Tooth defect detection in planetary gears by the current signature analysis: numerical modelling and experimental measurements

Monitoring transmission systems is a huge scientific focus to prevent any anomaly and malfunctioning damaging the system. Several methods were used to investigate the gears behaviour and mainly its state. And until the last century, vibrations signals were the most performing technique in this field. However, nowadays, other alternatives are considered more accurate and accessible such as controlling the motor current signals to study the behaviour of the mechanical system. Within this context, this paper aims to study the electromechanical interaction between a double stage of planetary gearboxes driven by an asynchronous machine. The model used is based on a Park transformation for modelling the asynchronous machine and a torsional model to describe the dynamic behaviour of the double-stage planetary gearbox. Through this approach, the numerical simulations illustrate the impact of the tooth gear defect on the signature of the motor current. The results obtained from the simulations will be presented in the time domain and the frequency domain using the fast Fourier transform and the Hanning window to highlight the mechanical frequencies in the phase current spectrum. This work will be distinguished by validating the numerical results using experimental measurements, which will be displayed in order to justify the sensitivity of the model developed.The authors would like to acknowledge the help provided by the project “Dynamic behaviour of gear transmissions in nonstationary conditions”, ref. DPI2017-85390-P, funded by the Spanish Ministry of Science and Technology. They would like to thank the University of Cantabria cooperation project for the doctoral training to Sfax University students

Electrical Signature Analysis of Synchronous Motors Under Some Mechanical Anomalies

Electrical Signature Analysis (ESA) has been introduced for some time to investigate the electrical anomalies of electric machines, especially for induction motors. More recently hints of using such an approach to analyze mechanical anomalies have appeared in the literature. Among them, some articles cover synchronous motors usually being employed to improve the power factor, drive green vehicles and reciprocating compressors or pumps with higher efficiency. Similarly with induction motors, the common mechanical anomalies of synchronous motor being analyzed using the ESA are air-gap eccentricity and single point bearing defects. However torsional effects, which are usually induced by torsional vibration of rotors and by generalized roughness bearing defects, have seldom been investigated using the ESA. This work presents an analytical method for ESA of rotor torsional vibration and an experimentally demonstrated approach for ESA of generalized roughness bearing defects. The torsional vibration of a shaft assembly usually induces rotor speed fluctuations resulting from the excitations in the electromagnetic (EM) or load torque. Actually, there is strong coupling within the system which is dynamically dependent on the interactions between the electromagnetic air-gap torque of the synchronous machine and the rotordynamics of the rotor shaft assembly. Typically this problem is solved as a one-way coupling by the unidirectional load transfer method, which is based on predetermined or assumed EM or load profile. It ignores the two-way interactions, especially during a start-up transient. In this work, a coupled equivalent circuit method is applied to reflect this coupling, and the simulation results show the significance of the proposed method by the practical case study of Electric Submersible Pump (ESP) system. The generalized roughness bearing anomaly is linked to load torque ripples which can cause speed oscillations, while being related to current signature by phase modulation. Considering that the induced characteristic signature is usually subtle broadband changes in the current spectrum, this signature is easily affected by input power quality variations, machine manufacturing imperfections and the interaction of both. A signal segmentation technique is introduced to isolate the influence of these disturbances and improve the effectiveness of applying the ESA for this kind of bearing defects. Furthermore, an improved experimental procedure is employed to closely resemble naturally occurring degradation of bearing, while isolating the influence of shaft currents on the signature of bearing defects during the experiments. The results show that the proposed method is effective in analyzing the generalized roughness bearing anomaly in synchronous motors

In-wheel motor vibration control for distributed-driven electric vehicles:A review

Efficient, safe, and comfortable electric vehicles (EVs) are essential for the creation of a sustainable transport system. Distributed-driven EVs, which often use in-wheel motors (IWMs), have many benefits with respect to size (compactness), controllability, and efficiency. However, the vibration of IWMs is a particularly important factor for both passengers and drivers, and it is therefore crucial for a successful commercialization of distributed-driven EVs. This paper provides a comprehensive literature review and state-of-the-art vibration-source-analysis and -mitigation methods in IWMs. First, selection criteria are given for IWMs, and a multidimensional comparison for several motor types is provided. The IWM vibration sources are then divided into internally-, and externally-induced vibration sources and discussed in detail. Next, vibration reduction methods, which include motor-structure optimization, motor controller, and additional control-components, are reviewed. Emerging research trends and an outlook for future improvement aims are summarized at the end of the paper. This paper can provide useful information for researchers, who are interested in the application and vibration mitigation of IWMs or similar topics

