Location Of Unbalance Research Articles

Dynamic Parameter Estimation for a Washing Machine

In this study, an analytical concept is explored in the simulation environment, and an unbalanced load detection technique is examined to determine its applicability. To continue the development process, a mathematical model for a horizontal washer is developed to comprehend the characteristics of an unbalanced load with respect to various sizes of balanced loads. The mathematical model is then divided into a regressor vector and an estimator vector. Finally, estimates of the unbalanced load, the unbalance location, and the rotational moment of inertia are compared to their references in the simulation environment.

Unbalance Localization of a Multi-Disc Rotor by Hybridizing Wavelet Transformation and Neural Network

Rotating machinery is widely working within the industry, and fault diagnosis and prognosis of them may be a vital issue that can save money continually. Unbalance is a crucial fault in rotary systems, and it is focused by many researchers to develop methods to detect that for correcting before global failure happening within the machine. Hence, the establishment of a procedure that will estimate the unbalance location and its specifics are going to be valued and practical for correcting operations. The recent study exemplifies a model that can detect the unbalance parameters, for example, the location of unbalance mass and value of that based on the hybridizing Wavelet Transformation and artificial neural network (ANN) model. The inputs of the model are wavelet coefficients derived from the bearing acceleration signal. It includes two hidden layers constructed by six neurons within each layer. The parameters estimation accuracy was attained 95%, 97%, and 96% for the disc number, the eccentric radius, and unbalance mass values, correspondingly.

Unbalance Estimation for a Large Flexible Rotor Using Force and Displacement Minimization

Mass unbalance is one of the most prominent faults that occurs in rotating machines. The identification of unbalance in the case of large flexible rotors is crucial because in industrial applications such as paper machines and roll grinders, high vibrations can adversely affect the quality of the end product. The objective of this research is to determine the unbalance location, magnitude and phase for a large flexible rotor with few measured coordinates. To this end, an established force-based method comprising of modal expansion and equivalent load minimization is applied. Due to the anisotropic behavior of the test rotor, the force method required at least six measured coordinates to predict the unbalance with an error of 4 to 36%. To overcome this limitation, an alternate method, eliminating the use of modal expansion, is proposed. Here, displacements generated by varying the location of a reference unbalance along the rotor axis, are compared to measured displacements to detect the unbalance location. Furthermore, instead of force-based fault models, the minimization of displacements at measured locations determines the unbalance parameters. The test case in this study is the guiding roll of a paper machine and its different unbalance states. The algorithm is tested initially with a simulation-based model and then validated with an experimental set up. The results show that the displacement method can locate the unbalance close to the actual location and it can predict the unbalance magnitude and phase with only two measured coordinates. Lastly, using measured data from 15 measurement points across the tube section of the test rotor, a comparison shows how the selection of the two measured locations affects the estimation accuracy.

The Application of the Bispectrum Analysis to Detect the Rotor Unbalance of the Induction Motor Supplied by the Mains and Frequency Converter

This article presents the effectiveness of bispectrum analysis for the detection of the rotor unbalance of an induction motor supplied by the mains and a frequency converter. Two diagnostic signals were analyzed, as well as the stator current and mechanical vibrations of the tested motors. The experimental tests were realized for two low-power induction motors, with one and two pole pairs, respectively. The unbalance was modeled using a test mass mounted on a specially prepared disc and directly on the rotor and the influence of this unbalance location was tested and discussed. The results of the bispectrum analysis are compared with results of Fourier transform and the effectiveness of unbalance detection are discussed and compared. The influence of the registration time of the analyzed signal on the quality of fault symptom analyses using both transforms was also tested. It is shown that the bispectrum analysis provides an increased number of fault symptoms in comparison with the classical spectral analysis as well as it is not sensitive to a shorter registration time of the diagnostic signals.

