Xiang Huang

Bio: Xiang Huang is an academic researcher from Nanjing University of Aeronautics and Astronautics. The author has contributed to research in topics: Point cloud & Transformation (function). The author has an hindex of 5, co-authored 18 publications receiving 85 citations.

On-line calibration and uncertainties evaluation of spherical joint positions on large aircraft component for zero-clearance posture alignment

Abstract: With the improvement of performance requirements for modern aircraft, such as speed and leak tightness, the posture alignment of large components without clearance is now extremely required in the aircraft industry. Nevertheless, the inherent errors of both the components themselves and the posture alignment system lead to high risk of collision during the inserting stage, among which the positional errors of spherical joints that connecting the large component to the numerical controlled locators are identified as the primary error source by existing studies. In this paper, a novel method for on-line correction and uncertainties evaluation of the positions of spherical joint centers (SJCs) is presented. Firstly, the rough positions of SJCs are identified based on the nominal model, and the finite element analysis (FEA) method is applied to preliminarily compensate the self-weight deformation of the component. Secondly, the on-line correction model of SJCs is further established, majorly on the basis of the displacements of locators and the relative postures between the initial posture and the new posture after each motion. Thirdly, to improve the correction accuracy, a new relative posture evaluation model considering the anisotropic measurement uncertainties of key points is suggested and solved by particle swarm optimization, and the correction uncertainties are then analyzed using Monte Carlo simulation. According to the numerical experiments, the proposed relative posture evaluation method has demonstrated more robustness evaluation results than the conventional approaches, and also leads to lower correction uncertainties of SJCs. Moreover, since the relative posture evaluation is a common problem in robot calibration, it also provides a promising alternative or supplement for the conventional optimal posture selection method to improve calibration accuracy. The practical application for a wing to fuselage assembly has verified the effectiveness of the correction method, in which the largest positional error of SJCs has decreased from about 14.2 mm to less than 0.4 mm after correction, and the displacement calculation error has been accordingly reduced from 0.1 mm to smaller than 0.01 mm. Therefore, the security of posture adjustment in confined clearance has been largely enhanced.

A coaxial alignment method for large aircraft component assembly using distributed monocular vision

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

Uncertainties evaluation of coordinate transformation parameters in the large-scale measurement for aircraft assembly

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.

Coordinate transformation uncertainty analysis and reduction using hybrid reference system for aircraft assembly

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.

Feature extraction from point clouds for rigid aircraft part inspection using an improved Harris algorithm

Abstract: In the process of feature extraction, geometric information about feature points is based on the nearest 1-ring field points, which are usually the edge points of the face adjacent to the feature line. The high structural complexity of rigid aircraft components leads to recognition of false feature points. Therefore, this paper proposes an improved Harris algorithm designed to improve the accuracy of feature extraction. It combines the discrete curvature and the normal vector in a way that is suitable for use with point clouds. Key to this approach is the use of changes in the gradient rather than changes in the curvature to identify corner, plane, and crease points. Our method accurately eliminates pseudo-feature points that are too close to actual feature points in order to refine potential feature points. We demonstrate the efficiency and robustness of the proposed method by validating it against standard models and actual scan data and by comparing it with other feature detection algorithms.

A review on remanufacturing assembly management and technology

Abstract: Remanufacturing has been regarded as a key technology for the sustainable development of the world economy. However, the quality of remanufactured products is difficult to meet the needs of customers, which has become a bottleneck restricting the development of remanufacturing industry. Therefore, remanufacturing assembly management and technology has more important engineering significance to improve production efficiency and quality of remanufactured products. Aiming at the lag of the research on management and control of remanufacturing assembly, this paper summarizes the research status of remanufacturing assembly on the basis of studying the characteristics and connotation of remanufacturing assembly system. Intelligent robot of remanufacturing assembly driven by large data and intelligent manufacturing will become an important development direction in the future. The research direction of remanufacturing assembly is summarized, and the future research trend of remanufacturing assembly is pointed out. It can be predicted that the intelligent robot of remanufacturing assembly will be the key to the flexibility, intellectualization, precision, and integration of remanufacturing assembly system in the future. This study provides a direction for the development of remanufacturing industry.

Design and management of assembly systems 4.0: systematic literature review and research agenda

Abstract: Assembly systems (ASs) have moved into the era of mass customisation and Industry 4.0 (I4.0). Mass customisation involves a shift from the production of high quantities of the same product to the p...

A Measurement Method for Robot Peg-in-Hole Prealignment Based on Combined Two-Level Visual Sensors

Abstract: Vision measurement plays a significant role in robot automatic assembly. In this study, a new measurement method for robot peg-in-hole prealignment via a combined two-level vision system is proposed. The assembly system and a global coordinate system calibration procedure based on a dynamic coordinate system are developed to construct an accurate transformation between the coordinate systems. The subsequent hole pose is obtained with the proposed image processing method and the hole edge matching method, followed by the 3-D hole reconstruction and spatial circle fitting algorithm. A low-cost pose determination is proposed based on hole edge point selection. The experiment and analysis indicate that the hybrid measurement system has high precision in the local hole pose and global robot pose measurement accuracy. The peg-in-hole assembly results verify the measurement and calibration accuracy sideways. Our hybrid measurement system enhances the vision measurement range, local accuracy, and robot automation.

On-line calibration and uncertainties evaluation of spherical joint positions on large aircraft component for zero-clearance posture alignment

Abstract: With the improvement of performance requirements for modern aircraft, such as speed and leak tightness, the posture alignment of large components without clearance is now extremely required in the aircraft industry. Nevertheless, the inherent errors of both the components themselves and the posture alignment system lead to high risk of collision during the inserting stage, among which the positional errors of spherical joints that connecting the large component to the numerical controlled locators are identified as the primary error source by existing studies. In this paper, a novel method for on-line correction and uncertainties evaluation of the positions of spherical joint centers (SJCs) is presented. Firstly, the rough positions of SJCs are identified based on the nominal model, and the finite element analysis (FEA) method is applied to preliminarily compensate the self-weight deformation of the component. Secondly, the on-line correction model of SJCs is further established, majorly on the basis of the displacements of locators and the relative postures between the initial posture and the new posture after each motion. Thirdly, to improve the correction accuracy, a new relative posture evaluation model considering the anisotropic measurement uncertainties of key points is suggested and solved by particle swarm optimization, and the correction uncertainties are then analyzed using Monte Carlo simulation. According to the numerical experiments, the proposed relative posture evaluation method has demonstrated more robustness evaluation results than the conventional approaches, and also leads to lower correction uncertainties of SJCs. Moreover, since the relative posture evaluation is a common problem in robot calibration, it also provides a promising alternative or supplement for the conventional optimal posture selection method to improve calibration accuracy. The practical application for a wing to fuselage assembly has verified the effectiveness of the correction method, in which the largest positional error of SJCs has decreased from about 14.2 mm to less than 0.4 mm after correction, and the displacement calculation error has been accordingly reduced from 0.1 mm to smaller than 0.01 mm. Therefore, the security of posture adjustment in confined clearance has been largely enhanced.