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In this paper, the influence of stator teeth deformation on electromagnetic force and acoustic noise of claw pole alternators was investigated. The characteristics of stator teeth deformation caused by welding and assembly were first illustrated, and the influence of stator teeth deformation on the frequency and spatial order of electromagnetic force harmonics was deduced analytically. Then the electromagnetic forces of three alternators with different stator teeth deformation types were simulated by the finite element method, and compared with the electromagnetic force of nominal alternator. In addition, a multi-physics simulation model was established and the electromagnetic noise of the above three different stator teeth deformation alternators was calculated. Finally, the changes in phase current and output current of claw pole alternator with and without stator teeth deformation were analyzed. The analysis results were verified by back-EMF bench test and noise bench test. Results showed that although stator teeth deformation would not change the frequency components of the electromagnetic force, but would generate additional electromagnetic force harmonics. When the number of deformed teeth was not an integer multiple of the rotor pole-pair number, the electromagnetic force harmonics with extra spatial order would appear. [ABSTRACT FROM AUTHOR]

This paper proposes a novel simulation method to analyze the characteristics of the electromagnetic noise of claw pole alternators under stator winding interturn short circuit faults. For the two types of faults: short circuit between two wires of the same phase and short circuit between turns of the same wire, a general circuit model built in Matlab/Simulink was introduced to obtained the phase current and output current signals. The phase current was then used as current source and the claw pole alternator was simulated as an electric motor rather than a generator to analyze the magnetic force and electromagnetic noise by using 3-D finite element method and boundary-element method, respectively. A noise bench test was conducted to verify the simulation results. It is shown that under the stator winding interturn short circuit faults, the output current harmonics and electromagnetic noise of the three-phase 12-pole/36-slot claw pole alternator would increase greatly. The 12th order noise replaces the 36th order noise as the most dominant order noise at low speed. The method proposed in this paper can also be used to diagnose the stator winding interturn short circuit faults of claw pole alternators. [ABSTRACT FROM AUTHOR]

• The navigation line fitting error can be reduced by post-processing methods. • Getting accurate navigation paths requires precise classification of seedling points. • Based on the seedling point information, a navigation path can be obtained. Compared to tillage, transplanting, and harvesting operations in paddy fields, field management operations such as spraying and weeding require completing tasks along the rice seedling rows to minimize seedling damage and reduce operational losses. Visual navigation, as a commonly used navigation method, can identify rice seedling rows, but it is susceptible to complicated paddy field environments. To address these challenges, our study combines UAV (unmanned aerial vehicle) surveying technology with the YOLOv5s object detection algorithm and proposes a navigation method for paddy field management based on seedling coordinate information. Firstly, the YOLOv5s object detection algorithm was used to identify and locate rice seedling points in the UAV image, and a coordinate transformation model was established to extract the geographic coordinates of the seedling points. Secondly, in order to classify the recognized seedling points into different seedling rows, a classification algorithm was proposed, and the improved RANSAC algorithm further promoted the classification effect. Once again, to obtain a smooth navigation path for agricultural machinery navigation, B-spline curves were used to approximate the classified seedling points. Finally, the generated navigation paths were written into the navigation controller, and the navigation performance was tested on flat ground and paddy fields using a vehicle platform. The results of the flat ground test indicated that different bending degrees have a significant impact on the lateral error. When the bending degree was large, the maximum lateral error was less than 7 cm, and when the bending degree was small, the maximum lateral error was less than 4 cm. The navigation accuracy of RMS in the flat ground test was 2.7 cm. In the paddy field experiment, due to the influence of loose soil surfaces and potholes, the maximum lateral error was about 16 cm. The navigation accuracy of RMS in the paddy field experiment was 5.9 cm, which can meet the operational requirements. The experimental results show that the proposed navigation method can achieve automatic navigation of agricultural machinery along curved rice seedling rows under complex paddy field environments, such as light change, seedling shortage, uneven road surfaces, and curved seeding rows. [ABSTRACT FROM AUTHOR]

