Key Technology And Experimental Research On High Power Magnetorheological Fluid Coupling

Magnetorheological fluid coupling is a new type of solid-liquid electromagnetic integrated power transmission device.It uses the rheological properties of magnetorheological materials to instantaneously change the output torque characteristics through the external magnetic field,which can improve the impact resistance of the power transmission system,reduce the vibration of the system,and realize the active control of the rotational speed and overload protection.It is especially suitable for the mechanical and electrical equipment with complex load work and high requirements for anti-impact and noise reduction of equipment.However,due to the weak mechanical properties of magnetorheological materials,the temperature rise characteristics under large slip conditions and the complexity of the solid-liquid coupling transient nonlinear speed control model,the application of magnetorheological fluid transmission technology has been limited to small torque and low power transmission system.In this dissertation,the high-power magnetorheological fluid coupling is taken as the object,and the key technical problems such as torque enhancement mechanism,temperature variation law and speed control strategy are studied in the following aspects.(1)The torque transfer enhancement mechanism of highpower MFR coupling in shear-extrusion mode was studied.The composition of magnetorheological fluid and the formation principle of rheological effect are expounded.The flow,shear and extrusion modes of magnetorheological fluid transmission device and their respective characteristics are analyzed,and the constitutive model of power transmission of magnetorheological fluid coupling is obtained.The forming method of magnetorheological fluid magnetic chain was explored.According to the dipole moment theory and metal plastic deformation theory,the arc flux linkage was theoretically analyzed.The magnetic field distribution law of arc surface was verified by electromagnetic field simulation,and the magnetic field distribution of elliptical arc surface was summarized.According to the formation mechanism of arc flux,it is verified that the torque transfer density of magnetorheological fluid coupling can be effectively enhanced based on hybrid working mode.(2)The structure,magnetic circuit design method and key parameter optimization theory of elliptical disk magnetorheological coupling based on shear-extrusion mixed mode are obtained.The elliptical arc surface is applied to the active disk surface of multi-disk coupling,and its basic working principle and magnetic circuit model are analyzed theoretically.The transmission torque models of planar and elliptical disk couplings are established respectively.The influence of key parameters in the mathematical model on the mechanical properties of the coupling such as magnetic output torque,viscous resistance torque and torque adjustable ratio is discussed by control variable method.The sensitivity simulation analysis of these parameters is carried out,and the optimization method of key design parameters such as elliptical parameter angle,number of ripples and elliptical long and short axis size is obtained.Finally,the effectiveness of the designed magnetic circuit is verified by electromagnetic field simulation.(3)The variation and distribution of steady & transient temperature field of high-power magnetorheological fluid coupling are revealed,and the method of allowable slip power verification is obtained.According to the basic heat transfer equation and temperature field calculation equation,the temperature field mathematical model and heat balance model of high-power magnetorheological fluid coupling are established.Aiming at the heat source and heat dissipation conditions under different working conditions,the finite element analysis and numerical simulation of the temperature distribution of the magnetorheological fluid coupling are carried out,and the temperature field distribution and temperature change with the slip time under the stable working state and slip start state are obtained.According to the established steady-state operation and transient slip thermal equilibrium model of magnetorheological fluid,a scientific method for approving the allowable slip power of high-power magnetorheological fluid coupling is obtained.(4)The speed control model based on solid-liquid coupling transient nonlinear transmission system is proposed,and the speed control strategy and current compensation optimization algorithm of magnetorheological fluid coupling are formulated.According to the dynamic equation of the mechanical system,the mathematical model of the speed control of the output end of the magnetorheological fluid coupling is established,and the speed control equation is solved.The response characteristics of magnetorheological fluid speed control under different load characteristics are analyzed,and the key factors that may affect the dynamic control performance of the system are revealed.By comparing different control strategies,the magnetorheological fluid speed adaptive fuzzy PID controller is designed,and the numerical simulation verifies that the proposed control method can effectively improve the dynamic response characteristics of the coupling.In view of the disturbance factors of coil resistance change caused by the temperature rise of magnetorheological fluid,a double closed-loop current compensation control strategy is developed to further improve the control accuracy of the system magnetorheological drive system.(5)The design method and control strategy of the proposed high-power magnetorheological fluid coupling are tested and verified.Compared with ordinary disc magnetorheological fluid coupling no-load characteristics,magneto-induced transmission compression,multiple dynamic transmission shafts,slip/transient temperature field distribution,maximum slip power and time response characteristics,compared with different control strategies.The speed control performance of the coupling verifies the state of the high-power magnetorheological fluid structure,circuit design method and speed control strategy.The research results from this dissertation have certain guiding significance for improving the design theory and method of magnetorheological fluid coupling,and provide technical support for its application in high-power mechanical transmission system.