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The alignment accuracy between the hemispherical resonator and the electrode carrier directly impacts the assembly performance of the hemispherical resonator gyro. Currently, the assembly process suffers from low efficiency as well as accuracy due to its reliance on manual pose adjustment based on capacitance uniformity. To address this issue, a mathematical model is developed in the spherical coordinate system to calculate capacitance considering non-ideal poses, allowing us to analyze the effect of pose errors on capacitance. Additionally, a finite element model is established using COMSOL Multiphysics software to account for assembly pose errors and capacitance. The accuracy of the mathematical model for assembly pose errors and capacitance is validated through this approach. This research provides a theoretical basis for adjusting the assembly pose between the hemispherical resonator and electrode carrier, resulting in significant improvements in both the assembly quality and efficiency of the hemispherical resonator gyro. [ABSTRACT FROM AUTHOR]

Copyright of Lubrication Engineering (0254-0150) is the property of Editorial Office of LUBRICATION ENGINEERING and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Lubrication Engineering (0254-0150) is the property of Editorial Office of LUBRICATION ENGINEERING and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

To tackle performance issues stemming from assembly errors in practical fuel cell applications, a criss-crossed matching design for anode and cathode bipolar plates (BPP) is proposed. The effectiveness of the proposed design is assessed by joint simulations of finite element analysis (FEA) and computational fluid dynamics (CFD). Concurrently, the orthogonal experimental method is utilized to investigate the performance of the criss-crossed matching design at various operating conditions. The results show that the GDL deformation rate of the criss-crossed matching design with error in practical assembly is merely 4.8%, significantly lower than the 19.9% observed in the aligned matching design. Furthermore, the criss-crossed design performance could be improved by 5.9% compared to the aligned matching design in practical assembly with error. The criss-crossed matching design consistently outperforms the aligned matching design at various operating conditions. Notably, the highest performance growth rate, observed in high stoichiometric ratio and high humidity, reaches 12.38%. • A criss-crossed matching design of the bipolar plate is proposed. • Criss-crossed design performance is seldomly impacted by assembly errors. • Criss-crossed matching design increases performance by 5.9% over aligned design. • Criss-crossed matching design works well in various conditions. [ABSTRACT FROM AUTHOR]

Due to machining errors, location inaccuracies, human error, and various other factors, it is challenging to avoid assembly errors during the production of spiral bevel gears (SBGs). When SBG assembly errors occur, it can cause the appearance of edge contact and may even lead to severe tooth tip chipping. In this study, we propose an improved method based on loaded tooth contact analysis (LTCA) to examine mesh characteristics, including time-varying mesh stiffness (TVMS), unloaded transmission error, and contact stress. Furthermore, we explore the effects of assembly errors and tooth tip chipping. Moreover, it is observed that assembly errors can alter the contact area of SBGs and potentially reduce the peak-to-peak value of TVMS. Additionally, the occurrence of tooth tip chipping decreases TVMS within the chipping region, lowers transmission error, and increases maximum contact stress. Notably, when assembly errors are present, the reduction in TVMS due to tooth tip chipping exceeds that of a properly assembled SBG pair. [ABSTRACT FROM AUTHOR]

Wear is the main failure form of the gear transmission interface, runs through the whole life cycle of gear service, and the distributed error of the tooth surface due to the introduced assembly error will make the actual meshing state of the tooth surface different from the ideal meshing state, thus affecting the tooth surface wear trajectory and state. Therefore, considering the coupling relationship between assembly error and tooth surface contact analysis, the variation laws of the wear amount of the gear transmission interface of the variable hyperbolic circular-arc-tooth-trace cylindrical gear were studied under the consideration of assembly error in this article. Based on the tooth surface contact analysis method and Hertz contact theory, the transient linear load, the combined radius of curvature, the length axis and short axis of the contact ellipse, and the instantaneous sliding velocity were calculated. Through revising the calculation method of adhesive wear of variable hyperbolic circular-arc-tooth-trace cylindrical gears, the correlations between the tooth surface wear amount and gear parameters of variable hyperbolic circular-arc-tooth-trace cylindrical gears under different assembly errors were analyzed. The results show that the maximum wear occurs at the root of the tooth, and the wear at the indexing circle approaches zero, whether it is standard installation or non-standard installation. The vertical axial error and horizontal axial error have little effect on the wear, while the center distance error will aggravate the wear. The proposed method comprehensively considers the influence of assembly error and gear parameters on tooth surface wear, and this method can provide a theoretical reference for the design and analysis of anti-wear, wear reduction, and life extension of variable hyperbolic circular-arc-tooth-trace cylindrical gear tooth surface. [ABSTRACT FROM AUTHOR]

A calibration system was designed to evaluate the accuracy of linear optical encoders at the micron level in a fast and economical manner. The system uses a commercial interferometer and motor stage as the calibrator and moving platform. Error analysis is necessary to prove the effectiveness and identify areas for optimization. A fixture was designed for the scale and interferometer target to meet the Abbe principle. A five-degree-of-freedom manual stage was utilized to adjust the reading head in optimal or suboptimal working conditions, such as working distance, offset, and angular misalignment. The results indicate that the calibration system has an accuracy of ±2.2 μm. The geometric errors of the calibration system, including mounting errors and non-ideal motions, are analyzed in detail. The system could be an inexpensive solution for encoder manufacturers and customers to calibrate a linear optical encoder or test its performance.

