This study focuses on material characterizations of Magneto-rheological fluid (MRF) on performance characteristics of magneto-rheological brake (MRB). In this study, three different types of MRF (low viscosity, medium viscosity, and high viscosity) are considered for several types of MRB. Firstly, the optimization solution of the MRB design is proposed based on the Bingham plastic model of the MRFs and finite element analysis of MRB magnetic circuit. From optimal design of the MRBs with different MRFs, performance characteristics of the MRBs such as braking torque, off-state torque, and power consumption are evaluated. In addition, the compact size of MRB using different MRFs is also studied. Finally, some observations and guidance on selection of MRFs in MRB design are summarized.

In this study, a new configuration of Bidirectional Magneto-Rheological Actuator (BMRA) is proposed, optimally designed and experimentally evaluated. The BMRA has two discs rotating in opposite directions at the same speed. The two discs are placed inside a housing which is connected to the haptic devices. The BMRA has two coils placed directly on each side of the housing. The coils are separated with the Magnetorheological Fluid (MRF) by a thin wall of the housing. With this configuration, the inner face of the side housing, which is interfaced with the MRF, is continuous. This allows the MRF duct being manufactured more easily and accurately. After the introduction of the proposed configuration, braking torque of the proposed BMRA is analyzed based on Bingham-plastic rheological model of the MRF. Optimization of the proposed BMRA is then performed considering maximum torque and mass of the actuator. Based on the optimal result, detailed design of the BMRA is conducted and a prototype of the BMRA is manufactured. Experimental works on the prototype is then performed and performance characteristics of the proposed BMRA are figured out. 

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