Robotic compliant assembly for complex-shaped composite aircraft frame based on Gaussian process considering uncertainties

Robots are finding increasing application in aircraft composite structure assembly due to their flexibility and the growing demand of aircraft manufacturers for high production rates. The contact force of the composite frame in a robotic assembly of the aircraft composite fuselage panel can hardly be controlled due to the multi-surface variable contact stiffness caused by compliance and complex shape with multiple mating surfaces. The paper proposes a robotic assembly system for the aircraft composite fuselage frame with a compliant contact force control strategy using the Gaussian process surrogate model. First, a robotic assembly system is introduced, and the global coordinate system transformation model is built. Then, a compliant force control architecture is designed to generate the desired output force. Subsequently, a Gaussian process surrogate model with uncertainties is utilized to model the complicated relationship between the robot’s output force and the normal contact force acting on the mating surface of the composite frame. Furthermore, an optimal contact force control strategy is implemented to improve the contact quality. Finally, an experiment demonstrates that the proposed methodology can ensure that the contact force on each surface is within the limit of the engineering specification and uniformly distributed, improving the quality compared to the traditional assembly process.