A calibration system was designed to evaluate the accuracy of linear optical encoders at the micron level in a fast and economical manner. The system uses a commercial interferometer and motor stage as the calibrator and moving platform. Error analysis is necessary to prove the effectiveness and identify areas for optimization. A fixture was designed for the scale and interferometer target to meet the Abbe principle. A five-degree-of-freedom manual stage was utilized to adjust the reading head in optimal or suboptimal working conditions, such as working distance, offset, and angular misalignment. The results indicate that the calibration system has an accuracy of ±2.2 μm. The geometric errors of the calibration system, including mounting errors and non-ideal motions, are analyzed in detail. The system could be an inexpensive solution for encoder manufacturers and customers to calibrate a linear optical encoder or test its performance. [ABSTRACT FROM AUTHOR]

In order to solve the problem of calculation efficiency and accuracy of time-varying meshing stiffness of spur bevel gears, a slice calculation method of meshing stiffness of spur bevel gears considering the coupling effect of tooth pairs is proposed. Based on the slice discretization method, the bevel gear tooth and the gear body are discretized into several slices with the same width along the tooth width direction and the axis direction respectively, and the slices are expanded based on the back cone equivalence principle. When the slice width is small enough, the bevel gear can be approximated as a series of spur gears, and the meshing stiffness of each slice can be calculated by the energy method. In order to consider the coupling effect of multi-tooth meshing, the correction coefficient of gear stiffness is introduced in the calculation of double tooth meshing stiffness, which reduces the calculation error of double tooth meshing stiffness. The meshing stiffness model of bevel gears under the error condition is established. The meshing stiffness of spur bevel gears, the angular displacement of the center point of each slice and the load distribution of the tooth surface under the ideal and assembly error conditions are calculated and analyzed. Finally, the accuracy and efficiency of the proposed method are verified by comparing with the finite element calculation results.

Satellite laser communication is a promising technology for the next-generation communication system. Its communication performance is subject to the APT beam-pointing accuracy. One of the most important problems is reducing the coaxiality error before the APT starts working. However, the coaxiality error is difficult to correct effectively owing to the lack of empirical guidance based on qualitative analysis. We study the inducement that will generate coaxiality errors. The mathematical model of the influence of the CCR dihedral angle error and planeness error on the spot centroid measurement are built, and an analysis is performed. The model of the beam-pointing error induced by the APT element's assembly error is built, and the pointing error change rule is explored. Furthermore, the coaxiality performance simulation is performed in the presence of a CCR geometrical error while considering the assembly error. The results show that the coaxiality error has a nonlinear characteristic. The CCR planeness error has a greater influence on coaxiality deviation than that of dihedral angle error under certain conditions. This research is relevant to the design and test work of the APT system. [ABSTRACT FROM AUTHOR]

Due to machining errors, location inaccuracies, human error, and various other factors, it is challenging to avoid assembly errors during the production of spiral bevel gears (SBGs). When SBG assembly errors occur, it can cause the appearance of edge contact and may even lead to severe tooth tip chipping. In this study, we propose an improved method based on loaded tooth contact analysis (LTCA) to examine mesh characteristics, including time-varying mesh stiffness (TVMS), unloaded transmission error, and contact stress. Furthermore, we explore the effects of assembly errors and tooth tip chipping. Moreover, it is observed that assembly errors can alter the contact area of SBGs and potentially reduce the peak-to-peak value of TVMS. Additionally, the occurrence of tooth tip chipping decreases TVMS within the chipping region, lowers transmission error, and increases maximum contact stress. Notably, when assembly errors are present, the reduction in TVMS due to tooth tip chipping exceeds that of a properly assembled SBG pair.

A face gear is typically used in fishing spinning reel mechanism owing to its easy fabrication and good reel handle rotation. As face gears without tooth flank modification are sensitive to assembly errors, the fishing reel sensation becomes unstable in mass production. Previously, tooth flank modification with a transmission error (TE)-controlled curve was used to solve this problem. The TE-controlled curve stabilized the fishing reel sensation for assembling. However, in mass production, the manufacturing error of a pinion and face gear must be considered along with the assembly error. In a previous study, we analyzed all the eight error factors, including the manufacturing error, individually. Thus, we clarified that pressure angle deviation of the pinion and tooth rotational error of the face gear have a significant effect on TE. However, in mass production, these errors are combined in a complicated manner. In this study, an experiment was conducted using the L18 orthogonal array to elucidate the interaction between error factors. No peaks and troughs were observed in the curve of each factor, thus showing that there is little interaction due to the combination of factors. Although the proposed model was less affected than the conventional model by most errors, the proposed model was affected by the pressure angle deviation of the pinion and the tooth rotational error of the face gear. These results were the same as that of the single-factor experiment in the previous report. By analyzing the path of contact using a three dimensional simulation, we confirmed that uneven TE waveforms were caused by edge contact due to insufficient tooth flank modification. The unevenness in the TE waveform occurred when the factor levels of the assembly and manufacturing errors were large, when these error factors were combined, and when the amount of tooth flank modification of the face gear was small. This phenomenon was regarded as a trochoidal interference, which was caused by the contact of the tooth tip of the pinion, and it was also confirmed using prototype gears. The combination of these errors must be carefully considered in the manufacturing process. Consequently, we have elucidated that avoiding the interference due to combination of errors was significantly important to improve the fishing reel sensation.

