Design and Simulation of Magneto-Rheological (MR) Brake for Automotive Application

Abstract

Magneto-rheological (MR) fluid is a type of smart material which has ability to change its flow resistance on the application of magnetic field. This property of changing viscosity of the fluid due to application of magnetic field is utilized in the MR brake. MR brake typically consists of multiple rotating disks immersed in MR fluid and an enclosed electromagnet. The controllable yield stress produces shear friction on the rotating disks, generating the braking torque. Of late MR brakes have been explored for automotive applications. Literature review reveals that the torque output of MR brake is not sufficient for braking of mid-sized car. Hence, it is worthwhile to investigate its application for a two-wheeler where the braking torque requirement is low. This paper presents design and simulation of MR brake performance for its torque output. Design of MR brake involves deciding the configuration of MR brake in terms of number and sizing of disks, selection of MR fluid and design of magnetic circuit. The response of MR brake in terms of torque output with respect to influencing parameters like speed, current, number of disks, MR fluid properties and intensity of magnetic field can be observed with the help of simulation in order to save cost and time associated with experimental testing. MATLAB/SIMULINK software environment has been used for this simulation. Introduction of MR Fluid Magneto-rheological (MR) fluid is the material that responds to an applied magnetic field with a dramatic change in rheological behavior. MR fluid is in a free-flowing liquid state in the absence a magnetic field, but under a strong magnetic field its viscosity can be increased by more than two orders in a very short time (milliseconds) and it exhibits solid-like characteristics [1]. The magnetizable particles (mainly iron) are suspended in an appropriate carrier liquid. The carrier fluid serves as a dispersed medium and ensures the homogeneity of particles in the fluid. A variety of additives (stabilizers and surfactants) are used to prevent gravitational settling and promote stable particles suspension, enhance lubricity and change initial viscosity of the MR fluid [2]. Figure 1 Chain-Like Structure Formation in Controllable Fluids [3] In the presence of an applied magnetic field, the iron particles acquire a dipole moment aligned with the external field which causes particles to form linear chains aligned to the magnetic field, as shown in Figure