A multiphysics simulation model that consists of electromagnetic field, mechanical field, and acoustic field was established to predict the electromagnetic vibration and noise of claw pole alternators. First, magnetic force exerted on the stator inner surface was calculated by three-dimensional (3-D) transient electromagnetic field analysis and the characteristic of magnetic force was analyzed. Second, finite-element modal analysis of alternator assembly was conducted while taking into account the anisotropy of the stator core and armature winding and the installation condition. Simulation result was validated by modal test. Afterward, magnetic force was transferred to the structural mesh using mesh mapping method and the vibration and noise were predicted by using mode superposition method and boundary-element method, respectively. Simulation results agree well with those measured by experiments. Finally, the mechanism of electromagnetic vibration and noise of the claw pole alternator was revealed with the help of 2-D Fourier transform of magnetic force and the mode participation factor of each mode. Results show that for three-phase 12-pole/36-slot claw pole alternator, electromagnetic vibration, and noise are mainly caused by the zeroth-order (circumferential spatial order) force harmonics whose frequencies are 36kfr (k = 1, 2, 3,...) and the sixth-order (circumferential spatial order) force harmonics whose frequencies are (36k ± 6)fr (k = 1, 2, 3,...).

This study provides a detailed finding of the influence of pole and slot combinations on vibration and noise in external rotor axial flux in‐wheel motors (AFWMs). Firstly, electromagnetic force exerted on the surface of permanent magnet is discussed and a two‐dimensional fast Fourier transformation is implemented to analyse its spatial distribution and frequency characteristics. Then, a multiphysics model is developed to predict the vibration and noise and figure out the main origin from the perspective of electromagnetism. The influence of pole and slot combinations on vibration and noise is also analysed via the proposed model. Finally, the effect of load on vibration and noise in AFWMs is further investigated. It turns out that zeroth spatial order of axial electromagnetic force is the main origin of vibration and noise in axial flux motors, which is quite different from radial flux motors. Moreover, AFWMs with larger lowest common multiple (LCM) of pole number (2 p ) and slot number ( Q _s ) show lower noise level and for the motors that satisfy LCM(2 p,Q _s ) ≠ 6 p , vibration and noise are greatly influenced by load. This study provides guidance for the design of low noise AFWMs.

As internal combustion engine in automobile operates much quieter than before, the noise emitted by claw-pole alternator becomes more non-negligible. To address this problem, the magnetic force, which caused acoustic noise, was analyzed. Force harmonic relevant to the noise peak was identified and set as an optimization object to weaken. The influence of each rotor structural parameters on the force harmonic and output current was analyzed, and the four most influential parameters were chosen as the optimization variables. With the genetic algorithm, an optimum rotor shape generating minimum force harmonic, without severely deteriorate the output performance of the alternator, was obtained. Calculated by the noise predicting model which was verified by experiment, acoustic noise produced by the optimized claw-pole alternator was 14.3 dB (A) less than the initial one, with the output current decreased within 5 percent.

This study analysed the characteristics of electromagnetic force and noise of claw pole alternators with different pole and slot combinations and different phase number. The magnetic flux density in the airgap was first derived based on the magnetomotive force and permeance. Then the electromagnetic force was obtained using Maxwell stress tensor method. According to the analytical model, the spatial order and frequency of electromagnetic force can be expressed as the function of pole‐pairs number p , slot number s and phase number m . Afterwards, the electromagnetic noise of three different alternators was tested in a semi‐anechoic chamber. Combined with the 2D fast Fourier transform of electromagnetic force, the main force harmonics that caused the electromagnetic noise were distinguished. Finally, the relationship between the frequencies of electromagnetic force and noise and the number of pole‐pairs and phase were established. Analysis result shows that for m ‐phase 2 p ‐pole/ s ‐slot integer slot claw pole alternators, the spatial order of electromagnetic force is kp ( k = 0, 1, 2, 3,…) and the corresponding frequency of these force harmonic is [±2 mpk ′ + (± kp )] f _r ( k ′ = 0, 1, 2, 3 …). The main order (frequency domain) of electromagnetic noise is 2 mp which is independent of the slot number.

Soil texture is a significant attribute of soil properties. Obtaining insight into the soil texture is beneficial when making agricultural decisions during production. Nevertheless, assessing the soil texture in specific laboratory conditions entails substantial dedication, which is time-consuming and includes a high cost. In this paper, we propose a soil texture detection network by embedding the frequency channel attention network and a texture encoding network into the representation learning paradigm of the ResNet framework. Concretely, the former is reliable in exploiting the feature correlations among multi-frequency, while the latter focuses on encoding feature variables, jointly enhancing the ability of feature expression. Meanwhile, the clay, silt, and sand particles present in the soil are exported through a ResNet18 fully linked layer. Experimental results show that the correlation coefficient for predicting clay, silt, and sand content are 0.931, 0.936, and 0.957, respectively. For the root mean square error, the quantitative scores are 2.106%, 3.390%, and 3.602%, respectively. The proposed network also exhibits proposing generalization capability, yielding quite considerable results on different soil samples. Notably, the detection results are almost in agreement with the conventional laboratory measurements, and, at the same time, outperform other competitors, making it highly attractive for practical applications.