Tooth surface equations of a curvilinear cylindrical gear with parabolic modification are derived based on the gear meshing theory. The solving method of the initial contact position of the gear finite element model is studied, a finite element model of the gear pair is established using the parameterized finite element technology, and the loaded transmission error is extracted from the finite element analysis results. With more than 20 sets of calculation examples, the effects of assembly errors, modification amount, curvature radius of the cutter, and offset of modification curve on loaded transmission errors are studied, respectively. The research results show that, assembly errors can reduce the fluctuation range of loaded transmission errors; larger modification amount can reduce the fluctuation range of loaded transmission errors; larger curvature radius of the cutter can reduce the value of loaded transmission errors and its fluctuation range; the offset of the modification curve has slight effect on loaded transmission errors. In summary, the use of a larger curvature radius of the cutter can be used to machine curvilinear cylindrical gears with better transmission performance.

Abstract Background False duplications in genome assemblies lead to false biological conclusions. We quantified false duplications in popularly used previous genome assemblies for platypus, zebra finch, and Anna’s Hummingbird, and their new counterparts of the same species generated by the Vertebrate Genomes Project, of which the Vertebrate Genomes Project pipeline attempted to eliminate false duplications through haplotype phasing and purging. These assemblies are among the first generated by the Vertebrate Genomes Project where there was a prior chromosomal level reference assembly to compare with. Results Whole genome alignments revealed that 4 to 16% of the sequences are falsely duplicated in the previous assemblies, impacting hundreds to thousands of genes. These lead to overestimated gene family expansions. The main source of the false duplications is heterotype duplications, where the haplotype sequences were relatively more divergent than other parts of the genome leading the assembly algorithms to classify them as separate genes or genomic regions. A minor source is sequencing errors. Ancient ATP nucleotide binding gene families have a higher prevalence of false duplications compared to other gene families. Although present in a smaller proportion, we observe false duplications remaining in the Vertebrate Genomes Project assemblies that can be identified and purged. Conclusions This study highlights the need for more advanced assembly methods that better separate haplotypes and sequence errors, and the need for cautious analyses on gene gains.

Accurately identifying the error transfor path of the meta-action unit was the premise of error analysis. A new method was proposed to judge the error transmission path of the meta-action units based on the concept of DOF constraints in mechanical systems. Firstly, the DOF constraint requirements of the precision output parts and the initial error transfer path were determined by analyzing the functions and the structures of the meta-action units. Secondly, the constraint properties of the joint surfaces were analyzed, and the DOF constraint properties of the precision output parts were calculated along the error transfer path. The error transfer path was determined by comparing the obtained constraint property with the designed constraint property. Compared with traditional methods, the proposed method improves the efficiency of the analysis and identification of the error transfer paths greatly. [ABSTRACT FROM AUTHOR]

• Two incidences of failures of collective control rods of a particular type of helicopter were investigated. • In both the cases, the failure occurred at the threaded region of Al-alloy tube by fatigue mechanism. • Reasons for the two failures were different; manufacturing deficiency in one and assembly error in the other. This paper presents two incidences of failures of collective control rods which resulted in accidents to a particular type of helicopter. The control rods were made of 2024 Al-alloy tubes fitted with fork at one end and a spherical bearing at the other end (eye-end). In terms of physical appearance, the two failures in the control rods were identical to each other wherein there was fracture in the Al-alloy tube at the eye-end. Fractography study confirmed that in both the cases, multiple fatigue cracks had initiated over a sector at the internal thread roots on the Al-alloy tubes corresponding to 1st/2nd thread on the eye-end stud. After initiation, the cracks had propagated progressively into the tube-wall and then along the circumferential direction. As the crack propagation progressed, the load bearing capacity of the tubes diminished resulting in final overload fracture under the operational load at the time of accidents. Although failures in both the control rods looked alike in terms of failure location, fracture pattern and fracture mechanism, the primary reasons of failures were found to be different. Investigation revealed that premature fatigue crack initiation was due to non-uniform stress distribution on the internal threads of the control tube with increased level of stress over a sector. In one case, the non-uniform stress distribution resulted from thread manufacturing deficiency, and in the other case, it was due to incorrect assembly at the eye-end. [ABSTRACT FROM AUTHOR]

