The Study On Dynamics And Control For On-orbit-servicing Spacecraft To Approach Target

On-orbit-servicing is one of the key trends for spacecraft technology development and its essential task is to repair the discrepant or disabled spacecraft on orbit. To fulfill the goal, relative guidance, navigation and control for non-cooperative target should be explored. The dissertation covered a thorough research on the relative guidance, navigation and control theory during the process for on-orbit-servicing spacecraft to approach target.Aiming at the state uncertainty of target spacecraft on-orbit-servicing in the eccentric orbit, the dissertation studied the approaching trajectory safety by radial impulse, tangential impulse and continuous thrust. Also the dissertation presented trajectory programming strategy of V-bar radial impulse approach and R-bar tangential impulse retreat. Meanwhile a strategy to capture the target spacecraft based on service spacecraft attitude synchronous rotation was detailed to solve the target spacecraft attitude rotation when out of control.The dissertation illustrated the relative state estimation based on cameras and microwave radars. Characterizing the target spacecraft shape, the dissertation established a relative state observation equation based on dual quaternion and presented a method to determine target spacecraft rotation inertial and relative state via IEKF by multiple frame images. In order to promote the estimation accuracy, a method based on relative state coordinated estimation by cameras and microwave radars was presented, providing necessary navigation information for service spacecraft approaching non-cooperative spacecraft.To satisfy the maneuver flexibility for service spacecraft towards target spacecraft under the circumstance restrained by time and space, a multiple impulse gliding guidance method, by which, the relative velocity followed distance variation was presented and optimized combined with constraint of service spacecraft guidance accuracy and safety velocity. The method ensured active approaching, capturing and retreating towards target spacecraft; meanwhile, the dissertation proposed a passive approaching and capturing algorithm in the case of service spacecraft ordinary supervision, which supported to increase the system reliability and to reduce power consumption.The dissertation studied relative orbit and attitude control strategy which satisfied the requirement of eclipse orbit service spacecraft control. Considering that the relative orbit control model varies along with time, the dissertation presented a characteristic polynomial assignment and accordingly a controller with time-varied gain was designed ensuring the stability and control accuracy of service spacecraft closed-loop system. Focusing at the attitude control model variation, a model independent attitude maneuver strategy was established based on restraining offset from Eula axis, which realized attitude large angle maneuver with constrained rotating velocity and saturated control torque, and the same strategy was valid to achieve attitude synchronous rotation.Finally, the dissertation presented a hardware-in-the-loop simulation method to validate on-orbit-servicing spacecraft dynamics and control during approaching. An on-orbit-servicing spacecraft attitude simulation system was established by a three-axes bearing platform and a single-axis bearing platform. The simulation testified the feasibility of fast large angle maneuver and high accuracy attitude synchronous rotation methods applied to on-orbit-servicing.