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Article
Publication date: 8 April 2021

Wenmin Chu, Xiang Huang and Shuanggao Li

With the improvement of modern aircraft requirements for safety, long life and economy, higher quality aircraft assembly is needed. However, due to the manufacturing and…

Abstract

Purpose

With the improvement of modern aircraft requirements for safety, long life and economy, higher quality aircraft assembly is needed. However, due to the manufacturing and assembly errors of the posture adjustment mechanism (PAM) used in the digital assembly of aircraft large component (ALC), the posture alignment accuracy of ALC is difficult to be guaranteed, and the posture adjustment stress is easy to be generated. Aiming at these problems, this paper aims to propose a calibration method of redundant actuated parallel mechanism (RAPM) for posture adjustment.

Design/methodology/approach

First, the kinematics model of the PAM is established, and the influence of the coupling relationship between the axes of the numerical control locators (NCL) is analyzed. Second, the calibration method based on force closed-loop feedback is used to calibrate each branch chain (BC) of the PAM, and the solution of kinematic parameters is optimized by Random Sample Consensus (RANSAC). Third, the uncertainty of kinematic calibration is analyzed by Monte Carlo method. Finally, a simulated posture adjustment system was built to calibrate the kinematics parameters of PAM, and the posture adjustment experiment was carried out according to the calibration results.

Findings

The experiment results show that the proposed calibration method can significantly improve the posture adjustment accuracy and greatly reduce the posture adjustment stress.

Originality/value

In this paper, a calibration method based on force feedback is proposed to avoid the deformation of NCL and bracket caused by redundant driving during the calibration process, and RANSAC method is used to reduce the influence of large random error on the calibration accuracy.

Details

Industrial Robot: the international journal of robotics research and application, vol. 48 no. 4
Type: Research Article
ISSN: 0143-991X

Keywords

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Article
Publication date: 21 April 2020

Wenmin Chu, Xiang Huang and Shuanggao Li

Posture adjustment plays an important role in spacecraft manufacturing. The traditional posture adjustment method, which has a large workload and is difficult to guarantee…

Abstract

Purpose

Posture adjustment plays an important role in spacecraft manufacturing. The traditional posture adjustment method, which has a large workload and is difficult to guarantee the quality of posture adjustment, cannot meet the requirements of modern spacecraft manufacturing. This paper aims to optimize the trajectory of posture adjustment, reduce the internal force of the posture adjustment mechanism and improve the accuracy of the system.

Design/methodology/approach

First, the measuring point is measured by a laser tracker and the position and posture of the cabin is solved. Then, Newton–Euler method is used to construct the dynamic model of the posture adjustment system (PAS) without internal force. Finally, the adjustment time is optimized based on Fibonacci search method and the trajectory of the cabin is fitted by the fifth order polynomial.

Findings

The simulation results show that, compared with the other trajectory planning methods, this method can effectively avoid the internal force of posture adjustment caused by redundant driving, and the trajectory of velocity and acceleration obtained are continuous, meeting the engineering constraints.

Originality/value

In this paper, a dynamic model of PAS without internal force is constructed. The trajectory planning of posture adjustment based on this model can improve the quality of cabin assembly.

Details

Assembly Automation, vol. 40 no. 3
Type: Research Article
ISSN: 0144-5154

Keywords

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Article
Publication date: 27 March 2020

Shuanggao Li, Wenmin Chu and Xiang Huang

The measurement of aircraft barycenter is a verification of theoretical barycenter and is an important step of aircraft development. In the traditional measurement method…

Abstract

Purpose

The measurement of aircraft barycenter is a verification of theoretical barycenter and is an important step of aircraft development. In the traditional measurement method of aircraft barycenter, the posture of the aircraft needs to be adjusted manually and is measured by optical instruments. The efficiency of posture adjustment depends on the proficiency of workers, and the accuracy of measurement is not high. In view of these problems of the current barycenter measurement method, this paper aims to propose an aircraft barycenter measurement method based on multi-posture.

Design/methodology/approach

In this method, the numerical control locator is used as a supporting part to fix and adjust the aircraft, and the calculation model of aircraft barycenter is established according to the principle of rigid body rotation and the principle of moment balance. Then, the influence of the main error sources on the measurement accuracy of aircraft barycenter is analyzed by Monte Carlo simulation, and the measurement accuracy is compared with that of the barycenter measurement method based on horizontal posture. Finally, the experiment platform of barycenter measurement was built in the laboratory and the experiments were carried out.

