Platform Vibration Research Articles

Określenie zmian ciśnienia podczas wiercenia otworu z półzanurzalnej platformy wiertniczej

The article states that a ship in the open sea is in a complex oscillatory motion due to the aerodynamic force of water flow and hydrodynamic pressure. Among the lateral, keel, horizontal, and vertical vibrations, only the vertical vibration of the vessel primarily affects the technological process of drilling a well. The article determines the magnitude of the hydrodynamic pressure that arises in the wellbore from the oscillation of the semi-submersible drilling platform in the absence of well flushing and a telescopic string, a compensator for vertical movement. When formulating the problem accurately, one should take into account the presence of natural vibrations of both the drilling tool and the semi-submersible drilling platform from which the well is to be drilled. The semi-submersible drilling platform was awarded by Caspian Drilling Company to two subsidiaries of Keppel offshore & Marine Company with Caspian Rigbuilders and Caspian Shipyard Company. This platform, named after Heydar Aliyev, is the first and the only drilling platform in the world with a 1,400-atmosphere system technology. Its carrying capacity is 5,600 tons, and its displacement is 47,500 tons. Vertical vibrations of the semi-submersible platform, caused by hydrometeorological conditions, set in motion the drilling tool associated with the semi-submersible drilling platform, along with the flushing solution that fills the well during drilling without a riser. This leads to a change in the hydrodynamic pressure in the well. Therefore, the change in hydrodynamic pressure in the well must be checked using a special installation that simulates the vibrations of the vessel and drilling tool in a well filled with drilling fluid.

Design and Vibration Isolation Investigation of a Load-Adjustable Quasi-Zero Stiffness Isolator

Quasi-zero Stiffness (QZS) isolators offer significant advantages in low-frequency vibration isolation. Nonetheless, the complexity of the structure and the limited load adaptability hinder the practical application of such isolators. Therefore, this paper proposes a novel load-adjustable QZS isolator based on a compliant mechanism. By integrating the positive stiffness of the curved beam and the negative one of the inclined beam, a comprehensive design strategy for the QZS flexible beam is introduced. The optimal geometric parameters of the structure are determined using a genetic algorithm, and the finite element simulations are employed to numerically validate the QZS characteristics of the structure as well as the low-frequency vibration isolation performance. Leveraging the same structural design and a kind of temperature-sensitive materials-Thermoplastic Polyurethane (TPU), a unit cell of load-adjustable QZS isolator controlled by electric heating is developed and fabricated via 3D printing. Static and dynamic tests are conducted to explore the QZS platform characteristics and vibration isolation performance of the isolator subjected to various voltage inputs. The results demonstrate that the QZS characteristics of the isolator can be effectively regulated by adjusting the input voltage, ensuring effective low-frequency vibration isolation under different loads. Moreover, the incorporation of serial and parallel arrangements of unit cells could further enhance the range of load adjustability. This study offers novel insights into the design of load-adjustable QZS isolators.

Tuned two-mass dampers for vibration control of offshore platforms

A Tuned Two-Mass Damper (TTMD) for minimizing vibrations of an offshore platform is developed in this study. TTMD is a passive vibration absorber, and it consists of two parallel undamped tuned mass dampers connected by a dashpot. The influences of its parameters on the vibration absorption capacity are studied through numerical examples. Next, the optimum parameters of TTMD are found, and the performance and robustness of TTMD are determined. The results from this study show that, for absorbing the structural vibration, an optimum TTMD is more effective than a conventional TMD with the same weight as TTMD. In other words, using TTMD significantly reduces the added weight to the main structure compared with using TMD based on the same condition and obtained effectiveness. Moreover, while maintaining the same performance and weight, an optimum TTMD is much more robust than an optimum TMD for resisting the change in structural stiffness.

