A clamping force prediction method considering the effect of initial gap was proposed based on the principle of gap eliminating in order to accurately estimate the

clamping force used in robotic drilling. Firstly, the influences of the stiffness of a fuselage panel on the demanded clamping force at the drilled positions in automatic robotic drilling were analyzed. And the region of the fuselage panel were divided according to the panel’s structure characteristics. In robotic drilling, different interlayer gaps demand different clamping forces to close them. Therefore, the formation of the interlayer gap in robotic drilling and the effects of the interlayer gap on the demanded clamping force were further analyzed. Based on the constructed finite element model related to aircraft panel and the method of influence coefficient, the stiffness matrices of skin and stringer were  obtained. Initial gaps between skin and stringer were produced by Monte Carlo simulation. The clamping forces of all drilling positions, which were applied to close the interlayer gaps, were calculated based on the elastic mechanics. The drilling experiments were conducted on the developed robotic drilling platform by using the predicted clamping forces. The experimental results show that burr height is less than 0.1 mm, which can meet the quality requirements of drilled fastener holes in aircraft assembly. Therefore, clamping force can be accurately estimated based on the proposed clamping force prediction method for robotic drilling. Hence burr formation is effectively suppressed in automatic drilling process for aircraft panel, and the drilling quality of the drilled fastener holes is ensured. The proposed method provides efficient aircraft automatic assembly with technical support.