Gearbox Design Research Articles

Design and Analysis of 2-Stage Gearbox for ATV Applications

Abstract: The main objective of this project is to design and develop a 2-Stage- Reduction gearbox for all terrain vehicles application. Gearbox is a mechanical unit consisting of series of gears within a housing (casing) or a simple gear train. It is the main component of the powertrain system as it provides speed and torque conversions from the Engine or CVT to the wheels. The gears inside of gearbox can be any one of a number of different types of the gear that are available in the market i.e., from spur gears to worm gears and planetary gears as well. In this report the gearbox is made from a helical gear train. This report focuses on selection of overall reduction ratio of the gearbox, material selection, selection of gear dimensions, selection of shaft dimension, design of key and bearing selection from SKF bearing catalogue. The bending and wear strengths are calculated to determine factor of safety and later, Finite element analysis is performed to validate the results. Keywords: Geartrain, Shaft Design, SKF Bearings, Solidworks, FEA

Minimum friction losses in wind turbine gearboxes

Improving the mechanical efficiency is not the most important objective in the design of wind turbine gearboxes since the available wind energy is abundant and costless. The most important criteria for dimensioning the gearbox are the fatigue strength—bending and pitting—, noise emission, vibrations, and maintenance requirements. Nevertheless, mechanical losses increase the lubricant temperature and induce thermal stresses, which increases wear and cracking risk. This means that friction losses should be reduced as much as possible, but always regarding the contact and tooth-root stress levels, as well as the other operating parameters which should be kept for ensuring the required operating conditions.In this paper, a study on the variation of the friction losses with the tooth shift coefficients is presented. All the other geometrical parameters—number of teeth, tooth height, pressure angle, helix angle, face width, and center distance—are unalterable, since all of them have been chosen according to more important design requirements. In addition, to keep the contact and tooth-root stress levels, the shift coefficients of the sun, planets and ring are calculated in such a way that the transverse contact ratios are kept, and therefore the critical load points for bending and pitting are also unchanged. The radial clearance is also kept in order to allow the proper evacuation of the lubricant. Finally, all the geometrical constraints (undercut, pointing, root interference, secondary interference, backlash) are also imposed. With all these restrictions, the optimal shift coefficients for all the gears are calculated to minimize the friction losses.

Automation of gearbox design

In order to respond to a shortened development time of today’s transmission systems, the automation of certain steps in the design process is essential for ensuring an efficient development process. Computer-aided tools are widely used for analyzing given design configurations because standardized methods are available to evaluate the load carrying capacity of all key components of a simple gear train, namely bearings, shafts and gears. At an early stage of development, requirements and restrictions need to be synthesized to design concepts. During this step, engineers typically rely on their experience and proven practice. Design optimization usually is achieved through an iterative and time-consuming process of analyzing and tuning towards an optimization objective. In this paper a time-saving, automated and systematic method for the design of weight optimized helical gearboxes is proposed. The underlying method has been derived from both, norms and guidelines, which exist for the design and layout of shafts, bearings and gear wheel bodies. Starting with only few input parameters, a detailed shaft geometry with different diameter sections can be derived. A discrete set of values from standard tables and rolling bearing catalogs represents the method’s framework for all realizable shaft diameters in each section. A mixed integer nonlinear optimization problem results from the interdependence between these distinct values. For this purpose, a systematic iterative approach has been developed and implemented in an established design program for gearbox systems. The algorithm uses the results drawn from an analytical calculation of the shaft load carrying capacity to directly adjust the shaft’s diameter and length values. The dimensioning of the wheel body, the service life calculation of rolling element bearings and the selection of specific machine elements are embedded in a systematic sequence. As a result, the model is capable to work out a weight-optimized gearbox that consists of gear meshes, shafts and bearings, taking all three components into consideration at a time.

