Study On Novel Brake Based On Magnetorheological Fluid

With the advances of automotive industry,commercial vehicle is gradually developed to high speed and large-scale,the braking function of vehicle is faced to bigger challenge.Installation of auxiliary braking device is an effective way to achieve the safety braking for large-scale vehicle.Magnetorheological(MR)brake is a novel braking device utilizing the shear stress of MR fluid to generate braking torque,which has stable braking torque,easy control,low braking noise and simple structure,and it can effectively compensate for the poor low-speed performance and high current consumption of the conventional auxiliary brakes.However,due to the limitation of shear stress of MR fluid and magnetic saturation,MR brake is difficult to achieve great increase of baking torque,which restricts its engineering application in some high braking torque situation.To enhance the performance of MR brake,,a novel high torque MR brake is designed,manufactured and tested based on the combined effect of magnetorheological and eddy current in this paper.First,we analyze the working principle of MR brake and eddy current retarder,and propose a novel concept which utilizes the combined effect of eddy current and magnetorheological to increase the total braking torque of MR brake,while the feasibility and superiority of the novel concept are also discussed.Based on the novel concept,we proposed a novel MR brake,and the mathematical model of braking torque is built for the subsequent design as well.Secondly,according to the working principle of the novel MR brake,a appropriate structure is designed.By using MCR302 rheometer,the performance of MR fluid is studied and the appropriate MR fluid is selected as work medium.Meanwhile,the magnetic circuit is designed and analyzed.Based on the designed structure,the performance of the selected MR fluid and the mathematical model of braking torque,we get the specific design parameters of the novel MR brake,and the braking function of the novel brake is analyzed theoretically.Thirdly,the magnetic field of the novel MR brake is simulated and analyzed to verify the design of magnetic field in Ansoft software.The whole magnetic field distribution,the magnetic flux density of working area and its impact factor are also studied.Based on the simulation result of magnetic field,the magnetic field of both the novel MR brake and eddy current retarder are brought in comparison to verify the design of magnetic field.Then,to dissipate the large heating generated by the novel brake,several coolant flow path is designed based on the brake structure.The heat transfer inside the novel MR brake and thermal loads are analyzed.To verify the design of cooling system,the temperature distribution of the novel MR brake is simulated in ANSYS software,and the temperature of the important parts in typical work conditions is studied as well.Finally,according to the design parameters obtained before,a novel MR brake prototype is manufactured and assembled.The contents of experiment are decided,and a test platform is built to test the braking performance of the prototype.The superiority and reliability of the braking function of the novel MR brake are verified.The innovation of this article is that we propose a novel concept which unites the effect of eddy current and magnetorheological to achieve greater braking function to improve the braking torque of the MR brake.Based on this novel concept,a novel MR brake with low excitation current,good braking performance at low speed and high braking torque at high speed is designed and developed.The mathematic model of the braking torque is also established and verified.This paper also provides a novel concept to develop the novel auxiliary braking device and makes contribution to promote the engineering application of MR brake.