Research On Transmission Properties Modeling And Control Technology Of MR Clutch

Benefit from the excellent performance of MRF,MR clutch has become a potential alternative means of electrical,hydraulic transmission and pneumatic servo mechanism.In the robot arm posture and force control,human-computer interaction in the compliant drive and tactile feedback,as well as the master-slave shaking teleoperation of medical robot and other areas began to play an important role.With the continuous development of transmission technology and the expansion of control applications,transmission and control system has put forward higher requirements on the performance of MR clutch,which urgently needs larger torque/mass ratio,faster response speed and higher control accuracy on the basis of compact structure,adjustable torque and stable work.Therefore,this thesis focuses on the structural development of MR clutch,the research on transmission characteristics modeling and control technology,and comprehensively uses theoretical modeling,simulation analysis and experimental verification methods to carry out in-depth research on the following aspects.(1)A compound mode MR clutch with uniform distribution of radial magnetic field was designed.Based on the effect of squeeze strengthening,a squeeze-shear MR clutch was developed,and the transmission and control in two modes could be realized through electromagnetic and electro-hydraulic composite control.A new magnetic circuit structure was proposed to solve the problem that the magnetic circuit of disk MR clutch is easy to cause the radial non-uniform distribution of magnetic field in the working space of MR fluid.Compared with the traditional disk magnetic circuit,the magnetic circuit structure can ensure that the magnetic field is uniform and concentrated vertically through the MR fluid workspace,so as to effectively reduce the energy consumption of the coil and improve the theoretical prediction accuracy of the transfer torque.The magnetic circuit is calculated by equivalent reluctance method and verified by finite element method.The static,dynamic and open-loop control characteristics of MR clutch in single shear mode and the transmission characteristics of MR clutch in squeeze-shear composite mode were studied experimentally.(2)A nonlinear equivalent magnetic circuit model is proposed,which comprehensively considers magnetic saturation,flux fringing and magnetic leakage effects.The model can process the geometric size and material properties of magnetic circuit,and reveal the mechanism of the device electromagnetic parameters and magnetic field information in the magnetic circuit.According to the specific structure of MR clutch,the calculation formulas of nonlinear magnetic permeances,fringing permeances and leakage permeances are deduced,and the model results are obtained by numerical method.The accuracy of the model is verified by magnetic field simulation and experimental test.The effects of constant permeability,nonlinear permeability,MRF fringing effect,air fringing effect and magnetic leakage effect on the model accuracy are discussed,and the comparison between linear equivalent magnetic circuit model,nonlinear equivalent magnetic circuit model and finite element model in the number of elements,calculation time and accuracy is conducted.The results show that the nonlinear equivalent magnetic circuit model is a kind of lumped parameter method with high precision and good calculation efficiency,which is beneficial to the performance calculation and design optimization of MR devices.(3)The dynamic analytical models of electrical circuit subsystem and magnetic circuit subsystem of MR clutch are established.Based on the lump-parameter method,the coil RL model of MR clutch was established,and the relationship between inductance,resistance and coil configuration parameters was obtained.On this basis,the mathematical model of MR clutch electrical circuit subsystem including PWM control buck circuit and coil RL load was established based on equivalent circuit method.Electromagnetic simulation was used to analyze the current incentive frequency to influence flux lines distribution of magnetic circuit,on the basis,the magnetic circuit theory and the concept of effective magnetic resistance is adopted to establish mathematical model of the magnetic circuit subsystem contains eddy current effect,and the magnetic circuit geometry and material properties on the mechanism of the dynamic responses of the magnetic circuit is revealed.Finally,the transfer function between the input voltage of the voltage source and the output magnetic induction intensity of the magnetic circuit is obtained,and the validity and accuracy of the electrical circuit subsystem and the magnetic circuit subsystem model are verified by simulation and experiment.Finally,based on analytical model and orthogonal design method,range analysis and sensitivity analysis were used to obtain the importance and sensitivity of control circuit,magnetic coil configuration,structural size and material properties to the dynamic response of the MR clutch.(4)A torque control method of MR clutch based on linear active disturbance rejection algorithm is proposed.A digital PID controller and a linear active disturbance rejection controller(LADRC)are designed.The method of controller parameter configuration and convergence proof of PD controller and linear extended state observer are given.MATLAB/Simulink module was used to verify and analyze the LADRC algorithm.On this basis,Phar Lap ETS,a real-time operating system built by Lab VIEW real-time module,was used to carry out experimental research on the performance of MR clutch torque control based on PID and LADRC algorithm.The experimental results show that both PID algorithm and LADRC algorithm show fast and stable zero steady state error tracking characteristics in the global setting range.However,compared with the oscillation and overshoot phenomena of PID algorithm,LADRC algorithm can realize the rapid step input signal tracking without overshoot.(5)A set of MR clutch integrated measurement and control system based on virtual instrument is developed.The electro-hydraulic transmission platform based on the prototype of MR clutch was built.The computer aided test and real-time operation control system based on virtual instrument is developed.The software and hardware architecture of the measurement and control system is designed,and the functions of data acquisition and output,data display and storage,system identification,instrument communication and real-time closed-loop control are realized,which provides experimental basis for the performance test and control research of MR clutch.