Rotor Balancing Research Articles

Signal conditioning system for real-time monitoring of unbalanced mass and angular position in helicopter propeller rotor balancing

This paper outlines the design of a signal conditioning system developed to enable real-time monitoring of unbalanced mass and rotor angular position on a horizontal balancing machine. The system incorporates piezoelectric sensors with high sensitivity and a wide measurement range, allowing them to detect small variations in acceleration with great accuracy. Therefore, the proposed signal conditioning system relies on a lock-in amplifier, which can measure small signals even in the presence of considerable noise. The system achieved an error rate of 1% or less in the mass balance of a rotor at different speeds. These results revealed a consistent linear relationship between the unbalanced mass and the rotor velocity, which simplifies the interpretation and analysis of the data, allowing any variation in the signal to be directly related to changes in the unbalanced mass or rotor velocity, without any complications due to nonlinear effects.

A resonance-avoiding modal balancing method for multimodal balancing of high-speed flexible rotors

Abstract Conventional balancing methods for high-speed flexible rotors typically necessitate costly and potentially hazardous balancing tests conducted near their critical speeds. This paper first demonstrates the feasibility of achieving multi-mode balancing using measurements taken below the first critical speed, based on traditional modal balancing methods and rotor modal parameters. However, while theoretically viable, this approach is highly susceptible to measurement noise, complicating its practical implementation. To address this issue, we propose an innovative resonance-avoiding modal balancing (RAMB) method specifically designed for multi-mode balancing. In RAMB, balancing is performed mode by mode in a forward manner, effectively integrating the correction weights of lower modes into the balancing equation. This strategy eliminates the need to operate the rotor at unbalanced critical speeds, enhancing the effectiveness of multi-mode balancing while ensuring measurement safety. The effectiveness of both the conventional method and the RAMB approach is validated through numerical simulations and experimental tests as well. The results show that RAMB significantly enhances the vibration suppression over the entire operating speed range while avoiding resonance measurements and exhibits comparable robustness to noise, confirming the validity and superiority of the proposed balancing method

Development of Flexible Rotor Balancing Procedure Using Response Matching Technique

PurposeThe two main methods under use for balancing of flexible rotor know as Influence Coefficient Method (ICM) and Modal Balancing Method (MBM). It needs few trials to arrive at predicting the unbalance mass. In presence of initial bow along with unbalance these methods will fail to give accurate predictions. It becomes further complex when rotors are mounted on flexible supports. To overcome the limitations of these two methods, a new method called response matching method is disused here for flexible rotor balancing.MethodThe objective of present work is to develop a balancing procedure for flexible rotor balancing, wherein unbalance response of Finite element model (FEM) is matched with experimental response using iterative technique. Unbalance masses, moments and shaft stiffness of FEM model was iterated to match experimental unbalance responses at three distinct speeds below its first flexural critical speed. Further, unbalances mass was estimated iteratively to cross the bending critical speed with lower residual amplitudes at critical speeds.ResultsExperimental test setup was developed to validate the proposed method. Results show that present method predicts the unbalance masses and moments to compensate the bow more accurately.ConclusionResults shows that with single run, rotor unbalance masses and movements are predicted accurately. Corrected masses are used in experimental test setup to check the rotor amplitudes during its bending critical speeds. It shows rotor passes first bending critical speed without excessive amplitudes.

Improving the technological process of balancing electric machine rotors on a balancing machine