Satellite laser communication is a promising technology for the next-generation communication system. Its communication performance is subject to the APT beam-pointing accuracy. One of the most important problems is reducing the coaxiality error before the APT starts working. However, the coaxiality error is difficult to correct effectively owing to the lack of empirical guidance based on qualitative analysis. We study the inducement that will generate coaxiality errors. The mathematical model of the influence of the CCR dihedral angle error and planeness error on the spot centroid measurement are built, and an analysis is performed. The model of the beam-pointing error induced by the APT element’s assembly error is built, and the pointing error change rule is explored. Furthermore, the coaxiality performance simulation is performed in the presence of a CCR geometrical error while considering the assembly error. The results show that the coaxiality error has a nonlinear characteristic. The CCR planeness error has a greater influence on coaxiality deviation than that of dihedral angle error under certain conditions. This research is relevant to the design and test work of the APT system.

The face gear is a crossed gear similar to a hypoid gear. Owing to its compactness and good assemblability, it is used in geared motors and transmissions for helicopters. Studies on various aspects such as design, processing, and tooth modification methods have been conducted for face gears, which are typically used in fishing reels as spinning reels owing to their easy fabrication and small vibration during reel handle rotation. Because face gears without tooth flank modification are sensitive to assembly errors, the fishing reel sensation becomes unstable during mass production. Therefore, assembling and adjusting face gears to achieve a good fishing reel sensation is time consuming. Previously, tooth flank modification with a transmission error (TE)-controlled curve was used to solve this problem. The TE-controlled curve stabilized the fishing reel sensation for assembly. However, in mass production, the manufacturing error of a pinion and face gear must be considered in addition to the assembly error. In this study, we investigated the assembly and manufacturing errors when the pinion and face gear come in contact. Furthermore, we elucidated the meshing mechanism of face gear pairs under various assembly and manufacturing errors. As a result, it was confirmed that the TE-controlled curve was affected by manufacturing errors only. Moreover, a new interesting finding was obtained regarding the meshing of the face gear with a TE-controlled curve. The TE occurrence ought to be attributed to the pressure angle deviation. Hence, it is probable to replace the main cause of the transmission error with the pressure angle deviation. This consideration is the same for a cylindrical gear pair. The meshing of face gear, which was considered complicated, can be reconsidered as the meshing of a simple cylindrical gear pair. Consequently, we revealed that the TE-controlled curve is significantly useful for considering the meshing and design of a face gear pair, which is an advantageous feature.

The tooth root crack fault is a common fault type of the spiral bevel gear pair (SBGP). Affected by the strong bearing capacity, the early crack fault of the SBGP cannot be found in time. In this study, a finite element (FE) model of the SBGP is established and assembled through the tooth contact analysis. The maximum tooth root stress is analyzed considering the variation of assembly errors. Meanwhile, this study simulates the tooth root crack fault of the bevel pinion with different crack degrees. The initial position of the crack is located where the maximum tooth root stress appears. The time-varying mesh stiffness (TVMS) of the SBGP considering different degrees of the pinion tooth root crack fault is obtained. The TVMS and the non-load transmission error are brought into a hybrid FE dynamic model, and steady responses are solved. Based on this, the sensitivities of various statistical indicators for identifying the tooth root crack fault of SBGP under the influence of assembly errors are verified. This paper can provide the necessary theoretical basis for the analysis and diagnosis of tooth root crack faults in the SBGP transmission system. [ABSTRACT FROM AUTHOR]

Abstract Long-read de novo genome assembly continues to advance rapidly. However, there is a lack of effective tools to accurately evaluate the assembly results, especially for structural errors. We present Inspector, a reference-free long-read de novo assembly evaluator which faithfully reports types of errors and their precise locations. Notably, Inspector can correct the assembly errors based on consensus sequences derived from raw reads covering erroneous regions. Based on in silico and long-read assembly results from multiple long-read data and assemblers, we demonstrate that in addition to providing generic metrics, Inspector can accurately identify both large-scale and small-scale assembly errors.

When spur gear pair meshing with the assembly error，it will cause the edge contact and stress concentration，and affect the service life. In the meantime，because the parallelism error of vertical plane will produce a larger deviation of tooth contact，therefore，taking the spur gear pair with the parallelism error of vertical plane as the research object，then based on the systematic introduction of the numerical calculation theory of gear contact stress，and the contact stress，contact width and the corresponding load distribution coefficient along the tooth in the case of different assembly error and load conditions are calculated，and the results calculated by numerical calculation method and national standard calculation method in the case of no assembly error are made a comparative analysis. The results show that the results calculated by two methods in the case of no assembly error are close to each other，and the numerical calculation result can reflect the edge effect of the gear pair meshing. Under the same load，with the increase of the installation error，the uneven contact in the tooth width direction becomes worse，and one side disconnects. Under the same assembly error，the uneven contact is improved with the increase of load，the maximum contact stress presents nonlinear increase with the increase of assembly error and load.

