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In this paper, the characteristics of the electromagnetic noise radiated by an external rotor in-wheel motor (IWM) are investigated with the Doppler effect taken into consideration. First, Maxwell stress tensor method is employed to derive electromagnetic forces on the magnet surface. The effect of common current harmonics is also analyzed. Then, a structural model of the rotor is built and modal test is conducted to validate the model. Nodal forces, which are calculated by finite element method, are transferred from the electromagnetic mesh to the structural model for further vibration prediction. Finally, boundary element method is used to calculate the noise radiated by the rotor. In particular, the Doppler effect is considered. The calculated results are validated by the noise test. It is found that the end cap contributes more to the overall noise than the shell, and obvious sound directivity appears in the noise of the IWM. The noise measured perpendicular to the outer end cap is larger than that measured in other directions. In addition, the Doppler effect would induce additional side-frequency components around high-frequency peaks in the external rotor motor. [ABSTRACT FROM PUBLISHER]

A multiphysics model is proposed to predict electromagnetic noise and analyze sound quality of permanent magnet synchronous motor with a variable speed range. First, a two-dimensional electromagnetic finite element model is built and the current during run-up is tested to serve as the input of the model for force calculation. The force is transferred to structural model and the mode superposition method is used to predict vibration. Then, based on the structural mode information and acoustic transfer vector, noise transfer function between electromagnetic force and sound pressure is established. A balanced efficiency and accuracy of noise calculation during run-up is achieved with this function. Finally, psychoacoustical indices are calculated to evaluate the sound quality with the influence of current harmonics into consideration. The calculated vibration and noise are experimentally validated and the errors of noise level in the whole speed range are all below 4 dB. It is also concluded that current harmonics greatly deteriorate the sound quality. [ABSTRACT FROM PUBLISHER]

This paper first derives the characteristics of radial electromagnetic force considering different types of current harmonics. By using two-dimensional fast Fourier transform, the force calculated by the finite element method is decomposed to obtain the frequencies of the force components in specific spatial order. Then, a multiphysics model for electromagnetic vibration and noise calculation is proposed. A modal test is implemented to validate the equivalent stator model and the nonuniform distribution of electromagnetic force acting on the teeth surface is taken into account through the nodal force transfer method. The calculated vibration and noise agree well with those obtained from experimental test. Finally, vibration and noise under different supply currents are investigated, and the variation patterns of the noise and vibration peaks are explained by the amplitude changes of the lowest spatial order force due to current harmonics. It is found that the influence of current harmonics on vibration and noise depends on their effect on the lowest spatial order force, and in order to figure out this effect, the phase angle, phase sequence, and frequency of current harmonics should all be considered. [ABSTRACT FROM AUTHOR]

Understanding the dynamics during the seedling emergence process has important implications in creating favourable soil conditions for improved plant emergence. In this study, a model was developed using the discrete element method (DEM). The model simulated the emergence process of a canola seedling under six different soil compaction levels (L1 to L6). In the model, soil was represented by 2-mm spherical particles with bonds between particles. The bond parameters were calibrated using experimental data. The calibrated model was used to simulate the dynamics of the emergence process under different soil compaction levels. Depending on the soil compaction level, simulation results show that the calibrated bond normal stiffness is in the range of 3.10e+ 10–5e+ 11 N·m−3. The emerged canola seedling exerted great contact forces to the surrounding soil particles, which produced a dynamic influencing zone in the soil. The influencing zone was greater at higher soil compaction levels. The predicted canola emergence force (the total contact force between seedling and soil particles in the vertical direction) increased with the soil compaction level. The average emergence forces were 4.04, 5.81, 7.59, 8.18, 8.43, and 9.36 N for L1 to L6, respectively. The soil compaction levels (except for L1) were excessive for canola production, as they resulted in unacceptably low emergence rates. The study advances our understanding of the dynamics in the plant emergence process in a micro-scale soil environment. • A model was developed using the discrete element method (DEM). • The model simulated canola emergence process under six soil compaction levels. • The model calibrated using measurements had relative errors of 2.98–12.0%. • The predicted emergence forces of canola seedling varied from 4.04 to 9.36 N. [ABSTRACT FROM AUTHOR]