Faculty Publications
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Item Investigation of magnetorheological brake with rotor of combined magnetic and non-magnetic materials(Springer Nature, 2019) Acharya, S.; Kumar, H.Magnetorheological (MR) brakes are a type of electromagnetic brakes that make use of controllable viscoelastic properties of magnetorheological fluid for braking. The torque capacity of the MR brake depends on the magnitude of magnetic flux density generated in the MR fluid. In this study, the effect of combination of magnetic and non-magnetic materials for rotor disk of MR brake with the objective to maximizing the flux density in the MR fluid gap at the rotor periphery was investigated. Initially, the MR brake rotor disk radius and MR fluid gap thickness were determined by using Genetic Algorithm optimization technique for desired torque ratio and torque capacity. Magnetostatic analyses were performed at different current magnitudes to determine the magnetic field and flux density in the MR brake. Further, to enhance the magnetic field intensity in the MR fluid at the rotor periphery, the rotor was modeled with three different configurations of MR brake with combinations of magnetic and non-magnetic steel and magnetostatic analyses of the MR brake were performed. It was found that the leakage of flux away from rotor periphery was reduced and there is significant increase and concentration of the magnetic field and flux density in the MR fluid gap through the use of rotor disk with combined magnetic and non-magnetic materials which would subsequently increase the torque capacity of the MR brake. © 2019, Springer Nature Switzerland AG.Item Design of bypass rotary vane magnetorheological damper for prosthetic knee application(SAGE Publications Ltd, 2021) Saini, R.S.T.; Chandramohan, S.; Sujatha, S.; Kumar, H.Semi-active systems using magnetorheological fluids have been realized in many novel devices such as linear dampers, rotary dampers, brakes, and so on. Rotary vane-type magnetorheological damper is one such device that uses magnetorheological fluid as a hydraulic medium and a controllable magnetorheological valve to generate variable resistance. This device, due to its limited angle motion, lends itself to a natural application for prosthetic knee joint. In this article, a bypass rotary vane-type magnetorheological damper suitable for prosthetic knee device is designed. In the proposed design, the rotary vane chamber and the bypass magnetorheological valve are connected using hydraulic cables and ports. The design of rotary cylinder is implemented based on the largest possible dimensions within the envelope of a healthy human knee, while the magnetorheological valve is designed optimally using a multi-objective genetic algorithm optimization. Off-state braking torque, induced on-state braking torque and mass of the valve are selected as three objectives. The torque and angular velocity requirements of the normal human knee are used as design limits. The optimal solution is chosen from the obtained Pareto fronts by prioritizing the objective of weight reduction of magnetorheological valve. The optimal solution is capable of producing a damping torque of 73 Nm at a design speed of 8.4 rpm and current supply of 1.9 A. Potential benefits offered by this design when compared with multi-plate magnetorheological brake are flow mode operation, large clearance gap, and fewer design components, thus reducing the manufacturing complexity. © The Author(s) 2020.Item Selection of optimal composition of MR fluid for a brake designed using MOGA optimization coupled with magnetic FEA analysis(SAGE Publications Ltd, 2021) Acharya, S.; Saini, T.R.S.; Sundaram, V.; Kumar, H.The design of Magnetorheological (MR) brake and the composition of MR fluid (MRF) used in it have a significant effect on its performance and hence an effort has been made in this study to determine the optimal dimensions of MR brake and composition of MRF suitable for the brake application. Initially, optimum parameters of MR brake were computed considering the properties of commercially available MRF 132DG fluid using multi-objective genetic algorithm (MOGA) optimization. This was performed in MATLAB software coupled with magnetostatic analyses in ANSYS APDL software. The braking torque of designed MR brake utilizing MRF 132DG fluid was experimentally determined and validated with analytical ones. Further, selection of optimal composition of MRF was done considering In-house MRF samples composed of different combinations of particle mass fractions, mean particle diameters and base oil viscosities. A design of experiments (DOE) technique was employed and braking torque corresponding to the synthesized MRF samples at different speeds and current supplied were measured along with the variation of shaft speed during braking process. Grounded on the experimental results, using MOGA optimization technique, MRF composed of smaller sized iron particles (2.91 microns) with mass fraction of 80.95% and lower viscosity base oil (50 cSt) was selected as optimal composition of MRF for use in MR brake. Maximization of field induced braking torque and minimization of off-state torque were chosen as the objective functions for both the optimal design of MR brake and selection of optimal composition of MRF. Finally, the sedimentation stability of MRFs were investigated. © The Author(s) 2020.Item Effect of reduced geometric dimensions on torque generation in two plate rotor magnetorheological brake with in-house magnetorheological fluid(Institute of Physics, 2023) Kariganaur, A.K.; Kadam, S.; Kumar, H.; Arun, M.The present study is aimed to evaluate the torque generation capacity of a two plate rotor magnetorheological (MR) brake using in-house prepared MR fluid. The prepared MR fluids were studied for sedimentation rate at different temperatures and flow characterization at different currents and at specific temperatures. The yield stress of the fluid is explored through Herschel-Bulkley model. The results depict significant increase in sedimentation rate and decrease in yield stress with increase in temperature of the MR fluid. MR brake (model-1) is fabricated after finite element method magnetics exhibit magnetic field of approximately 0.145 T in the shear gap than other two models (model-2 and model-3) considered in this study. Characterization of the MR brake illustrates that there is an increase in torque with increasing current. Further tests have been carried out to identify the effect of sedimentation on torque generation at 52 °C after 15 h of sedimentation. The results indicate 16% reduction in the initial torque because of settling of particles. MR fluid and particles characterization illustrates that 322 °C and 400 °C are critical points in controlling the MR fluid input parameters. © 2023 IOP Publishing Ltd.