In order to solve the problem of measuring the assembly error of gear shafting in engineering， a method of measuring the assembly error of gear shafting based on stereo vision is proposed. In this method， the circular mark points arranged on the feature to be measured are used as the medium to obtain the spatial pose of the corresponding features through 3D reconstruction and mathematical fitting， and then the assembly error is calculated. Taking a bevel gearbox as an example， the complete technical process of the proposed method is given， and the influence of the number of States and the installation angle of the target plate on the fitting accuracy is systematically studied. A complete hardware and software system is developed， and the effectiveness and efficiency of the measurement method are verified by experiments.

Assembly error, misalignment of components, is inevitable in the fabrication of proton exchange membrane (PEM) fuel cells. It will induce complex and contradictory effects, such as the higher contact resistance and better gas permeability, making it difficult to evaluate the error tolerance. These coupled impact on the performance of fuel cell needs to be clarified. This study establishes a performance prediction model considering the contact resistance between bipolar plate (BPP) and gas diffusion layer (GDL), deformation of membrane electrode assembly (MEA), and distribution of porosity and permeability in GDL to analyze the effect of assembly error. Assembly error brings better performance due to the higher porosity, permeability, and a more uniform distribution of oxygen. However, contact resistance also increases. Cases with narrow channels, thinner GDL, and lower compression ratios are more susceptible to assembly error, mainly manifested in the higher contact resistance, lower porosity and permeability growth, and less oxygen distribution improvement. Cases with wider channels, thicker GDL, and higher compression ratios have a higher tolerance for assembly error. Considering that contact resistance has a greater impact in most cases, assembly error needs to be avoided. The tolerance of assembly error is proposed to guide the fuel cell fabrication. • A method for analyzing the effects of assembly error on performance is proposed. • Results of the assembly model are input into the performance prediction model. • MEA deformation, the distribution of GDL porosity and permeability are considered. • Effects of channel width, GDL thickness, and compression ratio are analyzed. • Tolerance of assembly error under different conditions is proposed. [ABSTRACT FROM AUTHOR]

The aeroengine industry has set strict upper limits for assembly errors in rotor-connecting processes, because assembly errors significantly affect aeroengine stability. Applications of multi-axis mechanisms have the potential to solve the low efficiency of traditional manual connection processes. However, multiple error sources are simultaneously introduced. Thus, an accurate prediction method of rotor assembly error considering multiple error sources is of vital importance, by which the applicability of the new mechanism to rotors can be tested. In this study, a new prediction method for rotor assembly errors is proposed based on the use of a novel multi-axis measuring and connecting mechanism. First, the error propagation among the rotor errors, measurement errors, mechanism errors, and mounting errors is analyzed. Second, reasonable characterization models for these error sources are established using homogeneous transformation matrices. Third, based on the abovementioned error models, a new rotor assembly error prediction algorithm is constructed. It is highly consistent with the actual connection processes. Finally, verification experiments are conducted. The experimental results show that deviation rates of the average values of six types of assembly errors relative to the predictions are all lower than 14%. The proposed prediction method has acceptable accuracy and practical significance. [ABSTRACT FROM AUTHOR]

It is industry tendency to accurately predict the dynamics of the mechanical systems with full consideration of errors. Based on the Hertz contact theory and general bearing modeling methods, this study proposed a more practical model using numerical method to investigate the influence of assembly error on the dynamics of linear guide slide platform. First, the modeling methods of five types of assembly errors are established, based on which, a nonlinear dynamic model is developed to investigate the influence of assembly error. In consideration of assembly error, the modeling method enables the sum of restoring forces and restoring moments equal to zero when no external load applied to the platform. Second, the simulation results indicate that the assembly error can cause uneven load distribution, change the dynamics of the system. In addition, different from previous research results, the stability of the system cannot be improved by simply increasing the preload. Last, in order to validate the proposed method, the proposed model is compared with previous fewer degrees-of-freedom model, and a series of experiments are conducted on a specialized platform to estimate the parameters of the system and verify the proposed model. [ABSTRACT FROM AUTHOR]

Focusing on a planetary gear transmission that uses line gear as core transmission elements， and the influence of assembly errors on its transmission precision is studied. The structural composition of the line gear transmission and the characteristics of different transmission schemes are analyzed， the space meshing coordinate system for the gear train are established， and the quantitative relationship of the parameters at the meshing moment is established among the sun line gear， the outer ring line gear and the planetary line gear. The causes of the angle error and displacement error are analyzed， both between the planetary line gear and the sun line gear and between the outer ring line gear and the planetary line gear. Tooth Contact Analysis （TCA） is subsequently adopted to carry out the numerical analysis of the assembly errors model for the line gear transmission. The results show that， among assembly errors of the planetary gears， the angular errors of its rotation around the horizontal axis， the displacement errors in the longitudinal section of the outer ring line gear， and the displacement errors in the cross section of the planetary line gear， are of more effect on its transmission. That is of significant to design and assembly of the planetary gears.

