| Permanent magnet synchronous linear motor(PMLSM)is widely used in laser cutting machine and the field of precision CNC machine tools because of its simple structure,direct drive mode,high acceleration and high precision.However,due to the structural reasons of linear motor itself,there are drawbacks of thrust ripple,which can easily cause speed oscillation,vibration and noise,and thus deteriorate the motor's motion performance,which seriously affect the accuracy of machine tool processing.Therefore,it is necessary to suppress the thrust ripple of PMSLM in order to ensure the accuracy and stability of motor operationIn this paper,the motion and structure characteristics of coreless dual-secondary PMSLM are analyzed,and the analytical model of motor thrust and thrust ripple is established.Based on the structural analysis and analytical results of PMSLM,two kinds of external restraint structures are designed:viscoelastic damping structure and electromagnetic damping-spring structure.The restraint theory of external restraint structure is deduced,and the restraint effect of thrust ripple is verified by simulation and experiment.For the linear motor studied in this paper and its two external restraint structures,the following research has been carried out:(1)The topological structure and winding characteristics of PMSLM are introduced.The air gap magnetic density and inductive electromotive force of PMSLM are analyzed by equivalent magnetization method.The analytical model of PMSLM thrust is established.The analytical formula of thrust fluctuation is expressed by Fourier series expansion.Combining with the topological structure and motion characteristics of PMSLM,two external restraint structures,viscoelastic damping structure and electromagnetic damping-spring structure,are designed to restrain thrust fluctuation.(2)According to the designed viscoelastic damping suppression system,under the excitation of thrust fluctuation,Kelvin model is introduced to establish the analytical model of viscoelastic damping force,and the correctness of theoretical analysis is verified by finite element method.Combined with the PMSLM thrust and viscoelastic damping force,the compound thrust of motor after viscoelastic damping is obtained.The composite thrust and motor thrust is simulated to verify the effectiveness of viscoelastic damping structure in suppressing thrust ripple.The prototype motor and viscoelastic damping structure are made,and the experimental platform of viscoelastic damping suppression system is built,which further verifies the feasibility of viscoelastic damping structure.(3)Considering the disadvantages of viscoelastic damper,such as large friction and short stroke,an electromagnetic damper-spring system is designed.PMSLM and electromagnetic damper-spring are integrated design.The thrust ripple is the excitation of the restraining system.The analytical expressio'ns of electromagnetic damping force and elastic force are established by using the principle of virtual work and Hooke's law respectively.Com'bining the expressions of electromagnetic damping force and elastic force,the restraining force of the electromagnetic damping spring restraining system is obtained,and the dynamic model of the restraining system is established.Combined with the PMSLM thrust and electromagnetic damping force,the compound thrust of motor after viscoelastic damping is obtained.The simulation of PMSLM thrust and composite thrust verify the effectiveness of the electromagnetic damping-spring system,and further optimize the structural parameters of the electromagnetic damping-spring system to achieve the best suppression effect.(4)PMSLM prototype and electromagnetic damper-spring structure are manufactured.Thrust fluctuation tests under different load and speed conditions are carried out respectively.The experimental results are analyzed to verify the effectiveness of the electromagnetic damper-spring suppression system. |
PDF Full Text Request