This work presents the analytical model of H-type linear permanent magnet eddy current brakes (H-type LPMECB). In the presented paper, firstly, the analytical model of the H-type LPMECB was established using the equivalent magnetic circuit method. Secondly, the braking performance of the H-type LPMECB was simulated with the Finite Element Model(FEM) and the analytical model, respectively. The analytical model performance results are consistent with those of the FEM, which validates the analytical model. Hereafter, the nonlinear relationship between the iron foils number of the H-type LPMECB and the braking force was found by the analytical model and the FEM, which provides a guide for the iron foil number selection in future work. Finally, the experimental results are in agreement with the results obtained from the simulations, which also proves the analytical model and the simulation results.
The wall-thinning defect is one of the critical flaws that have been posing a severe threat to the structural integrity of Glass Fibre Reinforced Polymer (GFRP) employed in the hostile environment. In this paper, a sweep-frequency microwave testing method based on Cross-polarization Microwave Reflectometry (CMR) is proposed for detection and imaging of subsurface wall-thinning defects in the unidirectional GFRP. The simulation model of CMR is established along with the scrutinization of the characteristics regarding the testing signal in Ka band (26.5 GHz∼40 GHz). In experiments, a microwave testing system is built up for inspection of GFRPs together with the CMR probe designed using a pair of Ka-band rectangular waveguides based on the simulation model. Imitative subsurface wall-thinning defects and an actual impact defect in GFRP samples are inspected by using the system, and further imaged by using the time-domain signal and Range Migration Algorithm (RMA). The superiority of the proposed method is quantitatively identified through comparison of the signal-to-noise ratio of the imaging result between the CMR and the single-polarization microwave reflectometry.
Touch is important for perceiving the shape and texture of objects. Therefore, its mechanism is utilized in sensors on robots and tactile presentation in virtual reality. However, the mechanism of human tactile perception has not been fully elucidated, although various perceptual phenomena have been confirmed. For example, the hardness and softness (HS) sensation is caused by humans perceiving differences in the rigidity and elasticity of objects; however, this can change depending on the surface properties (called tactile illusion). The purpose of this study was to clarify the HS sensation perception mechanism by focusing on tactile illusion. First, a sensory evaluation was conducted using five samples with the same Young’s modulus but different roughness values. Simultaneously, the contact force and fingertip velocity were measured. The experimental conditions were as follows: the touching motion was a stroking motion; elastic silicone rubber and rigid resin samples were used; and the sensory evaluation was repeated three times to consider the variations in the subjects’ evaluations. As a result, the subjects experienced differences in the HS sensation of samples with different roughness for both samples. For the silicone rubber sample, the microstructural deformation of the sample surface was related to the HS sensation. For the resin sample, the difference in slippage resistance was related to hardness sensation . Therefore, it was found that changes in several physical phenomena occurred when perceiving the HS sensation and that the evaluation criteria changed depending on the presence of deformation.
When addressing higher-order modes, it becomes crucial to adjust the nodal arrangement significantly to simultaneously achieve high accuracy and computational speed. In these scenarios, the meshless method, utilizing only nodes, emerges as a suitable approach. This study illustrates the adaptation of the meshless method to eigenvalue problems encountered in modal analysis, with a specific emphasis on condition numbers and spurious solutions.
The output performance of stick-slip piezoelectric actuators is comprehensively determined by the electro-mechanical responses of the driving unit, control strategy, and the contact status between the driving unit and the slider. Most previously developed inertial piezoelectric actuators face the problems of frequency dependence, motion speed, excessive volume, step resolution, and loading capacity. To exhaustively improve actuation performance, we propose a compact bi-directional piezoelectric-based rotary actuator incorporating the single excitation source, rhombic amplification mechanism, and adjustable preload. The numerical simulations are implemented based on the LuGre friction model, to guide the system optimization. A prototype is fabricated and examined, which accomplishes the maximum load torques of 27.78 and 30.87 N.mm in clockwise and anticlockwise directions, respectively, at the highest rotational velocity of 0.4720 rad/s. Compared with previously reported inertial actuators, the performance of the proposed actuator is significantly enhanced, promising in applications requiring nanometer resolution, long stroke, large holding, and driving forces.
Magnetostriction of electrical steel sheet used in transformer core is one of the main causes of transformer vibration and noise, which is more serious in the case of DC bias. The vibration and noise of transformer core under DC bias are studied in this paper. Firstly, B-H and B-λ of electrical steel sheet is tested under DC bias. Secondly, based on the Preisach model, the hysteresis model of electrical steel sheet under DC bias is derived, and describes the influence of DC component on hysteresis model. Thirdly, the vibration and noise of transformer under DC bias are simulated by FEM. The calculation results under different DC bias conditions are obtained. Finally, the vibration noise of transformer is studied experimentally, and the accuracy of simulation results is verified. This work supplements the derivation of Preisach model under DC bias and provides a basis for designers to understand the vibration and noise characteristics of transformer under DC bias.