Due to friction between components, significant amount of wasted energy is inevitably generated inside a rotary machine during operation. Such wasted energy is commonly in the form of thermal energy that is transferred to machine components through heat conduction, causing the components to expand in geometry. The amount of change also directly affects the machine’s processing accuracy. The study presented in this article aims to use a magnetic encoder and a magnetoresistive (MR) sensor to build a measurement system that can be directly embedded into a high-speed motor to monitor thermal elongation of the motor’s rotating shaft in axial direction. CoMnP is used as magnetic coating on which novel magnetic polarity patterns are magnetized incrementally along the shaft’s axis by utilizing permanent magnet. The proposed system discussed herein this article is designed to determine proper installation specifications and to examine the assembly tolerance, including the pitch, yaw, row, and flying height errors of the MR in a rotating machine. The results demonstrate that the measurement system senses with a 2 kHz sampling rate can real-time monitor the shaft’s thermal elongation while it rotates with high speed from 1000 to 24 000 r/min. Moreover, compared with a commercial product, the measurement system is found to be feasible to provide accurate the shaft’s thermal elongation values with satisfactory accuracy error. [ABSTRACT FROM AUTHOR]

Copyright of Lubrication Engineering (0254-0150) is the property of Editorial Office of LUBRICATION ENGINEERING and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This study is concerned with a three-pole active magnetic bearing (AMB) system with assembly error and non-uniform flux distribution. The assembly error, which is the result of the misalignment of the back-up bearing and the stator of AMB, induces strong nonlinear uncertainty in the AMB dynamics. The non-uniform flux distribution, which is mainly due to non-uniform material properties, manufacturing errors, etc., makes the magnetic force model more complicated. A stable-levitation controller is designed in consideration of the above factors. The controller is designed using the method of feedback linearization and integral sliding mode control (ISMC). Both simulation and experimental results indicate that the rotor can be levitated to the center of the back-up bearing, verifying the effectiveness of the proposed stable-levitation controller.

The tooth root crack fault is a common fault type of the spiral bevel gear pair (SBGP). Affected by the strong bearing capacity, the early crack fault of the SBGP cannot be found in time. In this study, a finite element (FE) model of the SBGP is established and assembled through the tooth contact analysis. The maximum tooth root stress is analyzed considering the variation of assembly errors. Meanwhile, this study simulates the tooth root crack fault of the bevel pinion with different crack degrees. The initial position of the crack is located where the maximum tooth root stress appears. The time-varying mesh stiffness (TVMS) of the SBGP considering different degrees of the pinion tooth root crack fault is obtained. The TVMS and the non-load transmission error are brought into a hybrid FE dynamic model, and steady responses are solved. Based on this, the sensitivities of various statistical indicators for identifying the tooth root crack fault of SBGP under the influence of assembly errors are verified. This paper can provide the necessary theoretical basis for the analysis and diagnosis of tooth root crack faults in the SBGP transmission system.

Due to the involute worm and helical gear drive is different from the parallel shaft helical gear drive and the worm drive, the plane meshing theory and the space enveloping principle cannot be directly applied for this worm drive when the meshing analysis is performed, there has been no good analysis method to accurately calculate the meshing situation. To satisfy the increasing requirements of low-noise and long-lifetime in the service robots and the modern intelligent house systems, especially the intelligent shading system in the modern intelligent house system, a novel meshing performance analysis method is proposed for the involute worm and helical gear drive based on the counterpart rack. By calculating the contact line between the counterpart rack and helical gear and the contact line between the counterpart rack and involute worm, we can get the contact point of involute worm and helical gear finally. This novel meshing performance analysis makes it possible to use the plane meshing theory and the space enveloping principle to analyze involute worm and helical gear drive. The meshing relationship between the involute worm and the counterpart rack, as well as the counterpart rack and the helical gear are presented, and the computational model of contact ratio and contact ellipse are obtained through the counterpart rack. The mathematic model for the instantaneous contact point and contacts trace of the worm drive with different assembly errors is established, and the meshing performances are investigated through the numerical analysis, simulation analysis and performance testing. The results show that this worm drive is insensitively to the assembly errors, and it is beneficial for reducing the vibration-noise and extending the service life. This theoretical research provides theoretical support for further optimizing the vibration and noise of involute worm and helical gear drive and improving the fatigue life. [ABSTRACT FROM AUTHOR]

The proton-exchange membrane fuel cell is a promising power source for automobile industry because of its zero pollution. However, its stack structure always faces increased contact resistance caused by assembly errors, leading to substantial energy loss during the working period. To enhance its output performance, the influence of assembly errors on contact resistance is studied for proton-exchange membrane fuel cell. The mechanical simulation model of fuel cell assembly process is established to provide contact resistance distribution with different assembly errors. An improved global sensitivity analysis method is proposed to evaluate the influence coefficient of each assembly error term on contact resistance based on a series of randomized simulation data. The case study of a single-layer fuel cell demonstrates the proposed method achieves higher efficiency than traditional sensitivity analysis methods, and finds out key assembly errors in regard to reducing contact resistance. [ABSTRACT FROM AUTHOR]

