| In a BBW(Brake-by-Wire) system, the brake pedal is decoupled with the brake actuator. It has several advantages over the conventional hydraulic brake system, such as more compact structure, better brake performance and faster response and so on. Therefore, BBW system tends to be a promising brake system of passenger vehicles. MRF(Magneto-Rheological Fluid) is a smart material in the form of suspension which consists of magnetic particles and carrier oil. When subjected to an external magnetic field, a quick, continuous, adjustable and reversible magneto-rheological effect will occur, transforming the fluid from a free flow state into a solid-like state. Due to these outstanding properties, MRF is suitable for the application in dampers and brakes. The brake torque of an automotive MRB(Magneto-Rheological Brake) can be adjusted by changing the magnetic field density via electrical signals. It belongs to BBW system and is promising to be the brake system of electric vehicles as well as hybrid electric vehicles.However, since the brake torque generated by MRB is not large enough, its application as automotive brake was limited. By improving the performance of the MRF or optimizing the structure of the MRB as well as the layout of the coils can enlarge the brake torque to some degree. However, cost of the achievement of a larger brake torque was normally a larger size and weight, which was beyond the available volume in the vehicles. A novel MRB which combines a wedge mechanism is proposed in this thesis. The generated torque of a MRA(Magneto-Rheological Actuator) will be transformed by a transformation mechanism into the input force of the wedge mechanism, thus braking the vehicle. The proposed MRB has a compact, small-sized and light structure, while the brake torque is significantly enlarged. In addition, the regeneration brake energy can be recovered by the generator mounted parallelly to the driving shaft. The proposed MRB provides a possible solution for the application of MRF in the automotive brake.After analyzing the recent research and development of MRB in terms of measures taken to enlarge its brake torque, the configuration and layout of the proposed MRB was designed on the basis of the working principles of MRA as well as the wedge mechanism. It also combined a generator to harvest the brake energy. Torque analysis as well as the mathematical modeling of the whole MRB including the generator and the battery was performed. Simulation was carried out via Matlab/Simulink to investigate the brake performance as well as the capability of energy harvesting of the proposed MRB. Moreover, finite element analysis of the magnetic field density and the temperature field of the MRA were done. The mechanical strength of critical parts was checked with the help of finite element analysis. Finally, a prototype of the proposed MRB as well as a test stand was designed and set up. Experimental study was carried out to verify the feasibility of the proposed MRB.The simulation and experimental results showed that the proposed MRB could generate a significantly enlarged brake torque, while keeping a relative small and light structure. Energy was recovered by the generator during braking processes. The theoretical and experimental study of the proposed MRB with a self-energizing and energy harvesting capability could be a reference for the future research of the automotive application of MRB. |
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