A MULTIBODY DYNAMICS MODEL OF ROCKETS INCORPORATING FLEXIBILITY AND CONTROL

A heavy-lift launch rocket faces a significant challenge that the flexible structure and the controller are coupled. The vibrations of the structure and the swing of the engine may become divergent if the controller parameters are designed unreasonably. It is an urgent task to develop a coupled model of rocket launch dynamics to verify controller parameters. This study presents a multibody model incorporating flexibility and control. The flexible structure of the rocket is discretized into rigid bodies, every two of which are linked by the massless Timoshenko beam. The controller is coupled in the system by simultaneously solving the controller's state space equation and the rocket body's dynamic equation. The multibody model can capture the coupling of the structure and control, and accurately represent the rocket launch dynamics. A high-precision result of rocket launch dynamics can be obtained in a short simulation time using a numerical integration method named backward differentiation formula. A single-stage rocket is used as an example to confirm the effectiveness of the multibody model. The multibody model is an effective tool for rocket design.