Design and performance evaluation of a non-uniform gap disc-type magnetorheological fluid brake

Abstract This paper presents a non-uniform gap disc-type MR brake which has an uneven surface morphology, aiming to increase torque by improving the magnetic field strength within the magnetorheological (MR) fluid gaps. Firstly, the configuration and functioning mechanism of the non-uniform gap disc-type MR brake are outlined, and then a magnetic circuit model is developed. The dependence of braking torque on structural and magnetic circuit parameters has been mathematically derived and thoroughly analyzed. Next, an optimized design of the MR brake structure has been determined, in order to achieve consistent magnetic field strength of MR fluid gaps. Then, electromagnetic field simulation analysis is carried out to observe the field strength at various locations in the gaps, and the temperature field simulation has also been completed to demonstrate the heat distribution across the brake assembly. Finally, a non-uniform gap disc-type MR brake prototype is manufactured. A smooth-surface disc with uniform gap sizes has been also developed for comparison with the non-uniform disc. Under the coupled magnetic-thermal field simulation, the simulated temperature values of the MR brake align well with the experimental data. The experimental findings confirm that the magnetic field strength within the MR fluid gaps of the non-uniform gap disc-type MR brake is substantially uniformly distributed along the radial direction, and its braking torque is 120.6% of the conventional smooth-surface disc-type MR brake.