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

Int J Adv Manuf Technol

et al. 2023

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In the digital assembly system of large aircraft components (LAC), multiple numerical control positioners (NCPs) are usually used as actuators to adjust the position and posture of LAC to realize the docking of LAC. The posture adjustment mechanism (PAM) composed of multiple NCPs is a redundant actuated parallel mechanism (RAPM). The traditional full position control (FPC) method may lead to interference between NCPs, resulting in the deformation of NCPs and bracket, affecting the service life of the equipment and the accuracy of posture adjustment. This paper proposes a posture adjustment method based on hybrid control, which divides the motion axes of the NCPs into the position control axis and the force control axis to avoid the internal force of posture adjustment caused by the cooperative motion error of the NCPs. The driving force of the axis of the RAPM under the same posture adjustment trajectory is uncertain. To further reduce the internal force of posture adjustment, a driving force distribution method based on the dynamic model of PAM is proposed. Then, the principle of selecting the position control axis of the PAM is analyzed, and the optimization strategy of the position control axis based on the condition number of the Jacobian matrix is studied to improve the motion performance of the PAM. Finally, the posture adjustment experiment of LAC is carried out. The results show that the hybrid control method based on the optimum contact force can significantly reduce the interaction force between NCPs, and can effectively avoid the deformation of NCPs and brackets. The experimental results of posture adjustment accuracy verification show that the optimization strategy of position control axis makes the accuracy of single posture adjustment meet the requirements of LAC docking, which can effectively improve the docking efficiency of LAC.

Section: Posture Adjustment Principle Of Lacmentioning

confidence: 99%

Posture adjustment method of large aircraft components based on multiple numerical control positioners

Int J Adv Manuf Technol

et al. 2023

Self Cite

“…Chen et al (2016) analyzed the application of an asymmetric actuated three-PPPS parallel mechanism in aircraft wing adjustment, and used the kinematic calibration method to improve the posture alignment precision of the wing end. To improve the calibration accuracy of the ball joint center (BJC) position of the attitude adjustment mechanism, Deng et al (2019) proposed a new relative posture evaluation model considering the anisotropic measurement uncertainties of key points, and analyzed the correction uncertainties by Monte Carlo simulation. However, these two methods are only applicable for the PAM with some axes are follow-up axes (Zhu et al, 2010).…”

Section: Introductionmentioning

confidence: 99%

A calibration method of redundant actuated parallel mechanism for posture adjustment

Huang

2021

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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.

“…8,9 After the LCA is transported to the assembly shop through automated guided vehicle (AGV), the process of driving the NCL to make the ball head of LCA fall into the ball socket of NCL accurately is called the ball head positioning. After the ball head is positioned, the LCA is connected with the NCL by a ball joint (BJ) which is composed of a ball head and a ball socket, 10 and the ball head can rotate freely relative to the ball socket, as shown in Figure 1. The ball joint center (BJC) is the common point between the LCA and the NCL; let q i f = [ x i f y i f z i f ] T denote the coordinate of the BJCi in local coordinate system (LCS) of LCA and q i g = [ x i g y i g z i g ] T denote the coordinate of the BJCi in global coordinate system (GCS).…”

Section: Introductionmentioning

confidence: 99%

A ball head positioning method based on hybrid force-position control

Proceedings of the Institution of Mechanical Engineers, Part I:

Huang

et al. 2021

Self Cite

In the digital aircraft assembly system, the large component of aircraft is connected with the numerical control locator through a ball joint composed of a ball head and a ball socket. To ensure the posture adjustment accuracy of large component of aircraft, the clearance between the ball head and the ball socket is very small. Therefore, it is very difficult to accurately guide the ball head of large component of aircraft into the ball socket of the numerical control locator. Aiming at this problem, this article proposes a ball head positioning method based on hybrid force-position control, so that the ball socket can approach the ball head adaptively. First, according to the technical characteristics of the ball head positioning, the axes of the numerical control locator are divided into position control axis and force control axis, and the conditions to ensure the safety of ball head positioning are analyzed. Then the control model of ball head positioning based on hybrid force-position control is established and simulated by Simulink. Finally, a simulated posture adjustment system is built in the laboratory, and a series of ball head positioning experiments based on hybrid force-position control are carried out. The experimental results show that, compared with the traditional ball head positioning method, the ball head positioning process based on hybrid force-position control is more stable and faster, and the method can significantly reduce the lateral force. Moreover, the proposed method can be easily integrated into the existing posture adjustment system without additional hardware cost.