Gear System Research Articles

Optimization of Weight Reduction in Power Transmission Systems Using Bio-Inspired Algorithms and Composite Materials

Traditional optimization approaches for power transmission systems often optimize gear and shaft designs separately, rely on conventional materials, and face challenges handling mixed-variable problems involving discrete and continuous variables. These limitations hinder the potential for significant weight reduction and performance improvements in modern mechanical systems. This research presents an innovative optimization approach for reducing the gear pitch in a power transmission system comprising a shaft with two gears. By employing bio-inspired metaheuristic algorithms and utilizing materials common in additive manufacturing and composite materials, the study aims to minimize system weight while ensuring mechanical integrity. The optimization integrates gear and shaft design variables, accurately models mechanical constraints through penalty functions, and leverages the unique properties of advanced materials to enhance performance. In this work, we developed an integrated optimization model that overcomes the limitations of previous studies by combining advanced materials with bio-inspired algorithms to achieve significant weight reduction in gear systems. This approach effectively addresses the complexities of mixed-variable optimization and mechanical constraints, providing a practical and innovative solution for modern engineering applications.

Multi-state meshing characteristics and global nonlinear dynamics of a spur gear system considering local tooth breakage

Multi-state meshing characteristics and global nonlinear dynamics of a spur gear system considering local tooth breakage

Investigation of the Effects of Design Parameters on Tooth Profile Formation and Operating Performance in Cycloidal Reducers

Cycloidal reducers have a unique and complex tooth profile design compared to conventional gear systems. Unlike standardized gear profiles, cycloidal reducers provide significant flexibility in design parameters such as module, profile modification coefficient, and eccentricity. However, these parameters interact in a complex manner, affecting both tooth profile formation and the overall performance of the reducer. Inaccuracies in selecting parameters may lead to problems such as excessive contact stress, gear deformation or reduced load transfer efficiency. This study aims to investigate the effects of design parameters on the formation of cycloidal tooth profiles and the operating performance of reducers. By analyzing the relationships and interactions between these parameters, the research provides a deeper understanding that will improve design processes, enhance performance, and contribute to future standardization efforts. As a result, this study aims to contribute to the development of cycloidal reducers that are structurally robust, efficient and suitable for high-performance operation.

Dynamic Characteristics of Gear System Under Compound Fault of Tooth Root Crack and Bearing Outer Ring

Research on single faults like tooth root cracks and bearing outer ring failures is well-established. However, existing studies often replace the actual crack propagation path with a simplified linear crack model, neglecting the variation in stress intensity factors. They do not account for the coupling effect between gear teeth when calculating gear mesh stiffness. In practice, gearbox failures are predominantly compound failures involving both gears and bearings. This paper simulates the actual crack propagation path based on Workbench, introduces a dual-tooth meshing zone method to address the tooth-to-tooth coupling effect, and establishes a dynamic model of a system with compound faults of tooth root cracks and bearing outer ring defects. The dynamic response of the system under different levels of deterioration is then investigated. The findings indicate that the crack propagation path exhibits a concave shape, with the curvature of the path increasing as the crack deteriorates. The time-varying mesh stiffness calculated by considering tooth-to-tooth coupling effects aligns more closely with the finite element results. By analyzing the evolution patterns of the impact components and sidebands during the deterioration process, the dynamic evolution trends of the coupling phenomenon between tooth root cracks and bearing outer ring faults are clarified.

Dynamic simulation analysis of aircraft engine planetary gear system

The Geared Turbofan (GTF) engine is used for aircraft propulsion with fan drive, characterized by its complex structure and operation in challenging environmental conditions. During its operation, variations in gear meshing and loads on the transmission shaft exacerbate vibration within the transmission system, leading to a decline in engine performance. This paper established three-dimensional solid models of the X-type aviation engine planetary gear system, input shaft, and output shaft, and employed ADAMS for multibody dynamics analysis, achieving simulation of engine operational vibrations. Modal and harmonic response analyses were conducted using ANSYS to observe and analyze critical parameters such as vibration displacement, vibration acceleration, gear meshing forces, modal resonance, and harmonic resonance, evaluating the impact of vibration amplitude, frequency, and their effects on system performance and longevity, providing guidance for vibration control and optimization of aviation engine systems.