Analysis of Ball Bearing Defects in Synchronous Machines using Electrical Measurements

Rolling element bearings are used in most electrical machines, especially for small and medium size applications. Under non-ideal operating conditions, ball bearing condition degrades by fatigue, ambient vibration, misalignment, overloading, contamination, corrosion from water or chemicals, improper lubrication, shaft currents and residual stress left from the bearing manufacturing process. All of these conditions eventually lead to increased vibration and acoustic noise during machine operation which at some point in time results in unexpected bearing failure. Over the years, a great number of publications have been devoted to the detection of mechanical faults, including rolling element bearing defects and torsional defects, in electrical machines based on Electrical Signature Analysis (ESA). It has been observed that these faults can affect either the stator to rotor air-gap distribution or the running speed of the machine, which can be reflected in the signature of the electrical signals. However, the physical link between the mechanical degradation and the electrical signature is still not explained well. A multi-physics model is developed by joining the detailed mechanical model of a rotor bearing system and the electrical model of a synchronous machine in this research. This combined model is capable of describing the transmission of information originating from bearing faults and their impact on the variations of the measured electrical signals. The electrical machine model is developed based on winding function approach and its validity is demonstrated by a more accurate Finite Element Method (FEM) model. The mechanical model consists of a high fidelity rotor-bearing system with detailed nonlinear ball bearing model and a flexible finite element shaft model. It is validated using the housing vibration data collected from some experiments. Generalized roughness bearing anomalies are linked to load torque ripples and airgap variations, while being related to current signature by phase and amplitude modulation. Considering that the induced characteristic signatures are usually subtle broadband changes in the current spectra, these signatures are easily affected by input power quality variations, machine manufacturing imperfections and environmental noise. In this research, a new algorithm is proposed to isolate the influence of the external disturbances of power quality, machine manufacturing imperfections and environmental noise, and to improve the effectiveness of applying the ESA for generalized roughness bearing defects. The results show that the proposed method is effective in analyzing the generalized roughness bearing anomaly in synchronous machines. Furthermore, the electrical signatures are analyzed in a synchronous machine with bearing defects. The proposed fault detection method employs a Zoomed Fast Fourier Transform (ZFFT) and Principal Component Analysis (PCA) and it is also tested on the available experimental data. The results show that amplitude induced electrical harmonics are related to the level of vibration, and the electrical signatures are affected heavily by other variables, such as power quality and load fluctuation. The proposed method is shown to be effective on detecting generalized roughness bearing defects in synchronous machines

Soluciones para la medición de par y velocidad en bancos de ensayos de controladores de máquinas eléctricas

The continuous search for improvement in electromechanical developments requires a clear understanding of the torque measurement required in each application. The decisions made will have a profound impact on the quality and cost of the results. This article presents the principles normally used for sensing mechanical torque on a shaft and the reasons for the widespread use of strain gauges. The importance of differentiation between static and dynamic measurements and the current technologies used in each case are discussed. The relevant factors that define a transducer are described and a comparative analysis between them is carried out, to then examine the possible mounting methods, with their benefits and limitations. Finally, different low-cost solutions are proposed for the design of the torque and speed measurement section without sacrificing system performance, for different test benches for electrical machine controllers, including the necessary signal conditioning electronics. The article aims to be a tutorial compendium of topics to study to successfully implement a test bench without damaging the torque transducer or introducing measurement errors, since the information on these topics is scattered and it is difficult to access knowledge of the selection criteria and project procedures.La continua búsqueda de la mejora en los desarrollos electromecánicos impone una clara comprensión de la medición de par necesaria en cada aplicación. Las decisiones tomadas tendrán un profundo impacto en la calidad y el costo de los resultados. En este artículo se presentan los principios comúnmente empleados para el sensado de par mecánico en un eje y el porqué de la utilización extendida de las galgas extensiométricas. Se discuten la importancia en la diferenciación entre las mediciones estáticas y dinámicas, y las tecnologías actuales utilizadas en cada caso. Se describen los factores relevantes que definen a un transductor y se realiza un análisis comparativo entre ellos, para luego examinar los posibles métodos de montaje, con sus beneficios y limitaciones. Finalmente se proponen distintas soluciones de bajo costo para el diseño de la sección de medición de par y velocidad sin sacrificar el rendimiento del sistema, para diferentes bancos de ensayos para controladores de máquinas eléctricas, incluyendo la electrónica de acondicionamiento de señal necesaria. El articulo pretende ser un compendio tutorial de temas a estudiar para implementar con éxito un banco de ensayos sin dañar al transductor de par ni introducir errores de medición, ya que la información sobre esos temas está dispersa y es difícil acceder al conocimiento de los criterios de selección y procedimientos de proyecto

