213 KUMAR et al: DESIGN ANALYSIS OF DAMPING MECHANISM FOR ADAPTIVE PROSTHETIC FOOT Journal of Scientific & Industrial Research Vol. 72, April 2013, pp. 213-216 *Author for correspondence E-mail: neel5278@gmail.com, neel5278@csio.res.in Design Analysis of Variable Damping Mechanism Using Magnetorheological Fluids for Adaptive Prosthetic Foot Shubham Verma, Neelesh Kumar*and Amod Kumar Biomedical Instrumentation Unit, Central Scientific Instruments Organization, (CSIO), Sector 30-C, Chandigarh 160030 India Received 19 July 2012; revised 6 December 2012; accepted 07 February 2013 The applications of Magnetorheological (MR) fluids to act as mechanical dampers are new and increasing day by day. This paper proves to be an attempt in applying variable damping properties of a MR fluid in a new application of adaptive variable damper prosthetic foot. A 3-D model of the prosthetic foot was developed on the software Autodesk Inventor Professional 2011. Design analysis of prosthetic foot was carried out and damping coefficients were calculated with the help of Dynamic Simulation Environment of Inventor. Typical specification of MR fluid was suggested to act as damper for the prosthetic foot. Keywords: Magnetorheological (MR) Fluid, Prosthetic foot, Variable Damping Introduction Prosthetic feet have advanced significantly in the past years with respect to innovative design ideas and better materials 1 . Prosthetic foot with variable damping is required and researched. The damping available in the foot will play important role in transferring vertical ground reaction force impact at knee and hip joints. Few researches have been done in the field of viscoelastic modeling of the prosthetic foot. A viscoelastic model consists of combination of springs and dampers. In this paper the capability of magnetorheological fluids has been discussed to act as dampers for the viscoelastic model of the foot 2,3 . Magnetorheological (MR) fluids are materials that respond to an applied field with a dramatic change in their rheological behavior. A typical MR fluid consists of micron sized magnetizable iron particles suspended in a base fluid like silicone oil or water. The essential characteristic of these fluids is their ability to reversibly change from a free-flowing, linear, viscous liquid to a semi-solid with a controllable yield strength in milliseconds when exposed to a magnetic field 4 . In the absence of an applied field, MR fluids are reasonably well approximated as Newtonian liquids. MR fluids can be converted from a liquid state to a solid state and vice versa by a magnetic field 5 . A magnetorheological damper is a damper filled with magnetorheological fluid, which is controlled by a magnetic field, usually using an electromagnet. This allows the damping characteristics of the shock absorber to be continuously controlled by varying the power of the electromagnet 6,9 . The MR damper has a built-in MR valve across which the MR fluid is forced. The piston of the MR damper acts as an electromagnet with the required number of coils to produce the appropriate magnetic field 10 . A design of a prosthetic foot consisting of 4 springs in parallel arrangement was developed by the authors using Autodesk Inventor Professional. There are few limitations of designed spring based damping mechanism like non linearity, non uniform distribution of ground reaction force. We planned to use basic properties of magnetorheological fluid to provide uniform damping. The research aim is to replace the spring arrangement with a MR fluid damper. This new approach helps to reduce the weight as well as at the same time enhance the efficiency. Materials and Methods Design Approach Figure 1 shows the 3-D model of the prosthetic foot developed using Autodesk Inventor Professional software. The SACH area of available conventional foot was replaced with four identical spring. The spring were designed for patient weight from 50 Kg to 70 Kg.