Research On Mechanism And Performances Of Magnetorheological Transmission Devices

Magnetorheological fluid(MRF,or MR fluid)a kind of smart material composed of micron-size ferromagnetic particles dispersed in the carrier fluid.In the presence of the applied magnetic field,MRF rheological properties can change rapidly.This change is rapid,continuous,and reversible.MRF has wide application prospects on the fields of torque transmission and vibration control.This research presents a new magnetorheological transmission device(MRTD)structure with electromagnetic coils as part of the stator.It is a multipole magnetorheological transmission device based on MRF controllable rheology.The working mode of MRF in the transmission process is a combination of shear and extrusion modes.The new MRTD can provide controllable torque and speed by adjusting the external applied magnetic field,with fast response and continuously adjustable output characteristics.This kind of structure reduces the adverse effect of the centrifugal force and improves the performance of MRTD.In this dissertation,the working modes of MRF and the material selection of MRTD were analyzed.The mathematical model and design method of the new MRTD was established.An external multipole electromagnetic MRTD was developed.The internal magnetic field of MRTD was analyzed by a finite element simulation software package.The basic principle and control method of output torque has been analyzed.A new experimental platform for MRTD was built.The transmission characteristics of the MRTD prototype were analyzed,which mainly included equipment torque characteristics,no-load characteristics,torque transmission characteristics,speed control characteristics,dynamic response,and constant torque characteristics.Equipment torque refers to starting torque produced by experimental equipment.No-load characteristics refer to the torque produced by the friction between components such as bearings,seal,and the viscosity of MRF with no magnetic field applied.The torque transmission characteristics refer to the torque transmitted by the MRTD under the application of magnetic,which also reflects the transmission capability of MRTD.Speed control characteristic reflects the relationship between the output speed of MRTD and the excitation current applied through the coil.The time response of MRTD torque under different operating conditions was analyzed through dynamic response characteristics.Constant torque analysis refers to the torque transmitted by the MRTD when the slip speed is kept constant,while the applied excitation current varies with a determined increment value.Results show that torque increases gradually as excitation current increases;the relationship between torque and excitation current is linear.When the excitation current is 2A,the maximum torque transmitted by the MRTD is about 6.6 N/m.The output speed increases significantly with a certain increment value.As the current increases to a certain extent,the MRTD can reach synchronous speed.The difference in response time is due to the anisotropy of magnetic particles in MRF under the applied magnetic field.The effect of input speed on the dynamic response time is small.The new MRTD can realize controllable speed and torque and has good transmission performance.