Frame Vibration Research Articles

Preliminary Investigations of Machine Frame Vibration Damping Using Eddy Current Principle

A novel approach to vibration attenuation, based on the eddy current principle, is described. The combined effects of all magnetic forces acting in the oscillatory system attenuate frame vibrations and, concurrently, decrease the damped natural frequency. A mathematical model of the forces balance in the oscillatory system was derived before. Some experimental results from a mock-up machine frame excited by an asynchronous motor are presented.

Reduction in vibration of a washing machine by means of a disengaging damper

This paper presents a new semi-active technique for reducing the vibration of a washing machine frame during the spin cycle. A new electromechanical damper was proposed for this purpose. The damper is disengaged during the spin cycle, which results in the reduction of the vibration of the frame. A unit for switching the state (on/off) of the damper is presented. A dynamic model of the washing unit was developed to simulate the motion of the system after the damping forces are disengaged. Numerical results proved that there is no danger of the collision between the drum and the frame. The model also allowed estimation of the forces transmitted from the drum onto the frame through the suspension. The model was validated by the experiments carried out at a stand dedicated to measuring the vibration of the washing unit suspended on original and new dampers. The reduction of the frame vibration without perceptible increase in the drum vibration was observed.

Two-Mass Dynamic Absorber of a Widened Antiresonance Zone

Abstract Attempts to perform synthesis of a passive vibroinsulation two-mass system intended for the simultaneous reduction of machine frame vibrations and forces transmitted to foundations by supporting elements were undertaken in the study. In view of the variable frequency of the machine operation, it was necessary for the frequency interval, encompassed by the vibroinsulation system operation, to be within given limits. On the grounds of properties of the linear massive-elastic system formulated in the works of Genkin and Ryaboy (1998), the problem of vibroinsulation system synthesis was formulated in the parametric type optimisation approach with equality and inequality limitations. For piston compressor vibroinsulation, the mass and elasticity matrices of the vibroinsulating system, as well as its physical structure, were determined. Its operation was verified on the basis of simulation investigations, taking into account the system loss and transient states

Milling vibration attenuation by eddy current damping

Machining vibrations are harmful to workpiece surface quality and tool life, especially for thin-walled parts. A lightweight damping device is proposed by utilizing eddy current damping, and it can be easily attached onto the workpiece surface by glue. The cylindrical device is mainly composed of a magnet, an aluminum cylindrical conductor, and two springs. An induced repulsive force due to the machining vibration is generated and transmitted to the workpiece and then contributed to the vibration attenuation. Dynamic response evaluation on a cantilever beam by hammer tests demonstrates that the device is able to damp vibration mode and the effect of additive mass on the beam dynamics is investigated by roving the attaching point. Moreover, the device is applied to damp multiple modes and attenuate machining vibration of a thin-walled frame. Machining tests under different configurations of cutting parameters are carried out, and its effectiveness of wide band and adaptability to the varying machining processes are validated.

Knowledge extraction using data mining for multi-class fault diagnosis of induction motor

The feature extraction capability of rough set theory (RST) and genetic algorithm (GA) are used to extract knowledge from radial frame vibration signal for fault diagnosis of induction motor. This knowledge can assist in selecting scales for continuous wavelet transform (CWT) and mono-components required for Hilbert transform (HT) to extract fault related information from the vibration signal. Thus, the computational complexity of the signal processing tools is considerably reduced making both CWT and HT hardware friendly and suitable for real-time applications. For machine learning based automatic multi-class fault diagnosis, the performance of the classifiers are also considerably improved with significant reduction in computational burden since the redundant and irrelevant information can be effectively removed. The information obtained using data mining technique is successfully used to detect six types of induction motor faults. The results obtained are also verified in presence of high level of noise which has not been attempted earlier. The main contribution of the paper is to combine the advantages of two powerful signal processing tool like CWT and HT to extract hidden information from vibration signal in conjunction with data mining technique making them computationally efficient and easy to implement.