Dual-channel aperture-splitting snapshot spectral imaging detection system

The contemporary spectral imaging detection systems commonly employed, such as pushbroom and stare systems, often necessitate motion-based imaging mechanisms such as scanning motors. This reliance on motion renders the imaging process vulnerable to platform vibrations, resulting in intricate post-image correction procedures and precluding dynamic target detection. Consequently, the advent of snapshot spectral imaging detection systems has ensued. Currently, there are significant challenges in the miniaturization design and rapid data acquisition aspects of snapshot spectral imaging systems. In this study, linear variable filters were employed as spectral components, and, through optical system simulation and design, the design of the nonspherical monolithic lens system and telescope system in the dual-channel aperture-splitting snapshot spectral imaging detection system were separately completed. The spectral range covered 400–1000 nm, with a spectral resolution of 27.3 nm, and each channel had a spatial sampling of 409×409 pixels. Additionally, based on the optical system design results, the system structure design and assembly were completed. Performance testing and preliminary spectral image fusion research were conducted on the assembled prototype. The instrument demonstrated excellent spectral imaging performance, thereby enhancing the efficiency of spectral imaging detection in snapshot spectral imaging.

Multivariate processing of airborne natural source electromagnetic data—application to field data from Gobabis (Namibia)

SUMMARY As deep-seated ore deposits become increasingly relevant for mineral exploration, the demand for time-efficient and powerful deep-sounding exploration methods rises. A suitable method for efficiently sensing ores at great depth is airborne electromagnetics (EM) using natural signal of atmospheric origin. The method relates airborne magnetic field recordings in the audio-frequency range to reference magnetic field recordings measured at a ground-based site and can achieve greater penetration depths when compared to controlled source airborne EM techniques. However, airborne natural source EM data are prone to noise caused by platform vibrations especially deteriorating data quality at low frequencies and thus narrowing the depth of investigation. Motional noise manifests as coherent noise on all airborne magnetic field components demanding for a powerful processing tool to remove such kind of noise. Unlike the bivariate approach, which is widely used in natural source EM, the multivariate approach is capable of detecting and reducing the effect of coherent noise. We introduce a robust multivariate processing for airborne natural source EM data and present the code implementation. The code was applied to a large-scale data set from the Kalahari–Copper–Belt in Namibia covering over 1000 km2. We obtained spatially consistent and smooth sounding curves in a frequency range of 10 to 1000 Hz including frequencies with prominent motional noise. Transfer functions are in good agreement with other geophysical and geological information.

Study on the Impact of Cutting Platform Vibration on Stalk Cutting Quality in Industrial Hemp

In response to the unclear impact of header vibration on cutting performance (stalk cutting quality and cutting energy consumption) during field operations of industrial hemp harvesters, this study utilized a vibration recorder to collect information on header vibration during the operation of industrial hemp harvesters. Through data processing, the dominant range for the resonant frequency and amplitude of the cutting platform is primarily concentrated between 5–45 Hz and 0–35 mm, respectively. Using numerical simulation techniques, a quadratic orthogonal rotation combination experiment was conducted with vibration frequency and amplitude as experimental factors and stalk cutting quality and cutting energy consumption as indicators. Regression equations were established to reveal the relationships between indicators and factors, elucidating the influence of each factor and its interactions on the indicators. Specifically, for the crack length indicator, the amplitude has a highly significant influence on the model, and there is a significant interaction effect between vibration frequency and amplitude on the model. As for the cutting energy consumption indicator, frequency and the interaction between frequency and amplitude significantly affect the model, while amplitude has an extremely significant impact on the model. Through comprehensive fuzzy evaluation, the optimal vibration parameter combination satisfying comprehensive cutting performance indicators was determined as a vibration frequency of 37.86 Hz and an amplitude of 5.34 mm. Furthermore, the reliability of the model has been further validated. This research can provide a reference for improving the field performance of industrial hemp harvesters.

