Effects and Prospects of the Vibration Isolation Methods for an Atomic Interference Gravimeter

An atomic interference gravimeter (AIG) is of great value in underwater aided navigation, but one of the constraints on its accuracy is vibration noise. For this reason, technology must be developed for its vibration isolation. Up to now, three methods have mainly been employed to suppress the vibration noise of an AIG, including passive vibration isolation, active vibration isolation and vibration compensation. This paper presents a study on how vibration noise affects the measurement of an AIG, a review of the research findings regarding the reduction of its vibration, and the prospective development of vibration isolation technology for an AIG. Along with the development of small and movable AIGs, vibration isolation technology will be better adapted to the challenging environment and be strongly resistant to disturbance in the future.

Tunability for anomalous refraction of flexural wave in a magneto-elastic metasurface by magnetic field and pre-stress

This letter reports the design of a magneto-elastic metasurface composed of arrayed Terfenol-D pillars deposited on a homogeneous Aluminum plate, aiming to realize the tunability of flexural wave anomalous propagation without altering the structure. Considering the magneto-mechanical coupling of magnetostrictive materials, the phase shift and transmission of functional unit can be calculated. The anomalous refraction of incident flexural wave (i.e., negative refraction) can be accomplished by adjusting magnetic field and pre-stress properly, the refraction angle is remarkably affected by magnetic distribution. The proposed metasurface provides a method for flexible tunability of elastic wave in the fields of vibration/noise control.

Characteristic Analysis and Experimental Verification of Electromagnetic and Vibration/Noise Aspects of Fractional-Slot Concentrated Winding IPMSMs of e-Bike

In this study, we performed the electromagnetic and mechanical characteristic analyses of an 8-pole 12-slot interior permanent magnet synchronous motor (IPMSM). Permanent magnet synchronous motors are classified into surface permanent magnet synchronous motor and interior permanent magnet synchronous motors according to the type of rotor. The IPM type is advantageous for high-speed operation because of the structure where the permanent magnet is embedded inside the rotor, and it has the advantage of having a high output density by generating not only the magnetic torque of the permanent magnet, but also the reluctance torque. However, such a motor has more vibration/noise sources than other types, owing to changes in reluctance. The sources of motor noise/vibration can be broadly classified into electromagnetic, mechanical, and aerodynamic sources. Electromagnetic noise sources are classified into electromagnetic excitation sources, torque pulsations, and unbalanced magnetic forces (UMFs). Vibration and noise cause machine malfunctions and affect the entire system. Therefore, it is important to analyze the electromagnetic vibration source. In this study, the electromagnetic characteristics of an IPMSM were analyzed through the finite element method to derive the UMF. Vibration and noise analyses were performed by electromagnetic–mechanical coupling analysis, and vibration and noise characteristics based on electromagnetic noise sources were analyzed.

Control algorithm to improve the vibronoise characteristics of synchronous multi-phase magnetoelectric electric drive

Vibrations and noises occur during the operation of synchronous motors. To reduce them, more advanced engine designs and special control algorithms are used. The application of a multiphase (m > 3) synchronous motor design allows you to influence the configuration of the magnetic field in a wider range. Thus, the task to develop a control algorithm that improves the vibration-noise characteristics of a multiphase motor is relevant. The finite element method is used to calculate the magnetic field in a 2D formulation, implemented in the Elcut software package. Also, the simulation methods with the MatLab Simulink package are applied. The authors suggest the algorithm to control multiphase synchronous motors with permanent magnets that reduces the level of vibrations. Improvement of vibration-noise characteristics is achieved when the motor is supplied with currents of the certain form, and they compensate the pulsation of electromagnetic forces that occur between various parts of the electric machine. This algorithm is based on the measurement of the electromagnetic forces and the torque directly in the process of control. The results of modeling the operation of the engine with the developed control algorithm are presented. The authors have compared the characteristics obtained using the developed control algorithm and the characteristics that correspond to the sinusoidal source supply. The vibration-noise characteristics of a permanent magnet synchronous motor can be improved by using the control system. This control system generates currents in an appropriately synthesized form. In this case, the power consumption will increase slightly.

