Sujatha Srinivasan

Abstract: Prosthetic feet have generally been designed experimentally by adopting a trial-and-error technique. The objective of this research is to introduce a novel numerical approach for the a priori evaluation of the roll-over shape (ROS) of a prosthetic foot for application in its systematic design and development. The ROS was achieved numerically by employing a non-linear finite element model incorporating the augmented Lagrangian and multi-point constraint contact formulations, a hyperelastic material model and a higher-order strain definition. The Ottobock Solid Ankle Cushion Heel (SACH) foot was chosen to experimentally validate the numerical model. The geometry of the foot was evaluated from optical scans, and the material properties were obtained from uniaxial tensile, shear and volumetric compression tests. A new setup was designed for an improved experimental determination of the ROS, with the inclusion of an extended moment arm and variable loading. Error analysis of the radius of curvature of the ROS between the numerical and experimental results showed the percentage error to be 7.52%, thereby establishing the validity of the model. A numerical design model of this kind can be utilised to vary the input design parameters to arrive at a prosthetic foot with specified performance characteristics effectively and economically.

Abstract: 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.

Abstract: Hand rehabilitation requires intensive training of various gross and fine movements Robotic devices have been developed and tested for implementing intense training of different hand functions in the current literature Current hand rehabilitation robots can be broadly grouped into two categories: (a) simple robots with one or two degrees-of-freedom (DOF) that train only one or two hand functions; or (b) complex robots with several DOF capable of training a wide range of functions Thus, to train different hand functions, we either need a set of simple robots or one complex robot, both of which are not economically viable solutions A potential solution is to have a single DOF robot that can train a wide range of functions, ie a robot with a single actuator, along with a set of easily pluggable passive mechanisms for different hand functions In this paper, we present the design and analysis of various kinematic mechanisms for a single DOF hand rehabilitation robot plug and train hand rehabilitation robot (PLUTO) Three different kinematic mechanisms have been designed and analyzed to train four different functions: wrist flexion/extension, wrist ulnar and radial deviation, forearm pronation/supination, and gross hand opening-closing Proper alignment of the robot and human joints is essential for safe and appreciate interaction with a human Misalignment in the robot and human joints can cause undesired forces on the human joint, makes the interaction potentially unsafe The problem of misalignment was addressed in the proposed mechanisms through the use of appropriate passive DOFs between the robot and human joints This paper presents the design and analysis of the three mechanisms for the different hand functions The analysis of the mechanisms were carried out by considering variations in human hand anthropometry, and uncertainty in the robot-human axis alignments

Abstract: Hand rehabilitation requires intensive training with various gross and fine movements. Thus, rehabilitation robots for the hand that accommodate for the different degrees of freedom are often complex and expensive. This work presents the design of a portable plug-and-train robot (PLUTO), which tackles the problem by having a single actuator that can be coupled with different passive mechanisms for training wrist flexion-extension, ulnar-radial deviation, hand opening-closing, and forearm pronation-supination. The robot is capable of providing training in active and assisted regimes. Training is through performance adaptive computer games to provide feedback to the patients and to motivate them during training. The usability was evaluated in patients, caregivers, and clinicians with standardized questionnaires: System Usability Scale (SUS) and User Experience Questionnaire (UEQ). Patients and caregivers were administered the questionnaire after two training sessions. Clinicians, on the other hand, had a single session demo after which their feedback was obtained. In this paper, we present the initial results of 5 clinicians, 5 caregivers, and 5 patients. All groups found the system to be highly usable (180 scores on the system usability scale). Furthermore, the scores from UEQ feedback were all positive, and all groups found the system attractive. The patients and the clinicians rated the system positively in both pragmatic and hedonic scales. We believe that a simple approach proposed here can result in a compact tool with a high benefit-to-cost ratio for both in-clinic and home-based hand rehabilitation.

Abstract: Abstract Large MR (MR) dampers are popular due to their higher damping force capabilities which makes them suitable in the field of civil engineering, structural engineering, suspension bridge structure, mining engineering, and agricultural engineering applications. This paper presents a comprehensive review of large MR dampers. The classifications and applications of large MR dampers, the principle of operation, different fluid models, their structural design and control systems are classified and reviewed in this paper. The large MR dampers have higher damping force controllability than conventional MR dampers. The review indicates that the large MR dampers have enough vibration mitigation ability and higher damping performances.

Abstract: This paper has two main goals in the development of a novel flow-mode magnetorheological brake (MRB): (1) produce a mathematical model of a flow-mode MRB and (2) predict the torque density of the proposed MRB compared to the other type of MRB. In this design, the flow mode MRB is made by screw pump to make the Magnetorheological Fluid (MRF) flow through the radial and annular channel. The serpentine path flux is developed in the proposed MRB to make the annular channel an active region as well. With the proposed design concept, the work of a pure flow-mode serpentine path MRB can be accomplished. In this study, Finite Element Method Magnetics (FEMM) is used to calculate the magnetic field applied to the active regions and analytical approach used to obtain the output damping torque. The simulation results show that the magnetic fluxes flow through the radial channel and annular channel as well. The radial and annular channel is activated, which led to higher output damping torque. The mathematical modelling shows that the helical angle of the screw pump significantly affects the damping torque. The results show that the output damping torque density can be adjusted from 42.18 N/mm2 in the off-state with 0 rpm to around 40,518.96 N/mm2 at 20 rpm. The torque density of the proposed MRB is higher than the shear mode MRB.

Abstract: 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...