Findings

The experimental results show that the barycenter measurement method proposed in this paper has obvious advantages in measurement accuracy and efficiency compared with the traditional method.

Originality/value

This method can be used to measure the barycenter of different types of aircraft quickly and automatically.

Details

Sensor Review, vol. 40 no. 2
Type: Research Article
ISSN: 0260-2288

Keywords

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Article
Publication date: 19 October 2018

Shuanggao Li, Zhengping Deng, Qi Zeng and Xiang Huang

The assembly of large component in out-field is an important part for the usage and maintenance of aircrafts, which is mostly manually accomplished at present, as the…

Abstract

Purpose

The assembly of large component in out-field is an important part for the usage and maintenance of aircrafts, which is mostly manually accomplished at present, as the commonly used large-volume measurement systems are usually inapplicable. This paper aims to propose a novel coaxial alignment method for large aircraft component assembly using distributed monocular vision.

Design/methodology/approach

For each of the mating holes on the components, a monocular vision module is applied to measure the poses of holes, which together shape a distributed monocular vision system. A new unconstrained hole pose optimization model is developed considering the complicated wearing on hole edges, and it is solved by a iterative reweighted particle swarm optimization (IR-PSO) method. Based on the obtained poses of holes, a Plücker line coordinates-based method is proposed for the relative posture evaluation between the components, and the analytical solution of posture parameters is derived. The required movements for coaxial alignment are finally calculated using the kinematics model of parallel mechanism.

Findings

The IR-PSO method derived more accurate hole pose arguments than the state-of-the-art method under complicated wearing situation of holes, and is much more efficient due to the elimination of constraints. The accuracy of the Plücker line coordinates-based relative posture evaluation (PRPE) method is competitive with the singular value decomposition (SVD) method, but it does not rely on the corresponding of point set; thus, it is more appropriate for coaxial alignment.

Practical implications

An automatic coaxial alignment system (ACAS) has been developed for the assembly of a large pilotless aircraft, and a coaxial error of 0.04 mm is realized.

Originality/value

The IR-PSO method can be applied for pose optimization of other cylindrical object, and the analytical solution of Plücker line coordinates-based axes registration is derived for the first time.

Details

Assembly Automation, vol. 38 no. 4
Type: Research Article
ISSN: 0144-5154

Keywords

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Article
Publication date: 17 October 2016

Yifan Jiang, Xiang Huang and Shuanggao Li

The purpose of this paper is to propose an on-line iterative compensation method combining with a feed-forward compensation method to enhance the assembly accuracy of a…

Abstract

Purpose

The purpose of this paper is to propose an on-line iterative compensation method combining with a feed-forward compensation method to enhance the assembly accuracy of a metrology-integrated robot system (MIRS).

Design/methodology/approach

By the integration of a six degrees of freedom (6DoF) measurement system (T-Mac), the robot’ movement can be tracked with real-time measurement. With the on-line measured data, the proposed iterative compensation for absolute positioning and the feed-forward compensation for relative linear motion are integrated into the assembly process to improve the assembly accuracy.

Findings

It is found that the MIRS exhibits good performance in both accuracy and efficiency with the application of the proposed compensation method. With the proposed assembly process, a component can be automatically aligned to the target in seconds, and the assembly error can be decreased to 0.021 mm for position and 0.008° for orientation on average.

Originality/value

This paper presents a 6DoF MIRS for high-precision assembly. Based on the system, a novel on-line compensation method is proposed to enhance the assembly accuracy. In this paper, the assembly accuracy and the corresponding distance parameter are given by a series of experiments as reference for assembly applications.

Details

Industrial Robot: An International Journal, vol. 43 no. 6
Type: Research Article
ISSN: 0143-991X

Keywords

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Article
Publication date: 3 June 2019

Yifan Jiang, Xiang Huang, Shuanggao Li and Zhengping Deng

The purpose of this paper is to propose an assembly coordination modelling approach based on measured data for assembly quality control of multi-constrained objects in…

Abstract

Purpose

The purpose of this paper is to propose an assembly coordination modelling approach based on measured data for assembly quality control of multi-constrained objects in aircraft assembly. This approach aims to establish a high-precision digital mirror of physical assembly system in the virtual environment, with which the assembly process in the virtual environment can be performed synchronously with that in the physical world.