The object of research is the process of dynamic balancing of rotors on a balancing machine in the process of restoring electric machines. The work is aimed at improving the quality of balancing rotors in the process of major repairs of traction electric motors for electric trains. The problem addressed was the quality of balancing the rotors of electric machines on stationary balancing machines. According to the conventional balancing technology, the rotor to be balanced is mounted on the supports of the balancing machine with support surfaces that usually have mechanical defects. These defects cannot be eliminated by machining due to the peculiarities of rotor repair technology. Theoretical and experimental studies of the effect of damage to the rotor support surfaces on the balancing parameters have been carried out. It has been proven that the properties of the bearing surfaces of the rotor during its balancing on a balancing machine significantly affect the results of determining the imbalance. At the same time, the difference in the mass values of balancing loads can reach 25 %. This is because damage to the bearing surfaces of the rotor generates false signals unrelated to the imbalance. In order to increase the accuracy of determining the mass of balancing loads during rotor balancing, it is proposed to improve the technological process of balancing. The improvement involves the inclusion of a frequency filter in the signal conversion chain of acceleration sensors. The filter is designed to separate signals with a frequency greater than the rotational frequency of the rotor. A condition for the practical application of the research results is the expediency of introducing a frequency filter of signals of acceleration sensors with a threshold frequency of filtering signals that exceeds the rotational frequency of the rotor into the schematic diagram of the balancing machine.

Digital Simulation of Coupled Dynamic Characteristics of Open Rotor and Dynamic Balancing Test Research

An aero engine, as the core power equipment of the aircraft, enables safe and stable operation with a very high reliability index, and is an important guarantee in flight. The open rotor turbine engines (contra-rotating propeller) have stood out as a research hotspot for aviation power equipment in recent years due to their outstanding advantages of low fuel consumption, high airspeed, and strong propulsion efficiency. Aiming at the problems of vibration exceeding the standard generated by imbalance during the operation of the dual-rotor system of aircraft development, the difficulty of identifying the coupled vibration under the micro-differential speed condition, and the complexity of the dynamic characteristic law, a kind of numerical simulation of the dynamics based on the finite element technology is proposed, together with an experimental research method for the fast and accurate identification of the coupled vibration of the dual-rotor system. Based on the existing open rotor engine structure design to build a simulation test bed, establish a double rotor finite element simulation digital twin model, and analyze and calculate the typical working conditions of the dynamic characteristics of parameters. The advanced algorithm of double rotor coupling vibration signal identification is utilized to carry out decoupling and dynamic balancing experimental tests, comparing the simulation results with the measured data to verify the accuracy of the technical means. The results of the study show that the vibration suppression rate of the finite element calculation simulation test carried out for the simulated double rotor is 98%, and the average vibration reduction ratio of the actual field test at 850 rpm, 1000 rpm, and 3000 rpm is over 50%, which achieves a good dynamic balancing effect, and has the merit of practical engineering application.

Dynamic balancing of rigid rotors by the influence coefficient method

Applied to rigid rotors, the influence coefficient method is the most adaptable method for rotor dynamic balancing because it uses only experimental information. The sole requirement for balancing rotors with this method is that there exists proportionality between mass unbalance located at correction planes and vibration measured at measuring planes. Hence, the rotors only need to be described by correction and measuring planes. The sensitivity of the measuring planes compared to the correction planes determines the response of the amount of unbalance for a specified rotation speed. The paper aims to describe in detail the experiment for dynamic balancing of rotors to verify the influence coefficient method. The direct calibration on two-plane rigid rotor using this method showed that a significant reduction of unbalances can be obtained. The results can be helpful for the design and safety assessment of dynamic systems equipped with rotors for marine engineering. Keywords: Rotor dynamic balancing, influence coefficient method, residual unbalances, Discrete Fourier Transform

Development of Rotor Balancing Algorithm for a High-Precision Rotor System considering Dynamic Reliability through Automatic-Adaptive DBSCAN

Recently, the demand for high-precision balancing of rotors has increased in the automobile industry, as more rotors are designed to rotate at ever-higher speeds to maximize energy efficiency. The accumulation of measurement uncertainty in the balancing process decreases the accuracy of the unbalanced mass estimation, which is the ultimate goal of balancing. Here, the problem of uncertainty is shown through a Monte Carlo simulation of signals acquired from an actual production line. To reduce the effect of measurement uncertainty in the balancing procedures, a signal-processing technique that increases the dynamic reliability of the signal is proposed. The suggested method is based on density-based spatial clustering of applications with noise (DBSCAN) with the use of the orthogonality-based averaging method. Specifically, by adjusting radius values while clustering samples through the use of the DBSCAN method, the outliers that arise due to uncertainty are successfully removed. In this work, our proposed automatic-adaptive DBSCAN (AA-DBSCAN) method is validated by applying it to a balancing machine used for blower rotors in fuel cell electric vehicles. The results show that the deviation of the extracted influence coefficients is up to 0.0050, whereas the proposed method reduced it to less than 0.0037. In addition, the suggested procedure reduced the deviations of the unbalanced mass phase estimation by 35.2% as compared to the results found by the conventional method. Consequently, through the validation test, the suggested method was found to have the largest vibration decrease of any method considered in the study.

