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Contact bounce is a common phenomenon in the closing process of electromagnetic relays, which seriously affects the electrical contact reliability of the system. The whole closing process of flexible spring components consists of the free movement stage and the contact bounce stage, which increases the complexity of analyzing the electrical contact behaviors of electromagnetic relays. In this study, a novel nonlinear dynamic model of the flexible spring components in electromagnetic relays is established to analyze the physical mechanism of the electrical contact bounce. Considering the electromagnetic effect, flexible deformation, contact collision, and welding force, the proposed mathematical model can capture the dynamic closing process accurately and collect bounce parameters efficiently. The Kelvin–Voigt viscoelastic contact model is employed to evaluate the nonlinear contact force between the static and movable contacts. Based on the Galerkin method, the nonlinear equations of motion for the movable spring within electromagnetic relays are formulated. A series of experimental work are designed to measure the typical waveforms of displacements of the movable contact and currents in the coil during the closing process of the movable spring. Furthermore, the theoretical results are validated by comparing with the experimental data. The dependences of some key factors, including the structural, material, and electrical contact parameters on the contact bounce characteristics, are investigated explicitly. The theoretical results attest that the proposed model can accurately predict the dynamic behaviors of the movable spring, and the contact bounce can be effectively suppressed by adjusting the parameters of the flexible spring component. [ABSTRACT FROM AUTHOR]

There are various challenges in designing a life-cycle robust permanent magnet actuator (PMA) to satisfy the application-oriented requirements of quality consistency. In particular, ubiquitous uncertainties from manufacturing and operating process that cause unstable or even infeasible solutions significantly increase the difficulty of the life-cycle robust design of PMA. Conventional methods usually treated these uncertainties as fixed design constraints, which neglect the nonlinear characteristic of time-dependent degradations, cannot reflect authentic impacts on the life-cycle robustness of PMA. To address this issue, this study propose a method of life-cycle dynamic robust design optimization for batch production PMA. An innovative time-dependent global sensitivity analysis-based classification method is first proposed to divide design variables into three categories: nonlinear, degradation insensitive, and degradation sensitive variables. Then, a modified Spatiotemporal Kriging model with Karhunen-Loeve expansion is applied to establish the life-cycle robustness model of PMA with consideration of uncertainties. This model can valid describe the nonlinear fluctuation of the life-cycle robustness. Furthermore, on the basis of the three categories of design variables and life-cycle robustness model, a multistage dynamic robust design optimization strategy is derived, which realizes the synchronous control of life-cycle robustness deterioration rate (mean value) and fluctuation (standard deviation). Finally, taking a case of rotary PMA, the effectiveness of the proposed method is verified. [ABSTRACT FROM AUTHOR]

Conventional electromagnetic acoustic transducers (EMATs) are generally only used to generate and detect guided waves with a single wavelength, which increases their sensitivity at that particular wavelength but limits their application scenarios and the accuracy of defect assessment. This article proposes a design method for multiwavelength EMATs based on spatial-domain harmonic control. First, the EMAT model is analyzed, where it is then outlined that the eddy-current density distribution of the specimen is equivalent to the spatial low-pass filtering of the coil-current density distribution. This shows that the multiwavelength guided waves can be achieved as long as the spatial distribution of the coil-current density contains those multiple harmonics that are desired. It is then proposed that the structure of the EMAT coil is equivalent to the spatial sampled pulse sequences of a spatial signal. The coil parameter design based on pulse modulation technology is proposed. Taking a dual-wavelength EMAT design for Lamb waves as an example, details of the coil parameter design are presented. The simulation and experiment with the dual-wavelength EMAT proved the correctness of the proposed method. Finally, an experiment with a three-wavelength EMAT demonstrated the feasibility of the proposed method in designing multiwavelength EMATs. [ABSTRACT FROM AUTHOR]

Contact bounce is a common phenomenon in the closing process of the electromagnetic relay under capacitive loads. The investigations on the contact characteristics are mainly conducted by experimental methods. However, the experimental method is extremely complicated and time-consuming in structural design, and it cannot clearly reveal the mechanism of contact bounce. Therefore, a new theoretical model is proposed to investigate the dynamic characteristics of the electromagnetic relay under capacitive loads. The model allows for simulating dynamic process and collecting bounce parameters in a simple and effective way compared with conventional simulation and experimental methods. The physical mechanism of contact bounce for the electromagnetic relay is presented. The nonlinear contact force between the fixed and moving contacts is evaluated according to the Kelvin–Voigt viscoelastic contact model. The equations of motion considering the coupling of electromagnetic and mechanical fields are established. The theoretical results obtained in this study are validated by comparison with experimental data. The influences of the structural parameters, coil current, surge current, and contact resistance on the contact bounce are analyzed. The numerical results well demonstrate that the contact bounce can be effectively weakened by adjusting the parameters of contact spring and the mass of the moving contact. [ABSTRACT FROM AUTHOR]