Analysis Comparison of PSMEID With Preview for Controlling Shock Vibration of UAV’s Landing Gear System

Semi-active dampers reduce the effects of shock vibrations because they can operate at specific vibration frequencies at a lower cost than more complex active dampers. PSMEID is one of the alternative methods developed in the semi-active damping system. PSMEID has been developed by adapting it by adding a PSMEID active time prediction system when an impact occurs. This research attempts to compare two types of PSMEID with active time prediction, where the position of each model offered has a different PSMEID mass position when applied to the landing gear damper of an Unmanned Aerial Vehicle (UAV). This comparison aims to give the user a choice among these optimal models suitable for use in multiple conditions. When simulated using the same parameter values, the PSMEID placed on the unsprung mass can reduce acceleration amplitude by up to 6.6 percent when the landing gear is dropped at 0.15 meters from the ground. The model that places the PSMEID on the sprung mass can help reduce the velocity amplitude up to 8.8 percent when dropped at a height of 0.05 meters, and the spring constant value of the PSMEID (KPS) is 1600 N/m. All these simulations show that the PSMEID should be activated just before the landing gear hits the runway surface (TB < TL).

A New Technique to Qualify Rotary Electro-Mechanical Actuator for Tactical Class of Missile System

A novel technique has been adopted to establish the functionality and to qualify the Rotary Electro-Mechanical Actuator (REMA) system developed for a typical tactical class of weapon system in addition to the conventional method of checking the functionality through On-Board Computer in-loop simulation, Actuator in-loop simulation and Hardware in-loop simulation. The REMA along with full scale fin surface subjected to wind tunnel tests at the actual flight Mach number and flight dynamic pressure conditions. Flight hardware of REMA and fin assembly has been used in the tests so as to derive direct conclusions without applying any corrections to the measured results. This technique revealed the capability of the actuator, the dynamic functionality of its components such as gear systems, bearings and structural integrity of the whole actuator under the flight aerodynamic load on the full scale fin surface and vibration environments. The test conducted is being the most critical condition and the REMA and fin combination performed the intended commands as predictable and survived without any structural dis-integrity qualifies for further flight use. Subsequently flight tests were conducted and found the performance of REMA was as anticipated. Based on these results, recommendation made that it is mandatory that the all the actuation systems developed for fin actuation in missiles has to undergo the wind tunnel tests and qualify further actual use. The details of wind tunnel tests and the results of typical REMA with full scale fin are presented in this paper.

Electromechanical dynamic behavior of gear systems caused by transient mixed lubrication of rubbing surface

Electromechanical dynamic behavior of gear systems caused by transient mixed lubrication of rubbing surface

Influence of the driving environment on the dynamic characteristics of a DCT vehicle starting considering the longitudinal and vertical coupling model

The most significant external excitation affecting the dynamic characteristics of a vehicle is its driving environment. This type of excitation leads to issues such as slow initial response during starting, significant vibrations in the transmission system, and overall performance instability. A longitudinal–vertical coupled dynamics model has been developed to analyse the impact of driving conditions on the dynamic characteristics of vehicles with Dual-Clutch Transmission (DCT) during starting. This model takes into account factors such as the engine’s harmonic torque, the time-varying meshing stiffness of the gear system, the nonlinear torsional behaviour of the dual-mass flywheel, the deformation and torsion of the powertrain mounts, tire deformation, and random road excitations. Utilizing the established coupled model for DCT vehicle transmission systems, the impact of varying road roughness, adhesion coefficients, and road slope on the dynamic performance of DCT vehicles. To verify the accuracy of the simulation results of the influence of the driving environment on the dynamic characteristics of the DCT vehicle starting process, the experimental and simulation results of the influence of the driving environment on the vehicle dynamic characteristics of flat road surfaces, B-level uneven road surfaces, wet road surfaces, and 10% road slopes were compared. The overall trend of the simulation results of the clutch master and slave end speeds, vehicle longitudinal and vertical impact degrees, etc., was in good agreement with the experimental results, confirming the accuracy of the established DCT vehicle transmission system coupling dynamic model.

