Development of Mathematical Model of Magneto- Rheological Damper

Abstract

Dampers are an important part of a vehicle suspension, which dissipate the energy of the motion of the suspension as thermal energy. A mathematical model can be an important tool in the understanding and design of a damper. A mathematical model of a twin tube damper was developed to represent the physical behavior of the damper and predict the force as a function of velocity. The model has included the provision of explicitly defining the viscosity of the damper system which will enable the model to accommodate the changes that may occur in the design. This also enables to calculate the variation of force with the change of viscosity which is the case of MR dampers. The model produced results concurrent with that available in literature. The viscosity change for the MR damper for the change in current excitation applied to it has been predicted. The results show that when a current of 0.5 A is applied, magnetic flux of 0.002 T is induced. This results in a viscosity of 0.4 Pa.s. In comparison, the viscosity of MR fluid not subjected to magnetic field has a typical viscosity of about 0.11 +/- 0.02 Pa.s. When this viscosity and its variation is applied to the model a 29% increase in damping force has been calculated, over the range of 0 to 0.5 A, with a maximum of 138 N obtained for the damper with a mechanical excitation of amplitude 20 mm and frequency of 2 Hz. The results obtained through the model have been compared with the experimental results found in literature for validation and the comparison has shown that the results are appropriate.