Shaft System Research Articles

The stability analysis and nonlinear vibration control of shaft system for hydraulic generating set under multi-source excitation considering effects of dynamic and static eccentricities

Aiming at nonlinear vibration problems of shaft system for hydraulic generating set caused by multi-source excitation, based on the construction of unbalanced magnetic pull considering dynamic and static eccentricities, a coupled bending–torsional vibration model of shaft system and corresponding differential equations under the action of multi-vibration sources are established. Nonlinear dynamic analysis is conducted by the shooting method, and the Floquet theory is applied to investigate the stability of system periodic solution. On this basis, discrepancies of dynamic characteristics for systems whether mixed eccentricities are excluded are compared, disclosing that dynamic features of system change dramatically when composited eccentricities are taken into account, and effects from mass eccentricity, excitation current, as well as static and dynamic eccentricities on oscillation response of system are revealed thoroughly by means of numerical method. The magnetorheological fluid damper is incorporated into the system for the purpose of suppressing the nonlinear vibration during operation, and corresponding suppression laws on vibration of rotor and runner are disclosed. While reducing the amplitude of system, fixed eccentricities also increasing the probability of chaotic motion, in addition, the new dynamic phenomena including period 3, period 5 and period 6 are revealed. The rotor displacement will be altered by the fluctuation of excitation current, which affects the dynamic response of runner through stiffness item indirectly. The high dissipation capacity of magnetorheological fluid damper can effectively ameliorate the unsteady dynamic response of system, reduce the amplitude and inhibit the irregular movement of rotor and runner to a certain extent, so as to further increase the stability of unit. The relevant research results can provide references for fault diagnosis and vibration control of hydraulic generating set, as well as for the optimal design.

Vibration and stability analysis of a spinning shaft with arbitrary boundaries subjected to partial load

This paper deals with the flexural vibration and dynamic stability of a spinning shaft subjected to partial load. Based on the theorem of moment of momentum and the theorem of motion of center of mass, the governing equation of motion for the spinning shaft system is obtained. Four kinds of boundary conditions including pinned-pinned, clamped-clamped, free-free, and elastic supports are considered. The exact whirl frequency equation is derived analytically for different boundary conditions. The obtained model is confirmed by comparing with the results reported in the available literature, and excellent agreement is presented. A numerical investigation is carried out to examine the effects of support stiffness, mass ratio, eccentric distance, and slenderness ratio on the whirl characteristics and stability of the system in terms of the obtained model. The results show that the whirl frequency and critical spinning speed of the system are dependent on these parameters, and the stability is mainly governed by the mass ratio and eccentric distance.

ПОЛИМОДЕЛЬНОЕ ОПИСАНИЕ ЭЛЕКТРОЭНЕРГЕТИЧЕСКОЙ СИСТЕМЫ СУДНА

The article presents a complex of mathematical models of various classes and types and the results of their
 application in the description of the ship's electrical power system. The technique for determining the frequency
 characteristics of the propeller shaft system is shown. The ship electric power system is presented in the form
 of three levels, which include main engines, generators, control systems, power converters, and an electric
 propulsion system. It is shown how transient processes take place in the system when the load is turned on and
 external moments change

Design and Development of the Transmission for a Fully Actuated 5-Degrees-of-Freedom Compliant Robot Manipulator With a Single Motor

AbstractThis article presents a novel architecture for the actuation and transmission system of a 5-degrees-of-freedom (DOFs) compliant robot manipulator. The compliant behavior of the robot is achieved using inherently compliant magneto-rheological (MR) clutches introduced in antagonistic pairs in every joint of the manipulator. All five antagonistic MR clutch pairs are driven using a single brushless DC motor located in the base of the robot. The MR clutch pairs are coupled to the motor through a system of shafts, belts, and gears. Several possible architectures for realizing a suitable drive train are presented, and the advantages and disadvantages of each concept are analyzed. The most efficient architecture for the drive train is selected to complete the design of the manipulator. The kinematics of the manipulator using the adopted architecture is further analyzed, and the workspace of the system is presented. To the best of our knowledge, this is the first 5-DOF, fully actuated, compliant robotic manipulator that uses a single DC motor to achieve five independent axes of rotations.

Importance of Power Load Characteristics in ERS

The pursuit of realism in the ERS environment is progressing with ICT development. On the other hand, there is no discussion focused on reproducibility that includes comprehensive load side characteristics, such as propeller characteristics through the shaft system and hull resistance characteristics, which is one of important knowledge requirements specified in IMO Model Course 2.07. In this report, the author focuses on load side characteristics in ERS performance in order to make clear typical challenges facing ERS, advance marine engineer training and promote research and development related to ship engine operation management, all of which are rarely considered in the current general ERS.

