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

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. 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. 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.