The load sharing structure design and FE analysis of planetary gearbox with flexible pin

The paper first introduced the unequally load sharing in the planetary gear set and explained the cause of unequally load sharing in traditional design. Then a new floating structure of planetary gear with flexible pin has been designed to improve unequally load sharing of planetary gear set. In order to verify the flexible pin structure effects on the load sharing, two integrated finite element models have been built. Each one consists of two coupled planetary gear sets. One finite element model has been built with flexible pin structure and the other with fixed pin. The same load and boundary conditions have been applied to the two different finite element models. After analysis, the vonmises stresses of different parts such as ring gear, planetary gear, bearing and pin etc. in two different models have been compared. From the analysis result verification, the maximum vonmises stress of flexible pin of planetary gear set is much higher than that of planetary gear set with fixed pin in different mesh position. Although it is in the design range of material strength, its increase indicates that flexible pin structure makes the higher unequal mesh load of planetary gear shared with other pinions, the deflection of flexible pin make the load sharing with other pinions possible. Whereas the maximum vonmises stresses of other parts such as ring gear, planetary gear, bearing and sun gear decreases in a certain degree with the flexible pin deflection. It really indicates that the effect of flexible pin in the planetary gear set is obvious against fixed pin. When the higher unequally sharing load becomes smaller, maximum vonmises stresses of all planetary gear set parts except flexible pin become smaller and safer.

Time-Domain Dynamic Modeling and Analysis of Complex Heavy-Duty Gearbox Considering Floating Effect

Expert insights into the time-domain dynamic behavior of heavy-duty gearboxes form the foundations of design evaluation and improvement. However, in the existing lateral–torsional coupling (LTC) modeling method for gearboxes that is normally used for frequency-domain dynamic behavior, the meshing forces are modeled as spring dampers with fixed acting points on the meshing gears to simulate only the transient LTC effect, and thus the steady state characteristic in the time domain cannot be obtained due to the unrealistic distortion of positions and orientations as the gear angles increase. In this paper, a novel and generally applicable LTC modeling method for heavy-duty gearboxes, mainly planetary gear sets with floating components, is proposed by using space-fixed spring dampers with floating acting points on the meshing gears to study the time-domain dynamic response and to support the dynamic design of heavy-duty gearboxes. Based on the proposed method, a LTC model of a 2 megawatt (MW) wind turbine gearbox with floating components considering the time-varying meshing stiffness, bearing stiffness, torsional stiffness, and floating effect was established. The simulated results of representative components were in accordance with experimental results on a test rig, and dynamic behavior was calculated.

Experimental investigation of the dynamic load sharing of planetary gearboxes

Due to their compactness and power density, planetary gearboxes are used for a wide range of high-performance applications in the automotive, aviation and marine sector. Aerospace applications in particular benefit from a full use of the load capacity potential to meet the requirements for lightweight construction and efficiency. Against this background, the load sharing between the individual planetary gears plays a decisive role. A uniform load sharing enables the design of the single tooth meshes without load increases and oversizing. However, due to manufacturing and assembly deviations, a perfect load sharing is technically not feasible. These load increases are taken into account in the standard calculation of the load capacity of planetary gearboxes by the mesh load factor Kγ. The load sharing in planetary gearboxes is influenced by a number of factors, such as the rigidity of shafts, housing and bearings, the number of planets, the quality of the gear wheels and the operating conditions. Detailed simulations or extensive experimental measurements are required to determine the exact load sharing. For new designs of planetary gearboxes, there are only simplified assumptions available, based on the number of planets and a rough estimation of the operating range. Especially additional dynamic forces, due to operation in high-speed ranges or near resonance frequencies, can lead to a considerable change of the dynamic load sharing compared to the static load sharing and cause an uncertainty in the design. Thus, in this paper the dynamic load sharing behaviour is investigated from 0 to 6800 rpm sun speed for different loads. Based on the experimental data recommendations for the design of planetary gearboxes under consideration of the operating conditions are derived.

Topology Optimization of an aircraft engine gearbox

Topology Optimization (TO) is a mathematical method extensively employed to optimize material layout within the design space, for a given set of boundary conditions with the goal of maximizing the performance of the system. This process takes a three-dimensional design space and whittles material away within it to achieve the most efficient design. Currently, engineers use this mathematical approach at a concept level of a design process, leading to results which are often fine-tuned for manufacturability. In some cases, the optimized geometry can be directly manufactured using additive manufacturing, indeed, TO is a key part of design for additive manufacturing. This work aims to apply TO in order to minimize the mass of an engine gearbox while maintaining an acceptable mechanical performance when compared to the original design. Numerical simulations are carried out by means of CAD and FEM software in order to improve the design of an aircraft gearbox composed of four gears, therefore, irrelevant parts of material are removed in the design space to meet the goal of minimizing the mass of the gearbox. The application of TO allows to obtain a better, lighter, and more efficient design of the gearbox by keeping its mechanical performance unchanged.

