The Magnetorheological fluid brakes can be divided into two types: a) Disk brakes & b) Drum brakes. The Magnetorheological brakes are quite smooth acting, compact and easy to control. They are operated in the direct shear mode. The MR fluid is filled directly into the gap between the rotor and the housing. The rotor is mounted on the shaft which can rotate in relation to housing by through bearings. The viscosity of the MR fluid can be changed by magnetic flu and the resistance torque depends on it. The viscosity of the carrier fluid transmits torque when there is no magnetic field. MR fluid brake is used because it has a very less response time i.e. <1 milliseconds . • W. H. Li and H. Du (2003)  gave a new design prototype of MR fluid brake and it was also fabricated and tested as shown in fig 9.The equations were derived for transmitted torque to evaluate MR disk brake. Finite element method was followed for analysis of electromagnet. For static magnetic analysis ANSYS/Emag 2D was used for an efficient magnetic field analysis and design. The performance of MR brake was experimentally evaluated by special designed test rig. Also the results were experimentally presented and discussed keeping transmitted torque in concern. A magnetic circuit of I-Shaped was designed for good performance and simplicity as shown in fig 10(a) and the cross sectional view of the MR brake with I-shaped electromagnet is shown in fig 10(b). The picture of testing setup is as shown in the figure 11. MR brake was rotated at 300rpm for 1 min and desired magnetic field was applied for the same time to settle and distribution of fluid to be stable. By servomotor speed was applied to the brake shaft. Torque detector was used to detect the transmitted torque. With increasing magnetic field strength transmitted torque increases gradually. Finite element analysis was used for designing high efficiency electro-magnet. Amplifying factor was used to evaluate the braking performance which can be controlled by varying the magnetic field strength and rotary speed as 1--, 300 and 500 rpm. • Takehito tikuchi & Keigo Kobayashi (2011)  Cylindrical MR fluid brake for the force control of the cycling system was developed using rotational cylinder. For the effective braking multiple coils structure was developed on rotor cylinder for generating high range magnetic flux. It focuses on the study of virtual cycling system for force feedback realization for virtual environment. MR fluid used was Lord -132DG by Lord Corp. USA having 32% iron particle volume in hydrocarbon based oil with additives keeping particle size of 0.88 to 4.03 μm. Basic setup is as shown in fig 12(a). The magnetic coil was placed in the base of the testing cell which helps to control 1T of the magnetic flux density in the fluid gap up to 1A current. DC servo motor was used to control the speed of the turning table. The analytical model and cross section of the magnetic flux density for 1A magnetic circuit brake is as shown in the fig 12(b).The electric current was controlled between 0.0 A to 1.0A for each velocity. The rotational velocities were taken as 1.0, 5.0, 6.28 rad/s2. The experimental results of all velocities are shown in fig 13. There is little difference in the rotational velocities (shear rate) and all results of all velocities get overlapped in the near value of torque. The result shows error due to friction of seal but the cylindrical brake was develop having maximum torque of 10N. The brake was implemented as torque generator for virtual cycling system to control resistance created by slopes.• Nyguyen Q. Hung & Choi S. Bok (2012)  proposed a configuration of T-shaped MR fluid brake in order to replace the conventional rear drum brake of a motorcycle as shown in fig 14. The optimal design was proposed to maximize the braking torque which shows constant deceleration of 0.75g and also the temperature of the MR fluid to be smaller than the critical value i.e. 120°C at 120km/h cruising speed . The optimal design was proposed which satisfies both the constraints. The applied current is limited by 2A at that point the drum reaches to the saturation value as shown in fig 15. The braking torque of the brake was 441 Nm and the required braking torque was 430 Nm. The XV535-110 VIRAGO motorcycle of YAMAHA was taken as example Finite Element Analysis software was used for the magnetic density calculations. Average Magnetic density value was taken as it was assumed magnetic density remains constant in MR gaps. ANSYS software was used for the analyses of the magnetic circuit of MRF brake. • Yaojung Shaiao & Quang-Anh Ngyun (2014)  gave a design of MR fluid brake having multiple electromagnetic poles surrounded by number of coils for improving the braking torque by generating high magnetic field strength as shown in fig 16Optimization flowchart was given for optimal design of the multi pole MR brake. The higher power input creates better magnetic field strength. The effect on the structure of brake and power supply for torque enhancement was investigated. The design was found using Sequential Nonlinear programming (SLNP) optimizer. The magnetic simulation result shows the operational concept of MR brake which shows the high braking torque achieved by the brake as shown in fig 17. The fluid layer of 0.5, 0.75 and 1mm was used to investigate the chain connection property for output torque. The comparisons of the fluid were also done and 140 CG MR Fluid proves that it produces higher braking torque at same input than other fluids.The optimum torque of 25.1 Nm was achieved by keeping 0.5mm fluid layer and using AISI 1018 steel for rotor and stator material.