Modelling of shaft unbalance: Modelling a multi discs rotor using K-Nearest Neighbor and Decision Tree Algorithms

Multi discs rotors are widely used in the industry. Shaft unbalance in multi-discs’ rotors is the main failure origin that leads to global failures in rotary systems. Unbalance parameters that must be detected in the shaft are focused on this study. Unbalance parameters are eccentric mass value, eccentric radius, and disc number which are presenting an unbalance location. The main aim of the current paper is to identify unbalance parameters of a rotating shaft having multi-discs by artificial intelligent methods namely KNN and Decision Tree Algorithm. For both algorithms, data derived from a fabricated test rig consists of a shaft in which four discs are mounted on that. The results show that the KNN presents more accuracy in estimating of unbalance parameters compared to the Decision Tree in terms of unbalance locating.

Unbalance Rotor Parameters Detection Based on Artificial Neural Network

Unbalance is an important fault that can damage or shut down vital rotary systems such as the gas turbine, compressors, and others, so to avoid this trouble, the balancing process is very crucial, even though it is time-consuming and costly. Thus, having a technique which can predict the unbalance location and its parameters will be valuable and practical. The current study represents a model that can identify the unbalance’s mass, radius, and location of the eccentric mass based on the artificial neural network (ANN) model. The inputs of the proposed ANN, which is based on a feed forward with back propagation model, is the bearing acceleration signal in the frequency domain. It has 10 hidden layers with 10 neurons through each layer. The accuracy in prediction was acquired at 96%, 96%, and 94% for the disc number (plane), the eccentric radius, and eccentric mass values, respectively.

Unbalance detection in rotor systems with active bearings using self-sensing piezoelectric actuators

Abstract Machines which are developed today are highly automated due to increased use of mechatronic systems. To ensure their reliable operation, fault detection and isolation (FDI) is an important feature along with a better control. This research work aims to achieve and integrate both these functions with minimum number of components in a mechatronic system. This article investigates a rotating machine with active bearings equipped with piezoelectric actuators. There is an inherent coupling between their electrical and mechanical properties because of which they can also be used as sensors. Mechanical deflection can be reconstructed from these self-sensing actuators from measured voltage and current signals. These virtual sensor signals are utilised to detect unbalance in a rotor system. Parameters of unbalance such as its magnitude and phase are detected by parametric estimation method in frequency domain. Unbalance location has been identified using hypothesis of localization of faults. Robustness of the estimates against outliers in measurements is improved using weighted least squares method. Unbalances are detected in a real test bench apart from simulation using its model. Experiments are performed in stationary as well as in transient case. As a further step unbalances are estimated during simultaneous actuation of actuators in closed loop with an adaptive algorithm for vibration minimisation. This strategy could be used in systems which aim for both fault detection and control action.

Effects of unbalance location on dynamic characteristics of high-speed gasoline engine turbocharger with floating ring bearings

For the high-speed gasoline engine turbocharger rotor, due to the heterogeneity of multiple parts material, manufacturing and assembly errors, running wear in impeller and uneven carbon of turbine, the random unbalance usually can be developed which will induce excessive rotor vibration, and even lead to nonlinear vibration accidents. However, the investigation of unbalance location on the nonlinear high-speed turbocharger rotordynamic characteristics is less. In order to discuss the rotor unbalance location effects of turbocharger with nonlinear floating ring bearings(FRBs), the realistic turbocharger of gasoline engine is taken as a research object. The rotordynamic equations of motion under the condition of unbalance are derived by applied unbalance force and nonlinear oil film force of FRBs. The FE model of turbocharger rotor-bearing system is modeled which includes the unbalance excitation and nonlinear FRBs. Under the conditions of four different applied locations of unbalance, the nonlinear transient analyses are performed based on the rotor FEM. The differences of dynamic behavior are obvious to the turbocharger rotor systems for four conditions, and the bifurcation phenomena are different. From the results of waterfall and transient response analysis, the speed for the appearance of fractional frequency is not identical and the amplitude magnitude is different from the different unbalance locations, and the non-synchronous vibration does not occur in the turbocharger and the amplitude is relative stable and minimum under the condition 4. The turbocharger vibration and non-synchronous components could be reduced or suppressed by controlling the applied location of unbalance, which is helpful for the dynamic design, fault diagnosis and vibration control of the high-speed gasoline engine turbochargers.

