ObjectiveTo address numerous discrete tooth number combinations, unclear planet number arrangement and stage ratio allocation patterns, and the lack of rapid criteria for preferred topology family identification in early configuration design of high power wind turbine gearboxes, a physics based surrogate evaluation method was proposed for discrete feasible domain analysis of three stage NGW planetary gear trains.MethodsA physical surrogate model composed of the summed volumes of the sun gear, planet gears and ring gear rim was established based on contact strength-dominated scale estimation. The system surrogate volume and the outer diameter of the first-stage ring gear were adopted as surrogate indices to characterize the overall scale and radial envelope of candidate schemes. Under the constraints of concentricity, assembly, adjacency and transmission ratio error, full-domain enumeration was performed for tooth number combinations and planet number combinations. The effects of the planet number and staged transmission ratios on the surrogate indices were analyzed, and the stability of the obtained laws was verified by parameter perturbation and rechecking via detailed parametric optimization sorting.ResultsThe 12.5 MW case yielded 101 534 schemes and 57 topology families. Low surrogate volume schemes were mainly concentrated in regions with a large first stage planet number, relatively low first stage transmission ratio, and relatively high final stage transmission ratio. The planet number non increasing rule covered all schemes in the top 0.1% of surrogate volume and reduced candidate schemes by 45.04% while retaining 98.43% of the top 0.5% schemes. The Spearman rank correlation coefficient between average topology family surrogate volume and average mass after detailed parameter optimization was 0.956, indicating that the model supports early configuration pattern identification and preferred topology family screening.
ObjectiveAs the core component of a wind turbine pitch system, pitch bearings must endure complex fatigue loads generated by blades throughout their entire life cycle. Cracking at the plugging hole is one of the most common failure modes. To address this issue, the stress components driving the failure were analyzed, the potential reasons for the actual service life being shorter than the design simulation results were pointed out, and an on-site rectification scheme was proposed for engineering application practices.MethodsFirstly, the macroscopic morphology of the crack fracture at the plugging hole was analyzed to preliminarily identify the damage type. Secondly, a global finite element model (FEM) of the entire pitch system and a sub-model of the plugging hole were established and solved. The stress state and fatigue life at the plugging hole were evaluated, and the direction of the driving stress causing the crack was identified. Thirdly, considering the actual manufacturing process and fracture observation, the influence of surface scratches on the bearing life was discussed. Finally, an on-site rectification scheme involving the installation of a flange at the plugging hole was proposed, and its feasibility was analyzed using the FEM.ResultsThe results demonstrate that the circumferential stress along the intersection line between the plugging hole and the pin hole acts as the driving factor for the fatigue life of the plugging hole. During the bearing manufacturing process, surface defects such as scratches significantly reduce the bearing life. The rectification scheme using an additional flange not only substantially extends the bearing life but also features low cost and easy implementation. This study provides a methodological reference for ring fatigue assessment during the pitch bearing design phase, offers process control recommendations for practical production, and presents a feasible solution for risk mitigation in operational wind turbines.
ObjectiveChallenges including filtering distortion, outlier interference and non-stationary component resolution exist in gear tooth surface waviness extraction, and conventional approaches fail to achieve both geometric fidelity and high spectral resolution. A robust method for waviness extraction and spectral characterization along gear feature lines was proposed.MethodsFirstly, normal deviation signals were constructed along gear feature lines and detrending processing was completed, so as to realize one-dimensional dimensionality reduction of three-dimensional tooth surface errors and provide a unified geometric benchmark for waviness separation. Secondly, a robust Gaussian regression filtering model was established, and M-estimation and biweight iterative mechanism were introduced to suppress boundary distortion and spike interference and ensure the geometric fidelity of main waviness morphology. Then, adaptive multi-scale decomposition of the filtered signals was performed using CEEMDAN-HHT, and a space-frequency-energy characterization framework was constructed to analyze the multi-scale features of non-stationary waviness components. Finally, comparative tests were conducted based on simulation and measured data to quantitatively verify the filtering performance and characterization accuracy of the method.ResultsThe results show that compared with the standard Gaussian filter, the robust Gaussian regression filter improves the outlier suppression capability from 1.13 dB to 5.0 dB and reduces the boundary error by about 80%. Compared with FFT, CEEMDAN-HHT reduces the reconstruction root mean square error from 0.70 μm to 0.63 μm. The adaptability of the method under complex interference is verified by measured data, and local transient waviness defects and global dominant undulations can be clearly identified, which provides reference for quantitative evaluation and cause tracing of gear tooth surface waviness.
ObjectiveA shipborne 6-degree-of-freedom (DOF) parallel platform can compensate for the 6-DOF motions generated by vessels, thereby improving the reliability and safety of offshore operations and extending the operational time window. Such platforms possess advantages including a large workspace, high load-carrying capacity, and low susceptibility to singularities within the workspace. For shipborne application scenarios, a multi-scale comprehensive study was conducted with the F-norm condition number, natural frequency, and stiffness index selected as optimization objectives.MethodsFirstly, the required workspace of the 6-DOF parallel platform was analyzed based on the motion response of ships at sea, and this workspace was used as a constraint for the dimensional synthesis of the mechanism. Secondly, considering the practical requirements of high response speed, high frequency response, and high precision for shipborne 6-DOF parallel platforms, the F-norm condition number, natural frequency, and stiffness were adopted as multi-objective optimization performance indices to analyze the influence of mechanism parameters on these indices. Thirdly, the non-dominated sorting genetic algorithm Ⅱ (NSGA-II) was employed for multi-objective optimization, and the optimal mechanism parameters for the shipborne 6-DOF parallel platform were selected from the obtained Pareto-optimal set. Finally, simulation verification was carried out.ResultsThe simulation results demonstrate that, under the same control gain, the optimized parameters of the 6-DOF parallel platform achieve superior compensation performance. The residual motion amplitudes along the X, Y, and Z directions and around the X, Y, and Z axes are reduced by 44.6%, 66.7%, 65.6%, 70.5%, 26.3%, and 40.1%, respectively.
SignificanceAiming at the strict requirements for lubrication performance of face gear transmission in helicopter transmission systems, as well as the problems that the analysis system of tooth surface contact-lubrication coupling characteristics in existing research needs to be improved and the engineering application technical path is not clear, the research progress of face gear lubrication technology was systematically sorted out, and the core technical direction and development trend were clarified. [Analysis] Firstly, the research context of face gear lubrication technology for helicopter transmission scenarios was sorted out, and the core research boundary of this field was defined; secondly, the core technology of tooth surface contact characteristic analysis of face gear was disassembled to provide key input parameters for lubrication characteristic analysis; thirdly, the analysis methods and research results of tooth surface lubrication characteristics of face gears were summarized to clarify the key influencing factors of lubrication performance; finally, combined with the engineering requirements of helicopter transmission, the future key development directions of this field were prospected.