Design/methodology/approach

This paper presents a realistic geometrical representation model based on measured point cloud, as well as the multiple constraints modelling methods for local and global constraints with the proposed representation model. For the assembly target optimization, a novel optimization method based on the evaluation of multi-dimensional tolerance zone is proposed, where the particle swarm optimization and simulated annealing algorithm are combined to calculate the optimal solutions.

Findings

As shown in the validation results, the minimum easiness value for easiness model in global optimization is 3.01, while the best value for weighting model by adjusting weights for more than 10 times is 1.94. The results verify that the proposed coordination modelling approach is effective to the assembly of multi-constrained objects, and the optimization model has an obvious advantage over the traditional weighting method.

Originality/value

This paper provides a new idea for the fine control of assembly quality of non-ideal components by introducing the measured data into the on-line assembly process. Besides, a novel optimization method based on the evaluation of multi-dimensional tolerance zone is proposed, which overcomes the problem of traditional weighting model wherein the weightings are difficult to determine.

Details

Assembly Automation, vol. 39 no. 2
Type: Research Article
ISSN: 0144-5154

Keywords

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Article
Publication date: 12 March 2018

Zhengping Deng, Shuanggao Li and Xiang Huang

In aircraft assembly, standard reference points with nominal coordinates are commonly applied for coordinate transformation between multiple measurement stations and the…

Abstract

Purpose

In aircraft assembly, standard reference points with nominal coordinates are commonly applied for coordinate transformation between multiple measurement stations and the assembly coordinate system. For several reasons in practical application, these points often fail to envelop the key assembly space, which leads to large transformation uncertainty. This paper aims to analyze and further reduce the coordinate transformation uncertainty by introducing a new hybrid reference system (HRS).

Design/methodology/approach

Several temporary extension points without known coordinates are added to enhance the tightness between different stations, especially at the weakness area in the network, thus constituting an HRS together with the existing standard reference points. The coordinate transformation model of the HRS-based measurement network is established based on an extend Gauss–Markov model. By using the geometrical differential property and variance-covariance propagation law, the covariance matrixes in the transformation model are calculated, and the analytical solution of the uncertainties of transformation parameters are ultimately derived. The transformation uncertainty of each check points is presented by Helmert error expression.

Findings

The proposed analytical solution of transformation uncertainty is verified using the state-of-the-art Monte Carlo simulation method, but the solution process is simpler and the computation expenses are much less.

Practical implications

The HRS with three temporary extension points is practically applied to a tail boom in-site measurement for assembly. The average transformation uncertainty has been reduced by 26 per cent to less than 0.05 mm.

Originality/value

The hybrid coordinate transformation model is proposed for the first time. The HRS method for transformation uncertainty reduction is more economical and practical than increasing the number of standard reference points.

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Article
Publication date: 1 March 2018

Zhengping Deng, Shuanggao Li and Xiang Huang

For the measurement of large-scale components in aircraft assembly, the evaluation of coordinate transformation parameters between the coordinate frames of individual…

Abstract

Purpose

For the measurement of large-scale components in aircraft assembly, the evaluation of coordinate transformation parameters between the coordinate frames of individual measurement systems to the assembly frame is an essential task, which is usually completed by registration of the enhanced reference system (ERS) points. This paper aims to propose an analytical method to evaluate the uncertainties of transformation parameters considering both the measurement error and the deployment error of ERS points.

Design/methodology/approach

For each measuring station, the measured coordinates of ERS points are first roughly registered to the assembly coordinate system using the singular value decomposition method. Then, a linear transformation model considering the measurement error and deployment error of ERS points is developed, and the analytical solution of transformation parameters’ uncertainties is derived. Moreover, the covariance matrix of each ERS points in the transformation evaluation is calculated based on a new uncertainty ellipsoid model and variance-covariance propagation law.

Findings

For the transformation of both single and multiple measuring stations, the derived uncertainties of transformation parameters by the proposed analytical method are identical to that obtained by the state-of-the-art iterative method, but the solution process is simpler, and the computation expenses are much less.

Originality/value

The proposed uncertainty evaluation method would be useful for in-site measurement and optimization of the configuration of ERS points in the design of fixture and large assembly field. It could also be applied to other registration applications with errors on both sides of registration points.