Research of Fatigue Life Prediction for Optimization of the Gearbox Design Based on MSC.Patran

Research of Fatigue Life Prediction for Optimization of the Gearbox Design Based on MSC.Patran

Catia Customization for Design and Modeling of Two Stage Spur Gearbox

In this paper, we describe how the customization of design task, in solid modeling with CATIA V5 for two stage spur gearbox can be approached, by means of macros (piece of code) and with GUI form. The user has to supply some basic requirements of the gearbox and rest of the different parameters for design of gearbox is calculated by formulas. And then with the help of these parameters, part model of gearbox is created.

Sensor selection for cost-effective virtual torque measurements on a wind turbine gearbox

Measuring the operational torques during the lifetime of a wind turbine gearbox offers a valuable source of information for design, monitoring, predictive maintenance and control, and can help reduce operational expenses and downtime. In this paper we investigate indirect sensing as a valuable alternative to direct sensing, which is costly and intrusive. The resulting virtual torque sensor makes use of an Augmented Extended Kalman filter (AEKF), a physics based model, and measurements. The measurements considered are encoders on the high- and low speed shaft together with strain sensors, which are easy to install on the gearbox housing. We first discuss the theoretical background of the AEKF and methods for tuning the AEKF parameters. We then give an overview on the models used. Next, we focus on a sensor selection algorithm that can select the most performant (e.g. high signal-to-noise ratio) sensors. Finally, we validate the virtual torque sensor numerically. We show that with encoder measurements on the high speed shaft and 7 strain gauges placed on the housing we can achieve a Normalized Root Mean Squared Error (NRMSE) of 1.27% and 0.02% for the low- and high speed shaft torque, respectively. Without any strain gauges (i.e., only with the encoders), the estimation accuracy degrades to an NRMSE of 1.37% and 0.12%. A further analysis of the estimation results with different amounts of strain gauges shows that the amount of strain gauges can be reduced without a significant loss in estimation accuracy. These results show the potential of virtual torque sensing as a mean to obtain operational torque information for the design, monitoring and control of wind turbine gearboxes.

Effects of wake on gearbox design load cases identified from fleet-wide operational data

Drivetrains play an essential role in guaranteeing the reliability of wind turbines. A challenge in their design is the wide range of loading conditions they are exposed to. Several design load cases are required to be simulated in order to ensure that the ultimate loads are not exceeded, and to validate that the fatigue lifetime matches the design requirements. These loading conditions include among other (emergency) stops, start-ups, and normal and parked operation in different ambient conditions (wind speed, wave height, …). The design requirements are validated through a combination of functional, robustness and system tests when the turbine is operated in the design load cases. Within the context of Industry 4.0, turbines are becoming increasingly equipped with sensors. This offers opportunities for the in-depth validation of design hypotheses, as it allows to obtain detailed insights in the occurrence of loading events to which turbines are exposed to throughout their lifetime. This can be incorporated in future design iterations to further optimize the design based on more realistic loading conditions. The goal of this paper is to automatically and continuously classify SCADA data of an offshore farm in the aforementioned design load cases on a farm-wide level. Using this framework, the effects of wake on loading conditions are assessed in a data-driven manner.

OPTIMAL CONTROL OF AN ACTUATOR OF A ROBOTIC GEARBOX

Problem. Despite the vigorous development of electric vehicles, the task of facilitating the driver to handle with elements of mechanical transmission remains relevant. For this purpose, the automation of mechanical transmission units is performed. For instance, so-called robotic gearboxes are widespread. The principle of operation of such gearboxes is similar to mechanical ones, but special separate actuators carry out the selection and shifting into the desired gear. The design of a robotic gearbox was proposed at the Automobile Department of Kharkiv National Automobile and Highway University. At this gearbox, two DC motors are used as actuators. The efficiency of this gearbox largely depends on the efficiency of the DC motors control system, which should provide smooth but at the same time fast and accurate positioning of their shafts. In previous works, PID controllers were used to controlling the actuator of the gearbox. However, although the PID controller provides satisfactory quality of the control system, it is not an optimal controller. Goal. The goal of this paper is to develop an optimal controller for the actuators of the robotic gearbox mentioned above. Methodology. To meet this goal, it was proposed to use a linear-quadratic controller (LQR). The analysis of the impact on transient processes in the control system of the values of the weighting factors in the quadratic performance criterion is performed. Results. The LQR synthesized provides high speed of response (within of 0.5 s) at the desired gear selecting and more than two times less overshoot compared to the PID regulator. Originality. The regularities in the gearbox drive performance when changing the values of the weighting factors in the performance criterion have been established. An optimal control system for the robotic gearbox actuator has been developed. Practical value. The implementation of the designed controller will increase the efficiency of the gearbox under consideration.

