A novel calibration method for ball joint position in a posture adjustment system

Abstract

In posture adjustment systems for large components of aircraft (LCA), composed of several numerical control locators (NCLs), the position deviation of the ball joint (BJ) connecting the LCA to the NCL is an important factor affecting the adjustment accuracy of LCA. Due to manufacturing and installation errors, it is impossible to calculate the precise position of the ball joint center (BJC) relative to the LCA via theoretical design models. To address this problem, a novel calibration method of the BJC position is proposed in this paper. Firstly, the influence of the position deviation of the BJC on the posture adjustment precision of the LCA is studied. Secondly, the calculation model of the BJC position is established in accordance with the relationship between the Z-axle displacement of the NCL and the position and posture variation of the LCA after each NLC rise. Thirdly, based on this model, the uncertainty of the BJC calibration is analyzed by Monte Carlo simulation. Finally, a simulated posture adjustment system, built in the laboratory and the BJC position is calibrated, using the method of force-position hybrid control (FPHC). The experimental results show that, compared with the conventional calibration method, the method proposed in this paper can calibrate the BJC position more accurately, and can greatly improve the precision of posture adjustment.

Trajectory planning method for docking of large aircraft components

“…It can be seen from equation ( 6) that the posture and position of LAC in the GCS can be adjusted by moving the position of the BJC so as to realize the spatial six degrees of freedom adjustment and positioning of LAC (Chu et al, 2020).…”

Adaptive positioning method for ball head based on impedance control

“…The ball socket will move along the direction of force with the floating device after being subjected to force, thereby compensating for the relative position deviation between the ball head and ball socket; the entire positioning process is completed in a floating state without generating forced contact stress (Lara-Molina et al, 2018). Floating positioning eliminates the complex force-position coupling relationship during contact between the ball head and ball socket through a special mechanical device (Chu et al, 2020a(Chu et al, , 2020bLiu and He, 2010) and has advantages such as simple operation and fast positioning speed. However, in practical applications, floating devices' design and manufacturing costs are relatively high, and their self-stability is poor, making it difficult to ensure stable support of the adjustment mechanism during the adjustment process.…”

“…Then, the locator was driven to maintain consistent relative position information between each ball socket and ball head. Finally, each ball head is lowered into its corresponding ball socket through hoisting (Chu et al, 2020a(Chu et al, , 2020b. In addition to laser tracker-based ball head measurement-based positioning, Liu et al (2019aLiu et al ( , 2019b) also proposed a vision-based ball head positioning method without calibration, which uses real-time visual measurement to obtain relative position information between the ball head and ball socket and drives the locator to actively find the correct ball head (Lei, 2017).…”