Examining the behavior of a two-connected-spring pendulum according to non-resonance and resonance conditions

This paper focuses on the planar forced oscillations of a particle linked to its support point through a system comprising two nonlinear springs arranged in series with two viscous dampers. The motion of this point is restricted to being on an elliptic route. Three degrees-of-freedom (DOF) characterize the system’s motion, explained by two differential equations (DEs) and another algebraic equation derived using Lagrange’s equations. The traditional method of multiple-time scales (MMTS) is applied in the context of the time realm. The dynamics of forced and damped oscillations is explored in this work, highlighting non-resonant conditions along with two distinct external resonances. Furthermore, stationary periodic states influenced by external resonances are examined, and the stability of each case is evaluated. The asymptotic solutions of the controlling equations are solved up to the third approximation. The classification of resonance cases is based on the second and third order of the approximate solutions. Therefore, the solvability criteria and the modulation equations (ME) are obtained. The Routh–Hurwitz conditions (RHCs) serve as the basis for assessing the stability and instability criteria. A discussion and graphical representations of the time histories, frequency response curves (FRC), and stability regions are provided to demonstrate the beneficial effects of different physical parameter inputs on the system’s performance. The obtained outcomes can improve the performance of spring-based mechanical systems like vibrational isolation devices, shock absorbers, and suspension mechanisms. Additionally, they have the potential to enhance stability and control in robotic limbs and aircraft landing gear systems, ensuring better stress absorption and stability.

Early Failure Diagnosis of Scraper Conveyor Gearboxes Based on DS Evidence Theory and Multimodal Data Fusion

ABSTRACTA scraper conveyor is one of the important equipment to ensure reliable, efficient and stable mining and transportation of coal. As the most important transmission system of the scraper conveyor, the gearbox takes the role of transmitting power and torque. Due to the influence of working conditions in underground coal mines, the gear transmission system is often subject to the impact of nonuniform large loads, which is very prone to failures, and affected by environmental interference, it is difficult to detect the early abnormal signals of the scraper conveyor gearbox in the conventional industrial scenarios of fault monitoring methods. To ensure the stability and reliability of its work, this paper carries out the research on the multi‐parameter fusion of gearbox early fault diagnosis method under strong background noise interference. Aiming at the problem that the change of fluid physical and chemical characteristic parameters can reflect the early health condition of the gear transmission system and the single vibration signal is difficult to be extracted under the strong background noise, a model based on the fluid physical and chemical characteristic parameters and vibration signals is constructed by utilizing the RBF neural network and the Random Forest algorithm, and the body of evidence of the two models is fused at the decision‐making level through the DS evidence theory, which forms the fluid‐vibration multi‐parameter fusion judgment of the early fault diagnosis method of scraper conveyor gearbox. Through comparison, it is found that compared with the fusion methods, such as high‐dimensional variational self‐encoder, and single diagnosis methods, such as the Random Forest Algorithm, the method researched in this paper is more suitable for the early fault warning of the scraper conveyor gearbox of the well coal mine, and the experimental validation finds that the average accuracy rate of the early fault recognition can be up to 96.6%.

Defect diagnosis of high contact ratio spur gear system with increasing level of fault

Breakage of tooth is common in power transmission gear systems with continuous running. Model of a system (virtual prototype) serves as a tool for generating large amount of data and can replace expensive experimentation. Dependability of a model depends on the purpose for which the data is generated. Two models of spur gear system are considered in this work: (1) block diagram-based planer kinematics model of spur gear system developed in Simulink environment which does not consider the support and torsional effects and (2) detailed CAD based multibody dynamics model (includes bearings, drive, coupling, connecting rod and supports) that considers backlash, axial and torsional effects developed using MBS ADAMS software. A custom-made high contact ratio gear system is fabricated for experiments. The time and frequency domain characteristics of experimental and simulated signals are compared to draw the conclusions of fault related symptom of the systems with increasing level of faults and the utility of models.

