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Proceedings ArticleDOI

Design aspects of harmonic drive gear and performance improvement of its by problems identification: A review

20 Apr 2018-Vol. 1943, Iss: 1, pp 020016
TL;DR: The present article is started first making the comparative study of harmonic drive gear over conventional gear, highlighting its historical background, its application, limitation etc and then describing working principle of each and every components of it with detail dimensioning and modelling.
Abstract: The present paper aims at review on different aspects of harmonic drive gear to identify literature gap for future research. The present article is started first making the comparative study of harmonic drive gear over conventional gear, highlighting its historical background, its application, limitation etc. and then describing working principle of each and every components of it with detail dimensioning and modelling. The present article is further extended to study the different design aspects i.e. synthesis of tooth profiles, lubrication, stress, strain, torque, load sharing, kinematics error and vibration in details etc., identifying problems and then suggesting future perspective for the performance improvement of harmonic drive gear.
Citations
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Journal ArticleDOI
Hang Jia1, Junyang Li1, Guo Xiang1, Jiaxu Wang1, Ke Xiao1, Yanfeng Han1 
TL;DR: A method for analyzing the pure kinematic error of harmonic drive with machining and assembly errors is presented and the one possible new configuration of the wave generator is presented, which can improve the transmission performance of the drive.

20 citations

Journal ArticleDOI
TL;DR: In this paper, a double-circular-arc tooth profile for harmonic gear based on curve mapping and bidirectional conjugation is proposed, which can not only construct the mathematical relationship between basic parameters (modulus, number of teeth, deformation etc.) and tooth profile shape, but also realize the multi-tooth engagement of harmonic drive.

13 citations

DOI
29 Jun 2021
TL;DR: In this paper, a model-based approach is presented to better describe the behavior of an industrial robot in non-nominal operating conditions, in order to analyze its failure modes and their impact on the entire system.
Abstract: Industrial robots play a key role in production lines. As a direct consequence, even a slight degradation of their operating conditions could negatively affect the entire manufacturing process. To minimize economical losses, preventive measures such as planned maintenance or stand-by working stations are adopted and, in some cases, additional manipulators are installed to ensure line availability. However, since each robot performs a specific task, it degrades at a different rate from another one, so Planned Preventive Maintenance (PPM) should be replaced with Condition Based Maintenance (CBM) for a more efficient and cost-effective approach. In addition, collaborative robots (cobots) have become more and more popular in the past years increasing the level of automation, in particular in small and medium size companies. Therefore, a failure of an industrial manipulator could not only cause unexpected downtimes, but also jeopardize the safety of the personnel with whom it shares its workspace. A cobot, in fact, is labeled as safe as long as it works in nominal conditions, but this cannot be guaranteed otherwise. Within this framework, Prognostics and Health Management (PHM) techniques could be used for both a customized maintenance on a specific machine and for preventing undesired events like the aforementioned ones. An ongoing research activity at Politecnico di Torino is focused on a model-based approach able to better describe the behavior of an industrial robot in non-nominal operating conditions. In order to properly simulate faults and failures of a manipulator, it has been first necessary to analyze its failure modes and their impact on the entire system. A robot, in fact, is usually equipped with internal sensors and algorithms able to monitor its health status. However, this is only true for software or electrical failures (i.e. power supply, motor or sensors related), but it is not as effective in case of mechanical ones like bearings or gearbox wear. This paper firstly presents an overview of the possible failures related to harmonic drives which are often used in robotics due to their compact and light-weight design and the high reduction ratio. Then, it outlines the work done with the objective of providing an accurate, physics-based description of faults progression of harmonic drives used in industrial robots and the related high-fidelity models in the framework of a PHM system for fault and failure detection, isolation and remaining useful life (RUL) prediction.

9 citations


Cites background from "Design aspects of harmonic drive ge..."

  • ...According to Routh (2018), the main source of vibrations in HDs is caused by the continuous deformation of the FS....

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  • ...This property allows about 20-30% of the teeth to be continuously in contact (Routh, 2018), leading to ideally zero backlash, high position accuracy, and repeatability....

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  • ...According to Routh (2018), the main source of vibrations in HDs is caused by the continuous deformation of the FS. Proceedings of the 6th European Conference of the Prognostics and Health Management Society 2021 - ISBN – 978-1-936263-34-9 Page 354 EUROPEAN CONFERENCE OF THE PROGNOSTICS AND HEALTH…...