Process Development for Batch Production of Micro-Milling Tools Made of Silicon Carbide by Means of the Dry Etching Process

Downsized and complex micro-machining structures have to meet quality requirements concerning geometry and convince through increasing functionality. The development and use of cutting tools in the sub-millimeter range can meet these demands and contribute to the production of intelligent components in biomedical technology, optics or electronics. This article addresses the development of double-edged micro-cutters, which consist of a two-part system of cutter head and shaft. The cutting diameters are between 50 and 200 μm. The silicon carbide cutting heads are manufactured from the solid material using microsystem technology. The substrate used can be structured uniformly via photolithography, which means that 5200 homogeneous micro-milling heads can be produced simultaneously. This novel batch approach represents a contrast to conventionally manufactured micro-milling cutters. The imprint is taken by means of reactive ion etching using a mask made of electroplated nickel. Within this dry etching process, characteristic values such as the etch rate and flank angle of the structures are critical and will be compared in a parameter analysis. At optimal parameters, an anisotropy factor of 0.8 and an etching rate of 0.34 µm/min of the silicon carbide are generated. Finally, the milling heads are diced and joined. In the final machining tests, the functionality is investigated and any signs of wear are evaluated. A tool life of 1500 mm in various materials could be achieved. This and the milling quality achieved are in the range of conventional micro-milling cutters, which gives a positive outlook for further development.

Future Applications of Multilevel Inverter in Short Circuit Alternator for the Control of Shaft Voltages and System Harmonics

Future Applications of Multilevel Inverter in Short Circuit Alternator for the Control of Shaft Voltages and System Harmonics

Application of the stiffness method to the optimization analysis of a marine propulsion shaft system

Application of the stiffness method to the optimization analysis of a marine propulsion shaft system

An Experimental Setup to Detect the Crack Fault of Asymmetric Rotors Based on a Deep Learning Method

Crack is a common fault of rotor systems. The research on crack fault detection methods is mainly divided into numerical and experimental studies. In numerical research, the current fault detection algorithms based on deep learning are mostly applied to bearings and gearboxes, and there are few studies on rotor fault diagnosis. In experimental research, the rotors used in an experiment are mostly single-span rotors. However, there are complex structures such as multi-span rotor systems in the actual industrial field. Thus, the fault detection algorithms that have been successfully applied on single-span rotors have not been verified on complex rotor systems. To obtain a fault signal close to the actual asymmetric shaft system of an asymmetric rotor system and validate the fault detection method, the crack fault detection platform is designed and built independently. We measure the vibration signals of three channels under five working conditions and establish an intelligent detection method for crack location based on a residual network. The factors that influence fault detection performance are analyzed, and the influence laws are discussed. Results show that the accuracy and anti-noise performance of the proposed method are higher than those of the commonly used machine learning. The average accuracy is 100% when SNR (signal-to-noise ratio) is greater than or equal to −2 dB, and the average accuracy is 98.2% when SNR is −4 dB.

Analysis of Torsional Vibration of Diesel Shaft System using Hard Coupling with Working Machine

The model is built to analyze and calculate the torsional vibration of the internal combustion engine shaft system and the generator connected by hard coupling to assess the response to the free and forced vibration of the shaft system, thereby serving as a basis for devising a suitable plan to reduce or avoid the problem of shaft torsion vibration. The results of the research include: modeling and building a separate calculation program for shaft torsion vibrations using MATLAB software; free vibration response analysis including calculating the vibration mode frequency and corresponding vibration forms; analyzing the forced vibration response including the amplitude of vibration of the degrees of freedom and the torsion stress of each element.

ПРОГНОЗНЫЙ МОНИТОРИНГ ТЕХНИЧЕСКОГО СОСТОЯНИЯ ПУТЕМ АНАЛИЗА СОСТАВЛЯЮЩИХ СИГНАЛА ВИБРАЦИИ ПОДШИПНИКОВ ВРАЩАЮЩИХСЯ ЭЛЕКТРИЧЕСКИХ МАШИН

