Huajie Qu

Rolling element bearings are fundamental to the reliability of rotating machinery, yet detecting incipient faults under heavy background noise remains a significant challenge. To address this, this paper proposes a novel diagnostic method termed modulation bispectral slice-based kurtosis (MBSK). The MBSK method begins by applying time–frequency modulation bispectrum to demodulate the vibration signal, transforming it into a two-dimensional time–frequency representation. This process highlights the coupling between resonant bands and modulation frequencies, thereby enhancing key fault signatures while suppressing noise. Subsequently, the harmonic spectral kurtosis (HSK) indicator is introduced to quantify the periodic impulse energy within each modulation frequency slice. Robust identification of the fault characteristic frequency and its harmonics is achieved by analyzing the trend of HSK versus modulation frequency. Simulation and experimental results demonstrate that MBSK effectively extracts fault features from both the outer and inner rings of rolling bearings, maintaining high diagnostic accuracy and stability under strong noise interference. Compared to conventional modulation signal bispectrum methods, MBSK exhibits superior performance in both feature extraction capability and noise immunity.

To solve the drawbacks of conventional long-cycle wear tests for miniature standing- wave linear ultrasonic motors, an accelerated equivalent wear model and test system were proposed in this work. After primary screening of multiple pair materials, graphite and Al₂O₃ were adopted to modify epoxy films. The optimal friction pair is composed of 6061 hard anodic oxidation film and ECA105 composite film. The matched pair exhibits excellent driving stability and low wear loss, with fatigue wear as the main wear form. Graphite and Al₂O₃ exert synergistic anti-wear and load-bearing effects via forming a stable transfer film on the friction interface. Experimental results confirm that the accelerated test is equivalent to a full-life durability test. The presented method and optimized friction pair can effectively guide the development of high-performance ultrasonic motors.

To solve the drawbacks of conventional long-cycle wear tests for miniature standing- wave linear ultrasonic motors, an accelerated equivalent wear model and test system were proposed in this work. After primary screening of multiple friction pair materials, graphite and Al2O3 were adopted to modify epoxy films. The optimal friction pair is composed of 6061 hard anodic oxidation film and ECA105 composite film. The matched pair exhibits excellent driving stability and low wear loss, with fatigue wear as the main wear form. Graphite and Al₂O₃ exert synergistic anti-wear and load-bearing effects via forming a stable transfer film on the friction interface. Experimental results confirm that the accelerated test is equivalent to full-life durability test. The presented method and optimized friction pair can effectively guide the development of high-performance ultrasonic motors.

Ultra-precision measurement and manufacturing need high-precision machines, just as a photolithography machine needs air bearings. In gas lubrication, the use of compound restrictors with recesses has been widely proven to be an effective method to improve stiffness, which directly affects the accuracy of the machine. However, determination of the structural parameters of recesses is lacking in theoretical models. This paper has established a mechanical property model for a small-scale guideway, which can respond to the variation in force caused by micron-level changes in the recesses’ depth. To meet the requirements of high positioning accuracy and movement accuracy, this paper puts forward a high-stiffness guideway without an air tube. In order to improve rotational stiffness and determine the structural parameters of recesses, this paper found a guideway with the optimal gradient depth of recesses. Both AFVM (adaptive finite volume method) research and experimental results show that the gradient depth of recesses could significantly improve the rotational stiffness of guideways without air tubes.

This paper introduces the application of equipment monitoring and fault diagnosis system of industrial Internet. This system is mainly based on signals from rotating mechanical equipment (such as bearings and gears) to complete the design work of the MoniVIEW equipment operation status fault diagnosis system. This system not only includes algorithms such as statistical index analysis, time-domain analysis, frequency-domain analysis, and short-time Fourier transform in time-frequency analysis, but also includes relatively new adaptive time-frequency analysis methods such as EMD, ITD, and LCD. In mechanical rotating equipment, non-stationary and complex vibration signals are often encountered. Conventional fault diagnosis and analysis algorithms sometimes cannot determine the cause of faults. Introducing adaptive time-frequency analysis methods not only facilitates user fault identification and analysis, but also directly achieves data analysis and processing of vibration signals.

As a new type of driver, linear ultrasonic motor (LUSM) is widely used in the high-tech field because of its low speed, high thrust, low noise, and no electromagnetic interference. However, as an actuator used in microdevices, most of the existing LUSMs are large in size and not compact in structure. In order to overcome these limitations, a new structure of linear ultrasonic motors stator is developed in this paper. The stator is similar to a tuning fork structure, which is divided into three parts: two driving feet, two driving legs, and the driving body. By using the first-order longitudinal vibration mode of the whole stator and the unique partial second-order bending vibration mode of the driving legs to achieve vibration mode degeneracy, a mode hybrid linear ultrasonic motor that is easy to miniaturize is proposed. Its working principle is analyzed. The dynamic analysis of the stator is carried out by using finite element software. The structure dimension of the stator and the driving frequency under the working mode are determined. At the same time, the feasibility of driving feet synthesizing elliptical motion is verified theoretically and experimentally. In addition, the LUSM test setup is built. The effects of driving frequency and V_pp on stator stall force and average velocity are studied. The results show that the maximum stall force can reach 99mN, and the average velocity of the motor is 88.67mm/s with V_pp=320V and driving frequency 80.2kHz. The proposed LUSM is appropriate for use in occasions with quick return characteristics, like the controlling valve or nozzle of the printer. The research results provide guidance for the stator design of the linear ultrasonic motor.