| Magnetorheological(MR)brake,using magnetorheological fluid(MRF)as the working medium,is a new type of brake developed on the basis of characteristics of MRF whose rheological properties change sharply with the external magnetic field.The brake has the advantages of simple structure,quick response speed,convenient control,etc.,whose braking torque can be controlled continuously by the external magnetic field.Therefore,it has wide prospect for engineering application.In order to solve the problems of small torque and poor heat dissipation,the following research is carried out in this paper:(1)The basic theory of MR brake and the design theory of MR brake structure are researched.The basic structure of the high torque compression MR brake with the target value of 2000N·m is designed.Besides that,the cooling mode,compression mode and sealing method of the MR brake are introduced in detail.(2)The magnetic circuit parameters of the high torque compression MR brake are designed in detail based on the research of the basic theory of the magnetic circuit.The magnetic circuit of MR brake is simulated and the distribution of magnetic field in the working gap of MRF is obtained.The magnetic field test is carried out and the correctness of the simulation results is verified.(3)The basic theory of heat transfer and the working state of MR brake are introduced.The heat source of high torque compression MR brake is analyzed.The thermal parameters of MRF are solved by theory,experiment and simulation.The steady and transient temperature field of MR brake are analyzed based on ANSYS,and the influence of different brake slip power and cooling conditions on the brake temperature is studied.The temperature field test is carried out and the correctness of the simulation results is verified.(4)The experimental platform of high torque compression MR brake system is built,and the braking characteristics without compression,braking characteristics with compression and temperature characteristics are researched.The experiment result shows: The load torque is small,the braking torque regulation characteristics and constant torque characteristics are better,and the response speed is faster in the MR brake.The maximum braking torque is 1300N·m without compression.When the axial compression pressure is 1.5MPa,the braking torque can increase by 90%.In addition,when the radial compression pressure is 2MPa,the braking torque can increase by 40%.The highest working temperature of the brake is 90 degrees.And the temperature rise is affected by the slip power and cooling conditions.Under the condition of optimal cooling and compression,the braking torque can be up to 2540N·m,and the allowable slip power is 36.6kW. |
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