Applying Variable Speed Drives With Static Frequency Converters To Turbomachinery.

LecturePg. 35-46Today, the variable speed drive with AC motor and static frequency converter is an outstanding solution to control the speed of turbomachines in the power range up to 100 MW and more. A wide selection of variable speed drives, both mechanical and electrical, is available. These systems are listed and discussed. The aspects that are essential for their application are dealt with. A further issue is the integration of the variable speed drive into its application environment. From the itemized electrical variable speed drive's interfaces, two are treated in more detail, namely the interface to the power supply system and the one to the mechanical system (shaft train). Some practical cases concerning design and operation characteristics of the mechanical system are subject to reflection

A reliability study of the traction drive system in haul trucks based on failure analysis of their functional parts

The efficiency of a mining and processing plant depends on the level of complex mechanization of the production process. In mineral extraction, haulage is a major cost category, with haul trucks being the key component of the mining transportation system. To improve production performance, mining operations can increase their haulage turnover and reduce transportation costs, which necessitates making haul trucks more reliable. This can be done by improving their mean time to first failure (MTFF) indicators. This article analyzes the reliability status of the traction drive system inhaul trucks operating in the mineral resources sector. It provides a quantitative assessment of traction drive system failures resulting from part defects and discusses the associated repair costs. By examining failure data from 2018 to 2022 and the results of vibration tests performed on a diesel generator, the study reveals that the most expensive failures are associated with defects in the synchronous generator, which are primarily caused by elevated external vibrations. Based on basic vibration tests and vibration spectra tests at different operating modes, recommendations have been formulated concerning the generator’s robustness to external mechanical forces and the ways to increase the generator’s protection grade to prevent dust intrusion. The study also identifies the frequency range that poses the greatest risk of damage to the windings

Condition Monitoring of a Belt-Based Transmission System for Comau Racer3 Robots

This project has been developed in collaboration with Comau Robotics S.p.a and the main goal is the development in China of an Health Monitoring Pro-cess using vibration analysis. This project is connected to the activity of Cost Reduction carried out by the PD Cost Engineering Department in China. The Project is divided in two part: 1. Data Acquisition 2. Data Analysis An Automatic Acquisition of the moni.log file is carried out and is discussed in Chapter 1. As for the Data Analysis is concerned a data driven approach is considered and developed in frequency domain through the FFT transform and in time domain using the Wavelet transform. In Chapter 2 a list of the techiques used nowadays for the Signal Analysis and the Vibration Monitoring is shown in time domain, frequency domain and time-frequency domain. In Chapter 3 the state of art of the Condition Monitoring of all the possible ma-chinery part is carried out from the evaluation of the spectrum of the current and speed. In Chapter 4 are evaluated disturbances that are not related to a fault but be-long to a normal behaviour of the system acting on the measured forces. Motor Torque Ripple and Output Noise Resolution are disturbance dependent on ve-locity and are mentioned in comparison to the one related to the configuration of the Robot. In Chapter 5 a particular study case is assigned: the noise problem due to belt-based power transmission system of the axis three of a Racer 3 Robot in Endu-rance test. The chapter presents the test plan done including all the simula-tions. In Chapter 6 all the results are shown demostrating how the vibration analysis carried out from an external sensor can be confirmed looking at the spectral content of the speed and the current. In the last Chapter the final conclusions and a possible development of this thesis are presented considering both a a Model of Signal and a Model Based approach