MODELING APPROACH FOR A FLUID MOVEMENT INDUCED BY MAGNETIC FORCES FOR VISCOUS LOSS REDUCTION OF MRF BRAKES AND CLUTCHES

摘要

A challenge that is opposed to a commercial use of actuators like brakes and clutches based on magnetorheological fluids (MRF), are durable no-load losses, because a complete torque-free separation due to the permanent liquid intervention is inherently not yet possible. In this paper, the necessity of reducing these durable no-load losses will be shown by measurements performed with a MRF brake for high rotational speeds of 6000min~(-1). The detrimental high viscous torque motivates the introduction of a novel concept that allows a controlled movement of the MRF from an active shear gap into an inactive shear gap, enabling a complete separation of the fluid engaging surfaces. This behavior is modeled by the use of the ferrohydrody-namics and simulations are performed for different transitions between braking and idle mode. Images of high speed video capturing, showing the motion of MRF induced by a magnetic field, are presented for the validation of the modeling approach. Measurements performed with a realized proof-of-concept actuator show that the viscous induced drag torque can be reduced significantly.