The aeroengine industry has set strict upper limits for assembly errors in rotor-connecting processes, because assembly errors significantly affect aeroengine stability. Applications of multi-axis mechanisms have the potential to solve the low efficiency of traditional manual connection processes. However, multiple error sources are simultaneously introduced. Thus, an accurate prediction method of rotor assembly error considering multiple error sources is of vital importance, by which the applicability of the new mechanism to rotors can be tested. In this study, a new prediction method for rotor assembly errors is proposed based on the use of a novel multi-axis measuring and connecting mechanism. First, the error propagation among the rotor errors, measurement errors, mechanism errors, and mounting errors is analyzed. Second, reasonable characterization models for these error sources are established using homogeneous transformation matrices. Third, based on the abovementioned error models, a new rotor assembly error prediction algorithm is constructed. It is highly consistent with the actual connection processes. Finally, verification experiments are conducted. The experimental results show that deviation rates of the average values of six types of assembly errors relative to the predictions are all lower than 14%. The proposed prediction method has acceptable accuracy and practical significance.

Assembling plays a significant role in the performance of large-scale CNC gear profile grinding machines. An approach in the deviation evaluation of ground tooth surfaces taking into account assembly errors is proposed in this paper. Based on the error transmission chain of the profile grinding system and the conjugate motion relationship between the grinding wheel and the workpiece, the ground tooth surface model including assembly errors was established using the surface envelope method. Then, the effect of assembly errors on deviations of the profile grinding tooth surface was quantitatively analyzed. The optimized distribution of assembly errors and machining verifications were performed on large-scale CNC gear profile grinding machines. The results show that the proposed method is effective at ensuring ground tooth surface deviations for large-scale CNC gear profile grinding machines.

Cable termination faults are problematic in electrical networks almost always. Technology has solved problems somewhat, but there are many annual reports about damaged cable terminations. For analyzing the problems, faults in two regional electricity companies are studied. At first step, damaged cable terminations are analyzed statistically and grouped according to their problems. Then, some of the damaged cable terminations are checked to classify vulnerable areas. The investigation is completed by simulation, analysis and study of equivalent circuit. Conclusions underline important points which can be helpful for reducing the damages.

The speed integration gear is a new type of gear mechanism,which is meshed with cylindrical gears and non-circular face gear and can achieve speed integration transmission. Based on gear mesh theory,the tooth surface equation of non-circular face gear is deduced. Considering the angle error,intersected axis error and axis shift error,the contact model of tooth surface is established. An analysis of distribution characteristics of the contact path is made to obtain the influence of the assembly error on the point contact trace of the teeth. Simulation results indicate that the gradient of the contact path on each tooth of non-circular face gear increases with rate of change of the transmission ratio. The assembly errors cause the shift of the contact path to inner or outer radius,with its movement direction depending on the error direction.

Experimental measurement of transmission error and vibration of a gear pair with crown modification are developed. With the help of high-precision optical encoder, effects of gear misalignment on unloaded and lightly loaded dynamic transmission error, which are relative to gear rattle, are investigated. The gear mesh misalignment is introduced by eccentric sleeve assembled on the output shaft. Effects of modification and misalignment on the dynamic transmission error, are studied at different load and driving velocity conditions. The experimental results show that, with the increase of the crown amplitude, the peak-to-peak values of dynamic transmission error are decreasing dramatically. Impact deformation or elastic deformation is a very important part of the dynamic transmission error although they are unloaded or lightly loaded. The components in harmonics of meshing frequency will change distinctly comparing cases at low input shaft velocity without and with misalignment, but different phenomena are detected while increasing the input shaft velocity. Finally, the relation between transmission error and gear box vibration is illustrated, and spectrum kurtosis is introduced to reveal gear rattle. [ABSTRACT FROM AUTHOR]

The proton-exchange membrane fuel cell is a promising power source for automobile industry because of its zero pollution. However, its stack structure always faces increased contact resistance caused by assembly errors, leading to substantial energy loss during the working period. To enhance its output performance, the influence of assembly errors on contact resistance is studied for proton-exchange membrane fuel cell. The mechanical simulation model of fuel cell assembly process is established to provide contact resistance distribution with different assembly errors. An improved global sensitivity analysis method is proposed to evaluate the influence coefficient of each assembly error term on contact resistance based on a series of randomized simulation data. The case study of a single-layer fuel cell demonstrates the proposed method achieves higher efficiency than traditional sensitivity analysis methods, and finds out key assembly errors in regard to reducing contact resistance. [ABSTRACT FROM AUTHOR]