Интенсификация процесса очистки деталей погружением в моющий раствор

The quality of cleaning metal parts from contaminants depends on the physical and chemical properties of the washing medium and the intensity of the mechanical impact of the liquid on the surfaces subject to cleaning. Intensified cleaning of the parts is possible when there is an unsteady mode of a washing liquid flow, characterized by change of pressure and speed of a liquid in time and in each considered point of a surface subject to cleaning. In order to confirm the theoretical statement about the dependence of cleaning efficiency on the speed of the washing liquid flow, the authors made an experiment. They took a combined submerged washing machine using a combination of two hydromechanical methods of cleaning intensification. The parts subject to cleaning moved in the bath by means of the platform vibration. A helical blower provided the turbulent flow of the washing liquid relative to the object subject to cleaning. The authors used connecting rods of internal combustion engines as the objects to be cleaned. Their surfaces contained asphalt-resin contaminants, which were hard to remove. The cleaning process was studied in the aqueous solution of detergent Temp-100D with a concentration of 20 g/l at a temperature of 65 to 70°C. The cleaning lasted for 15 min. The quality of cleaning from contaminants was controlled by wettability of the cleaned surface with water. It was found that the intensity of cleaning, characterized by the liquid flow rate necessary for the detachment of dirt particles, depends on the vibration frequency of the platform holding the cleaned parts. Increasing the vibration frequency from 0.25 to 1.0 Hz leads to a three-fold increase in the flow rate of the cleaning solution, which provides an intensive removal of contaminants while increasing the quality of cleaning. When increasing the vibration frequency from 0 to 1.0 Hz, the cleaning efficiency increases in 2.5 times. The study results confirmed the theoretical supposition of the relationship between the cleaning efficiency and the washing liquid flow rate.

Damping vibration of platform structure using modified acoustic black holes

We propose waveguide absorbers (WGAs) to dampen structural vibrations of platforms supporting vibrating systems. The waveguide absorber is designed by modifing a spiral acoustic black hole (ABH) to improve its damping performance while saving installation space and weight. The proposed WGA absorbs the flexural wave propagating in a platform to its end, resulting in vibration damping in the platform. To maximize the damping capability of WGA, we analyze the structural intensity field of the platform and attach the WGA based on the intensity field. Numerical and experimental results show that large reductions of peaks in mobility are achieved using the WGAs, showing the possibility to utilize the WGA in practice.

The ice resistance of self-centering jacket offshore platform with concrete filled double-skin legs: Experimental study and numerical analysis

Ice loading is the main controlling design load for offshore platforms in Bohai Bay. The ice-induced vibration of offshore platform can be monitored every winter. Both the freezing and drifting sea ice can damage an offshore platform causing structural damage, discomfort for workers, gas leakage and other problems. Two platform designs were studied aiming to reduce ice-induced vibration. One design is the offshore platform with concrete filled double-skin legs (JOP-CFDSL). The other design is the self-centering offshore platform with concrete filled double-skin legs (SRJOP-CFDSL). Both platforms were tested in laboratory experiments, and the data were used to prepare numerical simulations. The results showed that the ice-induced vibration of the two novel jacket platforms are all reduced under push loads, and the SRJOP-CFDSL have better control effect. The replacement of jacket offshore platform's steel circle hollow section legs with concrete filled double-skin legs can effectively improve the structural stiffness. And prestressed tendons were found to improve the platform's performance even further, helping it to reset after lateral impact. It should be noted that the prestressed tendon as an important bearing member, must do some anti-icing protection. Thus, the influence of ice force on the prestressed tendon isn't considered in this paper.

On-Earth Observation of Low Earth Orbit Targets through Phase Disturbances by Atmospheric Turbulence

This paper addresses the challenges of ground-based observation of Low Earth Orbit (LEO) targets using on-Earth telescopes and proposes solutions for improving image quality and tracking fast-moving objects under atmospheric turbulence conditions. The study investigates major challenges, including atmospheric turbulence-induced aberrations, blurring, telescope platform vibrations, and spatial variations caused by the target motion. A scenario simulation is conducted considering practical limitations, such as feasible time slots for monitoring and the number of available frames within the Field of View (FoV). The paper proposes a novel method for detecting LEO targets using Harris corner features and matching adjacent images upon the corrected frames by Adaptive Optics (AO), with a 38% reduction in the Mean Squared Error (MSE) achieved for certain frames within the isoplanatic angle. Additionally, a refinement strategy for deblurring images is proposed, combining the post-processing with Singular Value Decomposition (SVD) filtering; with a proper filtering factor (β=0.1), an almost complete collection of 14 corner nodes can be detected. The feasibility of continuously tracking objects with uncontrolled attitudes, such as space debris, is successfully demonstrated with continuous monitoring of certain features. The proposed methods offer promising solutions for ground-based observation of LEO targets, providing insights for further research and application in this field.

