Research On Sliding Mode Control Method Of Water Lubricated Bearing Electromagnetic Loading Device

Highly accurate load simulation is essential in the study of water-lubricated bearing characteristics.In view of the current problems of unstable loading caused by hardware factors of non-contact electromagnetic loading devices,this paper conducts research on the operation mechanism of non-contact electromagnetic loading devices,non-linear equivalent magnetic circuit method model,accurate load modelling of magnetic circuit,non-singular terminal sliding mode control,expansion state observer and PLC digital control system implementation,etc.The main contents are as follows:(1)The operation mechanism of the non-contact electromagnetic loading device is studied.The dynamic magnetic permeability due to eccentricity and material differences and the eddy current magnetic field due to Maxwell’s electromagnetic induction principle are analysed based on the magnetic circuit,and the equivalent magnetic circuit model and Matlab/Simulink simulation model are established.(2)The load model is established based on the exact magnetic flux obtained from the equivalent magnetic circuit method model.The model transforms the load into the radial displacement of the axis through the deflection equation,analyses the magnetic circuit energy to establish a displacement-current dynamic mathematical model,and linearises the dynamic mathematical model to obtain a state-space model with current as input.The model is easy to implement and more suitable for controller design.(3)In order to solve the problem of unstable radial electromagnetic loading force of the loading device,based on the proposed load model,the non-singular terminal sliding mode control strategy is combined with the expanded state observer in the self-turbulence control,and a non-singular terminal sliding mode improvement control strategy is proposed,which improves the calculation accuracy of the controller and reduces the perturbation influence on the system performance,and the radial electromagnetic load controller of the electromagnetic loading device is designed by applying this improvement control strategy.(4)Design the hardware design and control main program of the control system of the electromagnetic loading device,write the digital filtering algorithm and the programs of the non-singular terminal sliding mode controller and expansion state observer.In order to verify the effectiveness and feasibility of the proposed improved sliding mode control strategy,a digital control system test platform for the electromagnetic loading device was designed and constructed based on a water-lubricated bearing test rig with PLC as the control core,and the start-up process and steady-state axial trajectory of the electromagnetic loading device under the control of the non-singular terminal sliding mode improvement controller were tested and analysed.The test results show that the odd terminal sliding mode improvement controller can achieve stable control of the electromagnetic loading device,and the dynamic performance and stability are better than the non-singular terminal sliding mode controller.