Induction Motor Vibrations Caused by Mechanical and Magnetic Rotor Eccentricity

Vibration reduction of induction motors is a significant problem that requires effective models for the effects of mechanical and electromagnetic unbalanced forces. This article presents a mathematical model of dynamics for induction motors with rotor mass eccentricity and static and dynamic magnetic eccentricity. The model allows for the influence of the gyroscopic torque of the rotor and considers the elastic-damping characteristics of each of the stator supports and their location. The model has eight degrees of freedom, which makes it possible to simulate transverse and axial vibrations of various designs’ rotors and housings of induction motors. The results of modeling the dynamics for a three-phase squirrel cage induction motor with 11 kW capacity agreed with those obtained by other authors. Simultaneously, new results were also obtained within the research. The simulation results showed that the static magnetic eccentricity causes the appearance of additional critical speed of the motor, and its value decreases in proportion to the growth of the number of pole pairs. The change of the moment of inertia of the motor at a mismatch of the main axis of symmetry of the stator and the rotor axis of rotation allowed for obtaining an actual frequency spectrum of free oscillations, including the rotational motion of the stator. Since the actual static magnetic eccentricity can additionally increase at operating frequencies due to the increase of bearing clearance caused by dynamic unbalanced load, it should be considered in the analysis of unbalanced magnetic pull. The angle of static magnetic eccentricity significantly affects the magnitude of radial vibrations. This feature should also be considered when selecting the locations of balancing weights during the rotor balancing procedure.

Theoretical and experimental applications of a rotor balancing technique without using trial weights based on augmented Kalman filter

Unbalance is the most common fault of rotating machines and efforts devoted to developing balancing techniques are the goal of several researchers around the world. The most common balancing approach is the well-known influence coefficient method, which requires the use of trial weights to determine the relationship between unbalance forces and vibration responses of the rotor; consequently, it is time-consuming regarding industrial applications. The present contribution investigates the augmented Kalman filter (AKF) technique to balance a flexible rotor without using trial weights. There are few studies in this area and the majority of the previous research works are dedicated to theoretical studies using simple or reduced rotor models. This paper considers a finite element (FE) model of a realistic rotor system and investigates the effectiveness of the AKF as a balancing technique by considering several unbalance conditions. Therefore, the novelty of the present contribution is characterized by a complete numerical and experimental AKF based balancing procedure that is performed by using a realistic rotor system. As mentioned above, limited experimental contributions are found in the literature involving real-world applications. Additionally, a sensitivity analysis on the force covariance matrix is proposed to investigate the most favorable conditions to apply the AKF technique in the context of rotor balancing. The methodology proved to be effective to deal with a variety of rotor balancing applications.

Advancing balancing machine technology: A cost-effective solution for laboratory and small-medium enterprises

Small-medium enterprises (SMEs) that provide maintenance services to power plant companies, notably on rotor components, encounter a significant challenge in balancing. The main concern is the high cost associated with outsourcing balancing services. The absence of portable balancing machines requires transporting components back to the workshop, resulting in substantial downtime lasting weeks before reinstallation. This paper presents a DIY-compatible balancing machine design and its assembly process, which can be applied to various balancing processes. The design primarily emphasizes mechanical aspects, excluding measurement and instrumentation components, which can be obtained or developed based on the user's software proficiency. The actual expenditure for developing this balancing machine is approximately RM11,698.00. In the development process, benchmarking, concept scoring, functionality evaluations, dynamic analysis, and ideation for workable balancing machine concepts were all involved. The modal analysis demonstrates that the first natural frequency at 279.5 Hz (equivalent to 16,770 rpm) is significantly higher than the motor's excitation frequency, which reaches a maximum speed of around 2800 rpm (46.67 Hz). This result indicates that the dynamic behaviour of the balancing machine does not significantly affect the dynamic results of the rotor balancing process.

