| Magnetorheological (MR) transmission adopts the magnetorheological fluid (MRF) asworking medium and relies on the shear stress of MRF between transmission interfaces forpower transmission. The transmitted torque can be continuously regulated throughcontrolling the applied magnetic field. As a new power transmission form, MR transmissionhas many advantages, such as a quick and reversible response, simple control and lowenergy consumption, as well as high anti-interference ability, etc.. Therefore, it possesses abroad application prospect in the fields of soft start, soft brake, stepless speed control andoverload protection for mechanical equipment. According to the existing problems incurrent studies of MR transmission, this dissertation will conduct an in-depth research fromthe following aspects.Formation mechanism of MR effect and constitutive model of MRF are explainedseparately from macro and micro aspects. A detailed introduction to basic compositions andkey performance indicators of MRF is conducted. Then, temperature effect on materialproperties of the MRF compositions, including magnetization performance of soft magneticparticle as well as dynamic viscosity and thermal expansion characteristic of carrier fluid, isstudied combining with theoretical analysis and experimental test. Several MRF samplesare prepared using the base-fluid replacement method. Thereafter, experimental tests arecarried out on the magnetism-temperature characteristic, shear stress-temperature propertyand temperature stability of MRF samples. And the influence mechanism and influencelaws of the temperature on material properties of MRF are obtained.An introduction to basic components, control principle and characteristic of MR speedcontrol system is performed. Then, mathematical control model for the output speed of thesystem is established and the time response of MR speed start is numerically calculated.The influence of excitation current, input speed and load torque on the response time isanalyzed as well. Both the temperature variation of MRF and the consequent torque declinein the speed control process are calculated. Then, a speed control model considering thetemperature effect is built and the effect of temperature variation on MR speed control isdiscussed. Moreover, a current fine-tuning compensation method for compensating thetorque decline caused by temperature rise is proposed and the speed control performanceswith/without temperature compensation method are contrastively studied.Aiming at the requirements for high-power transmission application fields, a novelhigh-power MR transmission device (MRTD) is designed. Then, finite element simulation is conducted on the designed magnetic circuit using the ANSYS software, and the overallmagnetic field distribution and the distribution laws and influence factors of magneticinduction in the working gap are obtained. An electromagnetic field experiment isconducted to verify the simulation results. Moreover, the influence laws of workingmagnetic induction and angular speed difference between drive and driven plate on powertransmission and speed control performance of the designed MRTD are theoreticallyinvestigated as well.Based on computational fluid dynamics (CFD) equations and temperature fieldcalculation equations, a heat-flow coupling model of MRTD is established and numericalcalculation is conducted with the CFD software CFX. Velocity and pressure fields ofinternal cooling liquid as well as steady and transient temperature fields of MRTD undervarious working conditions are obtained. Then, the influence laws of slip power, rotationalspeed, inlet speed and temperature, as well as cooling fluid characteristic on the heat-flowcoupling field of MRTD are discussed.An experimental system for high-power MR transmision is designed and fabricated.Then, a large number of experimental studies are conducted on the power transmission andresponse performance, as well as temperature rise characteristics of MRF under high slippower conditions. Moreover, maximum allowable steady and transient slip power are testedas well. Experiments results validate the reliability of the designed high-power MRTD andthe effectiveness of the proposed water cooling method.Research results from this dissertation play an important guiding significance to thethorough study of MR transmission technology and they could provide a technical supportfor the design of high-power MRTD and the widespread application of MR transmissiontechnology. |
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