## 2 Description of the Proposed MR Brake  
### Working Principle and Structural Design  
Magnetorheological brakes have received a lot of attention because of the visco-plastic behavior that achieves braking through the shearing effect of MRF, describing the critical influence on magnetic field intensity. The structural and thermal properties of the Lord MRF-140 CG, as shown in Table 1, are ideal for fluid braking and meet a variety of requirements, including viscosity without a magnetic field, operating temperature, shear stress gradient for the applied magnetic field strength, thermal conductivity, and coefficient of thermal expansion. The new structural design aims to significantly increase the active MR fluid chaining area and the corresponding shear stress on rotor surfaces, thereby increasing braking torque. The Lord MRF-140 CG fluid was selected for this MRB due to its high-yield stress gradient and accessibility. In the presence of a magnetic field, the rheology of MRF-140 CG fluid changes reversibly and instantly from a free-flowing liquid to a semi-solid with controllable yield strength. The proposed brake adopts a common double brake disc structure that has four magnetic layers and six magnetic poles, which is suitable for more complicated occasions with limited axial installation space. Figure 1 depicts the brake's major components, which include stator cases, rotor discs, magnetic poles, magnetorheological fluid layers, stator caps, and covers. Because of the magnetic properties, the shaft and MRB covers were made of non-ferromagnetic material. Stator cases were made of an aluminum alloy. Nonmagnetic materials connect two adjacent stators, allowing the produced magnetic flux to pass through MRF gaps. These case holes in the inner disc surface are intended for the insertion of magnetic poles that form a circular array, as shown in Figure 2. Magnetic poles with magnetically permeable cylindrical cores have heads and shanks inserted into those holes, and the core region has copper coil windings encircling it. Magnetically permeable rotor discs were positioned parallel to the surface of the stator cases and pole heads. MRF was used to fill the gaps between the outer cap and disc surfaces. The rotor rotates almost freely within the stator casing. [PERSON] et al. [3] achieved a multipole compact dual disc magnetorheological brake with a simple and light weight mechanical construction and optimized the structural dimensions of the brake through electromagnetic simulations. In this study, we use some of the fixed dimensions of an earlier designed brake, as shown in Table 2, because it achieves a higher torque density and a fairly quick response. When a copper coil is electrified, the brake is activated, the core heads become magnetic poles, and an induced magnetic field is generated in the working area of MR fluid. MRF particles form a chain structure at the top and bottom rotor surfaces, due to the MRF rheological effect that allows the magnetic flux to penetrate orthogonally. The multipole effect of the even number of coil-winded magnetic cores was arranged in such a way that the magnetic flux path in one pole was reversed to that of its two adjacent magnetic poles. The flux flow begins from one pole to the adjacent pole via the inner MR layer, rotor disc, and outer MR layer, as shown in Figure 3, and then returns on the opposite side of the