Estimation of Parameter for Different Magnetorheological Fluids Model for Varying Current M. Khusyaie M. Razali, Asan G. A. Muthalif * , N. Hidayati Diana Nordin Smart Structures, Systems and Control Research Laboratory (S 3 CRL), Department of Mechatronics Engineering, Kulliyyah of Engineering, International Islamic University Malaysia (IIUM), Jalan Gombak, 53100, Kuala Lumpur, Malaysia. * Corresponding author. Email: asan@iium.edu.my Manuscript submitted September16, 2017; accepted December 1, 2017. doi: 10.17706/ijcee.2018.10.2.127-134 Abstract: Magnetorheological fluids (MRF) are considered as smart material since the behavior of the fluid is interrelated with external magnetic field. The rheological behavior of the fluids is changed whenever the strength of magnetic field changed. One of the applications of MRF is Magnetorheological damper (MRD), a damper that can be controlled by magnetic field. Analytical model of the damper is important in order to understand the performance of MRD. Different types of model that depend on defined parameters were introduced by previous researchers, and investigation on those parameters is crucial to acquire a model with least value of error. A technique called nonlinear least squares fitting method is utilized in order to obtain those parameters. This study investigated five different MRD models and presents the result for parameter estimation for each model as a function of input current. Key words: Magnetorheological damper, magnetorheological fluids, MRF model, parameter estimation. 1. Introduction Magnetorheological (MR) damper has been regarded as one of the most promising latest technologies. MR damper implemented the usage of special fluid called Magnetorheological Fluid (MRF) where the rheological properties of this fluid can be controlled by external magnetic field [1]. In normal condition where no magnetic field is present, the behavior of MRF is in free flowing fluid state. At this state, MRF exhibits Newtonian-like behavior. The behavior of MRF changes from free-flowing fluid to semi-solids with controllable yield strength whenever the external magnetic field is present [2]. When an external magnetic field is present, the MRF particle will form linear chains parallel to the field due to the dipole moment of particle aligned with the magnetic field. This will solidify the MRF and restrict the movement of the fluid [3]. Few types of model were developed to represent the behavior of MR damper. Some of the famous models are the Bingham model, Simple Bouc-Wen model, Modified Bouc-Wen model, Hyperbolic Tangent Function model and Nonlinear Biviscous model [1]. To design an optimal MR damper model so that the behavior of the model is most identical with the behavior of the MR damper, some reliable parameter values are needed [4]. Parameter estimation of an MR damper model with varying input current was done since the magnetic field is directly proportional to the current [5]. However, there is not much empirical study on the parameter estimation with varying input current for all the models mentioned above[6]–[8]. This research is focused on parameter estimation with varying input current for the five different models. International Journal of Computer Electrical Engineering 127 Volume 10, Number 2, June 2018