Relevance In industry, any failures and unplanned downtime of machines or systems can degrade or interrupt a company's core business, potentially leading to significant penalties and irreparable loss of reputation. Existing traditional maintenance approaches (failure or routine maintenance) suffer from some assumptions and limitations, such as high prevention or repair costs and inadequate or inaccurate mathematical degradation processes. Due to the trend of intelligent manufacturing, data mining, and artificial intelligence, predictive maintenance control is proposed as a new type of maintenance paradigm only after analytical models predict certain failures or degradations. Equipment condition monitoring can reduce the likelihood of failures occurring. Successful technical diagnostics and monitoring of complex electromechanical subsystems and assemblies provides an increase in service life and reliability of the systems as a whole. Aim of research A general overview of maintenance aims and objectives, which mainly include detection and prevention of failures and malfunctions, maintaining performance within established limits, condition prediction in order to improve machine reliability and full use of its resource, cost minimization, maximization of availability/reliability and multi-criteria optimization. Object of research The object of the study is the technical condition of rolling bearings of rotating electric machines. The main defects that are characteristic of this object are analyzed. In addition, a practical and effective sequential preventive maintenance method for rotating electrical machines is proposed, consisting of four steps: feature generation and fault diagnosis selection, data dimensionality reduction and feature fusion, fault detection and diagnosis, and estimation of the remaining useful life of rotating electrical machine bearings. Vibration signal analysis (from the time domain waveform and spectrum of the original or derivative signal, characteristics can be calculated and their effectiveness in diagnosing a fault can be assessed). Research methods To verify the performance of the proposed method, bearing failure is simulated in the Simulink MATLAB module. The bearing failure is created by feeding the vibration perturbation into the shaft system. Results Based on the results of the simulation, a conclusion on the operability of the proposed method for investigating the technical condition of rotating electric machines is drawn.

Peculiarities of formation of fits of preferential application in the system of hole and shaft

The article deals with the issues of the influence of accuracy parameters on the reliability and durability of assembly units of machine units. The accuracy of the connection is determined by the type of fit, formed gaps and tightness. Compliance with accuracy standards significantly reduces the level of external losses from marriage. However, a variety of deviations and tolerances of the elements of parts can lead to a wide range of fits, which is not economically viable. Insufficient accuracy can lead to damage to parts, leakage of liquids and gases, as well as to a decrease in the performance of the machine as a whole. Therefore, machine manufacturers are striving to improve the accuracy of the connection of parts and the use of more precise production methods. Seating systems simplify the manufacturing process and reduce the number of metal cutting tools needed.

Research for reduction material-capacity of load-lift cranes with multi-engine electric drives on the base electromagnetic work shaft systems

This work is devoted to the study of multi-machine systems of coordinated rotation of the engines of handling equipment. The purpose of the work is to identify, by theoretical calculation, the reduction in the metal consumption of cranes equipped with multi-motor electric drives and operating on the principle of an electromagnetic working shaft, in comparison with the current ones. The analysis of the shifting moments of these systems in dynamics was made and conclusions were drawn about the reduction in the weight of the metal structures of cranes and the saving of metal in their production.

English

This paper aim to develop a low-cost Bambara groundnuts sheller that uses vertical spikes as the shelling mechanism. A vertical spike shelling machine was designed, constructed and evaluated. The Bambara groundnut shelling machine consisted of a hopper, shelling system, frame, motor and power transmission system. The Bambara groundnut sheller used a low-cost shelling mechanism of spikes and shaft system, as it has ability to break different sizes of the Bambara groundnut pods. The prototype was tested for shelling efficiency, percentage mechanical damage of nuts during shelling and machine capacity. The machine was evaluated for shelling efficiency, mechanical damage capacity and cleaning efficiency. The samples used for evaluation were set at different moisture content levels of 6, 15 and 20%.  The shelling efficiency of the machine declined from 71.7 to 21.9% as moisture content increased from 6 to 20%. The mechanical damage decreased from 3.66 to 1.46% as the moisture content increase while the machine capacity also declines from 145.6 to 80.1 kg hour-1. The prototype can therefore be viewed as feasible for implementation by small scale farmers. Key words: Shelling, vertical spikes, efficiency.

Crowning Method on Bearing Supporting Large Wind Turbine Spindle Considering the Flexibility of Structure of Shaft System

To meet the precision design of bearings on large wind turbine spindles, a crowning method of bearing on wind turbine spindles considering the flexibility of the support structure is proposed. Firstly, a finite element (FE) model of the shaft system with a flexible structure is constructed by connecting the shaft and bearing through constraint equations (CE) and multi-point constraint (MPC) algorithms and replacing the bearing rollers with nonlinear spring elements and dampers. Then, the Newmark integration algorithm is used to solve the model and analyze the effect of the structure’s rigidity on the load distribution of bearings. Then, perform convergence analysis of the sequences of the spring load distribution using a high-pass filter based on fast Fourier transform (FFT) and root mean square error (RMSE) to obtain a suitable number of replacement springs. Finally, a sub-model of the upwind bearing is constructed with structured mesh. With the maximum Von Mises stress of the roller profile as the design target, the optimal logarithmic crowning of the roller and its tolerance zone under the given working conditions are obtained. The results show that the FE model of the shaft system proposed has good convergence. The FE model of the shaft system considering the flexibility of the support structure can obtain more accurate load distributions of bearings and can make the accurate crowning design of the bearing rollers based on the actual working conditions. This provides support for the precision design of bearings in large shaft systems.