Optimized shock-protecting microstructures

Mechanical shock is a common occurrence in various settings, there are two different scenarios for shock protection: catastrophic protection (e.g. car collisions and falls) and routine protection (e.g. shoe soles and mattresses). The former protects against one-time events, the latter against periodic shocks and loads. Common shock absorbers based on plasticity and fracturing materials are suitable for the former, while our focus is on the latter, where elastic structures are useful. Further, we optimize the effective elastic material properties which control the critical shock parameter, maximal stress, with energy dissipation by viscous forces assumed adequate. Improved elastic materials protecting against shock can be used in applications such as automotive suspension, furniture like sofas and mattresses, landing gear systems, etc. Materials offering optimal protection against shock have a highly non-linear elastic response: their reaction force needs to be as close as possible to constant with respect to deformation. In this paper, we use shape optimization and topology search to design 2D families of microstructures approximating the ideal behavior across a range of deformations, leading to superior shock protection. We present an algorithmic pipeline for the optimal design of such families combining differentiable nonlinear homogenization with self-contact and an optimization algorithm. We validate the effectiveness of our advanced 2D designs by extruding and fabricating them with 3D printing technologies and performing material and drop testing.

Vibration source inversion-based fault diagnosis: Approach and application

The gear transmission system of industrial equipment is characterized by a highly integrated structure, non-stationary operating conditions, and large loads. Therefore, the attenuation of fault signal characteristics and the complexity of operating conditions in gear transmission systems significantly affect the effectiveness of vibration signal-based fault diagnosis. This paper proposes a unified diagnostic framework based on vibration source inversion for two typical transmission component fault signal phenomena: meshing frequency modulation sidebands and equally spaced fault characteristic frequency interval harmonic clusters. This approach incorporates the vibration transfer path analysis of passive subsystems and identifies bearing dynamic forces, followed by their decomposition, reconstruction, and sensitive frequency band localization. It enables accurate diagnosis of complex gear transmission systems under non-stationary conditions with limited vibration testing. The effectiveness and advantages of this method over existing mainstream signal processing techniques are validated through actual cases of gear and weak bearing fault diagnosis on a complex planetary gear transmission system test bench.

A calibration method of line laser 3D gear measurement system

It is of great importance to ensure the accuracy of measurements taken by the line laser three-dimensional (3D) gear measurement system through the calibration of system in an accurate manner. This paper established a relevant measurement model based on the principle of line laser 3D gear measurement using generalized polar coordinates, designed a dedicated Polyhedral Artefact (PA), and proposed an accurate calibration method to address the challenges posed by the representation of 6 degrees of freedom (DOF) parameters for line laser sensor data in measurement space. Among them, the PA includes features such as cylindrical plane, planar plane, and V-groove etc., which can meet the requirements of high-precision machining while maintaining consistency with gear installation accuracy to further improve the accuracy of sensor pose parameters. The calibration method uses nonlinear optimization equations with point cloud data to simultaneously solve the required parameters for accurate measurement. Calibration and gear measurement experiments reveal that the standard deviation and range deviation of the total tooth profile deviation, obtained from 10 repeated measurements of a single tooth flank, are 0.244 μm and 0.86 μm, respectively. The results of the tooth profile measurements after the calibration of the system show good consistency compared with the contact measurements, which verifies the effectiveness of the method.

The investigation of nonlinear dynamic characteristics of spur gear with angular misalignment error based on an improved dynamic model

Angular misalignment error is a prevalent occurrence in gear systems, mainly caused by manufacturing and installation errors in gearbox components. This significantly impacts the meshing characteristics of the system, making it necessary to carry out the nonlinear dynamic analysis of spur gear pairs with angular misalignment errors. In this study, a meshing stiffness model for a spur gear pair with angular misalignment error is established based on the Load Teeth Contact Analysis (LTCA) method. The effect of misalignment errors on the distribution of tooth surface stiffness are analyzed. Additionally, an improved dynamic model considering angular misalignment errors and variable backlash along the tooth width direction was proposed based on the lumped mass method and the slicing method. The effects of angular misalignment errors parallel and perpendicular to the meshing plane on the nonlinear dynamics of the system were studied. Frequency domain diagrams, Poincaré diagrams, and bifurcation diagrams were employed to comprehensively analyze the nonlinear characteristics of the system. The results indicate that with light loads, the system experiences a sequence of periodic and chaotic motions as θa increases, eventually returning to periodic motion. Conversely, θv shows minimal influence on the gear backlash, with the system exhibiting periodic motion when θv is small. As θv increases, the system transitions to chaotic motion before ultimately returning to periodic motion. Under heavy load conditions, as θa increases, the system transitions gradually from chaotic to periodic motion. However, regardless of the variations in θv, the system consistently remains in periodic motion.

