Abstract: With motor vehicle developing toward heavy and large-size, its braking safety issue becomes increasingly prominent. Additionally installing auxiliary braking device is one of the important ways to achieve the safety braking for heavy-duty vehicles. Magnetorheological (MR) brake has advantageous features of stable braking torque, low noise and small volume and mass etc., so is able to remedy the inadequacies of traditional auxiliary braking devices, e.g. the poor performance at low speeds. A new idea of combined retarding braking by utilizing both MR and eddy-current effects is put forward, the working principle of novel MR retarder is analyzed, the double-disk symmetric structure of novel retarder is designed and developed, the mathematical model for its braking torque is established and the effects of different parameters on braking performance are theoretically analyzed. According to the working features of high-power braking in heavy-duty vehicles, a testing platform for braking performance is constructed, and a test on braking torque characteristics is conducted. The theoretical analysis and test results show that the novel MR retarder has the features of stable braking performance at low speed and large braking torque at high speed, with its braking torque characteristics meeting the braking requirements of heavy-duty vehicles

Key words: heavy-duty vehicles, retarder, magnetorheological effect, eddy current effect, braking performance