of MR brake were computed considering the properties of commercially available MRF132DG fluid using MOGA optimization. Maximization of field induced braking torque and minimization of off-state torque were chosen as the objectives. This was performed in MATLAB software coupled with magnetostatic analyses in ANSYS APDL software. The braking torque of designed and fabricated MR brake utilizing commercial MR fluid, MRF 132DG (Lord Corporation) was experimentally determined and validated with computational ones. Selection of optimal composition of MRF was done considering In-house MR fluid samples composed of different combinations of particle mass fractions, mean particle diameters and base oil viscosities. A design of experiments technique was employed and braking torque corresponding to the synthesized MRFs at different speeds and current supplied along with the variation of shaft speed during braking process were measured. Based on the experimental results, MOGA optimization technique was used to determine optimal MR fluid composition with the objectives of maximizing field induced braking torque and minimizing off-state torque. Further, the effect of particle size and mass fraction of iron powder in the MRF on the vibration behaviour of MRF sandwich beams were studied. Six MRFs composed of combination of two particle sizes and three mass fractions of carbonyl iron powder were prepared and their viscoelastic properties were measured. The MRFs were used to fabricate different MRF core aluminium sandwich beams. Additionally, a sandwich beam with commercially available commercial MR fluid, MRF 132DG (Lord Corporation) as core was fabricated. The modal parameters of the cantilever MRF sandwich beams were determined at different magnetic fields. Further, sinusoidal sweep excitation tests were performed on these beams at different magnetic fields to investigate their vibration suppression behaviour. Finally, optimal particle size and mass fraction of iron powder suitable for sandwich beam were determined based on maximization of damping ratio and minimization of mass of MRF.
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    Dynamic Analysis of Magnetorheological (Mr) Fluid Based Semiactive Suspension System for Vehicular Application Using Nonparametric Approach
    (National Institute of Technology Karnataka, Surathkal, 2016) K, Hemanth; Kumar, Hemantha; Gangadharan, K. V.
    The magnetorheological (MR) fluid dampers belong to a category of semi-active devices, in which damping force can be varied within a few milliseconds through the application of a magnetic field. The main aim of this project is to investigate the performance of MR damper used as a semi-active suspension system in vehicle models to improve the ride comfort and road holding quality of the vehicle, when subjected to average random road profile and road bump as inputs. Research work starts with design and development of MR damper, which includes optimization of MR damper to study the variation of magnetic flux density with variation of electromagnetic circuit parameters such as current magnitude, number of turns in the coil, coil core length, fluid flow gap and flange length. The optimization study shows that, the magnetic flux density induced in the fluid flow gap increases with increase of applied current, number of turns in the coil and coil core length. The magnetic flux density is seen to decrease with increase of fluid flow gap and flange length. The optimum fluid flow gap, which is obtained from the optimization technique has been considered for fabrication of MR damper. Experimental studies on a developed MR damper with different proportion of MR fluid have been conducted by using dynamic testing facilities at 1.5Hz and 2Hz operating frequencies. Based on the experimental results, the optimum level of parameters such as proportion of MR fluid and operating frequency are evaluated by using Taguchi design of experiments. Then, dynamic behaviour of MR damper with optimum level of parameters has been investigated. Developed damper shows the capability of improving both stiffness and damping properties with variation of electric current. Magnetostatic analysis of MR damper has been carried out, in order to find total magnetic flux density induced in the fluid flow gap. Total magnetic flux density induced in the fluid flow gap is divided into five categories by using statistical categorization technique. The average total magnetic flux density obtained from thestatistical categorization technique has been used to evaluate the damper force. Based on this, non-parametric model has been developed and polynomial function is used to relate the damper force as a function of current. Bouc-Wen model has been used to benchmark the developed non parametric model. The parameters of the Bouc-Wen model are evaluated by minimizing the error between the experimental and predicted force using non-dominated sorting genetic algorithm II (NSGA-II) optimization technique. The hysteresis behaviour of the MR damper is predicted by both models (non-parametric model and Bouc-Wen model) and validated with the experimental investigations. Both parametric and non-parametric models predict the behaviour, which is having good agreement with experimental results. Different mathematical models such as quarter car model (2 DOF), half car model (4 DOF) and full car model (7 DOF) of the vehicle with passive and semiactive suspension systems are formulated. Newly developed non-parametric model of MR damper is used in vehicle model as semi-active suspension system with suitable control strategy. Ride comfort and road holding performances of passive and semiactive suspension systems are found under average random road profile as input. In comparison, the vehicle with MR based suspension system provides better vibration isolation for a vehicle than passive suspension system.
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    Characterization of Magneto-Rheological Fluid and Monotube Damper through Experimental and Computational Analysis
    (National Institute of Technology Karnataka, Surathkal, 2018) T. M, Gurubasavaraju; Kumar, Hemantha; M, Arun
    Magnetorheological fluid belongs to a class of smart materials which exhibit change in their rheological properties, when exposed to an external magnetic field and these properties are completely reversible. By utilizing these special characteristics, the damping force of the MR damper can be controlled and varied in real time applications. The main objective of this research work is to investigate the characteristics of MR fluid and MR damper through experimental as well as computational methods and to evaluate the semi-active suspension with MR dampers performance in terms of ride comfort and road holding of vehicles, when subjected to random road conditions. The rheological characterization of the MR fluid samples under different magnetic fields and fluid gap has been evaluated through experimentation. The measured fluid properties were used for computing the damping force of MR damper. Using single and multi-objective particle swarm optimization techniques, the optimal proportion of iron particles for MR damper application was determined to maximize the shear stress and damping force. The dynamic characterization of MR damper through experimental approach using dynamic test facility at 1.5 Hz and 2 Hz frequencies has been carried out. Also, the influence of material properties of MR damper components on the induced magnetic flux density and geometrical parameters on the damping force was investigated through finite element analysis as well as analytical methods. Multi-objective genetic algorithm and screening optimization techniques were employed to maximize the magnetic flux density and to identify the optimal values of the design variables. Using the analytical method, damping force of the damper was computed for the obtained optimal values of the design variables. It was observed that the damping force of the MR damper whose cylinder is made up of magnetic material was 2.79 times greater than that of MR damper whose cylinder is made up of non-magnetic material. Further, a coupled finite element analysis (FEA) and computational fluid dynamics (CFD) analysis was used for estimating the magnetic flux density and damping force for different input currents. The credibility of the shear mode monotube MR damperanalysis results were validated with experimental results. To overcome certain limitations of shear mode damper, an attempt has been made to realize the mixed mode damper by combining the flow and shear mode operations. The variations in the damping characteristics of flow and mixed mode MR damper under different input were compared with shear mode MR damper. Results showed that combination of two modes of operation could enhance the damping force to a significant level. The damping force of mixed mode MR damper was found to be 3 times greater than that of shear mode MR damper at 2 Hz frequency and 0.4 A current. Based on results obtained from computational analyses, a non-parametric representative model exhibiting the hysteretic behavior of MR damper was developed. The developed nonparametric model was implemented in a quarter car semi-active suspension to determine the dynamic response of the vehicle subjected to random road excitations. Further, this model was implemented in three-wheeler vehicle semi-active suspension system to evaluate its dynamic performance. The outcome showed that the vehicle with non-parametric based MR suspension system provided good vibration isolation for semi-active suspension than passive suspension system in terms of rice comfort and road holding.