Nonlinearity index theory for the dynamic modeling of suborbital reusable launch vehicle

Reentry of a suborbital reusable launch vehicle (SRLV) has strong nonlinearity and uncertainty, with a negative impact on dynamic modeling and control system design. This paper provides a nonlinear strength analysis method for SRLV dynamic modeling. A nonlinearity index is an important indicator of the nonlinear strength of a system. This method first analysed a linear model of SRLV, then calculated the static and dynamic nonlinearity indices over the entire flight envelope. The degree of nonlinearity of the system model over the entire flight envelope was ascertained, and therefore the characteristics of SRLV reentry dynamic model could be qualitatively and quantitatively represented. The simulation results show that the method is correct and appropriate.