Research And Application Of Restoring Force Model Of Magnetorheological Damper Based On Molecular Dynamics

The vibration control of MR damper can reduce the impact of earthquake on structure effectively.Concise and accurate restoring force model is the key factor affecting vibration control.In this paper,a two-dimensional magnetorheological fluid model is established and the main factors affecting the shear yield strength of magnetorheological fluid are studied by using molecular dynamics software LAMMPS.Based on molecular dynamics theory and experimental fitting,a non-linear hysteretic restoring force model of magnetorheological damper based on molecular dynamics is proposed.Based on the fuzzy theory and the principle of PID control,a fuzzy optimal PID control algorithm is proposed.Simulink toolbox is used to study the vibration control of three-layer magnetorheological damping Structure.The main research results are as follows:(1)A two-dimensional micro-shear model of magnetorheological fluid is established by using molecular dynamics LAMMPS software.The interaction between magnetic particles is analyzed,and the force field and boundary conditions of the model are set up.The micro-numerical simulation of the shear process of magnetorheological fluid in two-dimensional state is carried out.(2)Using molecular dynamics LAMMPS software,a non-linear hysteretic restoring force model based on molecular dynamics is proposed.The parameters of the model are non-linearly fitted by a self-developed magnetorheological damper.The model is in good agreement with the experimental restoring force data and has certain application value.(3)A nonlinear hysteretic fuzzy optimal PID control algorithm is proposed.The flow chart of the PID control algorithm is determined and the parametersK_P,K _D are adjusted.Combining the advantages of the fuzzy algorithm,the control parameters are feedback and adjusted in real time.The membership function of fuzzy optimal PID control is determined.(4)The effects of magnetic field strength,particle percentage,particle radius and temperature on the shear yield strength of magnetorheological fluid are analyzed.With the increase of particle volume percentage,the shear yield strength increases linearly.The shear yield strength increases rapidly at low magnetic field strength,but slows down at high magnetic field strength.In a certain range,the larger the particle radius is,the more concentrated the particle size distribution is,the greater the shear yield strength is.With the increase of simulated temperature,the shear yield strength keeps stable at first,and then decreases gradually.(5)Simulink vibration control simulation analysis of three-layer MR damped structure is carried out under the action of three kinds of seismic waves.The average control rates of displacement peak and acceleration peak are 47.39%and 34.61%respectively using the proposed nonlinear hysteretic fuzzy optimal PID control algorithm,which is obviously better than the traditional Bingham fuzzy optimal PID control algorithm.