This work presents a novel non-contact sensor system for non-conductive materials, aiming to address the limitations of traditional nondestructive evaluation (NDE) techniques. The research focuses on the development of an Electromagnetic Acoustic Transducer (EMAT) that can excite elastic waves in non-conductive samples using two configurations (a) direct and (b) induced. Unlike conventional ultrasonic methods that require physical coupling, the proposed EMAT technique uses patch type of coils to excite waves in a non-contact manner. Numerical simulations were validated experimentally, and the feasibility of generating elastic waves in non-conductive samples were demonstrated. By bridging this gap, the research aims to contribute to the advancement of automated inspection techniques and faster inspection procedures for non-conductive materials.
This paper aims to propose an improved probe for remote field eddy current testing (ECT) method with a ferromagnetic core inserted into coils, and to verify the effect of the improved detection sensitivity. The remote field eddy current testing method which installs an excitation coil and a search coil inside a pipe is known to be effective in detecting external surface defects in ferromagnetic pipes used in petrochemical or steel industries. In previous research, the phase angle between the flux density due to the excitation current and that due to the eddy current inside the pipe, when a magnetic field of several hundred Hz is applied to the excitation coil, was analyzed. It has been clarified that the detection signal sensitivity is reduced because of the phase angle approaches 180 degrees and cancel each flux density out. In this research, an improved remote field ECT probe with ferromagnetic core inserted in coils is proposed to increase the detection signal sensitivity. The measured sensitivity of the proposed probe is increased compared with the conventional one. The mechanism of different shapes and materials are analyzed in detail by using 3D nonlinear eddy current analysis using finite element method (FEM). It was found that that when a core of S45C was inserted in the excitation coil, the phase angle change became larger at the defect position because the phase angle of the flux density due to excitation current is delayed by eddy current in the core which affected the sensitivity improvement.
Carbon fiber reinforced plastic (CFRP) material is a lightweight, high-strength material that takes advantage of the characteristics of carbon fiber and resin. CFRP is widely used in parts that require high strength, such as aircraft and hydrogen tanks. Although it has high strength, receiving a large impact may cause internal peeling or internal defects. Detection of these delamination and defects is important for the strength and quality assurance of CFRP materials. In this research, an inspection method of the CFRP materials using electromagnetic force vibration is proposed. In this method, electromagnetic force vibration is impressed from the surface of the CFRP material with the internal defects, and the defects are estimated from the vibration intensity. When the proposed inspection method is applied to a CFRP plate with the internal defect, since the vibration intensity at the defect location is increased, the defect can be detected.
Energy harvesting, which refers to the generation of electricity from ambient sources using functional materials, has been extensively researched. In this paper, a cylindrical energy harvester that combines anti-vibration rubber and polyvinylidene fluoride piezoelectric film is proposed, and its characteristic evaluation method based on a theoretical model is also proposed. A forced vibration experiment using a servo hydraulic dynamic test system is conducted to determine the power generation characteristics. To evaluate the power generation performance, a characteristic evaluation model is constructed using the transfer matrix method for the governing equation of the longitudinal vibration of a bar. The results are compared with experimental results to verify the accuracy of the characteristic evaluation method.
Multivariate Empirical Mode Decomposition (MEMD) is a powerful tool to analyze nonlinear properties, however, it is very computationally time-consuming. The purpose of this study is to parallelize and accelerate MEMD, and to apply the accelerated MEMD to the analysis of electromagnetic wave propagation in photonic crystals, to improve the efficiency of generation of a demultiplexer. In the proposed method, part of the procedures that do not depend on channels of input signal were parallelized. Speedup which is based on 24 CPU threads of 5.12 times is achieved when 192 threads are adopted.
Influence of channel height, magnetic fluid concentration, Reynolds number and magnetic field intensity on heat transfer of magnetic fluid flow in mini-channel was investigated experimentally. Two mini-channels which has 1 mm and 5 mm of channel height and 1.6 vol% and 3.2 vol% of magnetic fluid are prepared in this study. Reynolds numbers are set to 100, 200 and 300, and magnetic field intensity is varied 100, 300 and 500 mT. The results show that heat transfer is enhanced for 5 mm of channel height by applying strong magnetic field, while heat transfer suppression can be observed for 1 mm of channel height.
