In engineering systems, vibration and noise arise from the coupling of mechanical energy across multiphysical fields. These phenomena are governed by complex excitation sources, nonlinear transmission paths, and system-specific modal characteristics. Consequently, purely narrowband (line-spectrum) or purely broadband (continuous-spectrum) vibration and noise signals are rare under operational conditions. Instead, structural resonances and other dynamic effects produce a mixed spectrum, characterized by narrowband line-spectrum components superimposed on a broadband continuous-spectrum background. This mixed-spectrum behavior necessitates advanced control strategies to effectively mitigate vibration and noise. Previous studies on active noise control technology mainly focused on the control of narrowband vibration and energy-eminent line spectrum noise with periodic characteristics, while they paid less attention to broadband vibration noise (with nonperiodic time-varying characteristics) that reduces the overall vibration damping effect. Vibration control for actual working conditions must break through the unimodal thinking of traditional algorithms and establish broadband and narrowband synergistic control algorithms so as to improve the overall vibration damping effect of the equipment.

Aiming at the actual vibration conditions close to the wideband and narrowband hybrid vibration model, a vibration reduction device based on the pretrained selection coefficient model of the mixed-spectrum hybrid vibration noise active control (MSN-HVNC) algorithm is designed and successfully used in the vibration abatement active control experiments. The hybrid control algorithm is used for vibration noise abatement. Moreover, the wideband noise control subsystem uses a pretrained neural network model to select filter coefficients for updating the coefficients of the filtered-x least mean square (FxLMS) algorithm and thereby controlling the wideband noise, while the narrowband noise control subsystem abates the line-spectrum noise, which is concentrated in energy. The overall damping level of the algorithm is measured in terms of the residual vibration noise to update the controller weights.

The damping effect of the vibration-damping device based on the MSN-HVNC algorithm is 23.0 and 21.3 dB under single-frequency 50 Hz excitation in Case 1 and single-frequency 75 Hz excitation in Case 2, respectively, and the damping effect under mixed excitation vibration signals in multisource coupled vibration scenarios in Case 3 is 12.0 dB. The average damping effect of the MSN-HVNC algorithm is better than that of the FxLMS algorithm for both the single-frequency narrowband line-spectrum noise case and the complex vibration noise case. The MSN-HVNC algorithm is better than the FxLMS algorithm for both single-frequency narrowband linear spectrum noise and complex vibration noise conditions and exhibits a good damping effect for vibration noise. The vibration damping device accelerates the speed of noise control in the form of integrated control with the pretrained coefficient model and independent subsystems, which better meets the engineering needs of modern equipment intelligence and high efficiency, and provides an innovative solution for vibration and noise control in fields such as ship power systems.

With the continuous advancement of underwater vehicle guidance and recovery technologies, acoustic and visual systems have proven effective for both long-distance and short-distance navigation. However, significant limitations persist in mid-range guidance. To address these blind spots in underwater mid-range guidance, this paper proposes a visible light guidance device based on a quadrant photodetector.

By leveraging the advantages of underwater optical technology, such as high precision, strong real-time performance, and low power consumption, the device provides an efficient and reliable technical solution for the mid-range recovery of unmanned underwater vehicles. A system prototype was implemented for horizontal guidance, with the same principles applicable for vertical guidance. Future work aims to integrate spatial theoretical models to address the challenge of accurately determining the position and orientation of underwater vehicles after extended missions as they approach a docking station. This paper begins by introducing the fundamental principle of using visible light and quadrant photodetectors to measure position and attitude data. In a simple setup with a single light source and detector, small changes in position or angle become difficult to detect over longer distances. To overcome this limitation, a “two-light, two-detection” model is proposed, utilizing two sets of LEDs (light emitting diodes) as light sources, with double-point analysis achieved through time-division illumination. The receiving end consists of two sets of quadrant photodetectors, enabling synchronized data collection from each light source. This model forms a network on the horizontal plane, facilitating effective measurement of relative position and attitude data. Extensive experimental data was collected using the prototype system, and a neural network model was developed by applying deep learning techniques. Finally, the two quadrant photodetectors on the horizontal plane simultaneously captured weak light signals instantaneously. These signals were processed using conversion, amplification, and noise reduction techniques to extract valid data. After further modularization and normalization, the processed data were fed into a pretrained model to calculate the relative distance, offset, and deflection angle on the horizontal plane, thereby providing real-time information on the position and orientation of the light source relative to the detector. In the experimental setup, parameters such as light source power, detector sensitivity, and circuit amplification factor were adjusted according to the measurement distance and environmental medium to ensure accurate data under varying conditions.

The experimental results demonstrate that the measurement error for the horizontal distance between the light source and the detector remains within 2%, with lateral offset errors limited to 2 centimeters and heading angle measurement errors controlled within 2°. Furthermore, incorporating additional light sources and detectors in the vertical direction, as well as increasing the number of measurement points and data volume, offers the potential to further optimize the experimental results. This study successfully met its objectives by employing multiple quadrant photodetectors and LED visible light sources, enabling accurate determination of the light source’s position and orientation at mid-range distances. This research provides valuable technical support for advancing underwater light guidance technology.

Vibration measurement is a fundamental means to ensure the safety and good condition of structures. Highly accurate vibration measurements provide precise structural dynamic properties for applications such as structural design, installation and commissioning, and health management.

Compared with traditional vibration measurement methods, video-based vibration measurement is an emerging noncontact and full-field method with high spatial density, high flexibility, easy operation, and cost-effectiveness. Through the video-based vibration measurement method, the vibration displacement information of the measured structure can be obtained from a long distance, which enables the direct observation of small vibration patterns of the structure and has received extensive attention in recent years. Therefore, summarizing the research on video-based vibration measurement technology is of considerable theoretical and applied significance. In the field of video-based vibration measurement technology, the currently commonly used measurement methods mainly include three types, namely, digital image correlation, target tracking, and optical flow methods. The digital image correlation method can obtain accurate three-dimensional vibration information using a dual-camera system. The target tracking method can conduct vibration displacement measurements of large dynamic structures with reliable markers. The optical flow method is a type of target-less video-based vibration measurement method, which can be classified into the intensity and phase optical flow methods according to the different objects to be processed on the surface of the object being measured. The camera arrangement, installation, and operation requirements are low when the object to be measured is small or difficult to access. The emergence of video motion amplification technology further expands the response range of video-based vibration measurement methods, enabling surveyors to more intuitively, rapidly, and dynamically obtain an understanding of the state of small vibrations.

In recent years, with the continuous development of machine vision, artificial intelligence, and other technologies, future video-based vibration measurement methods are expected to achieve further breakthroughs in measurement accuracy, computing efficiency, and anti-interference capability. Video-based vibration measurement technology in the field of vibration measurement has unique advantages and practical value, has broad application prospects, and has attracted increasing attention from technicians and researchers. Video-based vibration measurement methods can not only provide new solutions to vibration measurement problems but will also become a powerful complement to traditional vibration measurement methods, particularly in the full-field measurement and dynamic visualization of the vibration. Video-based vibration measurement methods can undertake more important measurement tasks. With the further development of machine vision and optical technology, video-based vibration measurement methods will have broader application prospects as well as higher application value and research significance.