Damping analysis of floating offshore wind turbines (FOWTs): a new control strategy reducing the platform vibrations

Abstract. In this paper, the coupled dynamics of the floating platform and the wind turbine rotor are analyzed. In particular, the damping is explicitly derived from the coupled equations of the rotor and floating platform. The analysis of the damping leads to the study of instability phenomena, thus obtaining the explicit conditions that lead to the non-minimum phase zero (NMPZ). Two NMPZs are analyzed, one related to the rotor dynamics and the other one to the platform pitch dynamics. The latter introduces a novelty, and an explicit condition is provided in this work for its verification. In the second part of the paper, from the analysis of the damping of the floating platform, a new strategy for the control of floating offshore wind turbines (FOWTs) is proposed. This strategy allows one to impose on the controller an explicit level of damping in the platform pitch motion that adapts with wind speed and operating conditions without changing the period of platform pitching. Finally the new strategy is compared to one without compensation and one with a non-adapting compensation by performing aero-hydro-servo-elastic numerical simulations of a reference FOWT. Generated power, motions, blade pitch and tower base fatigue are compared, showing that the new control strategy can reduce fatigue in the structure without affecting the power production.

Research on an Error Compensation Method of SINS of a Mine Monorail Crane

Underground coal mines belong to the GNSS-denied environment, and the Strapdown Inertial Navigation System (SINS) has a significant advantage in the precise positioning of equipment in this environment because of its operation without requiring interaction with external information and strong anti-interference capabilities. Nonetheless, the vibrations of the installation platform adversely affect the positioning accuracy of SINS. This article focuses on the monorail crane in coal mines as the subject of research, developing a dynamic model for the motion unit consisting of the “track + drive unit + driver’s cab”, while analyzing the relationship between track roughness conditions and the vibration excitation of this unit. Subsequently, utilizing the dynamic model, the study calculated the angular and linear vibration characteristics and formulated models to address coning error and sculling error specific to the SINS in this vibration condition. Lastly, by employing a multi-sample compensation algorithm, this article compensated for positioning errors in the SINS caused by track roughness-induced vibrations during uniform straight-line motion of the motion unit, thus achieving optimal positioning information for the monorail crane. The simulation results demonstrated that employing a four-sample compensation algorithm reduces the coning error in SINS positioning calculations by a minimum of 50% and decreases the sculling error by at least 31%, satisfying the positioning accuracy requirements for precise parking of the monorail crane during the transportation phase, while establishing the foundation for autonomous precise positioning and integrated navigation of underground track transport equipment in coal mines.

Mitigating jacket offshore platform vibration under wave loadings utilising nonlinear energy sinks

ABSTRACT The random vibrations of jacket offshore platforms caused by wave loadings can reduce the service life and fatigue failure of the offshore platforms. The nonlinear energy sink (NES) has great application potential because of its lightweight, high robustness and wide frequency band of vibration attenuation. The NES is introduced to mitigate the vibrations of the jacket offshore platform as a passive control device under wave loadings. The dynamic model of jacket platforms is developed with the NES system. The optimal parameters of the NES system are obtained by exhaustive search method. The results show that the NES system can effectively mitigate the responses of the deck level of jacket platforms under different wave states. The NES system could reduce the response under various deck's mass and stiffness of jacket platforms. The present study proves the feasibility of the NES system in the application of vibration control for marine structures.

Advanced root mean square propagation with the warm-up algorithm for fiber coupling.

