| With the continuous development of social economy in China,the urban population scale and urban construction area are expanding,and the communication between urban and satellite cities is increasingly close.The line mode of underground tunnel-ground-viaduct is widely used in modern urban transportation.The linear motor wheel-rail system has the advantages of strong climbing ability,small turning radius and low tunnel construction cost,which is widely used in urban rail transit system.However,in the turning,turnout,in and out of the depot section,the secondary can not be laid continuously,that is,the discontinuous secondary working condition.The primary current,thrust and normal force will produce violent fluctuations,which will cause damage to the switching devices of the traction drive system and irregular wear of the wheelset,and has a great challenge to the safe and stable operation of the train.On the basis of summarizing the principle,analysis theory and control strategy of linear induction motor,this thesis analyzes the characteristics and research status of LIM with the discontinuous secondary,and studies the electromagnetic characteristics,equivalent circuit and anti impact control strategy of the motor.Firstly,the field circuit joint finite element simulation model of linear induction motor with the discontinuous secondary is established by using ANSYS software.The distribution of magnetic field,eddy current and force density under different coupling conditions of primary and secondary is analyzed,as well as the variation characteristics of thrust,normal force,primary current and inductance under different missing length.Next,considering the special structure and end effect of linear induction motor,the motion model and electromagnetic field analysis model with the discontinuous secondary are proposed,and the distribution of magnetic field and eddy current is analyzed in depth.On this basis,the segmented equivalent circuit is proposed.Combined with the magnetic density,eddy current distribution model and the coupling of primary and secondary,the influence of coupling zone length change and longitudinal end effect on equivalent circuit parameters is analyzed comprehensively,and the equivalent circuit based on magnetic density distribution is proposed.The dynamic curves of thrust and efficiency by the two methods are calculated and compared with the experimental results.Then,according to the previous research on the electromagnetic characteristics and equivalent circuit of the motor,based on the secondary field oriented vector control,the anti-impact control strategy is proposed.Use optimization strategy: find out the optimal secondary flux and primary q-axis current command to minimize the mutation of primary current and normal force.Using piecewise linearization strategy: according to the relative position of primary and discontinuous secondary plates,the working condition with the discontinuous secondary is piecewise linearized,and the parameters of PI controller are dynamically adjusted.The simulation results show that the anti impact control strategy can effectively reduce the impact of current and force with the discontinuous secondary.Finally,the structure composition and design process of the test platform are introduced in detail. |
