Preliminary Multi-Physics Modelling and Characterization of a Magneto-Rheological Brake

Magneto-Rheological Fluid (MRF) is a smart material used in several applications for its ability to switch from fluid behaviour to solid-like conditions if a magnetic field is present. The dependency of viscosity on magnetic field makes this fluid suitable for braking system of electric vehicles, thanks to its high controllability and response time in the whole operative range. The main parameters that influence the behaviour of the fluid, and so the braking action of the system, are magnetic field and rotational velocity. In general, the variable physical properties make it complicated to simulate the system and its behaviour in different operating conditions. Therefore, it is usually necessary to build a physical prototype to experimentally verify the response of the braking system at different driving conditions. This paper presents the development of a virtual model of Magneto-Rheological Brakes (MRB) whose validity is extended to different driving conditions. This can be accomplished by creating two coupled model, an electro-magnetic and a fluid-dynamic, using respectively Ansys Electronics Desktop 2D Maxwell and Ansys Fluent. Both the models are validated by comparing the magnetic flux density and the braking torque obtained from the experimental test campaign of the braking system prototype at different coil currents. The simulation and experimental results present a good correlation and allow to evaluate a wide range of operative and driving conditions of the braking system. The validation allows to use the developed simulation methodology to design and to adapt the braking system to any other specific application.