Multi-class fault diagnosis of induction motor using Hilbert and Wavelet Transform

The information extraction capability of two widely used signal processing tools, Hilbert Transform (HT) and Wavelet Transform (WT), is investigated to develop a multi-class fault diagnosis scheme for induction motor using radial vibration signals. The vibration signals are associated with unique predominant frequency components and instantaneous amplitudes depending on the motor condition. Using good systematic and analytical approach this fault frequencies can be identified. However, some faults either electrical or mechanical in nature are associated with same or similar vibration frequencies leading to erroneous conclusions. Genetic Algorithm (GA) is proposed and used successfully to find the most relevant fault frequencies in radial (vertical) frame vibration signal which can be used to diagnose the induction motor faults very effectively even in the presence of noise. The information obtained by Continuous Wavelet Transform (CWT) was found to be highly redundant compared to HT and thus by selecting the most relevant features using GA, the fault classification accuracy has considerably improved especially for CWT. Almost similar fault frequencies were found using CWT+GA and HT+GA for radial vibration signal.

MODULATION EFFECT OF VIBRATION FREQUENCY OF AN UNSPRUNG HEAVY MACHINE UNDER THE VARIABLE ROAD ADHESION CONDITIONS

Mobile heavy machines as unsprung vehicles exhibit low dissipation ability, hence the ride even at low speeds may give rise to intensive vibration. Particularly dangerous situations occur when the road wheels break away from the road surface due to the ’galloping’ effect, being the result of excited vertical and angular vibration of the machine frame in the vertical plane of symmetry. That implies a major restriction on the ride velocity, which negatively impacts on the machine performance. Vibrations thus produced are mostly in the low-frequency range and hence energy dissipation in tyres will reduce the vibration intensity in a minor degree only. The motion of tired wheels will always involve some slipping. While investigating the feasibility of increasing the efficiency of the vibration reduction systems, one ought to take into account the variable adhesion of road wheels due to different dynamic loading acting on the vehicle axles during the ride. Observations of unsprung machines during the ride suggest the occurrence of self-excited vibration. Mobile machines constitute dynamic systems, which can be governed by nonlinear, sometimes non-stationary differential equations of motion. Their stability also depends on intensity of external vibrations. This study investigates the motion of unsprung mobile machines, taking into account the dynamic processes in the driving system under the conditions of the variable adhesion of road wheels. The model of interaction between a tired wheel and the terrain takes into account the relationship between the road wheel adhesion factor and the slipping action. Mathcad supported by Matlab-Simulink and in the frequency domain – simulations in the time domain. The purpose of the simulation procedure was to find the causes of the vibration modulation frequency and determine the conditions triggering the occurrence of self-excited vibrations. Simulations are supported by the analysis of motion stability.

Magnet assisted stage for vibration and heat reduction in wafer scanning

Wafer scanning stages must deliver high accelerations/decelerations at motion reversals to achieve high productivity. The resulting inertial forces cause vibration of the machine frame and overheating of the linear motor actuators, thus diminishing the accuracy and increasing the cost of the stages. The novel stage design presented in this paper uses magnetic repulsion to provide assistive forces to the linear motors during acceleration/deceleration to reduce actuation force requirements and overheating. Vibration is reduced by transmitting the assistive forces to the ground, not the machine frame. 66% and 55% reduction in vibration and heat, respectively, are demonstrated using a prototype stage.

Cause analysis of low frequency vibration of flexible support stator frame for giant hydro generator

There are low frequency horizontal vibration problems in varying degree on the stator frame for operating giant hydro generator unit, those who adopted flexible support. To determine the cause of excessive vibration, the horizontal vibration of the stator frame and core were measured under the operating conditions of variable rotate speed, variable load and variable excitation. The results showed that the low frequency vibration had similar vibration characteristics in each generator unit, that is, the vibration of the stator increased as the excitation increasing and it did not matter to the change of rotate speed and load. This low frequency vibration was obviously caused by the unbalance magnetic pull. Based on the uneven of air gap, which induced by uneven magnetic pole morphology and relative eccentricity of the stator-rotor, low frequency vibration was explained.