A Finite Element Model-Based Approach for Rotor Unbalance Detection and Balancing

A Finite Element Model-Based Approach for Rotor Unbalance Detection and Balancing

Numerical and experimental studies on unsupervised deep Lagrangian learning based rotor balancing method

Numerical and experimental studies on unsupervised deep Lagrangian learning based rotor balancing method

A two-stage deep-learning-based balancing method for rotating machinery

Purpose—balancing is essential to all rotating machinery. To make the balancing process convenient and inexpensive, new balancing technologies are needed. In this work, a two-stage deep-learning-based balancing method is proposed and validated. Design/methodology/approach—the architecture of the method is described. The whole balancing method has two stages. The first stage identifies the unbalanced force vector and the second stage identifies the correlation masses and phases from the unbalanced force series. Deep-learning-based modules can be trained using one-run response data and labeled support force data only. Findings—both numerical and experimental balancing performances are reasonable and comparative. The performances indicate that the proposed method is validated and robust. Originality—the proposed method combines deep learning technology with rotor dynamics knowledge. The proposed method achieves good performance without a weight trail process and provides a competitive approach for rotor balancing technology.

An Approach on V-Shaped Milling for Rotor Balancing of Armatures

In order to improve the dynamic balancing accuracy of the micromotor armature, a method of V-shaped milling based on a discrete vector model for unbalance correction is proposed. The discrete vector model is fitted according to the parameters of the milling cutter and rotor, and then all the unit unbalance vectors in the discrete vector model are added to the milling center. The numerical relationship between the milling depth and the removal of the mass unbalance vector is obtained, and the accuracy of the model is verified via comparison with the data of the simulation experiments. The complexity of the integral formula of the numerical milling model makes it difficult to apply in practice. The discrete vector model does not require integration of the numerical formula and only considers the milling area as being composed of countless discrete blocks, which greatly simplifies the process of solving the unbalance vector. In view of the different thicknesses of the tooth surface of the armature, in order to avoid damage to the armature during milling, the unbalanced vector is decomposed at the center of the tooth surface by force decomposition. The experimental results show that this proposed method can effectively improve the dynamic balancing accuracy of the micromotor armature.

On experiments of a novel unsupervised deep learning based rotor balancing method

Rotor dynamic balancing is essential in rotor industrial. The conventional balancing methods, including the influence coefficients method and modal balancing method, are effective, but lack economy and sufficient usage of the data. To overcome the disadvantages of the conventional balancing methods, a balancing method using unsupervised deep learning without weight trails had been proposed. The proposed network could identify the unbalanced forces from the data observed from just one run of the rotor and without labels. To validate the novel balancing method, an experimental rig is well-designed and established. Experimental validation and comparison with influence coefficients method are conducted. The experimental results show that the proposed balancing method gives consideration to both cost and accuracy. Compared with influence coefficients method, no extra weight trail process is needed and balancing performances are comparative. The experimental rig can be used for proving the scheme and for further same kind of research.

Balancing Technique for Turbo Machinery Rotor

Balancing process carried out in the thermal power station is very complex and complicated. The complete unit is to be cooled down for balancing this takes nearly 10 to 15 days. After cooling the unit is disassembled and the rotor is taken out for which again 10 to 15 days are required for balancing and assembly. Rotor is placed on the balancing machines for balancing which is carried out by Engineers of the testing department. Balancing of a bulky rotor is difficult and it is carried out step by step. After balancing, complete rotor is to be placed in the turbo machine which is a most difficult task as it has to match the all alignment and other conditions properly. The complete process takes period of nearly one and half month for balancing the rotor, so balancing of the rotor is called to be the costly project in the thermal power station. After the balancing procedure is completed, while starting the complete unit various parameters are to be controlled such as steam inlet temperature, pressure, flow of the steam and rpm of the unit to avoid any type of danger. Loss of production of power during the shutdown period is major loss of any power station. Paper details the automatic thermal balancing of turbo machinery rotor using heating coils.