Part error will cause the assembly contact state between parts to deviate from the nominal state, resulting in error accumulation and propagation. Therefore, reasonable tolerance has to be applied to control the corresponding errors. Currently there are a number of tolerance analysis methods, however, most of them typically only consider dimensional and geometrical tolerances in the design phase. Analysis results without considering part deformation which was commonly observed in the realistic working conditions could lead to possible assembly failures. In this paper, both manufacturing and deformation errors are taken into account to establish a more comprehensive deviation calculation model based on Polytope-Skin Model Shape method. The total assembly error can be determined by calculating the Minkowski sum. The effectiveness of the proposed method is verified in a case study about an assembly of one-joint manipulator in which the external force is the cause of the change on part shape and size. [ABSTRACT FROM AUTHOR]

Electric relay manufacture and assembly is an example of high-precision machining followed by an assembly process. During machining, parts exhibit dimensional variance and manufacturers have several techniques and strategies for how to maximise production and improve efficiency when variance is present. One approach is to measure the variance, select parts appropriately for the best match, perform the minimum amount of adjustment and rework, and then perform the assembly. This approach is difficult in practice because measurement errors also occur and confound the knowledge about each part's dimensions. In this paper, we consider a new matching approach to increase the production rate. We propose a part-combination selection method in which a pair of assembly parts in buffers is optimally selected using a target of an estimated assembly error, and an adjustment machine is then optimally selected using a range of estimated assembly errors. Furthermore, we consider an analytical approach to estimate the optimal control parameters for the proposed method that yield the maximum production rate. The analysis results show that the analytical approach can estimate the nearly optimal control parameters, including the nearly maximum production rate in any buffer capacity. The results also show that by installing a small buffer capacity, the production rate can be increased. [ABSTRACT FROM AUTHOR]

Based on the principle of gear meshing,the precise 3 D solid geometry model of spiral gear is established. Then the finite element model of spiral gear for loaded meshing characteristics analysis is built,and the grid size of model is reasonably determined by the Hertz contact theory. Taking six teeth as research objects,the positions of the maximum contact and bending stresses of the spiral gear are found,and the stress curves are plotted in a meshing period. The analysis of meshing characteristics including contact patterns and paths on the gear surface is carried out by selecting the loading condition and assembly error as the variable respectively. The results provide a remarkable guiding role in the design and practical application of spiral bevel gear.

• A linear time-varying model of a differential bevel gear set is proposed. • A 3D lumped parameter model of a differential bevel gear set is developed. • Free and forced vibration response of the differential bevel gear set is scrutinized. • The effects of the differential pinion position error are determined. A differential bevel gear set has a pivotal role in automotive applications. Unlike spur or helical planetary gear set, up to now, far too little attention has been paid to propose an adequate analytical model to analyze the dynamic behavior of the differential due to its complexities. One of the complexities is the fact that the differential pinion possesses simultaneous angular velocities about non-collinear axes. The aim of this paper is to investigate the dynamic response of the differential system whose bearings are deemed to be flexible and gear mesh stiffnesses are computed through potential energy. The analytical model of the differential bevel gear has been developed by means of Newton-Euler formulation and utilized it to scrutinize differential's natural frequencies and vibration modes. The sweep frequency analysis has been used to represent the dynamic response of the system. After that, we have incorporated the position error of the differential pinion into the differential model, and the obtained results have been compared with a healthy one. This work may be considered as an important threshold to get full dynamic details of the differential bevel gear set, and to offer insights for enhancing the differential design. [ABSTRACT FROM AUTHOR]

• • Presenting a method for calculating the gear mesh stiffness for high contact ratio gears. • • Performing the calculations using a gear dynamic model. • • Investigating the influence of modifying gear tooth addendum dimension on the generated vibration. • • Lowering the amount of noise is applied to examine the impact on enhancing the studied indicators. For the purpose of vibration-based fault detection and to avoid gear failure consequences it is necessary to investigate the possibility of early fault detection. A reduction in the gear time-varying mesh stiffness (TVMS) due to the existence of a crack can be used to detect and evaluate tooth damage. The reduction in TVMS has an impact on the system's dynamic response signal, and then the used fault detection indicators are affected. The current article sheds light on the fault detection possibility of high contact ratio (HCR) gears as compared to those standard ones of low contact ratio (LCR). The influence of modifying the gear tooth addendum dimension for obtaining a high contact ratio on the possibility of early fault detection is studied. Twenty different crack cases are examined by using both the LCR and HCR design cases. For every crack case, the mesh stiffness is evaluated and introduced to the used gear dynamic model for obtaining the system's dynamic response. The TVMS evaluation is presented for both the LCR and HCR gear cases. Four fault detection indicators, namely the RMS, kurtosis, peak value and crest factor are applied as different measures to enhance the research outcome. The results show that the studied indicators will have less increase when the crack size increases in the HCR design than in the LCR one. Therefore, the HCR design will be less sensitive or more difficult to detect from the fault detection perspective. Lowering the amount of signal noise is applied to the HCR case to examine the impact on enhancing the obtained indicators. The four applied indicators show different behaviours with reducing noise. [ABSTRACT FROM AUTHOR]