Fiber coupling plays an important role in applications such as free-space optical communication (FSOC) and self-referencing interferometry. However, the coupling efficiency is often affected by turbulence and platform vibrations, which requires dynamic coupling with optimization algorithms. In this paper, to further mitigate the effects of sudden disturbances and to expand the effective range of fiber coupling systems, we propose a new method called the advanced root mean square propagation with warm-up (ARW) algorithm. By adaptively adjusting both the gain rate and the perturbation rate with warm-up operations, the ARW algorithm can achieve higher effective range and acceptable steady-state coupling efficiency simultaneously. Simulation and experimental results demonstrate that the proposed method requires only 36.4% of the iterations of the SPGD algorithm to deal with sudden disturbances. Moreover, the effective range of the ARW algorithm is 530.50µrad in the specific coupling platform, which is 20% higher than the effective range of SPGD.

Payload-oriented control scheme for rotating payload satellite considering inertia uncertainties and measurement errors

For the remote sensing satellite with an unbalanced rotating payload suspended by an Active Magnetic Bearing (AMB), this paper proposes a payload-oriented control scheme where the high-precision payload attitude control is dominating. Firstly, to suppress the disturbances induced by payload inertia uncertainties and state measurement errors, an integrated framework of parameter identification and nonlinear predictive filtering is proposed to estimate payload inertia parameters and system states from multi-timescale, noise- and drift-contaminated measurement data, breaking the mutual constraint between identification and filter. Secondly, based on the estimation results, the control law and bearing electromagnetic force allocation strategy of the payload-oriented scheme are provided, so that the payload tracks the desired motion and the satellite platform follows payload to prevent the air gap of AMB from exceeding the safety threshold. Finally, the simulations are carried out to verify the advantages of the proposed control scheme in enhancing the payload control precision and isolating the platform vibration.

Vibration Detection and Degraded Image Restoration of Space Camera Based on Correlation Imaging of Rolling-Shutter CMOS.

To mitigate the influence of satellite platform vibrations on space camera imaging quality, a novel approach is proposed to detect vibration parameters based on correlation imaging of rolling-shutter CMOS. In the meantime, a restoration method to address the image degradation of rolling-shutter CMOS caused by such vibrations is proposed. The vibration parameter detection method utilizes the time-sharing and row-by-row imaging principle of rolling-shutter CMOS to obtain relative offset by comparing two frames of correlation images from continuous imaging. Then, the space camera's vibration parameters are derived from the fitting curve parameters of the relative offset. According to the detected vibration parameters, the discrete point spread function is obtained, and the rolling-shutter CMOS image degradation caused by vibration is restored row by row. The verification experiments demonstrate that the proposed detection method for two-dimensional vibration achieves a relative accuracy of less than 1% in period detection and less than 2% in amplitude detection. Additionally, the proposed restoration method can enhance the MTF index by over 20%. The experimental results demonstrate that the detection method is capable of detecting high-frequency vibrations through low-frame-frequency image sequences, and it exhibits excellent applicability in both push-scan cameras and staring cameras. The restoration method effectively enhances the evaluation parameters of image quality and yields a remarkable restorative effect on degraded images.

Mitigating deepwater jacket offshore platform vibration under wave and earthquake loadings utilizing nonlinear energy sinks

The random vibrations of jacket offshore platforms under wave and earthquake actions can reduce the service life and exacerbate fatigue damage of the offshore platforms. Aiming to mitigate those unwanted vibrations, this paper introduces the nonlinear energy sinks (NES) to the deep-water jacket offshore platform as a passive control device. Its coupling dynamic model is built with assumed parameters of wave and earthquake loads, and the wave forces of the platform structure are calculated by Morison's equation. Further, the optimal parameters of the NES system are obtained by an exhaustive search algorithm under the objective function. The results show that the NES system can effectively contribute to mitigating the maximum, minimum, and root mean squares (RMS) of deck-level responses of the platform structure. What's more, despite various mass or stiffness of platform structure, the NES system not only greatly reduces the response peaks, but also demonstrates a more steady phenomenon, in which the robustness is presented clearly. In this way, it strongly proves the feasibility and robustness of the NES system under wave and earthquake loadings.