Vibration Compensation for a Vehicle-mounted Atom Gravimeter

The performance of the absolute atom gravimeters used on moving platforms, such as vehicles, ships and aircrafts, is strongly affected by the vibration noise. To suppress its influence, we summarize a vibration compensation method utilizing data measured by a classical accelerometer. The measurements with the accelerometer show that the vibration noise in the vehicle can be 2 order of magnitude greater than that in the lab during daytime, and can induce an interferometric phase fluctuation with a standard deviation of 16.70π. With the compensation method, our vehicle-mounted atom gravimeter can work normally in these harsh conditions. Comparing the Allan standard deviations before and after the vibration noise correction, we find a suppression factor of 22.74 can be achieved in static condition with an interrogation time of T = 20 ms, resulting a sensitivity of 1.35 mGal/Hz1/2, and a standard deviation of 0.5 mGal with an average time of 10 s. We also demonstrate the first test of an atom gravimeter in a moving vehicle, in which a suppression factor of 50.85 and a sensitivity of 60.88 mGal/Hz1/2 were realized with T = 5 ms.

Recent Patents on Ball Bearing

Background: Ball bearings are widely used in industry. They are core components of mechanical equipment. The research on the structural improvement of ball bearings is beneficial to enhancing the performance of bearing. Comparing with traditional structure, novel ball bearing has brought a lot of advantages and solved many problems in the working. Objective: The study aims to report the latest research on the structure of ball bearings and provides a reference for scholars and engineers. Methods: This paper reviews various representative patents related to ball bearings in principal aspects, such as lubrication, sealing, temperature, vibration, noise, and intelligence. Results : Through retracing the characteristics of different types of ball bearings, the main existing problems in the current situation are summarized and analyzed. The future development of patents on the structure of ball bearing is discussed. Conclusion: The structural improvement of ball bearing is conducive to the development of bearing technology. Ball bearings with characteristics of simple structure, intelligence and integration will have a good prospect in the future.

A new approach to monitor wear tracks propagation on-site with electromechanical impedance technique

Generally, the determination of the wear in the mechanical systems is done by checking the critical components in periodic maintenance or by monitoring the secondary indicators such as vibration, noise, and temperature. These indicators can only be recognized after the wear reaches a certain level. In this study, an approach has been carried out on the use of the electromechanical impedance (EMI) method. In this study, EMI measurements were carried out depending on the different test samples, representing a different amount of wear level and wear location of the AISI 1040 steel block. The test samples were worn out in a controlled laboratory environment. The impedance measurements were taken before and after wear tests for each sample. Different measurements were made, and damage metrics were calculated and compared with the reference measurement made; the amount of the wear could be monitored primarily using the Root Mean Square Deviation (RMSD) method without dismantling the system. The location of wear could be determined by Correlation Coefficient Deviation (CCD) technique. In this study, it has been demonstrated that it could be possible to monitor the progress of wear in sensitive mechanical systems periodically without disturbing the integrity of the machine system.

A Method Combining Fractal Analysis and Single Channel ICA for Vibration Noise Reduction

Aiming at the problem that real engineering vibration signals are interfered by strong noise, this paper proposes a method combining single channel-independent component analysis (SCICA) and fractal analysis (FD) to reduce the effect of noise on the time-frequency analysis of vibration signals. First, phase space reconstruction is performed on the vibration signal to make the proper input for ICA algorithm. The original is then decomposed into several component signals. The fractal dimension of each component signals is calculated to determine whether the signal should be considered noise. Noisy component signals are then processed by wavelet denoising. Finally, the output signal after noise reduction is reconstructed using the filtered “right” component signals. This paper uses the method to analyze real noisy vibration signal. Experimental results show the effectiveness of the proposed method.