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Technical Paper

Dog Clutch Without Circular Backlash

Abstract The paper is dedicated to design of a new dog-clutch gearshift mechanism for passenger car gearboxes with external synchronization. There are two main targets of presented work:1 Replace the standard synchronizer with cheap and compact shift device, which will keep the internal architecture of classical manual transmission.2 Keep all the other important functions of synchronizer:a minimal circular backlash to avoid clash during change of sense of the torque flow,b prevent unwanted disengagement,c guarantee the shift anytime,d determine neutral position (preferably). Czech Technical University in Prague is for several years active in the field of design and testing of shift mechanisms, as well as in design of new shift clutches. The currently presented clutch is 3rd generation of inventions of dog clutch systems. All clutches were fabricated as prototype and tested. All designs will be briefly described in the paper.
Journal Article

Value of Optimal Wavelet Function in Gear Fault Diagnosis

Abstract Gear fault diagnosis is important in the vibration monitoring of any rotating machine. When a localized fault occurs in gears, the vibration signals always display non-stationary behavior. In early stage of gear failure, the gear mesh frequency (GMF) contains very little energy and is often overwhelmed by noise and higher-level macro-structural vibrations. An effective signal processing method would be necessary to remove such corrupting noise and interference. This paper presents the value of optimal wavelet function for early detection of faulty gear. The Envelope Detection (ED) and the Energy Operator are used for gear fault diagnosis as common techniques with and without the proposed optimal wavelet to verify the effectiveness of the optimal wavelet function. Kurtosis values are determined for the previous techniques as an indicator parameter for the ability of early gear fault detection. The comparative study is applied to real vibration signals.
Journal Article

Distinction of Roller Bearing Defect from Gear Defect via Envelope Process and Autocorrelation Enhancement

Abstract Bearing and gear condition monitoring are important to improve a mechanical system reliability and performance. In the early stage of bearing failures, the Bearing Characteristic Frequencies (BCFs) contain very little energy and are often overwhelmed by noise and higher-level macro-structural vibrations, an effective signal processing method would be necessary to eliminate such corrupting noise and interference. Referring to the non-stationary characteristics of roller bearing fault vibration signals, a roller bearing condition monitoring method based on Envelope Process to raw time-domain vibration signal and Autocorrelation enhancement to the residual signal is put forward in this paper. The concept of Envelope and Autocorrelation techniques and its implementation for defect identification are discussed. Also, distinction of bearing fault signal as cyclostationary from periodic signal for gear fault.
Technical Paper

Estimation of the Gearbox No-Load Losses

Abstract In the laboratories of CTU in Prague, an inertia test stand was recently built for endurance tests of the internal shift mechanisms of passenger cars. With regard to the instrumentation of the stand, it can be used also for determination of lost power of the not-loaded transmission. In this paper we present the values for the no-load losses measured during different conditions (temperature, shifted speed, speed of rotation) on the automotive mechanical gearbox for the transversal disposition of the drivetrain. For the further usage of the measured values is important to determine the proportion of the different sources of losses. We are mainly interested to identify the proportion of the churning losses and losses in the sealing, since these two losses remain the same, whatever the load of the gearbox will be. The losses of bearings on input and secondary shaft were calculated with the tool available from SKF.
Technical Paper

Application of Order Analysis for Gear Fault Diagnosis under Variable Speed Conditions

Abstract A vehicle gearbox serves for torque and speed conversion with help of rotating elements. Therefore the gearbox experiences periodic excitation forces with a fundamental frequency following the rotation frequency. These excitation forces give rise to corresponding periodic response signals, i.e. signals having content at the fundamental (rotational) frequency and its harmonics. Order analysis is an analysis technique which is used to extract these harmonic orders from the response signals. This article intends to use the order tracking analysis for gearbox fault diagnosis under variable speed conditions to compare between healthy and faulty cases by using order extraction. Finally, determine maximum Root Mean Square (RMS) as severity index.
Journal Article

Application of Optimal Morlet Wavelet Filter for Bearing Fault Diagnosis

Abstract When localized fault occurs in a bearing, the periodic impulsive feature of the vibration signal appears in time domain and the corresponding Bearing Characteristic Frequencies (BCFs) emerge in frequency domain. The common technique of Fast Fourier Transforms (FFT) and Envelope Detection (ED) are always used to identify faults occurring at the BCFs. In the early stage of bearing failures, the BCFs contain very little energy and are often overwhelmed by noise and higher-level macro-structural vibrations. In order to extract the weak fault information submerged in strong background noise of the gearbox vibration signal, an effective signal processing method would be necessary to remove such corrupting noise and interference. Optimal Morlet Wavelet Filter and Envelope Detection (ED) are applied in this paper.
Technical Paper

Innovative Configuration of the Closed-Loop Test Stand

Abstract The purpose of the article is to describe different possibilities of the innovative concept of the closed-loop test rig. The performed tests will be demonstrated with the example of measured data. Firstly the article will describe in detail the design of the test stand and both torque units. The power flow in the closed-loop circuit will be described and measured to find out the power losses of all parts. The measurement will be done for manual and planetary pretensioning mechanism. The comparison of the overall efficiency and demanded power for both torque units will be given. For evaluation of gearbox efficiency, the magnitude of power losses will be evaluated for different revolutions, torque levels and shifted speeds. For a long term tests, the unmanned operation is prepared. For this purpose is the stand equipped with electromechanical shift robots. The description of its concept and functioning will be part of the paper.
Technical Paper

