Contact force stabilization based on off-line trajectory correction in automated fiber placement

Automated fiber placement (AFP) is a key technology in aerospace manufacturing, in which the maintenance of rated load is a necessary condition for high-quality forming of composite parts. In order to realize the continuous and stable contact between the flexible roller and the complex mold in the process of robotic AFP, a constant force stabilization method based on off-line trajectory correction is proposed in this paper. In this method, the robot stiffness model and the contact mechanics model proposed in the previous work are used to accurately predict the robot deformation and roller deformation. The two kinds of deformation are compensated to the initial trajectory to keep the distance between the robot end and the roller constant, so as to reduce the burden of the pneumatic system and achieve the stability of the contact force. Static loading experiments demonstrate the accuracy of the proposed method for trajectory correction, and dynamic loading experiments verify the effectiveness of the proposed method for suppressing contact force fluctuations. Experimental results show that this method reduces the maximum error of contact force control from 18.3 % to 7.5 %. The experiment of fiber placement further elucidated the engineering value of this method for laying quality improvement.