Finite element stress analysis of three-stage gear box

The stress analysis of the three-stage gearbox is carried out by finite element analysis method using the Ansys commercial program. The triple reduction helical gearbox is made of AISI 5115 Steel (16MnCr5) and AISI 8620. Static structural and rigid dynamic analyzes are performed in this work. The three-stage helical gearbox is a three-stage gearbox transmitting 0.5 kW at 1390 rpm with a reduction ratio of 127.99:1. After setting the boundary conditions for helical gears, the analysis is performed. Rotational velocity is given to rotating gears for static structural analysis. Analyzing these types of gearboxes to be produced enables the product to be produced more consciously with optimum design parameters with its right safety coefficients. After the static analysis, dynamic analysis is also performed using the modal analysis option of Ansys software. After the mode shape analysis and natural frequency analysis are performed, the operation frequency values of the gearbox are calculated by considering the input and output rpm values in the gearbox. These calculated values are compared with the normal operating condition to see if there will be any resonance in the gear box design during normal operating conditions.

Reducing mass while improving the operational behavior: form optimization of planetary gearbox housings

The optimization of load sharing between planets is one of the most important goals in planetary gearbox design. Unevenly distributed load will cause locally higher flank pressures and therefore, less durability of gears and bearings. Furthermore, unevenly distributed or fluctuating loads can cause excitations in the gear mesh and structural vibrations. The load sharing in planetary gear stages depends on the individual stiffness conditions in each mesh position. The stiffness is not only influenced by the gear geometry but also by the surrounding structural elements like shafts, housings and torque arms. In wind industry these components are often designed very stiff in order to reduce their effect on the operational behavior.Within this paper, a method is presented, which allows combining the structural optimization process with a tooth contact analysis for planetary gearboxes. By means of this combined approach, it is possible to optimize the housing structure of the ring gear in terms of mass reduction while keeping the operational behavior in focus. With a weighted design objective function, it is possible to decide whether the main objective should be load distribution, excitation behavior, low mass or a balanced design.

A method for robust design in a coupled decision environment

Abstract The design of a connected engineered system requires numerous design decisions that influence one another. In a connected system that comprises numerous interacting decisions involving concurrency and hierarchy, accounting for interactions while also managing uncertainties, it is imperative to make robust decisions. In this article, we present a method for robust design using coupled decisions to identify design decisions that are relatively insensitive to uncertainties. To account for the influence among decisions, design decisions are modelled as coupled decisions. They are defined using three criteria: the types of decisions, the strength of interactions and the decision levels. In order to make robust decisions, robust design methods are classified based on sources of uncertainty, namely, Type I (noise factors), Type II (design variables) and Type III (function relationship between design variables and responses). The design of a one-stage reduction gearbox is used as a demonstration example. To illustrate the proposed method for robust design using coupled decisions, we present the simultaneous selection of gear material and gearbox geometry in a coupled decision environment while managing the uncertainties involved in designing gearboxes.

A comparative study on the dynamic behaviour of 10 MW conventional and compact gearboxes for offshore wind turbines

AbstractThis study compares the dynamic behaviour of a conventional and a compact gearbox for the DTU 10 MW wind turbine supported on a monopile offshore structure. The conventional gearbox configuration is composed of two planetary epicyclic stages and one parallel stage, while the compact gearbox configuration consists of a fixed planetary stage and a differential compound epicyclic stage. The design methodology for these two gearboxes is described, and the final gearbox specifications show a lighter weight and smaller volume for the compact gearbox design compared to the conventional one. Computational gearbox models are established using the multi‐body system dynamic analysis method. A decoupled approach is employed for the gearbox load effect analysis. Comparisons of the dynamic behaviour between these two gearboxes are conducted under pure torque load cases, tangential pin position error conditions and non‐torque load cases. The results demonstrate that the compact gearbox has better dynamic performance under different torque load cases and is more robust to withstand the effects of manufacturing errors and rotor non‐torque loads compared to the conventional gearbox. It is believed that the proposed compact gearbox concept is promising and would be a good alternative for multi‐megawatt floating wind turbines, although challenging with respect to the design and operation complexity.

