| As we all know,most of the current launch vehicles are expendable.If the launch vehicle can be recovered and reused with simple maintenance,it can effectively reduce the cost of space launch.For the reusable launch vehicle,the attitude control process and the soft landing impact process on landing platform are essential for its safe landing and reuse.The two processes are studied in this paper and the obtained results have value for the research on the recovery of vertical landing launch vehicle.The soft landing impact process of reusable launch vehicle: Firstly,based on the functional requirements of the rocket landing mechanism,the structural scheme of the landing mechanism is determined.Then,based on simplifications and assumption,the dynamics equation of the rocket landing on sea platform is established.Theoretical analysis is made for the landing process and two criteria for the landing stability are given.Subsequently,the simulation of the landing process has been implemented in ADAMS by setting different vertical velocities,center of gravity positions,attitude angles,horizontal velocities,and slopes of landing platform as landing conditions in two landing modes.The influence on the landing performance of these parameters is analyzed based on the simulation results.Finally,the critical conditions of the stable landing in two landing modes are determined.The attitude control process of reusable launch vehicle: Considering mass change,unmodeled dynamics and unknown disturbances,an actual dynamics model of the reusable launch vehicle is established.Then,a sliding-mode state observer and an adaptive parameter estimator are given to obtain the estimated value of the norm bounded uncertainties and disturbances.Subsequently,a dynamic surface tracking control law is proposed based on the derived estimations.Finally,numerical simulation results show that the proposed control law can realize a precise vertical landing recovery for reusable launch vehicle. |
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