•Novel local fault kinematic model for planetary gears is developed.•The effect of faulty tooth meshing location on impact response phase is studied.•Modulation mechanism considering the impact ...response phase variation is explored.•Spectrum structure with impact response phase variation is analyzed.•Proposed model is verified with numerical simulations and experiments as well.
A planetary gear train involves multiple components and has more complex kinematic relationships than a parallel gear train. Consequently, the fault characteristics extraction is more complicated. To ensure safe operation, it is necessary to properly understand the fault behavior of the planetary gear train. In the previous kinematic modeling, the relationship between the faulty tooth meshing location and the fault impact response phase is not fully considered. However, the fault impact response phase variation plays an important role in accurately characterizing the fault characteristics in the planetary gear train. To solve this problem, we analyze the relationship between the faulty tooth location variation and the fault impact response phase variation and then a novel fault response model is established. Based on this model, a revised planetary damage detection scheme is formulated. Through the simulated data analysis, it is revealed that the faulty tooth location variation not only affects the fault impact response phase, but also reallocates the sideband distributions in the response spectrum. Finally, using a laboratory planetary gear set, it is validated that the proposed model is able to reflect the real damage response better. Therefore, using the proposed model, more accurate damage features are able to be extracted from the measured vibration responses.
•The challenges of applying synchronous averaging in planetary gears is analyzed.•An effective and efficient fault feature separation scheme is formulated.•The amplitude modulation effect of ...extracted damage feature is preserved.•The proposed scheme is verified by simulations and experiments.
Synchronous averaging is an effective signal processing technique that has been demonstrated in damage detection of many fixed-axis gearboxes. However, its direct application to a planetary gearbox does not always yield satisfactory results, due to the complex meshing relationships among the components within the gearbox. Although the “vibration separation technique” can partially address this issue, the practical application of the technique often faces challenges, such as inefficiency in data utilization, inaccuracy in window positioning, and uncertainty caused by window size and shape. Moreover, the signal derived by this technique usually lost its physical meaning. In this paper, an effective and efficient fault feature separation scheme is formulated by analyzing the meshing dynamics unique to planetary gears. Compared to the traditional vibration separation technique, the proposed method offers three data processing advantages: 1. Optimal in data utilization; 2. Flexible in windowing position; 3. Adaptive in data length. The effectiveness of the proposed method is verified by simulations and experimental cases. The results indicate that the proposed method successfully separates the fault features of the sun gear and the planet gear. Especially in the case of limited data length, the proposed synchronous averaging strategy can still be flexibly adjusted to achieve the separation of fault features.
•Tooth wear is analytically evaluated with archard's equation.•Tooth wear is incorporated into TVMS, USTE and gear backlash.•A torsional dynamic model is applied to evaluate the effect of tooth wear ...on dynamic responses.
Gear wear is a typical and common early failure, which could lead to geometric deviation of tooth surface, further affecting vibration signal and transmission error. This paper is devoted to analyzing fault mechanism and dynamic characteristics of gear wear, which provides the basis for vibration-based fault diagnosis and monitoring of gear wear. For this purpose, a purely torsional dynamic model of planetary gear with gear wear is proposed where gear wear is evaluated by Archard's equation and it is incorporated into the dynamic model through time-varying mesh stiffness, unloaded static transmission error and gear backlash. Inspired by the work of Chen et al., gear wear is viewed as a kind of tooth deviation and the influence of gear wear on planetary gear dynamic parameters can be analyzed. Finally, the vibration responses of planetary gear under the effect of gear wear are analyzed.
•A rigid-flexible coupling model for planetary gear systems is developed.•An approach for simulating the pass effect is proposed.•Validation is performed through ANSYS modal analysis and vibration ...experiment.•Pre-emphasized noise excitation is introduced, aligning well with experiment.
A rigid-flexible coupling model for the planetary gear system is developed, in which the flexibility of the ring gear, input shaft, and carrier are considered. Subsequently, rotational modal projection is proposed to simulate the meshing of the flexible ring gear at any angle of planet gear revolution, and the coordinate transformation equations are presented to establish the coupling between rigid body and rotating flexible body. These two approaches incorporate the pass effect into the coupling model. Additionally, a method employing pre-emphasized noise to simulate random excitations is introduced. The model is validated by comparing computed modal frequencies and dynamic responses with those from ANSYS software and experiment, respectively. Results indicate that the proposed method accurately simulates the modulation signal observed in the experiment. Closely matched resonances excited by random excitations are apparent in experimental and simulated acceleration spectra, highlighting the validity of the proposed method and aiding in the determination of operational system modes. In addition, analyses of parameter influences are conducted, which further reveal the dynamic characteristics of the system.
Equally spaced planetary gearboxes are important power-train components for varied engineering systems. Their failures can result in significant capital losses and pose safety concerns. The vibration ...measurements perceived by a sensor mounted on the gearbox housing can provide valuable diagnostic information without normal gearbox operation interference. However, such vibration based monitoring techniques are difficult to implement in planetary gearboxes because of the complex nature of measured vibration spectra that is a result of planets revolving with respect to the stationary sensors mounted on the gearbox housing. Previous research with simulations and experiments using such measurements has reported distinct sideband patterns in the resulting vibration spectra, which differ significantly from the spectra of a normal fixed-axis/parallel gear pair system. In this paper, Fourier series analysis is used to explain these distinct sideband patterns that contain rich diagnostic information. The results obtained are useful to understand the cause of the observed vibration behavior in both healthy and faulty planetary gearboxes and identify the locations of additional frequency components introduced by the damaged gear in a complex measured vibration spectrum. Thus, the formulation presented in this paper can assist in developing robust feature extraction algorithms for early detection of planetary gearbox failures. The theoretical derivations presented in this paper are validated by both dynamic simulations and experiments on a dynamometer test bed using a 750kW gearbox damaged during its operation while installed in a wind turbine. The predicted frequencies for observed faults in the annulus and sun gears of the gearbox are vividly presented in the experimentally measured frequency spectrum.