Optimization of planetary gear of onboard gear-box using the method of differential evolution

Problem. Further modernization of combat vehicles, associated with the installation of additional equipment, requires the use of more powerful engines, which leads to increased loads on parts and components of the onboard gearbox. In modern conditions, the onboard gearbox of the T-64 tank works at the limit of its technical capabilities. To maintain the existing advantages and eliminate these short-comings, the design of the onboard planetary gear-box needs to be upgraded. Goal. The goal is to increase the load capacity and as a consequence to increase the service life of the elements of the onboard gearbox by carrying out optimization of the onboard planetary gearbox. Methodology. Methods for calculating planetary mechanisms and methods for analyzing the strength of gears were used to build a mathematical model. When constructing the optimal design algorithm, the method of differential evolution was used. Results. The literature review of the existing methods of multicriteria optimization of planetary gears has been made. According to the developed method of optimization of the onboard gearbox, a study of the parameters of planetary gear for optimality according to the criteria of maximum load capacity and minimum dimensions has been made. Originality. An algorithm for optimal design using the method of differential evolution for optimization of planetary gearboxes has been developed. Practical value. The use of the received design of a planetary gear reduce loading on elements of a transmission of the T-64 tank, thus the overall dimensions and design features of an onboard gearbox remain. The proposed approach to optimization of planetary gears can be used in the design of modern models of planetary gearboxes.

Dynamic Analysis of High-Speed Helical Gear Transmission in Pure Electric Vehicle Gearbox

This study is to systematically analyze the influences of time-varying meshing stiffness (TVMS) and meshing impact on the dynamic characteristics of high-speed gear transmission in the two-stage pure electric vehicle (PEV) gearbox, as well as the effect of tooth surface modification on the vibration control. First, the dynamic model was established, and the TVMS and meshing impact were calculated. Then, the vibration characteristics of single-stage and two-stage helical gear transmission were analyzed under three different excitation conditions, excitation of TVMS, excitation of meshing impact, and excitation of both. The results show that the effect of rotating speed on the system vibration is not significant outside the resonant region under the excitation of TVMS, while the effect of meshing impact becomes the main exciting component with the increasing rotating speed. The vibrations of the two gear pairs interact with each other; the vibration frequency of one gear pair contains both its meshing frequency and the coupling frequency of the other gear pair. Tooth surface modification in the input-stage gear pair can reduce the vibration of both the input- and the output-stage obviously; that is, more attention should be paid to the input-stage gear pair in the modification design of PEV gearbox.

Research on life prediction technology of wind turbine gearbox based on virtual simulation

As the core component of wind turbine energy conversion, the gearbox has been operating under variable frequency and variable load condition for a long time. The repair time is long after its fault, which leads to a large loss of power generation. This paper proposes a gearbox life prediction method. By collecting the design and manufacturing process parameters of gearbox, the gearbox virtual simulation model is established, the gearbox observable damage can be predicted accurately by inputting the actual operation load. According to the results, the maintenance and repair time of the gearbox can be arranged scientifically, which can effectively avoid the occurrence of serious faults, greatly reduce the gearbox replacement rate and unscheduled downtime, the economic benefits are obvious. After field application, the accuracy of this method can be 93.5%, which has a good prospect of application.

Prognosis of Wind Turbine Gearbox Bearing Failures using SCADA and Modeled Data


 
 
 Predictive maintenance and condition monitoring systems for wind turbines have seen increased adoption to minimize downtime, reducing operation and maintenance costs. On today’s wind power plants, the integrated supervisory control and data acquisition (SCADA) system provides low- frequency operational data that can be leveraged to quantify a wind turbine’s health. The aim of this study is to utilize machine-learning techniques to predict axial cracking failures in wind turbine gearbox bearings up to 1 month ahead of time. The failures are assumed to have occurred when the investigated bearing was replaced. While current SCADA systems show the overall condition of a wind turbine, often they do not allow for the investigation of specific gearbox bearings’ health. To enrich bearing fault signatures, additional data are computed through physics-based models using gearbox design information. Based on SCADA data, modeled data, and bearing failure log data from an actual wind plant, the performances of different machine-learning models on unseen data are then evaluated using industry-standard metrics such as precision, recall, and F1 score. Results show the overall system performance enhancement in predicting bearing failure when modeled data are included with SCADA data. The reduction in terms of false alarms is about 50%, and improvement in terms of precision and F1 score is about 33% and 12% respectively, based on the best modeling case in this study.