Understanding Vibration Spectra of Planetary Gear Systems for Fault Detection

2003 ◽  
Author(s):  
Marianne Mosher
Keyword(s):  
Fault Detection ◽  
Kinematic Model ◽  
Planetary Gear ◽  
Model Data ◽  
Vibration Measurements ◽  
Flight Data ◽  
Vibration Spectra ◽  
Gear Mesh ◽  
Gear Systems ◽  
Made In

This paper explores the vibration spectra for planetary gear systems by studying a kinematic model of vibration and comparing the model with measurements of two helicopter transmissions made in flight. The model and flight data include systems with both uniformly and nonuniformly spaced planet gears. This model predicts vibration to occur only at frequencies that are integer multiples of the planet spacing repetition frequency and clustered around gear mesh harmonics. Vibration measurements show the model correctly predicts the frequencies with large components around the first several harmonics of the gear mesh frequency. Measurements do not confirm some of the more detailed features predicted by the model. Some features in the spectra from the numerically derived model can be used to separate the model data with and without planted faults. These features were not found useful for detecting faults in the vibration measurements of real gearboxes in flight due to added complexity in the spectra from real gearboxes.

Detection of Carrier-Plate Cracks Using Vibration Spectra

2007 ◽  
Author(s):  
Romano Patrick ◽  
Al Ferri ◽  
George Vachtsevanos
Keyword(s):  
Experimental Data ◽  
Mathematical Analysis ◽  
Planetary Gear ◽  
Vibration Signals ◽  
Vibration Spectra ◽  
Vibration Sensors ◽  
Vibration Signature ◽  
Frequency Components ◽  
Planet Gear ◽  
Gear Systems

This paper examines the problem of identifying cracks in planetary gear systems through use of vibration sensors on the stationary gearbox housing. In particular, the effect of unequal spacing of planet gears relative to the rotating carrier plate on various frequency components in the vibration spectra is studied. The mathematical analysis is validated with experimental data comparing the vibration signature of helicopter transmissions operating either normally or with damage leading to shifts in the planet gear positions. The theory presented is able to explain certain features and trends in the measured vibration signals of healthy and faulty transmissions. The characterization offered may serve as a means of detecting damage in planetary gear systems.

scholarly journals Impact of backlash, manufacturing deviations and friction on the load sharing factor of planetary gear systems

2019 ◽  
Vol 287 ◽  
pp. 01003
Author(s):  
Athanassios Mihailidis ◽  
Anastasios Moisiadis ◽  
Andreas Psarros
Keyword(s):  
Planetary Gear ◽  
Automatic Generation ◽  
Load Factor ◽  
Strong Impact ◽  
Torque Distribution ◽  
Gear Mesh ◽  
Python Scripting ◽  
First Results ◽  
Gear Systems ◽  
Planetary Gear System

Techniques and software tools, which were recently introduced by the authors, allowed for effi-cient automatic generation of 3D gear flanks and selective meshing of the gears of a simple planetary gear system with backlash and manufacturing imperfections. Friction of the meshing gear flanks was neglected. First results were promising and showed that even in geometrically perfect planetary gear systems the torque distribution is not uniform. It was further verified that pitch errors have a strong impact on the load distri-bution and that a self-aligning sun gear significantly enhances the torque distribution among the planets. In the current study, the procedure mentioned above is enhanced in several aspects. First, the tooth friction is considered. The friction coefficient is assumed constant along the path of contact; however different values for the sun-planet and planet-ring gear mesh may be given to account for the different contact conditions. Second, deviations are generated between given limits in a stochastic way. This feature significantly reduces the time needed to setup a model. Third, the entire analysis procedure is further automated by extensively employing Python scripting, enabling the solution of successive snapshots in much shorter time. Besides the torque distribution among the planets, the mesh load factor Kγ and the deformation of the teeth, the planet bearing load is also shown.

Dynamic Characteristics of Double Helical Planetary Gear Train With Tooth Friction

2015 ◽  
Author(s):  
Fengxia Lu ◽  
Rupeng Zhu ◽  
Haofei Wang ◽  
Heyun Bao ◽  
Miaomiao Li
Keyword(s):  
Degrees Of Freedom ◽  
Sliding Friction ◽  
Planetary Gear ◽  
Gear Train ◽  
Variable Step Size ◽  
Step Size ◽  
Planetary Gear Train ◽  
Gear Mesh ◽  
Meshing Stiffness ◽  
Nonlinear Dynamics Model

A new nonlinear dynamics model of the double helical planetary gear train with 44 degrees of freedom is developed, and the coupling effects of the sliding friction, time-varying meshing stiffness, gear backlashes, axial stagger as well as gear mesh errors, are taken into consideration. The solution of the differential governing equation of motion is solved by variable step-size Runge-Kutta numerical integration method. The influence of tooth friction on the periodic vibration and nonlinear vibration are investigated. The results show that tooth friction makes the system motion become stable by the effects of the periodic attractor under the specific meshing frequency and leads to the frequency delay for the bifurcation behavior and jump phenomenon in the system.