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Journal ArticleDOI
TL;DR: In this article, the deformation difference between the inner and outer surfaces of the flexspline was analyzed to improve the transmission accuracy and operating life of the harmonic drive, and a new way for the optimization of the three-dimensional tooth profile design was proposed to ensure the tooth meshing effect.
Abstract: This paper aims to improve the meshing effect of the gear teeth. It is recommended to analyze the deformation difference between the inner and outer surfaces of the flexspline. The purpose of this paper is to modify the profile of the flexspline based on the deformation difference to improve the transmission accuracy and operating life of the harmonic drive.,In this paper, ring theory is used to calculate the deformation difference of the inner and outer surfaces of the flexspline, and the actual tooth profile of the flexspline is corrected based on the deformation difference. Then, the flexspline is divided into multiple sections along the axial direction, so that the three-dimensional tooth profile of the flexspline is modified to improve the gear tooth meshing effect.,This paper proves the effect of the deformation difference between the inner and outer surfaces of the flexspline on the tooth backlash, which affects the transmission accuracy and life of the harmonic drive. It is recommended to modify the tooth profile of the flexspline based on the deformation difference, so as to ensure the tooth meshing effect.,This paper provides a new way for the optimization of the three-dimensional tooth profile design of the harmonic drive.

5 citations

Journal ArticleDOI
TL;DR: In this paper, a piecewise method for calculating the deformation of flexspline assembled with a cam wave generator is presented, where the tooth is positioned on the equivalent neutral layer, which is the non-elongation layer within one gear pitch but offset from the geometric mid-layer.
Abstract: Deformation of the flexspline is the basis of analyzing tooth trajectory and designing tooth profile. Considering the tooth influence on the position of equivalent neutral layer, a piecewise method for calculating the deformation of flexspline assembled with a cam wave generator is presented in this paper. Firstly, a mechanic model of a ring of uniform thickness in contact with a rigid cam is established. The displacements of the ring inside and outside an unknown wrapping angle are determined by the geometric constraints of the cam profile and the equilibrium relationship, respectively. Meanwhile, the wrapping angle is solved according to the boundary conditions. The assembly forces are derived to investigate the circumferential elongation and strain. Then, considering the tooth effects on the neutral layer of flexspline, the tooth is positioned on the equivalent neutral layer, which is the non-elongation layer within one gear pitch but offset from the geometric mid-layer. The equivalent neutral layer is positioned by the empirical formula of the offset ratio, which is summarized by the orthogonal simulation on finite element models of racks. Finally, finite element models of a ring-shaped and a cup-shaped flexspline assembled with elliptical cam are established to verify the effectiveness and accuracy of the piecewise method. The results show that, compared with the geometric method, the tooth positioning deviation calculated by the piecewise method can be reduced by about 70% with a more accurate deformation description from the geometric condition and mechanic condition inside and outside the wrapping angle.

3 citations

References
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Journal ArticleDOI
TL;DR: In this paper, a model was developed to describe the vibration produced by a single point defect on the inner race of a rolling element bearing under constant radial load, incorporating the effects of bearing geometry, shaft speed, bearing load distribution, transfer function and the exponential decay of vibration.

792 citations

Journal ArticleDOI
TL;DR: In this paper, the cyclic spectral tools should be considered for diagnostics of rolling-element bearing vibrations, which can not only indicate the presence of a fault in high levels of background noise, but can also return a relative measure of its severity.

339 citations

Journal ArticleDOI
C.S. Sunnersjö1
TL;DR: The most fundamental cause of noise and unsteady running of rolling bearings is the so-called varying compliance vibrations that occur irrespective of the quality and accuracy of the bearing.

208 citations

Journal ArticleDOI
01 Jun 1996
TL;DR: This model was able to replicate many of the features observed in actual harmonic-drive dynamic response, and it seems unlikely that any comparably sufficient representation can be constructed with parameter values obtained from catalogs or simple experimental observations.
Abstract: Harmonic drives can exhibit very nonlinear dynamic behavior. In order to capture this behavior, not only must dynamic models include accurate representations of transmission friction, compliance, and kinematic error, but also important features of harmonic-drive gear-tooth geometry and interaction must be understood. In this investigation, experimental observations were used to guide the development of a model to describe harmonic-drive operation. Unlike less detailed representations, this model was able to replicate many of the features observed in actual harmonic-drive dynamic response. Unfortunately, since model parameters can only be derived from careful analysis of experimental dynamic response, it seems unlikely that any comparably sufficient representation can be constructed with parameter values obtained from catalogs or simple experimental observations.

197 citations