Fault Diagnosis of Rolling Bearing Based on Time Waveform Analysis

Abstract In this paper, a fault in rolling bearing is diagnosed using time waveform analysis. In order to verify the ability of time waveform analysis in fault diagnosis of rolling bearing, an artificial fault is introduced in vehicle gearbox bearing: an orthogonal placed groove on the inner race with the initial width of 0.6 mm approximately. The faulted bearing is a roller bearing located on the gearbox input shaft - on the clutch side. An optimal Morlet Wavelet Filter and autocorrelation enhancement are applied in this paper. First, to eliminate the frequency associated with interferential vibrations, the vibration signal is filtered with a band-pass filter determined by a Morlet wavelet whose parameters are optimized based on maximum Kurtosis. Then, to further reduce the residual in-band noise and highlight the periodic impulsive feature, autocorrelation enhancement is applied to the filtered signal.
Technical Paper

Gear Fault Diagnosis Based on Optimal Morlet Wavelet Filter and Autocorrelation Enhancement

Abstract An efficient condition monitoring system provides early warning of faults by predicting them at an early stage. When a localized fault occurs in gears, the vibration signals always exhibit non-stationary behavior. The periodic impulsive feature of the vibration signal appears in the time domain and the corresponding gear mesh frequency (GMF) emerges in the frequency domain. However, one limitation of frequency-domain analysis is its inability to handle non-stationary waveform signals, which are very common when machinery faults occur. Particularly at the early stage of gear failure, the GMF contains very little energy and is often overwhelmed by noise and higher-level macro-structural vibrations. An effective signal processing method would be necessary to remove such corrupting noise and interference. In this paper, a new hybrid method based on optimal Morlet wavelet filter and autocorrelation enhancement is presented.
Technical Paper

Robust Diagnostic Concept for Vehicle Gearbox with Artificial Pitting Defect in Gear using Vibration Measurements

Abstract Using the PULSE platform for vibration analysis, which has been developed as an advanced solution for vibration measurements, the Robust Diagnostic Concept (RDC) was elaborated. The PULSE setup is designed to aid in fault diagnosis of a vehicle gearbox - the main part of a vehicle powertrain. Time Domain, Continuous Wavelet Transformation Technique (CWT), FFT and order analysis measurements are used for detection of an artificial pitting defect in a gear by tracking the gearbox response at accelerated speed and different loads. The test stand is equipped with three dynamometers; the input dynamometer serves as the internal combustion engine, the output dynamometers introduce the load on the flanges of the output joint shafts. The pitting defect is manufactured on the tooth side of the fifth speed gear on the intermediate shaft. The effect of temperature on the vibration measurements was also investigated to study its impact on the fault diagnosis.
Journal Article

Synthesis of Efficient Powersplit CVT/IVT System

The target of the work is to find out the algorithm of definition of the ratios of mechanical part of complex powersplit CVT/IVT system with regard to the highest achievable efficiency. The presented synthesis is focused on powersplit systems, which will consist of a CVT part, differential and eventually by-pass gear. The algorithm will be programmed and become an integral part of the program Sungear developed on Czech Technical University in Prague for analyses and synthesis of planetary stepped transmissions and CVT/IVT powersplit systems. The article will mainly present the algorithm of definition of efficient powersplit system. For the search of the efficient powersplit system we assume that the following parameters are given: a Spread and efficiency of used CVT system.b Total spread of the whole powersplit CVT/IVT mechanism.c Optional: Ratios of the used CVT system.d Optional: Ratios of the whole powersplit CVT/IVT system.
Technical Paper

Analysis and Guidelines for Design of Efficient Power-Split Systems

The article is divided into two parts. The first part is dedicated to the analysis of mechanical systems by means of the matrix method. The power of the matrix method lies in its easy implementation in computer calculations. In this article we will present the program “SunGear.” This program is devoted to calculation of such Power-split systems and complete analysis of mechanical stepped planetary gearboxes. The second part of the article will describe the analysis of Power-split systems. In our study we focus on Power-split systems with mechanical CVT. The analysis will be presented by means of two examples: a) IVT (no shift elements) with the spread from reverse (ratio equals −2) up to the overdrive with a ratio of 0,6. The power is split between CVT (spread 0,25 up to 4) and mechanical gear set. The differential (planetary or bevel gear device with 2 degrees of freedom) is placed on the input or on the output of the mechanism.
Technical Paper

Computer-Aided Calculation of Planetary Gear Sets

The paper presents computer-aided calculation of planetary gear systems in automotive transmissions. We distinguish between two approaches to make the calculations: the direct problem and the inverse problem. The direct problem starts with a given nested gear set, calculated by means of the matrix method. This method, previously used only for nested gear trains consisting of simple planetary gear sets, is extended for computation of the Ravigneaux gear-sets as well. The matrix method-based program is presented. The inverse problem starts with the known kinematic parameters of a gear set. Two known methods used for defining of structure of nested planetary gear-box are briefly described: the iterative approach and the analytic parametric approach.