Vibration analysis, measurement and balancing of flywheel rotor suspended by active magnetic bearing

For the hybrid magnetically suspended flywheel (MSFW) with radial two degrees of freedom (DOFs) active magnetic bearing (AMB) and axial three DOFs AMB, the vibration analysis, measurement and balancing are conducted to mitigate the influences caused by unbalance terms in this article. Firstly, the force models of MSFW rotor are developed, and the vibration phenomenon caused by the residual unbalance mass of flywheel rotor is analyzed. Furthermore, the vibration testing platform for measuring the vibration of MSFW on five DOFs is introduced, and then the vibration balancing method is investigated. Finally, the vibration magnitude of MSFW rotor induced by the residual unbalance mass is analyzed by measuring dynamic displacements, and the effectiveness of vibration balancing method is verified by comparing vibration magnitudes and power spectrum densities of the MSFW system with different situations, the static unbalance term is reduced by 90.5%, and the dynamic unbalance term is reduced by 82.4%.

Model of virtual balancing of rigid rotors

Rotor imbalances have a significant impact on the level of their vibration and reliability. Reduction of rotor imbalances is achieved through static and dynamic balancing that we propose to accomplish by virtual balancing of rigid rotors in two stages. At the first stage mutual orientation of the rotor parts is calculated to compensate their imbalances and couple unbalance. At the second stage the values of the masses and angular coordinates of two correction weights that allow eliminating the residual imbalance of the rotor are determined. The correction weights are placed in two balancing planes of the rotor. A model of virtual balancing is proposed to implement the balancing stages. The model makes it possible to determine the relative angular positions of the rotor parts, the values of the mass of two correction weights and their angular coordinates in the balancing planes. The effectiveness of using the proposed model was verified by performing calculations using the finite element model (FEM) of the rotor in the ANSYS software package. In the course of the study, data were obtained on the values of vibration velocities on the rotor supports. The results obtained show a significant reduction in the vibration velocities of the supports, amounting to 80% of their initial value.

Balancing of Flexible Rotors Supported on Fluid Film Bearings by Means of Influence Coefficients Calculated by the Numerical Assembly Technique

In this paper, a new method for the balancing of rotor-bearing systems supported on fluid film bearings is proposed. The influence coefficients necessary for balancing are calculated using a novel simulation method called the Numerical Assembly Technique. The advantages of this approach are quasi-analytical solutions for the equations of motion of complex rotor-bearing systems and very low computation times. The Numerical Assembly Technique is extended by speed-dependent stiffness and damping coefficients approximated by the short-bearing theory to model the behavior of rotor systems supported on fluid film bearings. The rotating circular shaft is modeled according to the Rayleigh beam theory. The Numerical Assembly Technique is used to calculate the steady-state harmonic response, influence coefficients, eigenvalues, and the Campbell diagram of the rotor. These values are compared to simulations with the Finite Element Method to show the accuracy of the procedure. Two numerical examples of rotor-bearing systems are successfully balanced by the proposed balancing method.

An Optimized Modal Balancing Approach for a Flexible Rotor Using a Vibration Response While the Rotor Is Speeding Up

The modal balancing method (MBM) is an effective method for reducing the vibration caused by the unbalancing of a rotor. A rotor’s modal parameters, especially its modal shapes, need to be accurately calculated in this method. This paper proposes an optimized modal balancing approach for flexible rotors. The vibration modes of the rotor are first obtained with experimental modal analysis based on the rotor’s response signals while the rotor is speeding up. The rotor balancing strategy is subsequently optimized by the sensitivity analysis of the mode shapes. Orthogonal trial masses are obtained based on the orthogonality of each vibration mode, and the correction masses are finally calculated by using the influence coefficients of the trial masses. An experimental result is shown to demonstrate and validate that the proposed approach is able to achieve superior accuracy compared to the conventional MBM.