The electromagnetic noise of a claw pole alternator is minimized by rotor claw chamfering in this paper. Taguchi method was first applied to evaluate the importance of all of the six chamfer parameters on the output current and the main magnetic force harmonic, and three strongly influential parameters were later selected. Subsequently, the mathematical models of the output current and the sound power level with respect to the three chamfer parameters were developed using the response surface method. Finally, the three parameters were further optimized using the genetic algorithm. A prototype of the optimally designed claw pole alternator was manufactured and its performance was tested. Results show that the rotor claw chamfer does not decrease the output current but can reduce the noise significantly. The sound power level is decreased by more than 15 dB(A) after optimization. The trailing edge chamfer is better than the leading edge chamfer regarding noise reduction. [ABSTRACT FROM AUTHOR]

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 2p‐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 [±2mpk′ + (±kp)]fr (k′ = 0, 1, 2, 3 ...). The main order (frequency domain) of electromagnetic noise is 2mp which is independent of the slot number. [ABSTRACT FROM AUTHOR]

Soil dynamics has been the core of studying the mechanism of soil-tool interaction. However, it is very challenging to study the dynamics of paddy soil that contains a significant amount of water. In this study, a paddy soil model, namely coupling model was developed using the CFD-DEM coupling method. In the coupling model, spherical particles with Johnson-Kendall-Roberts (JKR) surface energy were used to represent paddy soil. The Volume of Fluid (VOF) gas-liquid two-phase flow model was used to represent the characteristics of the water in paddy field. A test and a simulation of soil rotation were performed to calibrate the critical model parameter of soil particle, JKR surface energy. The calibrated value was 2.5 J·m−2, and the relative average error between the simulation and the test was 1.27 %. To verify the accuracy of the coupling model, an experiment of a fertilizer banding opener was conducted in a paddy soil in laboratory conditions. Also, the interaction of the opener with paddy soil was simulated using the coupling model. Then, soil disturbance characteristics and the soil resistance force of the opener were compared between the experiment and model prediction. When using the coupling model to predict, the relative errors were less than 10 % for soil disturbance characteristics and less than 15 % for soil resistance force. This suggests that the model developed using the CFD-DEM coupling method is able to predict the dynamics of soil-tool interaction in paddy fields with reasonably good accuracies. • A coupling model was developed based on the CFD-DEM coupling method. • The calibrated model parameter, JKR surface energy, was 2.5 J·m−2. • The model was validated using an experiment of a fertilizer-banding opener. • The model can predict soil disturbance characteristics and resistance adequately. [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]

A feeding experiment was conducted to determine the optimum selenium requirement in juvenile Nile tilapia. Each of six purified diets with Se‐methionine levels at 0.05, 0.21, 0.41, 0.57, 0.79 and 1.00 mg/kg was assayed in triplicate with initial body weight of 3.00 ± 0.01 g for 8 weeks. The growth of fish was obviously increased when the dietary Se was less than 0.57 mg/kg diet and reached a plateau when the dietary Se was ≥0.57 mg/kg. Serum and hepatopancreatic glutathione peroxidase (GPx) activity increased markedly when the dietary Se was less than 0.57 mg/kg, but then decreased when the dietary Se was higher than 0.57 mg/kg. The malondialdehyde contents in hepatopancreas were significantly decreased when the dietary Se was higher than 0.79 mg/kg. No significant differences were observed in hepatopancreatic total antioxidant capability (T‐AOC) among the groups (p >.05). The results of this study indicated that Se addition as Se‐methionine was essential, while both the deficiency and excess levels of dietary Se would cause negative effects on growth or antioxidant capability in juvenile Nile tilapia. Based on broken‐line regression of WG and piecewise regression of liver GPx, the optimum requirement of Se for juvenile Nile tilapia is 0.57 mg/kg diet. [ABSTRACT FROM AUTHOR]

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 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 (2p) and slot number (Qs) show lower noise level and for the motors that satisfy LCM(2p,Qs) ≠ 6p, vibration and noise are greatly influenced by load. This study provides guidance for the design of low noise AFWMs. [ABSTRACT FROM AUTHOR]

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]