On dynamic responses of gear transmission system during rough tooth surface worn

On dynamic responses of gear transmission system during rough tooth surface worn

Time-varying Meshing Stiffness Calculation of Spur Gears with Asymmetric Spalling Defects

Gear systems are subjected to repeated loads during long-term operation, and factors such as insufficient lubricant to increase friction between gears, resulting in elevated temperatures and wear, are highly susceptible to tooth spalling. Tooth spalling is a common form of failure in gear failure. In previous studies, the vibration response of a gear pair with spalling defects at the tooth center near the pitch circle has been investigated. However, the location of the spalling defects offset from the center of the tooth flank is rarely studied. Tooth spalling faults occur in the pitch circle, but not necessarily in the center of the tooth, often formed on both sides of the center of the tooth and torsion in the meshing process. the symmetric and asymmetric rectangular spalling defects are considered, the torsional deformation is introduced. “torsional stiffness” is introduced into the overall TVMS due to the spalling defect. Therefore, it is meaningful to grasp the reasons for the formation of tooth spalling.

The effect of a 120 kg pontoon mass on the wave energy converter device due to heaving

The environment is negatively impacted by the use of fossil fuels as a source of electricity. Using sustainable ocean wave energy is one way to replace fossil fuels and maximize the usage of natural energy. Electrical energy is produced from mechanical energy by ocean waves. An apparatus for converting wave energy from the ocean is needed to absorb it. The wave energy converter uses the up-and-down action of a chain on a pontoon to rotate a generator, producing electrical energy. The mass of the pontoon and the force of the ocean waves that excite it both have an impact on its vertical movement. Thus, the impact of pontoon mass on the wave energy converter is examined in this research. Both a planetary gear system and one without were used in the investigation. The voltage and current obtained at a wave height of 35 cm were 2.28 Volts and 0.160 A, respectively, without the planetary gear and 160.41 Volts and 13.95 A, with the planetary gear. Furthermore, an evaluation of the wave energy converter machine's performance was carried out. Using a planetary gear and a wave height of 13 cm, the second experiment's minimum power production was 212.63 Watts, while the sixth experiment's maximum power output was 2237.72 Watts with a wave height of 35 cm. In the second experiment, the generator without a planetary gear produced 0.0327 watts of power with the same wave height, and in the sixth trial, the generator produced a maximum of 0.3648 watts with a 35 cm wave height. As a result, utilizing a generator with a planetary gear is preferable to using one without one

Analysis of the effect of a spring constant of 980 N/m on a wave energy converter device due to heaving

Indonesia is a country with a larger sea area compared to its land area. Therefore, utilizing ocean current or wave energy as a renewable energy source, specifically for generating electricity through Wave Energy Converters (WEC), is a suitable solution. Wave Energy Converters (WEC) work on the basic principle of converting wave energy into linear motion or rotation to drive a generator and then convert it into electricity. The rotation is generated by the up-and-down movement of the pontoon affected by the pontoon's spring constant, which originates from sea waves. Hence, this study aims to analyze the effect of the spring constant on the pontoon due to heaving motion in response to sea waves. The study uses a spring constant of 980 N/m and is conducted with and without a planetary gear system. The highest voltage and current were achieved at a wave height of 0.35 m, producing a voltage of 84.5 V with a current of 8.26 A and a power of 698 Watts for the generator with the planetary system. For the generator without the planetary system, it produced a voltage of 1.73 V with a current of 0.046 A and a power of 0.0795 Watts with a gearbox shaft rotation of 37.32 RPM. The lowest voltage and current were observed at a wave height of 0.15 m, producing a voltage of 39.6 V with a current of 3.58 A and a power of 141.8 Watts for the generator with the planetary system. For the generator without the planetary system, it produced a voltage of 0.53 V with a current of 0.021 A and a power of 0.0111 Watts with a gearbox shaft rotation of 21.62 RPM