Research On Consensus Vibration Control Technology For Large Flexible Spacecraft

With the development of space technology,high precision earth or target tracking and pointing and on orbit services put forward higher requirements to the position and attitude control ability of the spacecraft.The size of the flexible appendage of the spacecraft is becoming larger and larger.The modal frequency and the damping ratios are very low.Once the vibration is excited,it attenuates very slowly.The vibration produces coupling force and torque on the spacecraft,which will lower the precision and stability of the position and attitude control of the spacecraft,even lead to instability of the system.The vibration suppression of flexible structures is a key issue to further enhance the position and attitude control of spacecraft.In this paper,the active vibration control of the flexible structure of the spacecraft is taken as the target.The active vibration control is carried out by the piezoelectric element to the flexible structure,in order to improve the position and attitude control precision of the spacecraft position and attitude maneuver.The main research works are as follows:In order to solve the problem of flexible spacecraft modeling under unconstrained state,a global modal dynamic model is constructed based on Hamilton principle for the design of active vibration controller.The global position and attitude dynamics and flexible vibration dynamics are described in a unified form.Compared with the constrained modal dynamic model,the accuracy of the modal frequencies and shapes is higher in the global modal dynamic model,especially under the coupling state of the small center rigid body and large flexible structure.According to the simulation results,the conventional flexible spacecraft and the large flexible spacecraft are defined according to the rigid flexible inertia ratio,which lays the foundation for the design of vibration controllers.Aiming at the active vibration control of the flexible structure,based on the structure of distributed vibration control system,a distributed cooperative and consistent forward position feedback controller(CMPPF)is proposed through combining the modified positive position feedback(MPPF)and consensus control method.The stability conditions are studied by the Schur theorem.The control parameters are optimized by combining H? norm and M norm.The simulation results show that the vibration amplitude is lower and transition time is shorter for CMPPF compared with MPPF.The cooperative work between different control nodes is realized by CMPPF.Further simulations illustrate that CMPPF is robust to different node failures and different communication topologies.For the conventional flexible spacecraft with two symmetrical plates and the large flexible spacecraft with single large flexible panels,corresponding active vibration controllers are designed respectively: 1)For the active vibration control problem of the conventional flexible spacecraft with two symmetrical plates,a kind of integrated MPPF(IMPPF)controller is proposed based on constrained dynamic model.Combining the dynamic characteristics of the spacecraft and the MPPF controller,an integrated MPPF controller(IMPPF)is proposed based on a constrained modal dynamic model to solve the synchronous suppression of position coupling modes and attitude coupling modes.The simulation results verify the suppression of two coupled modes vibration in the position and attitude maneuver,the position,attitude,velocity and angle of the spacecraft.The amplitudes of position,attitude,velocity and angular velocity errors attenuate 70%,which indicates that the position and attitude control precisions of the spacecraft are improved.2)For the active vibration control problem of a spacecraft with a single side large flexible plate,a kind of CMPPF controller based on the global modal dynamic model is proposed,which solves the vibration control problem of the large flexible structure with the strong coupling effect between position and attitude control and the flexible structure's vibration.The stability and optimization methods are derived.The simulation results show that the CMPPF controller attenuates the position and attitude control errors' amplitudes by 10%,while the MPPF controller doesn't suppress the vibration due to the strong coupling between the position/attitude control and the flexible vibration during the position/attitude maneuver.During the position/attitude stabilization process,the CMPPF controller reduces the position/attitude control errors by 45%.The position and attitude control accuracies of the spacecraft are further improved.Active vibration control experiments are carried out for these two kinds of flexible spacecraft.The proposed controllers are verified: 1)based on the airbearing experimental system,the active vibration control experimental system is constructed for the conventional flexible spacecraft with two symmetrical plates.The constrained modal dynamic model is modified by the parameter identification technology.Experimental results are in agreement with the simulation results.The vibration amplitudes of the first order position coupling mode and attitude coupling mode attenuate 80%.During position and attitude maneuver,the errors' amplitudes of position,velocity,attitude angle and angular velocity attenuate about 20%.During position and attitude stabilization process,the amplitude of angular velocity error attenuates 65%.These results fully validate the effectiveness of the IMPPF controller.2)for the cantilever large flexible structure,the distributed vibration control experimental system is constructed for the first time.Experiment results indicate that the CMPPF controller attenuates the amplitude of the flexible structure by 90% and attenuates to 50% of the amplitude of the MPPF controller.The experiment results agree with the simulation results.The effectiveness of the CMPPF controller is fully illustrated.3)based on the air-bearing experimental system,the active vibration control experimental system is constructed for the first time for the large flexible spacecraft with single large flexible panels.Experiment results show that during position and attitude maneuver,the MPPF controller can not suppress the vibration,and the CMPPF controller attenuates the amplitudes of the position and attitude errors by more than 10%.During the stabilization process,the CMPPF is more effective than MPPF.CMPPF attenuate the vibration amplitude of the flexible structure.The amplitudes of position and attitude errors are reduced by 30%~55%.The results of the experiment are in agreement with the simulation results.The effectiveness of the CMPPF controller based on the global modal dynamic model is fully verified.