Dynamic Modeling and Vibration Characteristics Analysis for the Helicopter Horizontal Tail Drive Shaft System with the Ballistic Impact Vertical Penetrating Damage

Dynamic Modeling and Vibration Characteristics Analysis for the Helicopter Horizontal Tail Drive Shaft System with the Ballistic Impact Vertical Penetrating Damage

Compliant quasi-zero-stiffness isolator for low-frequency torsional vibration isolation

The structures of traditional torsional quasi-zero-stiffness (QZS) vibration isolators are too complicated to achieve the desired vibration isolation performance as theoretically predicted. To resolve this issue, this study proposes a compliant quasi-zero-stiffness (CQZS) isolator to isolate low-frequency torsional vibrations in the shaft system. First, the configuration of the CQZS isolator is devised using a compliant mechanism, and the stiffness characteristics of the CQZS isolator are deduced analytically based on the energy method and verified using the finite element method. Subsequently, a dynamic model of the shaft system integrated with the CQZS isolator is established. The equation of motion for the shaft system is solved theoretically using the harmonic balance method. Finally, a prototype is fabricated using 3D printing technology with polylactic acid material, and static and dynamic experiments are conducted to verify the theoretical prediction. The results indicate that the CQZS isolator can achieve ideal torsional QZS characteristics and fulfil low-frequency torsional vibration isolation. The proposed CQZS isolator is much more compact, lightweight, and easier to manufacture than conventional QZS isolators.

Analysis and Experimental Research on Dynamic Characteristics of Horizontal Shaft System of Photoelectric Equipment

In order to study the transmission characteristics of vibration in the shafting of optoelectronic equipment, a horizontal shafting test platform for optoelectronic equipment is designed. Firstly, according to the special structure and load conditions of the three-row ball-column combined turntable bearing used in the horizontal shafting, a quasi-static model of the bearing load was established to solve the load distribution of the bearing and further calculate the bearing stiffness. At the same time, the bearing system was established. The dynamic model of the system is used to calculate the frequency response function of the system under the conditions of radial load and axial load and analyze the vibration transmission characteristics of the shaft system. Based on the finite element method, a finite element calculation model is established, the shafting dynamic model established is used to simplify the bearing, the modal parameters of the equipment are analyzed, and the experimental verification is carried out using the Siemens dynamic test system. The results show that the established model is effective and reliable. It provides a reference for studying the dynamic characteristics of the shaft system of optoelectronic equipment.

Research on the Torsional Vibration Response Characteristics of Parallel Operation Steam Turbine Generator Unit Shafting

With the continuous increase of unit capacity and the widespread application of series compensation devices in power transmission systems, the risk of coupling oscillation between units and power grids and between units has increased significantly, which seriously endangers the safe operation of units and power grids. In this paper, the torsional vibration response of each unit after grid failure is calculated by establishing a lumped mass model of the shafting torsional vibration of the parallel unit. The effects of fault type, series compensation degree and fault location on the torsional vibration of parallel unit shafting are studied. The results show that the three-phase short-circuit fault in the grid has a greater impact on the unit; the influence of series compensation degree on the torsional vibration of the shaft system decreases first and then increases; when the transmission line fails, it will produce a certain torsional vibration excitation effect on the shafting of all units; when a short-circuit fault occurs at the outlet of a generator, the torsional vibration excitation of the unit is the largest, but it will also produce a certain degree of torsional vibration excitation to other units in the same network.

Diagnosis and Treatment of Burst Vibration Fault of Large Steam Turbine Generator Shaft System

Aiming at the burst vibration fault of a supercritical 600 MW steam turbine generator unit during the on-load operation, the characteristics of sudden vibration faults of the rotor system were compared and analyzed. By analyzing the weight-loss vibration response coefficient and the variation characteristics of the vibration vector, parts falling off fault at the low-low coupling of the rotor system were diagnosed. After inspection, it was confirmed that the burst vibration fault of the rotor system was caused by the falling-off of the blast baffle of the low-low coupling bolt. After the blast baffle was restored by hoisting the installation technique, the vibration of the steam turbine generator unit was stable during start-up and grid connection.