Finite Element Modal Analysis of a Semi-Trailer Frame

The paper carries out the finite modal analysis of a Semi-trailer frame and obtains the modal parameters such as frame natural frequency and vibration mode. It also compares the modal analysis results with the excitation frequency effect caused by the road on the frame, the conclusion supports a reference to improve the frame design.

High-Speed Photogrammetry Application for Percussive Rotary Cutting Tests of Deep-Ocean Cobalt-Rich Crusts

The cutting processes of drill rod under different surge pressures, rotate pressures and propulsion forces were recorded by the high-speed camera in the hydraulic percussive rotary cutting tests of deep-ocean cobalt-rich crusts. Meanwhile, the curves of impact vibration, torsional vibration and frame vibration during the cutting processes were plotted by digital picture processing technique. The impact frequency, torsional vibration frequency, torsional vibration amplitude, vibration amplitude of drill rod and the frame were calculated. The photogrammetry results are generally in agreement with the traditional test results. High-speed photogrammetry is a non-contact, wide range application, and high precision measurement, and the cutting process can be described visually and adequately.

Modal Analysis of School Bus Body Frame

In the process of exploiting and trial-manufacturing the bus school, we find the small stiffness is insufficient, and there exits such phenomenon that small skin fractures and deformations. This paper Builds a three-dimensional model of the school bus by using CATIA software, and then imports the model into Workbench software, establishing a body frame finite model for free modal analysis. Analyzing the free modal of the body frame based on Workbench, we get the body frame’s inherent frequency and vibration mode, and evaluate the body frame vibration characteristics, and put forward improvement proposal on the problem of body frame.

Investigation of wound rotor induction machine vibration signal under stator electrical fault conditions

This paper investigates wound rotor induction machine torque and vibration signals spectra for operation with and without a stator short-circuit or open-circuit winding fault. Analytical expressions that enable the healthy and faulty machine pulsating electromagnetic torque frequencies to be related to shaft speed are derived and validated for operating conditions of interest. A coupled-circuit machine model is used to investigate the healthy and faulty electromagnetic torque signal. Shaft torque and stator frame vibration are measured on a laboratory test rig comprising a 30 kW wound rotor induction machine. It is shown that the existence of a stator winding inherent electrical unbalance or that arising from fault gives rise to a range of pulsating torque frequencies that are transmitted to the machine frame and can be detected in the measured vibration signal. The magnitudes of the resulting vibration components are demonstrated to be largely determined by the unbalance severity and the mechanical system response. The presented experimental results clearly validate the analytical and simulation analysis for the operating range of the investigated industrial machine design.

Elimination of vibration noise from an impact-type grain mass flow sensor

Intensive vibration caused by uneven field terrain and imbalance of working components in a combine harvester is commonly experienced by yield monitors, causing a significant influence on the performance of impact-type grain flow sensors. A yield monitor test stand was constructed based on a commercial combine harvester, and a method was developed to eliminate the effects of vibration disturbance on impact-type flow sensors. The vibration caused by combine harvesters was simulated well in the experiment, and moreover the actual grain flow rate could be adjusted and measured precisely by the weighing sensors fixed under the grain feed tank in real time. An impact-type grain flow sensor was manufactured using two parallel-beam load cells: one was impacted by the grain flow, and the other was applied as a reference beam that was only excited by the vibration of the sensor frame. A harmonic extraction method was introduced to exploit the essential characteristics involved in the collision process between the grain and the impact plate driven by the elevator paddles of the combine harvester. Then adaptive interference cancellation was utilized to eliminate the vibration noise from the measurement of the impact force of the grain flow according to data from the reference parallel-beam load cell. The experimental results showed that the relative error was less than 2.2 % when the reference parallel-beam load cell was used alone, and relative error was reduced further to less than 1.6 % when both the data from the reference load cell and the harmonic extraction method were applied.

