| Summary: | 博士 === 國立臺北科技大學 === 機電科技研究所 === 101 === Magnetorheological (MR) brake stays within the term of brake-by-wire in vehicle engineering. The simple structure, low-power-supply requirement, fast respond and ease of maintenance have proven its possibility for further applications. However, MR brakes with conventional single ring-type electromagnetic pole have reached the limits of torque enhancement, which prevent it for larger area of applications. One major reason is the limitation of the magnetic field strength within the active area of the MR fluid due to the geometric constraints of the coil. Therefore, it is high requirement for enhancement of brake torque in MR brake. This research presents a new approach in the design and optimization of a novel multi-pole MR brake that employs magnetic flux more effectively on the surface of the rotor. The new MR brake design features multiple electromagnetic poles surrounded by several coils. The magnetic flux is forced to travel in a closed loop, from one pole, through the MR fluid gap, into the rotor, back to the MR gap and into the two adjacent poles. This new operation concept is very different from conventional MR brakes. As a result, the active chaining areas for the MR fluid are greatly increased, and significant brake torque improvement is achieved. The coil structure, as a part of the stator, becomes flexible and customizable in terms of space usage for the winding and bobbin design. In addition, this brake offers extra options in its dimensions for torque enhancement because either the radial or the axial dimensions of the rotor can be increased.
Magnetic circuit analysis was conducted to analyze the effects of the design parameters on the field torque. After that, simulations were done to find the optimal design under all major geometric constraints and a range of input power. Different types of MR fluid as well as steels were simulated with the brake model. After the optimal design was found, a prototype of multi-pole MR brake was experimented with different input power and rotational speeds. Static and dynamic tests were done to estimate the adaption of the brake with various operation conditions. The results show that the multi-pole MR brake provides a considerable braking torque increase while maintaining a compact and solid design. Moreover, by using above procedure, a case study was conducted by simulations to compare the performance and structure between inner rotor and outer rotor multi-pole MR brakes on motorcycle brake system. With the same operation concept, the comparison result confirms the precision of design procedure and the feasibility of the outer rotor brakes for actual braking applications.
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