Faculty Publications

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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.
Optimal design of ow mode semi-active prosthetic knee dampers
(Sharif University of Technology, 2022) Saini, R.S.T.; Kumar, H.; Chandramohan, S.
Magnetorheological (MR) fluid devices operate in four modes: ow, shear, squeeze, and pinch. Among these, the flow mode is the most efficient one and results in large field-induced pressure differences. Despite being the least efficient, shear mode is the most commonly used in numerous applications, including prosthetic knees, due to its ease of construction. Additionally, shear mode designs require larger shear areas and reduced fluid gap tolerance compared to their ow mode counterparts, resulting in a complex design such as the commercially available multi-plate MR brake. Therefore, in this study, two ow mode designs, twin-rod and rotary vane MR dampers, are optimally designed for prosthetic knee application. The optimal designs obtained from solving a multi-objective particle swarm optimization problem are fabricated and experimentally characterized for various harmonic excitations of varying amplitudes, frequencies, and currents. The optimal designs are compared with many MR fluid-based prosthetic knee design configurations. Based on the results, a twin-rod MR damper with a mass of 0.71 kg and a damping force of 1020 N at 1 A is identified as the optimal design configuration for prosthetic knee application. © 2022 Sharif University of Technology. All rights reserved.
Design and fabrication of cost effective semi-active vehicular suspension system and testing on full scale quarter car suspension rig
(Techno-Press, 2024) Puneet, N.P.; Saini, R.S.T.; Kumar, H.
Smart materials, such as magnetorheological (MR) fluid, have received considerable research attention in recent years due to their unique capabilities. MR fluid, which possesses a magnetic field controllable viscosity, has been extensively studied for vehicular applications with the aim of synthesizing optimal MR fluids, designing optimal MR dampers, and developing control strategies. However, a comprehensive study that primarily focuses on developing a cost-effective semi-active suspension system for a commercial vehicle in a developing nation is still lacking. This study addresses this gap by synthesizing an in-house MR fluid and studying its rheological properties. Subsequently, a novel single-sensor-based controller is developed and closed-loop simulations are conducted on a quarter-car semi-active model. Finally, the overall semi-active quarter-car suspension system is experimentally tested using a suspension test rig. The performance of the proposed system in terms of ride comfort and road holding is evaluated and is compared with simple control strategies. The dynamic range of the developed semi-active MR damper is found to be around 2.3, indicating a significant MR effect. The results suggest an intermediate response using the proposed acceleration-driven controller (ADV) at lower frequencies and similar performance to that of the skyhook controller at higher frequencies. The cost-effective methodology proposed in this study is effective and can be adapted for other semi-active engineering applications. © © 2024 Techno-Press, Ltd.

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