The low braking performance of MR brakes is the most challenging concern for their deployment in any vehicle. To overcome this, hybrid MR brakes have been proposed. However, a few problems, such as braking torque reduction due to heat generation during braking cycles and off-state torque, remain a significant challenge with MR brakes to date. By controlling the supplied current to MR brakes, the drop in braking torque due to the heating of the working medium can be cured. In the present work, two MR drum brakes, SE-MRDB and CE-MRDB, which can operate in shear mode as well as in hybrid mode, have been evaluated for control purposes. Their transfer functions have been formulated by considering all relevant aspects, including the number of inputs (current and load), off-state viscous torque, and MR fluid properties. Then, PID controllers have been designed using MATLAB Simulink. To optimise the PID gains, a MATLAB-based genetic algorithm tool has been used. Along with the analytical study, a physical controller has been designed using Arduino and tested for the SE-MR drum brake only for the shear mode. It was found that the designed controller successfully helps in maintaining the constant mean torque. It was observed in a reduction in standard deviation for the braking torque from 1.129 to 0.204.
Singh et al. (2026) studied this question.