An Analytical and Numerical Investigation of Modulation Sidebands of a Planetary Gear Under Fluctuated External Torque

2018 ◽  
Author(s):  
Yunbo Yuan ◽  
Wei Liu ◽  
Yahui Chen ◽  
Donghua Wang
Keyword(s):  
Planetary Gear ◽  
Transmission Error ◽  
Operating Conditions ◽  
Radial Acceleration ◽  
External Torque ◽  
Gear Mesh ◽  
Planetary Gear Sets ◽  
Static Transmission Error ◽  
Frequency Modulations ◽  
Mesh Phasing

Certain operating conditions such as fluctuation of the external torque to planetary gear sets can cause additional sidebands. In this paper, a mathematical model is proposed to investigate the modulation mechanisms due to a fluctuated external torque (FET), and the combined influence of such an external torque and manufacturing errors (ME) on modulation sidebands. Gear mesh interface excitations, namely gear static transmission error excitations and time-varying gear mesh stiffness, are defined in Fourier series forms. Amplitude and frequency modulations are demonstrated separately. The predicted dynamic gear mesh force spectra and radial acceleration spectra at a fixed position on ring gear are both shown to exhibit well-defined modulation sidebands. Comparing with sidebands caused by ME, more complex sidebands appear when taking both FET and ME into account. An obvious intermodulation is found around the fundamental gear mesh frequency between the FET and ME in the form of frequency modulations, however, no intermodulation in the form of amplitude modulations. Additionally, the results indicate that some of the sidebands are cancelled out in radial acceleration spectra mainly due to the effect of planet mesh phasing, especially when only amplitude modulations are present.

scholarly journals Reliability and Random Lifetime Models of Planetary Gear Systems

2018 ◽  
Vol 2018 ◽  
pp. 1-12 ◽  
Author(s):  
Peng Gao ◽  
Liyang Xie ◽  
Wei Hu
Keyword(s):  
Load Distribution ◽  
Planetary Gear ◽  
Working Process ◽  
Random Load ◽  
Working Mechanism ◽  
Dynamic Reliability ◽  
Reliability Models ◽  
Process Failure ◽  
Failure Dependence ◽  
Gear Systems

Conventional reliability models of planetary gear systems are mainly static. In this paper, dynamic reliability models and random lifetime models of planetary gear systems are developed with dynamic working mechanism considered. The load parameters, the geometric parameters, and the material parameters are taken as the inputs of the reliability models and the random lifetime models. Moreover, failure dependence and dynamic random load redistributions are taken into account in the models. Monte Carlo simulations are carried out to validate the proposed models. The results show that the randomness of the load distribution is obvious in the system working process. Failure dependence has significant influences on system reliability. Moreover, the dispersion of external load has great impacts on the reliability, lifetime distribution, and redundancy of planetary gear systems.

A Three-Dimensional Load Sharing Model of Planetary Gear Sets Having Manufacturing Errors

2015 ◽  
Author(s):  
Nicholas D. Leque ◽  
Ahmet Kahraman
Keyword(s):  
Three Dimensional ◽  
Planetary Gear ◽  
Load Sharing ◽  
Distribution Model ◽  
Gear Mesh ◽  
Position Errors ◽  
Proposed Model ◽  
Manufacturing Errors ◽  
Manufacturing Tolerancing ◽  
Planetary Gear Sets

Planet-to-planet load sharing is a major design and manufacturing tolerancing issue in planetary gear sets. Planetary gear sets are advantageous over their countershaft alternatives in many aspects, provided that each planet branch carries a reasonable, preferably equal, share of the torque transmitted. In practice, the load shared among the planets is typically not equal due to the presence of various manufacturing errors. This study aims at enhancing the models for planet load sharing through a three-dimensional formulation of N-planet helical planetary gear sets. Apart from previous models, the proposed model employs a gear mesh load distribution model to capture load and time dependency of the gear meshes iteratively. It includes all three types of manufacturing errors, namely constant errors such as planet pinhole position errors and pinhole diameter errors, constant but assembly dependent errors such as nominal planet tooth thickness errors, planet bore diameter errors, and rotation and assembly dependent errors such as gear eccentricities and run-outs. At the end, the model is used to show combined influence of these errors on planet load sharing to aid designers on how to account for manufacturing tolerances in the design of the gears of a planetary gear set.

A positive energy residual (PER) based planetary gear fault detection method under variable speed conditions

2019 ◽  
Vol 117 ◽  
pp. 347-360 ◽  
Author(s):  
Jungho Park ◽  
Moussa Hamadache ◽  
Jong M. Ha ◽  
Yunhan Kim ◽  
Kyumin Na ◽  
...  
Keyword(s):  
Fault Detection ◽  
Detection Method ◽  
Planetary Gear ◽  
Positive Energy ◽  
Variable Speed ◽  
Gear Fault

Locating Faulty Planet Gears Using External Vibration Measurements

2019 ◽  
Vol 9 (1) ◽  
pp. 14-17
Author(s):  
D Peng ◽  
W A Smith ◽  
R B Randall
Keyword(s):  
Vibration Signal ◽  
Processing Technique ◽  
Operating Conditions ◽  
Internal Vibration ◽  
Signal Processing Technique ◽  
Vibration Measurements ◽  
External Vibration ◽  
Gear Mesh ◽  
Mesh Phasing ◽  
Planet Carrier

In this study, a mesh phasing-based approach is developed to locate the positions of faulty planet gears using external vibration measurements. Previous studies have illustrated how this can be achieved using internal vibration measurements recorded from a sensor placed on the planet carrier. It was shown in these studies that the timing of identifiable fault symptoms in the vibration signal relative to the phase of the gear-mesh component depends on which of the planet gears carries a fault. A signal processing technique is then developed to locate the position of a spalled gear using internal vibration measurements. However, internally mounted sensors are not commonly used in planetary gearboxes and it is much more convenient to mount sensors externally, for example on the gearbox casing. Therefore, this study extends the concept of using mesh phasing relationships to locate faulty planet gears, this time using external vibration measurements. The updated procedure is validated using experimental data collected from a test-rig running under a range of operating conditions. The results show that the updated procedure is able to identify the locations of faulty planet gears so long as an absolute phase reference (for example from a tachometer) of the planet carrier is available.

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