Browsing by Author "Sujatha, S."

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Design of bypass rotary vane magneto rheological damper for prosthetic knee application
(International Conference on Adaptive Structures and Technologies, 2019) Saini, R.S.S.; Kumar, H.; Chandramohan, S.; Sujatha, S.
In this paper, a bypass rotary vane type magneto rheological (MR) damper suitable for prosthetic knee application is designed. The torque and angular velocity requirements of the normal human knee are used as design limits. In the proposed design, the rotary vane chamber and the MR valve are connected by hydraulic cables and ports and are designed separately. The rotary vane chamber is designed based on the cross-sectional size limits of the normal human knee, while the MR valve is designed with the objective of obtaining the maximum on-state damping torque, minimum weight, and minimum off-state torque. Â© copyright Environment and Climate Change Canada.
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.
Design of twin-rod flow mode magneto rheological damper for prosthetic knee application
(American Institute of Physics Inc. subs@aip.org, 2019) Saini, R.S.S.; Kumar, H.; Chandramohan, S.; Sujatha, S.
In the present study, a twin-rod magneto rheological (MR) damper working in flow mode is designed. The piston core, annular fluid gap, outer sleeve, and the outer cylinder forms the magnetic flow path. A nonlinear constrained optimization problem is formulated to obtain the geometric dimensions of the piston assembly. The flow mode equations of the damper and the electromagnetic circuit design equations, assuming constant magnetic field links are coupled together to form an optimization problem. The design torque and angular velocity requirements of the normal human knee are converted to damping forces and linear velocity using the knee and damper geometry based on the previous study. The damping force design constraints and the constraints related to current requirements and magnetic field saturation are imposed. The obtained optimum dimensions of the piston assembly yielded an off state damping force of 56.8 N and a maximum on-state damping force of 1582 N at a current of 1.6 A for a design velocity of 0.1 m/s. Magnetostatic analysis of the piston assembly using the optimized dimensions is performed which showed that the annular gap is exposed to a field of 0.6 T, as assumed and the piston core is subjected to a field of 1.8 T which is below the saturation limit of the core material. Â© 2019 Author(s).
Optimal Design of Rotary Magneto-Rheological Drum Brake for Transfemoral Prosthesis
(Springer Science and Business Media Deutschland GmbH, 2021) Saini, R.S.T.; Kumar, H.; Chandramohan, S.; Sujatha, S.
Semi-active technology offers good advantages in terms of controllability and adaptability. Magneto-rheological (MR) fluid is a class of smart fluids which display significant changes in its rheological properties under the influence of a magnetic field. Previous studies carried out using MR brake for the transfemoral prosthetic device were of multi-plate models which are complex in design and also to manufacture. Therefore, in the present study, a multi-coil rotary inverted drum brake is optimized with braking torque as the objective function. One of the advantages of the multi-coil design from multi-plate is that the former has fewer components and leads to a simpler design. The outermost geometric constraints are decided based on the knee cross-sections in anterior-posterior and mediolateral directions. Four design geometric variables are selected which are: coil depth, coil height, casing axial thickness, and casing radial thickness. A design of experiments technique is used to obtain 27 combinations of design variables. Magnetostatic analysis at each design point is performed and average flux densities in the annular and the radial gaps are determined. Regression analysis is conducted on the design data to obtain braking torque as a function of four design variables. Later, genetic algorithm is used to obtain the optimum geometric dimensions. A total maximum braking torque of 13.4 Nm is obtained using the optimum dimensions for a design current of 2 A. Â© 2021, The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.