Details

Sensor Review, vol. 38 no. 4
Type: Research Article
ISSN: 0260-2288

Keywords

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Article
Publication date: 1 August 2019

Dong Yan

The purpose of this paper is to examine the post-enactment status of China’s Labour Contract Law and Labour Dispute Mediation and Arbitration Law, focusing on the dramatic…

Abstract

Purpose

The purpose of this paper is to examine the post-enactment status of China’s Labour Contract Law and Labour Dispute Mediation and Arbitration Law, focusing on the dramatic rise in remuneration litigation amidst much criticism of weak or ineffective implementation of these laws.

Design/methodology/approach

This paper deploys both quantitative and qualitative analysis methods to investigate the features of remuneration litigation. Remuneration judgments by Beijing People’s Courts from 1 January 2014 to 31 December 2017 provide the primary empirical data. The intrinsic features of remuneration disputes are investigated to delineate subcategories of claims. Several judges were also interviewed to further explore the nature of remuneration disputes.

Findings

Four types of remuneration claims were identified: regular wage, minimum wage, overtime and others (including subsidies and welfare). Examination of these four types, especially how they are processed until concluded by court adjudication, provides a fuller picture of the post-enactment status of these laws and yields objective and rational findings. To explain the continuing steady rise in the volume of remuneration claims, as more workers have knowledge of their rights and access to the courts, this study identifies an increase in the number of factually complicated cases (e.g. overtime claims) and abmiguity in the relevant law, leaving some remuneration disputes difficult, if not impossible, to adjudicate. Conversely, the study also finds significant positive trends following these laws’ enactment, particularly a reduction in straightforward cases, such as disputes concerning non-payment of wages/minimum wages, on which the law is clear. It is evidently imperative to improve the clarity of the current laws through further legislation, as the most appropriate next step in China’s juridification process of developing its own rule of Labour Law.

Research limitations/implications

This study is purposely limited to examining remuneration litigation in Beijing’s courts from 2014 to 2017, which is representative of the national trend of dramatically rising remuneration disputes, and thus provides valuable insights. Future studies should cover a wider geographic territory and other categories of labour disputes to provide an even more comprehensive picture of the challenges and potential solutions.

Practical implications

By understanding the driving factors of rising labour remuneration disputes, the legislature, workers and employers can act accordingly to curb labour conflicts. The growing complexity and technicality of remuneration litigation indicates that the pressing need of labour juridification is to deploy a subtle, comprehensive method to improve legal clarity and judicial professionalism.

Originality/value

This study uniquely divides the types of remuneration litigation in Beijing, adopting methods and yielding findings absent from the prior literature. Both the progress and challenges in China’s rule of Labour Law process are reflected in this work, together with public policy and theoretical implications for further study.

Details

Employee Relations: The International Journal, vol. 41 no. 6
Type: Research Article
ISSN: 0142-5455

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Article
Publication date: 21 October 2019

Yifan Zhang, Qing Wang, Anan Zhao and Yinglin Ke

This paper aims to improve the alignment accuracy of large components in aircraft assembly and an evaluation algorithm, which is based on manufacture accuracy and…

Abstract

Purpose

This paper aims to improve the alignment accuracy of large components in aircraft assembly and an evaluation algorithm, which is based on manufacture accuracy and coordination accuracy, is proposed.

Design/methodology/approach

With relative deviations of manufacturing feature points and coordinate feature points, an evaluation function of assembly error is constructed. Then the optimization model of large aircraft digital alignment is established to minimize the synthesis assembly error with tolerance requirements, which consist of three-dimensional (3D) tolerance of manufacturing feature points and relative tolerance between coordination feature points. The non-linear constrained optimization problem is solved by Lagrange multiplier method and quasi-Newton method with its initial value provided by the singular value decomposition method.

Findings

The optimized postures of large components are obtained, which makes the tolerance of both manufacturing and coordination requirements be met. Concurrently, the synthesis assembly error is minimized. Compared to the result of the singular value decomposition method, the algorithm is validated in three typical cases with practical data.

Practical implications

The proposed method has been used in several aircraft assembly projects and gained a good effect.

Originality/value

This paper proposes a method to optimize the manufacturing and coordination accuracy with tolerance constraints when the postures of several components are adjusted at the same time. The results of this paper will help to improve the quality of component assemblies.

Details

Assembly Automation, vol. 40 no. 2
Type: Research Article
ISSN: 0144-5154

Keywords

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