Passing through resonance of the unbalanced rotor with self-balancing device

The slow dynamics of unbalanced rotors with a passive self-balancing system are investigated considering the interaction of the mechanical system with a limited power engine. The slow dynamics equations are obtained using the averaging technique for partially strongly damped systems. Stationary system configurations, different types of nonstationary solutions while passing through resonance, and areas of stability and attraction are investigated.

Diagnosis of Friction on an Unbalanced Rotor by Phase-Shift Empirical Mode Decomposition Integration and Recurrence Plot

The friction and imbalance of components in rotating machines are some of the most recurrent failures that significantly increase vibration levels, thus affecting the reliability of the devices, the shelf life of its elements, and the quality of the product. There are many publications related to the different techniques for the diagnosis of friction and imbalance. In this paper, an alternative and new phase-shift empirical mode decomposition integration (PSEMDI) method is proposed to transform the acceleration into its velocity and displacement in order to construct the phase plane and recurrence plot (RP) and analyze the friction. The focus of PSEMDI and RP is to analyze nonlinear failures in mechanical systems. In machinery fault diagnosis, the main reason for using RP is to solve the integration of acceleration, and this can be achieved by phase-shifting the intrinsic mode function (IMF) with the empirical mode decomposition (EMD). Although the highest IMFs contain some frequencies, most of them have very few; thus, by applying the phase shift identity, the integration can be carried out maintaining the nonlinearities. The proposed method is compared with Simpson’s integration and detrending with the EMD method (here referred to as SDEMDI). The experimental RP results show that the proposed method gives significantly more information about the velocity and displacement spectra and it is more stable and proportional than the SDEMDI method. The results of the proposed integration method are compared with vibration measurements obtained with an interferometer.

Multibody Models for Tower Vibrations With an Unbalanced Rotor

This paper compares different models that can be used to analyze the vibrations of an unbalanced rotor with horizontal axis over a flexible tower. Model results are compared with experimental results. The modeled system is equivalent to a wind turbine with perfectly rigid blades. The selected models are the linear elastic model that is obtained using the linear theory of vibrations and two multibody models. The first multibody model uses Component Mode Synthesis for the description of the tower flexibility while the second multibody model used a lumped properties approach. Experimental results validate with reasonable agreement the resonance speeds of an unbalanced rotor. Furthermore, the models, while low degrees of freedom, give valuable insight of inertial loads on drivetrain components based on tower top dynamic motion. The work presented in this paper showed the use of 3 low-degrees of freedom models to predict resonance and tower top displacements. All simulation models did exhibit slightly higher resonance frequencies than the experimental results. The results showed that the tower top motion for the rectangular tower resembles a figure eight type motion, while the square tower top shows an elliptical motion.

A Model To Estimate Synchronous Vibration Amplitude For Detection of Unbalance in Rotor-Bearing System

A numerical technique for detection of unbalance magnitude of a rotor-bearing system is proposed and verified by experimental analysis. Dimensional analysis is used for development of mathematical model of an unbalanced rotor-bearing system following rigid rotor approach. A developed mathematical model is solved by factorial regression analysis method using the experimental data obtained by a Box-Behnken design. The proposed approach integrates the rotor parameters, disc parameters, bearing parameters and operating conditions with the synchronous vibration amplitude. Confirmation experiments are conducted using Taguchi design methodology with unbalance mass, rotor speed, mass eccentricity and radial load as parameters with different levels assigned to them.

Unbalance detection in rotating machinery based on support vector machine using time and frequency domain vibration features

The automated diagnostics of the unbalance in a rotor system has been presented in this study based on an artificial intelligence technique called support vector machine. In order to develop a support vector machine–based unbalance diagnosis, first the raw vibration signals in time and frequency domain are measured experimentally from healthy and unbalanced rotor installed on machine fault simulator. Then, three critical statistical features, namely, standard deviation, skewness, and kurtosis are extracted from the time and frequency domain vibration signals. Further, the features are used for training and testing of the support vector machine for building the automated diagnostic system for unbalance in a rotating system. The results from the present study show that the unbalance fault diagnosis can be effectively done based on the developed support vector machine–based methodology. The automated diagnosis of unbalance is possible with the time domain as well as frequency domain features. The results are better with time domain features than frequency domain features. In addition, the diagnosis is performed and found to be robust at most of the operating speeds of the rotor; however, the diagnosis should be avoided to attempt using the present methodology at very lower operating speeds.