Application of Model Based Diagnosis in Two-Span Rotor System with Two Unbalance Faults

The model based fault identification method was used to identify the two unbalance faults in two-span rotor system. The unbalance location and magnitude were identified using least squares fitting approach by the system’s transient residual vibration. The all-phasic FFT technique was used to analyze the original phases of vibration signals. The unbalance location and magnitude of the rotor system can be detected by using only a few sensors. Numerical simulations and experiment on rotor system with two unbalance faults were used, which proved the efficiency of the method.

Unbalance Response of an Elastic Rotor in Damped Flexible Bearings at Supercritical Speeds

The unbalance response of a uniform flexible rotor in fluid-film bearings has been analyzed for speeds up to 20 times the lowest rigid-bearing critical speed. Rotor mass and elasticity are distributed uniformly along the length of the rotor. A single radial speed-dependent force is used to represent the rotor unbalance. The rotor is assumed to operate in stable plain cylindrical bearings which are represented by direct and cross-coupled spring and damping forces. The influence of rotor speed, bearing operating eccentricity, relative stiffness of rotor and bearings, and unbalance location along rotor on the performance of the rotor-bearing system has been determined. Results are presented as charts of rotor maximum whirl amplitude and of bearing maximum whirl transmitted force for wide ranges of the foregoing parameters. Mode shapes at critical speeds are also included.

The Dynamic Unbalance Test Installation

TH E necessity for adequate test equipment capable of the dynamic balancing of missile and rocket equipment, such as rocket motors, rotating launchers, flywheels, and turbo machines, has always presented designers with problems of test machine simplicity, size, and application. Aerophysics has recently solved this problem through the design and development of a simple vertical balancing machine capable of the dynamic balancing of equipment up to 5000-lb weight, 20,000-lb thrust, up to 36 in. diam, over-all lengths of 10 ft, and rotating speeds of 10,000 rpm. Dynamic unbalance may be measured on a spinning rocket motor, firing or not firing. The problem of dynamic balancing is one of bringing into coincidence the mass centerline and geometric centerline of a rotating mass. The unbalance is determined by measuring the amplitude and phase of motion of the freely suspended rotating mass. Weights for correction can then be applied in any two corrective planes if it is necessary. At a speed of 1000 rpm, a 200-lb rotor approximately 50 in. long has been balanced to an accuracy of approximately one-millionth of a radian. Displacement pickups on the test stand have measured displacement to an accuracy of within 0.000050 in. This corresponds to a weight correction of only /16 oz or 0.004 lb. The test stand consists of a rigid outer frame, and a stiff lightweight inner frame mounted on two or more flexure rods or cables. These flexure rods serve as vertical supports for the inner frame but do not constrain the lateral or pitching motion of the frame. Adjustments are provided for varying the lengths and attachment points of the flexure rods. In this way the natural frequency of the inner frame can be modified, as desired, to provide optimum response amplitudes. The adjustments will depend on the rotational speed of the equipment mounted in the inner frame. The freely suspended inner frame permits the resolution and recording of extremely minute amplitudes which are due to small amounts of unbalance in the rotating mass. The outer frame is stiff and comparatively heavy in order to minimize external disturbances to the balancing machine and to provide a fixed frame of reference for measurement. Rigid stops are provided in all directions for safety, convenience of operation, and protection of the flexure rods. The stops may be adjusted, as necessary, to allow motion within the measuring range of the pickups. Instrumentation is provided for measuring displacements in two correction planes and a phase angle (angular location of unbalance) at the various rotational speeds. The displacement and phase ! 1 1