•A mathematical model explains vibration signal measured on planetary-gear housing.•Such a model is further explored for diagnosis of equi-spaced planetary gear-sets.•Frequency features enabling detection of gear faults have been identified.•Evaluation of these frequency features depends only on the geometry of gear-sets.•The conclusions were validated based on data from 2.5MW dynamometer test rig.
•A dynamic model for a DPGS including all components is proposed.•The proposed model considers the planetary bearing roller and cage dynamics.•Effect of the sun gear speed on the contact force and ...vibrations of planetary bearing is studied.
Double planetary gear sets (DPGSs) are widely applied to high power and high torque mechanical transmission systems due to the high loading capacity, steady transmission, and high transmission efficiency. Most previous works studied the planetary bearing vibration characteristics without the gear excitations. This work establishes a dynamic model for a DPGS containing all components (sun gear, ring gear, carrier, inner planet, outer planet, planetary bearing roller, and planetary bearing cage). The components’ excitations in this work are more comprehensive than the reported references. The proposed model considers the planetary bearing roller and cage dynamics. Moreover, the gear interactions, planetary gear-bearing-carrier interactions, and roller-cage interactions are contained in the proposed model. The vibrations of planetary bearing roller, planet, carrier, and planetary bearing cage are analyzed. The effect of sun gear rotation speed on the planetary bearing contact force, planetary bearing roller-cage impact force, and vibrations of planetary bearing parts are studied. The simulated and experimental results are compared to prove the correctness of proposed model. Moreover, the results from proposed model and model without the cage are compared to show the advantage of proposed model.
The increased demands for driver comfort and stringent pollution control measures have resulted in a revival of planetary gearboxes for road applications, due to their possibility to change the ...transmission ratio under load in synchronism with engine operation. Modern boxes provide as many transmission ratios as possible from the least possible number of simple component planetary gear trains (PGTs) by providing links between elements of multiple component PGTs. The application conditions decide to prioritize either the maximum number of transmission ratios, or ruggedness and reliability. Power circulation, hollow shafts, or complex planet carrier arrangements are avoided if possible. This paper deals with multispeed complex PGTs composed of at least two interconnected simple component PGTs controlled by brakes and clutches. Several variants of complex PGTs and the placement of brakes and clutches on external shafts of the gear trains are examined, and the transmission ratio functions derived. The kinematics of multi speed gear trains are obtained as combinations of two or more two-speed gear trains. An analysis of several contemporary gearbox layouts is provided together with the transmission ratio functions, together with an overview of the procedure for the calculation of creation of multi-speed gear trains is given.
Established a dynamic model for HPGT with flexible support and floating sun gear.Researched the natural characteristics of HPGT.Studied the load sharing characteristic of flexible support when sun ...gear is floating.Studied the load sharing characteristic of flexible support when sun gear is normally supported.Compared the load sharing characteristic under these two conditions.
As an important part of reducers, herringbone planetary gear train (HPGT) has the advantages of small size, small mass, large transmission ratio, compact structure and strong carrying capacity. It has wide applications in the transmission fields such as aviation and ships. The flexible support stiffness and the floating components are largely influencing the load sharing characteristic, which is a key indicator to evaluate the bearing stability and reliability of planet gears. Therefore, it is necessary to study the influence mechanism of flexible support on the load sharing characteristic with floating sun gear. Based on the centralized parameters theory and the Lagrange method, a dynamic model for HPGT is established. At the same time, based on this model, natural characteristic is also researched. Particularly, the dynamic curves are expressed in a form of polar coordinate system, which can make the curves clearly show the changing law of dynamic characteristics. As shown in the studied results, when the sun gear is normally supported and the sun gear is floating, the natural frequency of the HPGT is calculated, and the influence mechanism of the flexible support on the load sharing characteristics is studied. In addition, the difference in load sharing characteristic is compared.
Two novel dual motor input powertrains are proposed to improve the energy efficiency of electric vehicles (EVs). The first powertrain is based on a dual motor with planetary gear transmission ...(DMPGT), which connects two motors to the sun gear and ring gear respectively, and the carrier is engaged with output shaft. Two band brakes equipped on the sun gear and ring gear can realize three driving modes. The second powertrain is based on a dual motor with parallel axle transmission (DMPAT). It also provides three driving modes through switching on and off the two motors. To evaluate the two proposed powertrains, they will be compared with the widely adopted single motor with 1-speed and with 2-speed powertrains. The gear ratios of the powertrains are selected aiming at the vehicle dynamic performance, while the gear or mode shifting is designed to maximize the efficiency of EVs through an instantaneous optimization algorithm. The simulation results of the two proposed powertrains in three typical driving cycles demonstrate that the EVs equipped with both DMPGT and DMPAT have a higher overall efficiency than the EVs equipped with single motor input powertrain.