Position sensitive detector based non-contact vibration measurement with laser triangulation method utilizing Gabor Transform for noise reduction

Measurement of vibration without having contact with the target is crucial for many applications. However, real time vibration signals are frequently mixed with various levels of dynamic noises. In this research, a non-contact type vibration measurement system based on laser triangulation method is proposed by using a PSD (Position sensitive detector) and here a single axis Brüel and Kjaer piezoelectric accelerometer is used to validate the experimental results. The primary goal of this measurement system is to develop a Gabor Transform based signal denoising technique, in order to eliminate noise from the real-time vibration data. Furthermore, PSD platform vibration, which might cause unanticipated inaccuracies in the detected vibration data, has also been eliminated by utilizing a self-vibration compensation approach using an ADXL-345 three-axis accelerometer. The self-vibration compensated vibration measurement technique has been designed using an NI (national instruments) cRIO (CompactRIO) 9074 real-time FPGA (field programmable gate array) based embedded controller. Consequently, a Gabor Transform and Expansion-based Signal Processing Technique is designed using NI cRIO-9074 real time platform to reduce external noise from the self-vibration compensated vibration data. It has been observed that the implementation of Gabor Transform has improved the performance of the system in term of enhancing the SNR (Signal-to-noise ratio).

Optimal control of jacket platforms vibrations under the simultaneous effect of waves and earthquakes considering fluid-structure interaction

Offshore platforms are very important structures that experience different types of dynamic loads throughout their service lives. In this study, the effects of the simultaneous occurrence of earthquakes and wave loads are investigated. The influences of earthquake-related water shaking on microwaves have also been considered. For this purpose, a case study is performed on the Ressalat oil platform in the Persian Gulf. The modified endurance wave analysis (MEWA) is used to produce waves corresponding to the structure's location. Moreover, the interactions between the fluid and the structure (FSI), as well as the effect of the added mass caused by the oscillation of the platform in the fluid are considered in the analysis. In order to control platform vibrations, the ideas of semi-active control using magnetic fluid dampers (MR), along with the fractional order proportional-integral-derivative (FOPID) control algorithm, are investigated. For online calculation of the gains of the control algorithm, an observer composed of 2-interval type fuzzy systems (IT2FLS) is used, whose orders, the membership functions of the fuzzy system inputs, as well as the fuzzy rules set, are optimized by Observer-Teacher-Learner-Based Optimization (OTLBO). This technique is a powerful meta-heuristic algorithm. In the used control process, the effect of actuator saturation, which is one of the problems of semi-active control systems, is considered. To evaluate the effectiveness of the proposed control, the maximum value and the root-mean-square (RMS) responses of the platform under 5 waves with different return periods and 7 far-fault earthquake records are compared. The results show that in the cases of simultaneous wave and earthquake loads, the wave load can partly reduce the maximum displacements caused by earthquakes. Also, the maximum and RMS displacement of the jacket platforms' level under wave load with a return period of 100 years and 7 earthquakes are reduced by an average of 35%, which can increase the service life of these structures by 4 times.

Analysis of atmospheric turbulence and vibration impact on the performance of satellite–ground laser communication beam

AbstractWith satellite laser communication, advantages can be achieved in high communication rate, precise beam pointing, high confidentiality, and light‐small terminal. Satellite–ground (SG) laser links also play a crucial role as trunk links. However, the SG link is influenced by atmospheric turbulence and platform vibration, these two factors will cause unstable link tracking. This paper focuses on the viewpoint of beam energy transmission, using the low‐frequency harmonic phase compensating method to establish the random phase screen. On the basis of this model, the laser beam energy distribution and the spot mass positioning error are analyzed considering turbulence taking vibration which is not considered in previous studies. The simulation results show that the spot mass center (SMC) is impressionable in strong turbulence under platform vibration, but in a weak turbulent environment, SMC is insensitive to vibration when turbulence and vibration are at the same noise level.