Pose and shape error control in automated machining of fastener holes for composite/metal wing-box assembly

Composite/metal wing-boxes are hard to drill by the conventional drilling method. In this paper, an automated machine-tool-based machining system equipped with a multifunctional end-effector is developed for helical milling, as well as circular and ellipsoidal dimple drilling of composite/metal wing-boxes. The system constitution, the control system, and the application software of the machining system are demonstrated. In aircraft manufacturing, the out-of-tolerance pose and shape of fastener holes deteriorate an aircraft's strength and fatigue performances. Thus, a multi-sensor information fusion and integration architecture is built for enhanced pose and shape accuracy of machined fastener holes. The relative pose error of the end-effector and an aerostructure is analyzed. A coarse-to-fine control method by the touch probe and LDSs is applied for controlling the error. The fastener holes' shape errors are controlled through the elaborate structure design and multi-sensor-based closedloop motion control of the end-effector. Experiments performed on the machining system show that the positioning errors, hole diameter errors, dimple depth errors, and ellipsoidal dimple shape can fulfill the wing-box assembly requirements.