Aiming at the uniformity of the gap magnetic field strength of the magnetorheological (MR) fluid in the traditional disc-type MR brake, a variable-gap disc-type MR brake is studied in this paper. Firstly, the basic structure and working principle of the variable-gap disc-type MR brake were introduced, and the MR brake magnetic circuit modelling was conducted. The mathematical model of braking torque was derived, and the relationship between braking torque and structural parameters as well as magnetic circuit parameters was studied and analyzed. In order to obtain uniform gap magnetic field strength, the structural design of the MR brake was completed by using the optimization of the structure and magnetic circuit. Then, based on the finite element simulation, the electromagnetic field simulation of the MR brake was carried out, and the torque simulation results were derived by combining the torque mathematical model. Finally, the prototype of the designed variable-gap disc-type MR brake was manufactured and the performance experiment was carried out. The results show that the magnetic field strength within the MR fluid gap in the designed MR brake is basically uniformly distributed along the radial direction, and the braking torque of the variable-gap structure is increased by 15 % compared with that of the conventional structure.

variable gap; disc type magnetorheological (MR) brake; magnetic field strength; uniformity; braking torque