Trajectory optimization of multistage launch vehicle based on an improved differential evolution-pseudo spectral method

This paper studies the orbital flight phase trajectory optimization of multistage launch vehicle based on an improved differential evolution (DE)-pseudo spectral method(PSM). PSM is a classic method which solves the trajectory optimization problem with a high precision and a fast convergence under the condition of good initial guess. However, the free motion of launch vehicle in the sliding phase usually causes bad initial state which will greatly affect the convergence and accuracy of PSM. To solve the problem, DE algorithm is adopted by employing its high search ability. Firstly, the cost function of the optimization problem is adjusted for the orbital flight phase which make it more suitable for the requirements of orbital elements. The adaptive operator of the mutation process in DE is adjusted to avoid falling into local optimum, and the fitness function is improved with the orbital elements. Then PSM shows the advantages of high accuracy and good convergence with good initial guess searched by DE. By comparing the simulation results, it is verified that the proposed algorithm can improve the accuracy of the launch vehicle in the orbital flight phase.