Abstract: Due to the working nature, the four -cable traction camera system in indoor aircraft maintenance is in static equilibrium when positioning, and the influence of internal disturbance on the cable length is mainly considered regardless of the dynamic characteristics in motion. In order to reduce the positioning error caused by the length of the suspension cable, improve the positioning accuracy of the four-cable traction system and maximize the reach range of the suspension cable, the relationship between the horizontal component of the suspension cable and the cable length is derived in the spatial O-XYZ coordinate system and a four-cable catenary model created based on the catenary principle and through the inverse solution analysis of the position. The SQP (sequential quadratic programming) algorithm is used to optimize the horizontal component of the suspension cable, so that the suspension cable tension is evenly distributed, the nonlinear equations are iteratively established to obtain the optimized suspension cable length. The simulation calculation shows that the algorithm has high accuracy, fast convergence and clear and simple calculation process. The cable force of the four cables is evenly distributed, which avoids the phenomenon of over-limit cable force and virtual traction.

Key words: aircraft maintenance, four cables traction, position inverse solution, catenary model, equential quadratic programming(SQP) algorithm