Magnetic flux analysis on magnetorheological actuators can detect external force variation

Magnetorheological (MR) fluids consist of a suspension of ferromagnetic micron-sized particles dispersed in a carrier fluid. A magnetic field induces the magnetization of the particles which then form chain-like structures aligned in the direction of the field. The structures interact with the magnetic poles, as a consequence, the relative displacement of the poles due to the action of an external force, inclines the particle chains and alters the magnetic environment. This phenomenon can be perceived as a magnetic reluctance variation on the fluid gap. The paper focuses on a MR-based brake equipped with a magnetic flux variation measurement system, which is able to detect when the chain-like structures begin to rupture. Based on the same principle, the system is also capable of detecting a change in the direction of an external force.