Prediction of Acoustic Noise in Switched Reluctance Motor Drives

Prediction of acoustic noise distribution generated by electric machines has become an integral part of design and control in noise sensitive applications. This paper presents a fast and precise acoustic noise imaging technique for switched reluctance machines (SRMs). This method is based on distribution of radial vibration in the stator frame of the SRM. Radial vibration of the stator frame, at a network of probing points, is computed using input phase current and phase voltage waveforms. Sequentially, the acceleration of the probing network will be expanded to predict full acceleration on the stator frame surface, using which acoustic noise emission caused by the stator can be calculated using the boundary element method.

Amending API 541: An Overview of the New Requirements and Improvements of the Fifth Edition

The fifth edition of American Petroleum Institute (API) 541 was written by a task force of users, consultants, and manufacturers to provide a common performance standard to cover the minimum requirements for form-wound squirrel-cage induction motors 375 kW (500 hp) and larger. The standard is designed to outline the requirements of all aspects of an induction machine. When compared to the earlier editions, this revision has enhancements that make purchasing and specifying a more durable machine easier. This edition has new requirements in the areas of frame vibration and insulation tests plus improved sections concerning dynamic analysis and thermal withstand capabilities. The standard is used in conjunction with the extensively modified data sheets. This article provides an overview of the revisions to API 541 contained in the new edition.

Feature Extraction using Wavelet Transform for Multi-class Fault Detection of Induction Motor

In this paper the theoretical aspects and feature extraction capabilities of continuous wavelet transform (CWT) and discrete wavelet transform (DWT) are experimentally verified from the point of view of fault diagnosis of induction motors. Vertical frame vibration signal is analyzed to develop a wavelet based multi-class fault detection scheme. The redundant and high dimensionality information of CWT makes it computationally in-efficient. Using greedy-search feature selection technique (Greedy-CWT) the redundancy is eliminated to a great extent and found much superior to the widely used DWT technique, even in presence of high level of noise. The results are verified using MLP, SVM, RBF classifiers. The feature selection technique has enabled determination of the most relevant CWT scales and corresponding coefficients. Thus, the inherent limitations of CWT like proper selection of scales and redundant information are eliminated. In the present investigation ‘db8’ is found as the best mother wavelet, due to its long period and higher number of vanishing moments, for detection of motor faults.

Vibration Analysis of Rail Engine-Alternator Set Mounted With Base Frame

A rail engine alternate set is the very important functional part of the rail. Impact excitations time varying transfer properties non stationary random response are typical characteristics of the rail engine alternator set vibration. These characteristics of the rail engine make its dynamic analysis and much more difficult than the other engines. Firstly, vibration frequency of the engine is going to find out at the various speed of engine. And also going to find the base frame vibration frequency to the various speeds. Based upon this analytic model of engine vibration frequencies are going to be an analysis with help of ansys .This includes software based synchronization for treatment of vibration signal is to determined. And going to find out resonance of the engine and the base frame. To get safety and comfortableness of the passenger while

Modal Analysis on Steel Frame-Energy Dissipation Support Structure

The energy dissipation device is put on the support bar of the steel frame structure so as to form the energy dissipation support. The structural performance can be adjusted and improved through the additional stiffness and damping so as to realize the structural damping result. As there are many elements that can affect the structural earthquake anti-seismic performance, modal analysis which is taken as the basic contents, is conducted on the application of the common support and steel frame structure of energy dissipation support and the analysis is also conducted on the influences of energy dissipation to the vibration and cycle of the steel frame so as to lay a good foundation for the analysis on the anti-seismic performance of steel frame-energy dissipation support structural system.

Prediction of Radial Vibration in Switched Reluctance Machines

Origins of vibration in switched reluctance machines (SRMs) are investigated. Accordingly, an input-output model based on the mechanical impulse response of the SRM is developed. The proposed model is derived using an experimental approach. Using the proposed approach, vibration of the stator frame is captured and experimentally verified.