This article presents a novel rope-driven antagonistic variable stiffness robot elbow joint based on permanent magnet spring and pulley block. The proposed joint enlarges both the range of motion and stiffness. The structure and working principles of the elbow joint are elucidated, along with the joint stiffness model. The changing pattern of joint stiffness is analyzed, and a controller is devised to decouple the stiffness and position of the joint. Experimental results verify the accuracy of decoupling and showcase the energy-saving characteristics of the joint. Furthermore, the paper investigates the impact of joint stiffness variation on joint position control.
Aiming to implement a more user-friendly powered prosthetic hand, this paper studies the real-time classification of intended hand motions using tactile sensors attached to the skin surfaces of a forearm. The proposed system used only two tactile sensors made of PVDF (polyvinylidene fluoride). Machine learning was applied to the classification of hand motion intentions using the tactile feature patterns. In this paper, we further studied the real-time motion classification methods in an online environment. We found that the average classification accuracy for the 6 types of motion in 8 experimental participants was 83.3 %. Participants reported no perceptible delay, which was also confirmed through video analysis. In conclusion, we showed real-time motion classification is possible by using two PVDF tactile sensors with simple training lasting for only several minutes.
The 3-D stray-field loss of the upgraded benchmark model TEAM P21e with the two-sided excitation (ADH2) under various complex harmonic and DC-biased magnetization is analyzed by the 3-D fixed-point harmonic-balanced finite element method using parallel computing. The calculated results of the stray-field loss are in good agreement compared to the measured results. It is shown that the AC source has a larger effect on the total stray-field loss than the DC source. The efficiency of the 3-D fixed-point harmonic-balanced method with parallel computing is analyzed and can be potentially improved by 60%.
For a proper application of the Kirchhoff migration algorithm for identifying small object in microwave imaging, complete elements of the scattering matrix must be collected. However, it is very hard to measure the diagonal element of scattering matrix in some real-world microwave imaging. In this paper, we set the diagonal elements as a fixed constant, apply the KM for imaging small objects, and theoretically show that zero constant choice guarantees good imaging results. Simulation results with synthetic and Fresnel experimental data are exhibited to verify the theoretical result and effect of constant choice.
According to statistics, short circuit faults in transformer windings account for 70% to 80% of the total faults. Therefore, the study of the short circuit withstand capability of transformers holds significant importance. This paper focuses on investigating the winding deformation and short circuit strength of a ODFPS-700000/750 single-phase four-column transformer during high-medium voltage operation and low-voltage side short circuit conditions. The influence of pads and struts offset on various aspects of windings is considered during the implementation. The paper presents the distributions of magnetic leakage field, current, winding deformation displacement, and electromagnetic forces under transformer short circuit conditions. This provides a novel approach for the verification of short circuit strength in large-scale transformer windings.
The positioning error of a linear feed system has a significant impact on the machining quality of parts. Thermal error is one of the main factors affecting machining accuracy. The error compensation method is an economically effective approach to improving positioning accuracy. The main problem is to establish an error model for error compensation to improve measurement accuracy. This paper proposes using the particle swarm optimization algorithm (PSO) to optimize the long short-term memory network (LSTM) and establish a thermal error model. Comparing PSO-LSTM with traditional LSTM and BP methods, the results show that the accuracy of the PSO-LSTM model reaches 99.76%. This model is practical for real-time comprehensive error compensation and can accurately reflect the feed axis’s comprehensive positioning error change trend under various working conditions.
To improve the cornering performance of a yaw moment control system that assists the self-spinning motion of a competition vehicle, in this paper, we propose a vehicle subjected to electric motor drive torque and brake torque using an actuator. This system is expected to improve the vehicle’s dynamic performance by allowing a rear brake system installed in the right and left tires to be individually actuated. Quasi-static vehicle dynamics analysis of a vehicle equipped with the proposed system was conducted to investigate the improvement of vehicle performance due to active yaw moment changes as a preliminary step to developing control laws for the proposed system. The results of the analysis showed that the maximum steady-state lateral acceleration at a constant vehicle velocity could be improved by 13% by evaluating the cornering performance of the vehicle with and without the system. The required yaw moment change was calculated, and the electric motor torque and actuator force were calculated to satisfy these requirements.
The optical loads on high-resolution satellites are very sensitive to vibration. Therefore, it is crucial to meet the pointing accuracy and micro-vibration suppression for the optical loads. In this work, a parallel platform with nine legs is designed for integrated micro-vibration and pointing control. The legs include six legs for micro-vibration and three legs for pointing control. Combining the decoupling of micro-vibration and attitude motion, a joint control model is built in Matlab/Simulink. The simulation result shows that the new platform can achieve good performance in both micro-vibration suppression and precision pointing control.
