In an aircraft assembly line

the aircraft posture is required to meet tolerance constraints. A novel optimization model was proposed to obtain the optimal aircraft posture parameters under tolerance constraints. Tolerance constraints

which was transformed into a penalty function

was combined with the sum of distance errors as an objective function for optimization by using PSO for constrained optimization problems (PSO-COPs). Further improvement on the above algorithm

the maximum distance error of the aircraft feature points could be further reduced by using an improved PSO algorithm (IPSO)

which was an iterative method by dynamically strengthening tolerance constraints. The simulation example and Monte Carlo simulation indicated that compared with the singular value decomposition method (SVD) and the basic PSO algorithm

PSO-COPs and IPSO can better guarantee the accuracy of aircraft posture for assembly under tolerance constraints.