Numerical design and experimental evaluation of a hybrid magnetorheological brake

Magnetorheological fluids exhibit magnetically sensitive rheological behavior. Thus, they are classified as "smart" materials. Magnetorheological fluid devices have attractive properties such as fast response time, higher yield stress, and relatively low power consumption. Magnetorheological devices distinguish among similar smart materials, as its properties are superior. Magnetorheological devices include dampers and brakes. Initially, magnetorheological brakes are developed for automotive and motorcycles. Recent studies focuses on increasing torque density in haptic systems. In this study, H-shaped MR brake is proposed to achieve higher torque density. Proposed brake is compared to drum and T-shaped MR brakes. All brakes are designed parametrically. Parametric designs are optimized using Particle Swarm Optimization. Gradient-based constraint handling method is used to handle constraints. Magnetic analysis is conducted using both developed iterative formulation and finite element approaches. Two approaches are compared, latter of which is shown to be the method of choice. Braking torques are deducted analytically using Bingham plastic model. Comparison of the optimum designs show that the torque density of H-shaped MR brake is 22% higher than drum type and 13% higher than T-shaped MR brake. Also, H-shaped MR brake generates 60% more braking torque than the drum type and 18% more than T-shaped MR brake. Experimental study validates the finite element approach while deductions are made about hysteresis characteristics. Time constant of the proposed brake is found to be 69 ms in response to 1.5 A step input. Sinusiodal excitation to the coil of the brake shows that proposed brake can be modeled as first order systems.