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

Abstract

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.